JP2025110784A - Power Supply System - Google Patents

Abstract

To provide a power supply system that can improve the ability of power supply to follow demand changes.SOLUTION: A power supply system 1000 comprises a plurality of power generation units 100 and a system controller 18. Each power generation unit 100 includes a power generation module 20, a power conditioner 16, and a local controller 17. In each power generation unit 100, the local controller 17 is configured to be able to execute output adjustment control, and the output adjustment control includes heteronomous output adjustment control for adjusting output power in a heteronomous manner and autonomous output adjustment control for autonomously adjusting output power. The system controller 18 divides all of the power generation units 100 into groups of output adjusters that execute output adjustment control, and, based on first information regarding power purchased from a commercial power system 500, coordinates the heteronomous output adjustment control and the autonomous output adjustment control so as to substantially equalize the output power of each output adjuster.SELECTED DRAWING: Figure 3

Description

The present invention relates to a power supply system using a fuel cell or the like.

Switching some of the commercial electricity consumers currently purchase from power companies to self-generated electricity is expected to lead to a reduction in carbon dioxide emissions. For example, while the primary energy efficiency of thermal power generation using coal or LNG as fuel is around 40%, the primary energy efficiency of solid oxide fuel cells (SOFCs), which generate electricity by reforming city gas, which is primarily composed of methane, is expected to be 50% to 65%. Therefore, increasing the proportion of self-generated electricity can contribute to reducing the environmental impact.

In addition, by realizing a system that can independently maintain power supplies during power outages caused by natural disasters, it is hoped that the negative impact on social life and economic activity can be reduced. For example, solid oxide fuel cells (SOFCs) can independently generate electricity and supply power to the outside world as long as the city gas supply is not cut off. In the case of an earthquake, depending on its scale, gas infrastructure may be damaged, but in the case of a typhoon, there is almost no impact on the gas infrastructure, so power supply can continue.

Patent Documents 1 and 2 disclose a power supply system (fuel cell system) that operates in parallel with a commercial power system and supplies power to power-demanding facilities. When there is a high demand for power during operation, such as at a power-demanding facility such as a factory, the power supply system is composed of multiple power generation units (e.g., fuel cell units).

In addition, the power supply system does not permit reverse power flow to the commercial power grid, regardless of the number of power generation units installed. Therefore, it is necessary to purchase electricity from the commercial power grid at all times.

JP 2016-019430 A JP 2016-019431 A

Demand from electricity demand facilities fluctuates depending on the operating status of factories and other facilities, with demand increasing during operating hours and decreasing during non-operating hours. Reducing the number of operating power generating units during periods of low demand can impair the ability of the power supply to respond to changes in demand.

For example, because SOFC units operate their power generation modules at temperatures between 600 and 800°C, restarting them after they have been shut down and become cold takes a very long time. Furthermore, keeping the power generation modules warm while they are on standby not only reduces power generation efficiency due to fuel loss, but also requires a certain amount of time to achieve minimum output power after waking up from standby. Therefore, it is not recommended to shut down or put some of the power generation units on standby during periods of low demand.

The present invention was made in consideration of the above-mentioned problems, and aims to provide a power supply system that can improve the ability of the power supply to respond to changes in demand.

The power supply system of the present invention comprises a plurality of power generation units operated in parallel with a commercial power system and a system controller that oversees the control state of the plurality of power generation units. Each of the plurality of power generation units has a power generation module, a power conditioner that converts the power generated by the power generation module into output power equivalent to the AC power of the commercial power system, and a local controller that controls the output power by controlling the power generated by the power generation module. In the plurality of power generation units, each of the local controllers is configured to execute output adjustment control that adjusts the output power within a range that is equal to or less than the rated output power and equal to or greater than the minimum output power. The output adjustment control includes heteronomous output adjustment control that heteronomously adjusts the output power and autonomous output adjustment control that autonomously adjusts the output power. The system controller divides all of the plurality of power generation units into groups of output adjusters that execute the output adjustment control, and oversees the heteronomous output adjustment control and the autonomous output adjustment control so as to substantially equalize the output power of each of the output adjusters based on first information regarding power purchased from the commercial power system.

The present invention provides a power supply system that can improve the ability of power supply to respond to changes in demand.

FIG. 2 is a schematic diagram showing the configuration of a power generation unit. FIG. 1 is a schematic diagram illustrating a configuration of a power conditioner. FIG. 1 is a schematic diagram illustrating a configuration of a power supply system. 1 is an explanatory diagram showing the relationship between actual purchased power from a commercial power supply system and reference purchased power in output adjustment control. 10 is a flowchart of overall control in a system controller. 10 is a flowchart of output adjustment control in the local controller. 10 is a flowchart of output adjustment control in the local controller.

Embodiments of the present invention will be described below with reference to the drawings.

1.1 Overview of the Configuration of the Power Generation Unit First, an overview of the configuration of the power generation unit used in the power supply system according to this embodiment will be described. Fig. 1 is a schematic diagram showing the configuration of the power generation unit according to this embodiment. As shown in Fig. 1, the power generation unit 100 is a type that uses fuel cells and includes a plurality of cell stacks 1, a reformer 2, a burner 3, an evaporator 4, an air preheater 5, an anode off-gas cooler 6, an anode off-gas condenser 7, a CO oxidizer (carbon monoxide oxidizer) 8, a condensed water recovery tank 9, a first raw fuel blower 10, a first air blower 11, a water pump 12, a second raw fuel blower 13, a second air blower 14, a third air blower 15, a power conditioner 16, and a local controller 17.

In this embodiment, a total of eight cell stacks 1 are provided, including those not shown in Figure 1.

The power generation unit 100 also has the following lines (pipes): a raw fuel line La, a mixed gas line Lb, an anode fuel line Lc, an anode offgas line Ld, a cathode air line Le, a cathode offgas line Lf, a combustion gas line Lg, a burner cooling air line Lh, a reforming water line Li, a startup air line Lj, a cooling air line Lk, and a condensed water recovery line Lw.

The anode fuel line Lc includes a first distribution manifold Ma, which serves as the main pipe for the anode fuel inlet, and the cathode air line Le includes a second distribution manifold Mb, which serves as the main pipe for the cathode air inlet. These distribution manifolds Ma and Mb have an inlet and multiple outlets corresponding to each cell stack 1, and allow the fluid that flows into the inlet to flow out from each of the outlets.

The anode offgas line Ld includes a first collection manifold Mc, which serves as the outlet pipe for the anode offgas, and the cathode offgas line Lf includes a second collection manifold Md, which serves as the outlet pipe for the cathode offgas. These collection manifolds Mc and Md have multiple inlets and outlets corresponding to each cell stack 1, and allow fluid that flows into each inlet to flow out from the outlet.

The combustion gas line Lg includes a heat radiation tube Za and a combustion gas pipe Zb. The cooling air line Lk includes a cooling pipe Zc and a collection pipe Lk1.

The raw fuel line La is a pipe connecting the fuel inlet E1 and the burner 3, and a second raw fuel blower 13 is disposed in this pipe. The second raw fuel blower 13 is a device that pressurizes the raw fuel gas Gf (e.g., methane-containing gas such as city gas 13A) taken in through the fuel inlet E1 and sends it downstream along the raw fuel line La, and is typically driven during start-up operation of the power generation unit 100.

The mixed gas line Lb is a pipe connecting the fuel inlet E2 and the reformer 2, and in this pipe, from upstream to downstream, are arranged the first raw fuel blower 10, the evaporator 4, and the first bellows-type expansion joint B1. The first raw fuel blower 10 is a device that pressurizes the raw fuel gas Ga taken in through the fuel inlet E2 and sends it to the downstream side of the mixed gas line Lb, and is typically driven when the power generation unit 100 is operating to generate electricity.

The anode fuel line Lc is a pipe connecting the reformer 2 and the anode of each cell stack 1. More specifically, from the upstream side, the anode fuel line Lc includes a pipe connecting the reformer 2 and the inlet of the first distribution manifold Ma, the first distribution manifold Ma, and eight pipes (branch pipes of the first distribution manifold Ma) connecting each outlet of the first distribution manifold Ma to the anode of each cell stack 1.

The anode offgas line Ld is a pipeline connecting the anode of each cell stack 1 to the burner 3. More specifically, the anode offgas line Ld has, from upstream to downstream, eight pipelines (branch pipes of the first collection manifold Mc) connecting the anode of each cell stack 1 to each inlet of the first collection manifold Mc, the first collection manifold Mc, and a pipeline (hereinafter referred to as "pipe line Ld1") connecting the outlet of the first collection manifold Mc to the burner 3. Along the pipeline Ld1, from upstream to downstream, a second bellows-type expansion joint B2, an anode offgas cooler 6, an anode offgas condenser 7, and an air-water separator Sa are arranged.

The cathode air line Le is a pipe connecting the air intake E3 to the cathode of each cell stack 1. More specifically, from the upstream side, the cathode air line Le includes a pipe (hereinafter referred to as "pipe Le1") connecting the air intake E3 to the inlet of the second distribution manifold Mb, the second distribution manifold Mb, and eight pipes (branch pipes of the second distribution manifold Mb) connecting each outlet of the second distribution manifold Mb to the cathode of each cell stack 1.

In the middle of the pipeline Le1, arranged in order from upstream to downstream are a first air blower 11, an anode off-gas cooler 6, an air preheater 5, and a third bellows-type expansion joint B3. The first air blower 11 is a device that pressurizes air Aa taken in through the air inlet E3 and sends it to the downstream side of the cathode air line Le, and is typically driven during power generation operation of the power generation unit 100. Furthermore, in the pipeline Le1, a bypass path Le2 is provided that bypasses the anode off-gas cooler 6 and the air preheater 5, connecting the midpoint between the air inlet E3 and the anode off-gas cooler 6 and the midpoint between the air preheater 5 and the third bellows-type expansion joint B3.

The cathode offgas line Lf is a pipe connecting the cathode of each cell stack 1 to the burner 3. More specifically, from the upstream side, the cathode offgas line Lf has eight pipes (branch pipes of the second collection manifold Md) connecting the cathode of each cell stack 1 to each inlet of the second collection manifold Md, the second collection manifold Md, and a pipe (hereinafter referred to as "pipe Lf1") connecting the outlet of the second collection manifold Md to the burner 3.

The combustion gas line Lg is a pipe connecting the burner 3 and the gas exhaust port E6. More specifically, the combustion gas line Lg has, from upstream to downstream, a heat radiation tube Za, a pipe connecting the heat radiation tube Za and the combustion gas pipe Zb, the combustion gas pipe Zb, and a pipe connecting the combustion gas pipe Zb and the gas exhaust port E6 (hereinafter referred to as "pipe Lg1"). Along the way in pipe Lg1, from upstream to downstream, a fourth bellows-type expansion joint B4, an air preheater 5, a CO oxidizer 8, and an evaporator 4 are arranged.

The burner cooling air line Lh is a pipe that connects the pipe Le1 and the startup air line Lj, and is provided with a flow rate adjustment means (such as an orifice) not shown in the figure. More specifically, the burner cooling air line Lh branches off at the midpoint of the pipe Le1 that connects the first air blower 11 and the anode off-gas cooler 6, and merges with the startup air line Lj downstream of the second air blower 14. It is configured so that a small flow rate of air Ab flows toward the burner 3 when the first air blower 11 is operating.

The cooling air line Lk is a conduit that connects the air intake E5 with a predetermined location on the conduit Lg1 (between the evaporator 4 and the gas outlet E6), and within this conduit, from upstream to downstream, are arranged a third air blower 15 and a cooling pipe Zc. The third air blower 15 is a device that pressurizes the cooling air Ad taken in through the air intake E5 and sends it downstream along the cooling air line Lk.

The reforming water line Li is a pipe connecting the condensed water recovery tank 9 and the evaporator 4, and a water pump 12 is disposed in this pipe. The water pump 12 is a device that sends the condensed water Wb stored in the condensed water recovery tank 9 to the downstream side of the reforming water line Li as reforming water Wa.

The startup air line Lj is a pipe connecting the air intake E4 and the pipe Lf1, and a second air blower 14 is disposed in this pipe. The second air blower 14 is a device that pressurizes the air Ac taken in through the air intake E4 and sends it downstream of the startup air line Lj, and is typically driven during start-up operation of the power generation unit 100.

The condensed water recovery line Lw is a conduit connecting the water-air separator Sa, located midway along the conduit Ld1, to the condensed water recovery tank 9. The water-air separator Sa separates the condensed water Wb generated in the anode off-gas condenser 7 from the anode off-gas Gd, and the separated condensed water Wb flows down the condensed water recovery line Lw. The end of the condensed water recovery line Lw is open to the gas phase without being immersed in the aqueous phase of the condensed water recovery tank 9, so that the amount of condensation does not increase or decrease due to the temperature of the stored condensed water Wb. The end of the condensed water recovery line Lw is not immersed in the aqueous phase to prevent changes in the flow rate of the anode off-gas Gd sent to the burner 3. This configuration is particularly effective when the anode off-gas Gd after separation of the condensed water Wb is recycled to the primary side of the cell stack or used for power generation in a subsequent cell stack. The water-air separation section Sa may be a T-shaped pipe with a horizontally oriented straight pipe section and a downward-facing branch pipe section. Alternatively, a small-capacity cylindrical container placed vertically may be used as the water-air separation section Sa.

Cell stack 1 is a power generation unit composed of a solid oxide fuel cell (SOFC). Solid oxide fuel cells are high-temperature operating fuel cells in which the solid electrolyte, anode, and cathode that make up the power generation cell are all made of ceramic, and a power generation unit in which a certain number of power generation cells are integrated via metal interconnect material (also known as separator material) is called a cell stack. The battery output of cell stack 1 is adjusted by power conditioner 16 before being supplied.

The reformer 2 uses steam to reform the raw fuel gas Ga, generating reformed gas Gc, which is then sent to the downstream side. The reformer 2 contains a catalyst for steam reforming, and reacts methane contained in the raw fuel gas Ga with steam to generate reformed gas Gc, which contains carbon monoxide and hydrogen. Steam reforming is an endothermic reaction, but the heat supplied by the burner 3 allows the reformer 2 to stably generate reformed gas Gc.

The burner 3 burns the incoming gas to generate heat and discharges the combustion gas Gg produced by the combustion into the combustion gas line Lg. The evaporator 4 is a device that performs indirect heat exchange between the reforming water Wa and the combustion gas Gg (heat source fluid), and serves to evaporate the reforming water Wa and heat the raw fuel gas Ga through heat exchange with the combustion gas Gg.

The air preheater 5 and the anode off-gas cooler 6 are both heat exchangers that perform indirect heat exchange between low-temperature fluid and high-temperature fluid. The air preheater 5 serves to preheat the air Aa in the cathode air line Le through heat exchange with the combustion gas Gg, and the anode off-gas cooler 6 serves to cool the anode off-gas Gd through heat exchange with the air Aa in the cathode air line Le.

The anode off-gas condenser 7 uses a fan 7a to cool the anode off-gas Gd and condense the water vapor contained in the anode off-gas Gd. In this embodiment, the anode off-gas condenser 7 is an air-cooled heat exchanger, but a water-cooled heat exchanger may be used instead, forming a cogeneration-type power generation unit in which heat recovery is performed.

The CO oxidizer 8 is a device that brings harmful carbon monoxide contained in the combustion gas Gg into contact with a catalyst and converts it into harmless carbon dioxide. The CO oxidizer 8 does not operate if the oxidation reaction in the burner 3 is complete, and only operates if the oxidation reaction in the burner 3 is incomplete.

The condensed water recovery tank 9 recovers the condensed water Wb discharged from the water-air separation section Sa and makes it reusable as reforming water Wa. The condensed water recovery tank 9 is equipped with a water level detector Sb and a drain valve Sc to adjust the level of the stored reforming water Wa within a predetermined range. When the water level detector Sb detects an upper limit water level, the drain valve Sc opens; when the water level detector Sb detects a lower limit water level, the drain valve Sc closes. In this way, the required amount of reforming water Wa is secured in the condensed water recovery tank 9. Note that to prevent anode off-gas Gd from leaking to the outside when the reforming water Wa is drained, the drain position of the drain valve Sc is set near the bottom of the condensed water recovery tank 9.

As shown by the dashed line frame in Figure 1, each cell stack 1, reformer 2, burner 3, each manifold Ma-Md, heat radiation tube Za, combustion gas pipe Zb, and cooling pipe Zc are arranged in the first region R1. The first region R1 is maintained at a temperature exceeding 600°C during power generation operation of the power generation unit 100, and independently maintains the heat balance between heat absorption and heat generation. Meanwhile, the evaporator 4, air preheater 5, anode off-gas cooler 6, and CO oxidizer 8 are arranged in the second region R2. The second region R2 is maintained at a temperature lower than that of the first region R1 but higher than room temperature during power generation operation of the power generation unit 100. The first region R1 and the second region R2 are each surrounded by an insulated box, and the two insulated boxes are integrated to form the power generation module 20. The anode off-gas condenser 7, condenser fan 7a, condensed water recovery tank 9, blowers 10, 11, 13, 14, and 15, water pump 12, power conditioner 16, and local controller 17 are located outside the power generation module 20 (in the room temperature area). The bellows-type expansion joints B1 to B4 mentioned above are used to absorb the expansion and contraction of the piping caused by temperature changes between cold and operating conditions.

Figure 2 is a schematic diagram showing the configuration of the power conditioner 16 according to this embodiment, illustrating the internal configuration of the power conditioner 16 and its connection to peripheral devices. As mentioned above, the power generation module 20 is configured to include elements such as the cell stack 1. In addition, the auxiliary equipment 30 for operating the power generation module 20 is configured to include components such as the raw fuel blowers 10 and 13, air blowers 11, 14 and 15, a water pump 12, and the fan 7a of the anode off-gas condenser 7.

The power conditioner 16 converts the power generated by the power generation module 20 into output power equivalent to the AC power of the commercial power system 500. The power conditioner 16 includes DC/DC converters 16a and 16b, a smoothing capacitor 16c, a grid-connected inverter 16d, switches 16e and 16f, and control circuits 16g and 16h.

The DC/DC converter 16a converts the DC power from the power generation module 20 into a boost circuit. The smoothing capacitor 16c smoothes the output power of the DC/DC converter 16a. The grid-connected inverter 16d converts the output power of the DC/DC converter 16a into AC power equivalent to that of a commercial power system.

The output side of the grid-connected inverter 16d is electrically connected to a distribution panel 610 for receiving commercial power, installed within a building, for example. The grid-connected inverter 16d and the distribution panel 610 can be switched between a parallel state and a disconnected state via switch 16e. The distribution panel 610 is electrically connected to the commercial power system 500 and power demand equipment 600. The power demand equipment 600 includes multiple distribution panel boards, and each distribution panel is electrically connected to load equipment such as lighting fixtures, power units, or outlets used within the building, for example.

The grid-connected inverter 16d is also electrically connected to the independent outlet 300. The grid-connected inverter 16d and the independent outlet 300 can be switched between a connected state and a disconnected state via switch 16f. The independent outlet 300 is made up of multiple outlets into which the power plugs of various power-using devices can be inserted.

The DC/DC converter 16b and the control circuit 16g function as a drive power supply unit that supplies drive power to the auxiliary equipment 30. The DC/DC converter 16b adjusts the DC voltage boosted by the DC/DC converter 16a to a DC voltage suitable for driving the auxiliary equipment 30. The control circuit 16g supplies the DC voltage adjusted by the DC/DC converter 16b to the auxiliary equipment 30, thereby driving the auxiliary equipment 30 appropriately. The above-mentioned auxiliary equipment 30 is driven using commercial power during startup and shutdown operations of the power generation unit 100, and is driven using generated power during power generation operation of the power generation unit 100.

The DC/DC converter 16a and control circuit 16h function as an operating power supply unit that supplies operating power to the load module 40. The load module 40 is composed of an electric heater 41 and a heat dissipation fan 42. When the power generation unit 100 is in standalone operation mode, the electric heater 41 generates heat, consuming excess power generated by the cell stack 1, and the heat dissipation fan 42 sends airflow to the electric heater 41 to promote heat dissipation. The load module 40 is located, for example, inside or outside the housing of the power generation unit 100.

The local controller 17 controls the operation of the power generation unit 100 in accordance with a control program that has been created and stored in advance. The local controller 17 is provided with a communication unit 17a that communicates with the outside of the power generation unit 100. The local controller 17 is also connected to a current sensor 200, which will be described later. Details of the local controller 17 will be provided later.

1.2 Overview of Operation of the Power Generation Unit Next, an overview of operation of the power generation unit 100 will be described with reference to Fig. 1. The raw fuel gas Ga supplied from the fuel inlet E2 into the mixed gas line Lb is sent to the downstream side by the action of the first raw fuel blower 10. In parallel with the supply of the raw fuel gas Ga, the reforming water Wa supplied from the condensed water recovery tank 9 into the reforming water line Li has its amount adjusted by the water pump 12 and flows into the mixed gas line Lb.

The reforming water Wa flows into the evaporator 4 together with the raw fuel gas Ga in the mixed gas line Lb, where it is heated by heat exchange to become water vapor (superheated steam). This water vapor mixes with the heated raw fuel gas Ga and flows into the reformer 2 as mixed gas Gb.

The reformer 2 uses the water vapor in the mixed gas Gb to reform the raw fuel gas Ga, generating reformed gas Gc, which is then sent to the downstream side. The reformed gas Gc sent from the reformer 2 passes through the anode fuel line Lc and is distributed to the anodes of each cell stack 1.

Meanwhile, in parallel with the supply of the raw fuel gas Ga described above, air Aa is supplied from the air intake E3 into the cathode air line Le. The air Aa in the cathode air line Le is sent to the downstream side by the action of the first air blower 11. This air Aa is heated by heat exchange in the anode off-gas cooler 6, and then further heated by heat exchange in the air preheater 5 before being distributed to the cathodes of each cell stack 1. Note that, in order to adjust the temperature of the air Aa, it is also possible to flow a portion of the air Aa, air Aa1, into the cathodes of each cell stack 1 via bypass path Le2.

Furthermore, air Ab is supplied into the burner cooling air line Lh in synchronization with the supply of air Aa to the cathode. The air Ab in the burner cooling air line Lh is sent to the burner 3 by the action of the first air blower 11. This air Ab acts as a coolant to lower the combustion temperature of the burner 3.

Each cell stack 1 generates electricity using reformed gas Gc that flows into the anode and air Aa that flows into the cathode. When reformed gas Gc and air Aa are supplied to the cell stack 1 and a current sweep is performed by the power conditioner 16, electricity generation in the cell stack 1 (electrochemical reaction between the reformed gas and oxygen) begins. During power generation operation in the cell stack 1, anode offgas Gd is discharged from the anode to the anode offgas line Ld, and cathode offgas Ge is discharged from the cathode to the cathode offgas line Lf. The anode offgas Gd contains reformed gas that did not react at the anode, and the cathode offgas Ge contains oxygen that did not react at the cathode.

The anode off-gas Gd discharged from each cell stack 1 to the anode off-gas line Ld is collected in the first collection manifold Mc, cooled by heat exchange in the anode off-gas cooler 6, and flows into the anode off-gas condenser 7. In the anode off-gas condenser 7, the anode off-gas Gd is cooled to below the dew point temperature, and the water vapor contained in the anode off-gas Gd condenses.

The anode off-gas Gd that passes through the anode off-gas condenser 7 is sent to the water-air separation section Sa where it is separated into water and air, and the condensed water Wb is collected in the condensed water recovery tank 9. The condensed water Wb collected in the condensed water recovery tank 9 is reused as reforming water Wa, as described above. The uncondensed portion of the anode off-gas Gd (anode off-gas Gd after water-air separation) is sent to the burner 3.

The cathode offgas Ge discharged from each cell stack 1 to the cathode offgas line Lf is collected in the second collection manifold Md, then mixed in pipe Lf1 with air Ab flowing in via the burner cooling air line Lh, and sent to the burner 3. Depending on the operating state of the power generation unit 100, raw fuel gas Gf supplied from the fuel inlet E1 is sent to the burner 3 via the raw fuel line La, and air Ac supplied from the air inlet E4 is sent to the burner 3 via the startup air line Lj.

The burner 3 receives the first burner gas Gx, which is raw fuel gas Gf and/or anode offgas Gd, and the second burner gas Gy, which is air Ac and/or cathode offgas Ge, and combusts them to generate heat. Specifically, the first burner gas Gx is either a mixture of raw fuel gas Gf and anode offgas Gd, or either raw fuel gas Gf or anode offgas Gd, and the state of the first burner gas Gx can vary depending on the operating state of the power generation unit 100, among other factors. The second burner gas Gy is either a mixture of air Ac and cathode offgas Ge, or either air Ac or cathode offgas Ge, and the state of the second burner gas Gy can vary depending on the operating state of the power generation unit, among other factors. In other words, the state of the gas supplied to the burner 3 changes appropriately depending on the power generation unit 100's startup operation, power generation operation (full load operation or partial load operation), shutdown operation, etc.

The raw fuel gas Gf is a type of hydrocarbon-containing gas. On the other hand, air Ac is a type of oxidant-containing gas. During combustion operation of the burner 3, air Ab is continuously supplied from the burner cooling air line Lh to adjust the combustion temperature.

The combustion gas Gg generated by combustion in the burner 3 is sent to the combustion gas line Lg, passes through the heat radiation tube Za, combustion gas pipe Zb, air preheater 5, CO oxidizer 8, and evaporator 4 in that order, and is discharged to the outside of the power generation module 20 through the gas outlet E6. The heat radiation tube Za and combustion gas pipe Zb are positioned so that the combustion gas Gg can be used to effectively heat the reformer 2. Furthermore, the combustion gas Gg in the combustion gas line Lg is used for heat exchange as it passes through the air preheater 5 and evaporator 4, and if it contains carbon monoxide, the carbon monoxide is converted to carbon dioxide as it passes through the CO oxidizer 8.

In addition, the cooling air Ad supplied from the air intake E5 to the cooling air line Lk serves to cool the inside of the power generation module 20 as it passes through the cooling pipe Zc. As described below, the cooling pipe Zc is installed near the cell stack 1, allowing the cooling air Ad to effectively cool the cell stack 1. The cooling air Ad then passes through the collection pipe Lk1 and is ultimately discharged to the outside of the power generation module 20 from the gas outlet E6 together with the combustion gas Gg.

In addition, the power generation unit 100 controls the heat quantity (temperature) inside the power generation module 20 by adjusting the flow rate of cooling air Ad introduced into the cooling pipe Zc. As an example, when the discharge temperature of the cathode offgas Ge flowing out from the cell stack 1 exceeds an upper limit temperature, the local controller 17 drives the third air blower 15 and controls the rotation speed of the third air blower 15 so that the discharge temperature of the cathode offgas Ge becomes a target temperature (a temperature that is a predetermined temperature lower than the upper limit temperature). As the rotation speed of the third air blower 15 increases, the flow rate of the cooling air Ad introduced into the cooling pipe Zc increases. Furthermore, the local controller 17 stops the third air blower 15 when the rotation speed remains below the lower limit for a predetermined period of time.

The cooling pipe Zc installed near the cell stack 1 can also be used to heat the cell stack 1 during startup operation of the power generation unit 100. Specifically, during startup operation of the power generation unit 100, the second raw fuel blower 13 and the second air blower 14 are first driven to combust the burner 3. The combustion gas Gg generated by this combustion flows through the heat radiation tube Za and the combustion gas pipe Zb, heating the cold reformer 2 from the outside by radiant heat transfer and raising its temperature. Furthermore, the combustion gas Gg serves as a heat source for the evaporator 4, generating steam from the reforming water Wa. This steam flows sequentially through the cold reformer 2 and the cell stack 1, heating these devices from the inside by thermal conduction and raising their temperatures. If there is residual heat in the combustion gas Gg discharged from the evaporator 4, the combustion gas Gg is allowed to flow from the pipe Lg1 into the collection pipe Lk1. This allows combustion gas Gg to flow through the cooling pipe Zc, allowing the cold cell stack 1 to be heated from the outside by radiant heat transfer and increase in temperature.

During the power generation operation of the power generation unit 100, balancing the heat balance between the heat generated by the electrochemical reaction between reformed gas Gc and oxygen in the cell stack 1, the heat generated by the combustion reaction between anode off-gas Gd and cathode off-gas Ge in the burner 3, and the heat absorbed by the steam reforming reaction between raw fuel gas Ga and steam (reforming water Wa) in the reformer 2 is called "thermal self-sustaining." Furthermore, recovering the water (reforming water Wa) produced by the electrochemical reaction between reformed gas Gc and oxygen and repeatedly using it for the steam reforming reaction is called "water self-sustaining."

When the power generating unit 100 is operating in power generation mode, the output power of the grid-connected inverter 16d is equal to the value obtained by subtracting the sum of the power loss due to operation of the auxiliary equipment 30, the power loss due to operation of the power conditioner 16, and the power loss due to operation of the load module 40. The load module 40 is operated in the isolated operation mode described below.

When the power generation unit 100 is operated at full load with rated output power, the local controller 17 sets the sweep current value for the cell stack 1 to the rated current value and supplies an amount of raw fuel gas Ga corresponding to this. When the power generation unit 100 is operated at partial load with less than the rated output power but equal to or greater than the minimum output power, the local controller 17 sets the sweep current value for the cell stack 1 to a range less than the rated current value but equal to or greater than the lower limit current value and supplies an amount of raw fuel gas Ga corresponding to this. When the power generation unit 100 is put into standby with zero output power, the local controller 17 sets the sweep current value for the cell stack 1 to be equivalent to the operating power of the auxiliary equipment 30 and supplies a minimum amount of raw fuel gas Ga while keeping the power generation module 20 warm. The state in which the power generation unit 100 is put into standby with zero output power is referred to as "hot standby."

The power generation operation of the power generation unit 100 includes a grid-connected operation mode and an independent operation mode. In the grid-connected operation mode, as shown in Figure 2, switch 16e is controlled to the on state and switch 16f is controlled to the off state. This causes the power generation unit 100 to operate in parallel with the commercial power system 500. In the independent operation mode, in contrast to Figure 2, switch 16e is controlled to the off state and switch 16f is controlled to the on state. This causes the power generation unit 100 to operate in a state of disconnection from the commercial power system 500.

The local controller 17 constantly monitors the commercial power system 500 for power outages, and when a power outage is detected, it transitions the power generation unit 100 from grid-connected operation mode to independent operation mode. In independent operation mode, when a power-using device is connected to the independent outlet 300, the output power of the grid-connected inverter 16d can be supplied to the power-using device as independent operation power. When the commercial power system 500 recovers from a power outage, the local controller 17 transitions the power generation unit 100 from independent operation mode to grid-connected operation mode.

When the supply of independent operation power exceeds the consumption in independent operation mode, the power generation unit 100 causes the load module 40 to consume the surplus independent operation power. The power consumption of the load module 40 can be adjusted by adjusting the heat generation amount of the electric heater 41 (for example, by adjusting the number of heaters that are energized or the on/off duty ratio of the power supply).

2.1 Overview of the Configuration of the Power Supply System Next, an overview of the configuration of the power supply system according to this embodiment will be described. Fig. 3 is a schematic diagram showing the configuration of the power supply system according to this embodiment. As shown in Fig. 3, the power supply system (fuel cell system) 1000 includes a plurality of power generation units 100 operated in parallel with a commercial power supply system 500 (grid-connected mode), and a system controller 18 that manages the control state of each unit. The power supply system 1000 supplies a total output power, which is the sum of the output power of each power generation unit 100, to the power demand facility 600.

In this embodiment, the power supply system 1000 includes a first power generation unit 101, a second power generation unit 102, a third power generation unit 103, and a fourth power generation unit 104. Each of the power generation units 101 to 104 has the same rated output power. For example, if each rated output power is 6 kW, the power supply system 1000 can supply a total output power of up to 24 kW.

<Number of power generating units installed>
The number N of installed power generating units 100 is determined so as not to generate a reverse power flow when all of the power generating units 100 are operating at their rated output power (i.e., when the power supply system 1000 is operating at its maximum available power). Specifically, the number N is determined so as to satisfy the following formula (1), where Qr [W] is the rated output power of each power generating unit 100, Qs [W] is the preset reference purchased power that is always purchased from the commercial power supply system 500, and D [W] is the minimum power demand for a predetermined period in the power demanding facility 600, and n is a natural number obtained by rounding down the decimal point of the number obtained by the calculation (D-Qs)/Qr.
2≦N≦n ... (1)

For example, if the rated output power Qr = 6 kW, the standard purchased power Qs = 2 kW, and the minimum demand power D = 27 kW, then n = 4 is calculated, and equation (1) estimates the number of units N to be installed to be 2 to 4. Here, to take advantage of the benefit of private power generation, which is minimizing purchased power costs, it is desirable to select the maximum number n, which is 4, within the estimated range of the number of units N to be installed.

When the actual number of installed units N is the maximum number n, the standard purchased power Qs is set to a predetermined positive value that is less than the difference between the minimum demand power D and the maximum supplyable power calculated by multiplying the maximum number of units n by the rated output power Qr.

The specified period for determining the minimum power demand D should be at least one week, and at most one year, and it is desirable not to include low-demand periods (nighttime or holidays) when factories and other facilities are not operating. By determining the minimum power demand D for high-demand periods when factories and other facilities are operating, it becomes possible to operate the four power generation units 100 at their rated output power during high-demand periods.

<Operation as an output regulator>
As described above, the power generating unit 100 can be operated at full load with rated output power, at partial load below the rated output power but above the minimum output power, or in hot standby with zero output power. That is, each of the power generating units 101 to 104 can be operated as an output regulator that operates in a range below the rated output power but above the minimum output power. Note that, since the power generating module 20 in this embodiment includes an SOFC cell stack, the minimum output power during partial load operation is set based on the minimum fuel supply amount that allows the power generating module 20 to maintain thermal independence and the minimum fuel utilization rate that allows the power generating module 20 to maintain water independence.

The maximum output power of the power generation unit 100 in grid-connected operation mode is equivalent to the rated output power (6 kW). Furthermore, the minimum output power of the power generation unit 100 in grid-connected operation mode is set to the lower limit at which, in addition to achieving both thermal and water independence, power generation efficiency during partial load operation does not decrease compared to power generation efficiency during full load operation. In this case, the minimum output power is, for example, equivalent to 50% (3 kW) of the rated output power (6 kW). Furthermore, if output adjustment below the minimum output power is required, the unit will transition to hot standby.

The output regulator adjusts the output power from the power conditioner 16 by increasing or decreasing the output current from the grid-connected inverter 16d. The local controller 17 increases the sweep current value for the cell stack 1 in parallel with an increase in the output current, and increases the supply amount of raw fuel gas Ga. Furthermore, the local controller 17 decreases the sweep current value for the cell stack 1 in parallel with a decrease in the output current, and decreases the supply amount of raw fuel gas Ga. As a result, the power generated by the power generation module 20 increases or decreases as the output current increases or decreases.

<Local Controller>
Each of the local controllers 17 mounted on each of the power generating units 101 to 104 is configured by a programmable logic controller (PLC). The PLC has a calculation unit, a storage unit, an input unit, an output unit, and a power supply unit, and executes required calculations and sequence control using a processing program that has been created and stored in advance. A current sensor 200, which will be described later, is connected to the input unit of the PLC.

Each local controller 17 is configured to be able to execute output adjustment control that adjusts the output power of the power conditioner 16 within a range that is equal to or less than the rated output power and equal to or greater than the minimum output power, based on first information regarding the power purchased from the commercial power system 500. The output adjustment control includes heteronomous output adjustment control that heteronomously adjusts the output power, and autonomous output adjustment control that autonomously adjusts the output power. Details of heteronomous output adjustment control and autonomous output adjustment control will be described later.

<System Controller>
Each of the local controllers 17 mounted on each of the power generating units 101 to 104 has a system control section that can function as a system controller 18. This system control section is a functional block incorporated in a PLC.

In this embodiment, each of the power generation units 101-104 is divided into one parent unit and the remaining child units. Specifically, the first power generation unit 101 is the parent unit, and the second power generation unit 102, third power generation unit 103, and fourth power generation unit 104 are child units.

The system control unit in the first power generation unit 101, which is designated as the parent unit, is enabled as the system controller 18. Meanwhile, the system control units in the second power generation unit 102, third power generation unit 103, and fourth power generation unit 104, which are designated as child units, are disabled as system controllers 18. As a result, the system controller 18 of the parent unit is configured to oversee the control status of its own unit and the child units.

<Information and communication functions>
The system controller 18 of the master unit and the local controller 17 of the master unit can exchange information with each other within the PLC. The system controller 18 of the master unit and the local controller 17 of the slave unit can also communicate with each other via a communication unit 17a attached to the PLC.

Each local controller 17 continuously transmits information about its own control state and output state (e.g., sweep current value for cell stack 1, output power of grid-connected inverter 16d, etc.) to the system controller 18. The system controller 18 uses this information received from each local controller 17 to oversee the heteronomous output adjustment control and autonomous output adjustment control of the output regulator.

<Current sensor>
The power supply system 1000 includes a current sensor 200 that detects a forward flow current flowing from the commercial power supply system 500 to the power demanding facility 600. The current sensor 200 includes a first current sensor 201 associated with the first power generating unit 101, which is a parent unit, a second current sensor 202 associated with the second power generating unit 101, which is a child unit, a third current sensor 203 associated with the third power generating unit 103, which is a child unit, and a fourth current sensor 204 associated with the fourth power generating unit 104, which is a child unit. The detection units of the current sensors 201 to 204 are disposed on the power transmission cable from the commercial power supply system 500 to the power demanding facility 600, on the power transmission cable upstream of connection points P1 to P4 of the output cables of the power generating units 101 to 104.

The detection information (current value information) of each current sensor 201-204 is input to the local controller 17 of the corresponding power generation unit 101-104. In the parent unit, the detection information is shared between the local controller 17 and the system controller 18.

2.2 Overview of Power Supply System Control The power supply system 1000 uses setting information related to the reference purchased power to cause each of the power generating units 101 to 104 to execute output adjustment control. Figure 4 is an explanatory diagram showing the relationship between the actual purchased power Qm from the commercial power system 500 and the reference purchased power in output adjustment control. When the actual purchased power Qm is on the positive side, it indicates that a forward flow of current is flowing from the commercial power system 500 to the power demand facility 600, and when the actual purchased power Qm is on the negative side, it indicates that a reverse flow of current is flowing from the power supply system 1000 to the commercial power system 500.

A first reference purchase power Q1 and a higher second reference purchase power Q2 are set for each of the system controller 18 and local controller 17. Furthermore, a third reference purchase power Q3 lower than the second reference purchase power Q2 is set for each of the local controllers 17.

The first standard purchased power Q1 is a set value (e.g., 2 kW) corresponding to the standard purchased power Qs used to determine the number of power generating units 100 to be installed. The first standard purchased power Q1 is a standard margin to prevent reverse power flow not only when all power generating units 100 are operating at full load but also when they are operating at partial load, and is a set value for determining a relatively slow decrease in demand that falls below the minimum demand power D.

The second standard purchased power Q2 is a set value that serves as a target value when reducing the output power of the power generation unit 100 to increase the actual purchased power Qm. The second standard purchased power Q2 is preferably determined so that a single reduction operation is completed within a specified time, regardless of the number of installed power generation units 100. For example, if the output current reduction rate of each unit is the same, if the second standard purchased power Q2 is too large, the fewer the number of installed units, the longer it will take to complete the reduction operation, resulting in poor responsiveness to demand changes. Therefore, the fewer the number of installed power generation units 100, the smaller the value of the second standard purchased power Q2 should be, so that the difference from the first standard purchased power Q1 does not become too large.

The second reference purchasing power Q2 also needs to be determined based on the maximum detectable current of the current sensor 200. For example, if the AC voltage value of the commercial power supply system 500 is 100 V and the maximum detectable current of the current sensor 200 is 100 A, the upper detection limit of the actual purchasing power Qm will be 10 kW, so the second reference purchasing power Q2 should be set to a value below this upper detection limit (for example, 8 kW).

The third standard purchased power Q3 is a marginal amount of power required to prevent reverse power flow even when all power generating units 100 are operating at partial load, and is a set value for determining a relatively sudden decrease in demand below the minimum demand power D. It is desirable that the third standard purchased power Q3 be set to a value (e.g., 0.5 kW) that ensures sufficient time before reverse power flow occurs, even if there is a slight response delay in suppressing the output of the power generating units 100.

Heteronomous output adjustment control and autonomous output adjustment control executed by each local controller 17 will be described below with reference to the flowcharts shown in Figures 5 to 7. Figure 5 is a flowchart of the overall control in the system controller 18, and Figures 6 and 7 are flowcharts of the output adjustment control in the local controller 17.

<Overall control of system controller based on first information>
First, the overall control will be described with reference to the flowchart in Fig. 5. In step ST101, the system controller 18 divides all of the power generating units 101 to 104 into groups of output adjusters that will execute output adjustment control, and transmits an execution permission signal for output adjustment control to each of the local controllers 17. By receiving the execution permission signal, each of the local controllers 17 becomes able to execute output adjustment control within a range that is equal to or less than the rated output power and equal to or greater than the minimum output power.

In step ST102, the system controller 18 calculates in real time the monitor value of the actual purchased power Qm from the commercial power system 500 based on the detection information (current value information) input from the corresponding current sensor 201 and the AC voltage value (e.g., 100 V) of the commercial power system 500. This actual purchased power Qm is used as first information for output adjustment control.

In step ST103, the system controller 18 determines whether the second output decrease control described below is being executed in any of the power generation units 101 to 104. If it is being executed (YES in step ST103), the process proceeds to step ST104. On the other hand, if it is not being executed (NO in step ST103), the process proceeds to step ST109.

In step ST104, the system controller 18 determines whether or not a report of the end of the second output decrease control has been received from all of the power generation units 101-104. If a report has been received (YES in step ST104), the process proceeds to step ST105. On the other hand, if a report has not been received (NO in step ST104), the process loops back to step ST104.

In step ST105, the system controller 18 transmits a third output reduction request to all of the power generating units 101-104. The third output reduction request is information for causing each local controller 17 to execute the third output reduction control described below. The third output reduction request also includes output reduction width information (output current reduction width) individually assigned to each local controller 17. This output reduction width information is information for increasing the actual purchased power Qm immediately after the execution of the second output reduction control to a state substantially equal to the second reference purchased power Q2, and is information for substantially equalizing the output power of each output adjustment device when the third output reduction control is completed. In other words, when each output adjustment device adjusts its output by the specified, unique output current reduction width, the actual purchased power Qm becomes substantially equal to the second reference purchased power Q2, and at the same time, the output power of each output adjustment device becomes substantially equal.

In step ST106, the system controller 18 determines whether the actual purchased power Qm is below the first reference purchased power Q1. If it is below the first reference purchased power Qm (YES in step ST106), the process proceeds to step ST107. On the other hand, if it is not below the first reference purchased power Qm (NO in step ST106), the process proceeds to step ST108.

In step ST107, the system controller 18 transmits a first output reduction request to all of the power generating units 101-104. The first output reduction request is information for causing each local controller 17 to execute the first output reduction control described below. The first output reduction request also includes output reduction width information (output current reduction width) equally allocated to each local controller 17. This output reduction width information is information for increasing the actual purchased power Qm, which is below the first reference purchased power Q1, to a state where it is approximately equal to the second reference purchased power Q2, and is information for approximately equalizing the output power of each output adjustment device when the first output reduction control is completed. In other words, when each output adjustment device adjusts its output by the same specified output current reduction width, the actual purchased power Qm becomes approximately equal to the second reference purchased power Q2, and at the same time, the output power of each output adjustment device becomes approximately equal.

In step ST108, the system controller 18 determines whether the actual purchased power Qm has remained above the second reference purchased power Q2 for a predetermined period of time. If it has (YES in step ST108), the process proceeds to step ST113. On the other hand, if it has not (NO in step ST108), the process returns to step ST102.

In step ST109, the system controller 18 sends an output increase request to all of the power generation units 101-104. The output increase request is information for causing each local controller 17 to execute the output increase control described below. The output increase request also includes output increase width information (increased output current width) equally allocated to each local controller 17. This output increase width information is information for reducing the actual purchased power Qm that exceeds the second reference purchased power Q2, and for roughly equalizing the output power of each output adjuster. In other words, when each output adjuster adjusts its output by the same specified increased output current width, the output power of the output adjusters is maintained roughly equal, while the actual purchased power Qm decreases toward the first reference purchased power Q1.

In step ST110, the system controller 18 determines whether the actual purchased power Qm is within the range from the first reference purchased power Q1 to the second reference purchased power Q2. If it is within the range (YES in step ST110), the system controller 18 stops sending the output increase request and ends the process. On the other hand, if it is not within the range (NO in step ST110), the process returns to step ST109 and continues sending output increase amount information (additional increased output current amount). At the end of step ST110, the actual purchased power Qm is within the range from the first reference purchased power Q1 to the second reference purchased power Q2 (e.g., slightly below the second reference purchased power Q2), and the output power of each output adjuster becomes approximately equal. Furthermore, if all output adjusters have reached their rated output power in step ST110, the process may end without making a determination regarding the actual purchased power Qm.

In step ST108, if a predetermined time (e.g., 10 minutes) has not elapsed since the end of the previous first output decrease control or second output decrease control, the process may wait before proceeding to step ST109. By setting such a waiting time, it is possible to avoid unintended reverse power flow being induced by increasing the output power in a situation where demand fluctuates greatly.

<Output Adjustment Control of Local Controller Based on First Information>
Next, the output adjustment control will be described with reference to the flowcharts of Figures 6 and 7. In step ST201, the local controller 17 calculates in real time a monitor value of actual purchased power Qm from the commercial power supply system 500 based on the detection information (current value information) input from the corresponding current sensors 201 to 204 and the AC voltage value (e.g., 100 V) of the commercial power supply system 500. This actual purchased power Qm is used as first information for the output adjustment control.

In step ST202, the local controller 17 determines whether the actual purchased power Qm is below the third reference purchased power Q3. If it is below the third reference purchased power Q3 (YES in step ST202), the process proceeds to step ST203. On the other hand, if it is not below the third reference purchased power Qm (NO in step ST202), the process proceeds to step ST209.

In step ST203, the local controller 17 executes second output decrease control. The second output decrease control is an autonomous output adjustment control that does not depend on a request from the system controller 18, and gradually decreases the output current from the grid-connected inverter 16d by a predetermined adjustment amount.

In step ST204, the local controller 17 determines whether the actual purchased power Qm has reached the third reference purchased power Q3 due to the output reduction operation of the local controller 17. If it has reached the third reference purchased power Q3 (YES in step ST204), the process proceeds to step ST205. On the other hand, if it has not reached the third reference purchased power Q3 (NO in step ST204), the process returns to step ST203, and the second output reduction control continues.

In step ST205, the local controller 17 ends the second output decrease control, fixes the output current, and transmits a report of the end of the second output decrease control to the system controller 18. Note that at the end of the second output decrease control, the output power of each output regulator is uneven.

In step ST206, the local controller 17 determines whether or not a third output decrease request has been received from the system controller 18. If a third output decrease request has been received (YES in step ST206), the process proceeds to step ST207. On the other hand, if a third output decrease request has not been received (NO in step ST206), the process loops back to step ST206 and waits for reception of the third output decrease request.

In step ST207, the local controller 17 executes the third output decrease control. The third output decrease control belongs to heteronomous output adjustment control in accordance with a request from the system controller 18, and gradually decreases the output current from the grid-connected inverter 16d by a predetermined adjustment amount based on the output decrease amount information (output current decrease amount) included in the third output decrease request.

In step ST208, the local controller 17 determines whether the output current reduction range (output reduction range) assigned to the local device has been reached. If it has been reached (YES in step ST208), the processing ends. On the other hand, if it has not been reached (NO in step ST208), the processing returns to step ST207, and the third output reduction control continues.

In step ST209, the local controller 17 determines whether or not a first output decrease request has been received from the system controller 18. If it has been received (YES in step ST209), processing proceeds to step ST210. On the other hand, if it has not been received (NO in step ST209), processing proceeds to step ST212.

In step ST210, the local controller 17 executes first output decrease control. The first output decrease control belongs to heteronomous output adjustment control in accordance with a request from the system controller 18, and gradually decreases the output current from the grid-connected inverter 16d by a predetermined adjustment amount based on output decrease amount information (output current decrease amount) included in the first output decrease request.

In step ST211, the local controller 17 determines whether the output current reduction range (output reduction range) assigned to the local device has been reached. If it has been reached (YES in step ST211), the processing ends. On the other hand, if it has not been reached (NO in step ST211), the processing returns to step ST210, and the first output reduction control continues.

In step ST212, the local controller 17 determines whether or not it has received a request to increase output from the system controller 18. If it has been received (YES in step ST212), the process proceeds to step ST213. On the other hand, if it has not been received (NO in step ST212), the process returns to step ST201.

In step ST213, the local controller 17 executes output increase control. The output increase control is a heteronomous output adjustment control that follows a request from the system controller 18, and increases the output current from the grid-connected inverter 16d in stages by a predetermined adjustment amount based on the output increase amount information (increased output current amount) included in the output increase request.

In step ST214, the local controller 17 determines whether the output increase request from the system controller 18 has stopped. If it has stopped (YES in step ST214), the processing ends. On the other hand, if it has not stopped (NO in step ST214), the processing proceeds to step ST215.

In step ST215, the local controller 17 determines whether the rated output power has been reached as a result of the output increase operation of the local controller. If it has been reached (YES in step ST215), the processing ends. On the other hand, if it has not been reached (NO in step ST215), the processing returns to step ST213, and the output increase control continues.

The first output decrease control described above is performed in situations where there is a relatively gradual decrease in demand below the minimum demand power D. By decreasing the output power of the power generation unit 100 at an early stage when demand is on a downward trend and sufficiently restoring the actual purchased power Qm, the occurrence of reverse power flow is prevented. On the other hand, the second output decrease control and the subsequent third output decrease control are performed in situations where there is a relatively sudden decrease in demand below the minimum demand power D. When an unexpected sudden decrease in demand occurs, the occurrence of reverse power flow is avoided by quickly restoring the actual purchased power Qm through two-stage output adjustment.

<Output Adjustment Control of Local Controller Based on Second Information>
Each of the local controllers 17 can be configured to be able to execute autonomous output adjustment control based on second information regarding the cooperative state between the local controller 17 and the commercial power system 500. Control based on the second information takes priority over control based on the first information.

[Control Example A Based on Second Information]
When the terminal voltage on the output side of the local power conditioner 16 exceeds a set value, the local controller 17 executes constant power factor control, which outputs reactive power so that the operating power factor is constant relative to the power generated (active power) of the power generation module 20. This constant power factor control is an operation for suppressing an increase in the grid voltage. If the terminal voltage does not become equal to or less than the set value even after executing constant power factor control for a predetermined time, the local controller 17 executes the second output decrease control described above, and forcibly shifts the power generation unit 100 to partial load operation. The condition for terminating the second output decrease control is when the terminal voltage becomes equal to or less than the set value.

[Control Example B Based on Second Information]
When the corresponding current sensor 201 to 204 detects a reverse power flow current (for example, when Qm≦−200 [W]), the local controller 17 transitions the power generating unit 100 to the hot standby state described above. In this embodiment, reverse power flow due to an unexpected sudden decrease in demand is basically avoided by the second output decrease control described above. Therefore, transitioning to the hot standby state is an emergency measure to be taken when the second output decrease control does not function sufficiently.

<Output Adjustment Control of Local Controller Based on Third Information>
Each of the local controllers 17 can be configured to be able to execute autonomous output adjustment control based on third information related to the internal temperature of the power conditioner 16 that is exclusively owned by that local controller 17. The control based on the third information has priority over the control based on the first information.

[Example of control based on third information]
The grid-connected inverter 16d has a function for monitoring abnormal temperatures of the switching elements, such as IGBTs, that constitute the power module, to prevent the elements from being damaged due to overheating. When the internal temperature of the power conditioner 16, i.e., the temperature of the switching elements, exceeds an upper limit, the local controller 17 executes the second output decrease control described above and forcibly shifts the power generation unit 100 to partial load operation. The condition for terminating the second output decrease control is when the internal temperature falls below the upper limit.

<Output Adjustment Control of Local Controller Based on Fourth Information>
Each of the local controllers 17 can further be configured to be able to execute autonomous output adjustment control based on fourth information regarding the thermal balance of the power generation module 20 exclusively owned by that local controller 17. The control based on the fourth information has priority over the control based on the first information.

[Control Example A Based on Fourth Information]
During the power generation operation of the power generation module 20, the local controller 17 adjusts the rotation speed of the fan 7a so that the cooling temperature of the anode off-gas Gd flowing out from the anode off-gas condenser 7 becomes a target temperature below the dew point at which water vapor condenses. If this rotation speed exceeds an upper limit, the local controller 17 executes the second output decrease control described above and forcibly shifts the power generation unit 100 to partial load operation. The second output decrease control is terminated when the rotation speed of the fan 7a falls below the upper limit.

If the temperature of the cooling air (outside air) sent by fan 7a is high and the anode off-gas Gd cannot be cooled below the dew point, the amount of condensed water Wb produced will decrease and water self-sustaining will not be maintained. Therefore, by reducing the power generated by the power generation module 20, the discharge temperature of the anode off-gas Gd flowing out of the cell stack 1 will be lowered, allowing the cooling air to be cooled below the dew point even when the temperature is high.

[Control Example B Based on Fourth Information]
During the power generation operation of the power generation module 20, the local controller 17 adjusts the rotation speed of the third air blower 15 so that the exhaust temperature of the cathode offgas Ge flowing out from the cell stack 1 becomes a target temperature. If this rotation speed exceeds an upper limit, the local controller 17 executes the second output decrease control described above and forcibly shifts the power generation unit 100 to partial load operation. The condition for terminating the second output decrease control is when the manipulated variable falls below the upper limit.

The discharge temperature of the cathode off-gas Ge flowing out of the cell stack 1 reflects the operating temperature of the cell stack 1. If the operating temperature of the cell stack 1 is too high even when cooling air Ad is flowing through the cooling pipe Zc, this may result in a deterioration in fuel utilization rate or accelerated deterioration of the power generation cells. Therefore, by lowering the power generation power of the power generation module 20, the heat of reaction between the reformed gas and oxygen is reduced, thereby lowering the operating temperature of the cell stack 1.

<Exclusion process from output adjuster>
If there are any power generating units 100 that are executing autonomous output adjustment control based on any of the second information, the third information, and the fourth information, the system controller 18 classifies the remaining power generating units 100 excluding these into groups of output adjusters in step ST101. Note that the output power of the power generating units 100 excluded from the output adjuster will be determined by the output adjustment control led by the local controller 17, and therefore only the groups of output adjusters are subject to output power equalization.

3. Other Modifications The cell stack 1 constituting the power generation module 20 may be a molten carbon dioxide fuel cell (MCFC) instead of a solid oxide fuel cell (SOFC). Like the SOFC, the MCFC is a high-temperature operating fuel cell and has high power generation efficiency.

The power generation module 20 using fuel cells is not limited to a type that generates power using a single cell stack 1, but may also be a type that generates power using two or more cell stacks 1. Specifically, water vapor is removed from the anode off-gas discharged from the previous cell stack to generate regenerated gas, which is then supplied to the anode of the next cell stack. When generating the regenerated gas, carbon dioxide contained in the anode off-gas may be removed using a separation membrane or absorbent. By configuring the module to generate power using two or more cell stacks, the fuel utilization rate can be significantly increased.

The fuel cell-based power generation module 20 is not limited to a configuration that supplies reformed gas to the cell stack; it may also be configured to supply pure hydrogen gas. Specifically, hydrogen gas supplied from an external hydrogen production site via transportation infrastructure is introduced into the anode of the cell stack. When hydrogen gas is used as the raw fuel, the components required for steam reforming and water self-sustaining (reformer 2, evaporator 4, anode off-gas condenser 7, steam-water separator Sa, condensed water recovery tank 9, water pump 12, etc.) can be omitted.

The power generation unit 100 is not limited to a type that uses a fuel cell, and can be modified to other types. The power generation unit may be a type that uses a solar cell, or a type that uses an organic Rankine cycle, a steam turbine, a gas turbine, or a gas engine to rotate a generator.

The system controller 18 may be a functional block incorporated into the local controller 17 (PLC), or it may be an independent controller separated from the local controller 17. In this case, each local controller 17 is connected to the system controller 18 via a communication unit 17a.

The power supply system 1000 can also include an additional second current sensor in addition to the first current sensors 201-204 connected to the local controller 17 of each power generation unit 101-104. This additional second current sensor is connected to the system controller 18 of the parent unit.

Some of the control functions performed by the local controller 17 (PLC) can also be configured to be performed by an internal controller provided in the power conditioner 16. In this case, the internal controller is essentially a component of the local controller 17. For example, the second output decrease control, control examples A and B based on the second information, and control example based on the third information described above may be control functions performed by the internal controller. Furthermore, monitoring power outages and power restorations, and issuing instructions for transitioning between grid-connected operation mode and isolated operation mode may be control functions performed by the internal controller.

The power supply system 1000 of this embodiment described above provides the following advantages:

(1) The power supply system 1000 comprises a plurality of power generation units 100 operated in parallel with the commercial power system 500, and a system controller 18 that oversees the control state of the plurality of power generation units 100. Each of the plurality of power generation units 100 has a power generation module 20, a power conditioner 16 that converts the power generated by the power generation module 20 into output power equivalent to the AC power of the commercial power system 500, and a local controller 17 that controls the output power by controlling the power generated by the power generation module 20. In the plurality of power generation units 100, each of the local controllers 17 controls the output power by controlling the power generated by the power generation module 20. The system is configured to be able to execute output adjustment control that adjusts output power within a range equal to or greater than the minimum output power, and the output adjustment control includes heteronomous output adjustment control (constant speed output decrease control A, constant speed output decrease control C, constant speed output increase control) that heteronomously adjusts output power, and autonomous output adjustment control (constant speed output decrease control B) that autonomously adjusts output power. The system controller 18 divides all of the multiple power generation units 100 into groups of output adjusters that execute output adjustment control, and, based on first information regarding power purchased from the commercial power system 500, coordinates the heteronomous output adjustment control and the autonomous output adjustment control so as to substantially equalize the output power of each output adjuster.

The multiple power generation units 100 are basically configured to operate at full load or partial load in grid-connected operation mode. The system controller 18 divides all of the power generation units 100 into groups of output regulators and oversees the heteronomous output regulation control and autonomous output regulation control by the local controllers 17. This allows all of the power generation units 100 to operate constantly as output regulators, improving the ability of the power supply to respond to changes in demand. Because all of the power generation units 100 in this operating configuration are output regulators, the power supply system 1000 is suitable for supplying power to power demand facilities 600 where the range of demand fluctuations between high and low demand periods is relatively large.

The system controller 18 also oversees the heteronomous output adjustment control and autonomous output adjustment control by the local controller 17 to ensure that the output power of each output adjuster is approximately equal. Because the output power of each power generation unit 100 is approximately equal, the load on the power generation modules 20 and auxiliary equipment 30 is also roughly equal, resulting in little variation in the degree of deterioration or remaining lifespan. This allows for planned maintenance such as part replacement to be performed at the same time for all power generation units 100.

(2) The power supply system 1000 of (1) is equipped with a current sensor 200 that detects the forward flow current flowing from the commercial power system 500 to the power demand facility 600. The system controller 18 calculates the actual purchased power Qm from the detection information of the current sensor 200 as first information, and when the actual purchased power Qm is lower than the first reference purchased power Q1, causes each local controller 17 to execute first output decrease control with an output decrease range equally allocated to each local controller 17 so that the actual purchased power Qm becomes approximately equal to a second reference purchased power Q2 that is higher than the first reference purchased power Q1. When the actual purchased power Qm exceeds the second reference purchased power Q2, causes each local controller 17 to execute output increase control with an output increase range equally allocated to each local controller 17 until the actual purchased power Qm falls within the range from the first reference purchased power Q1 to the second reference purchased power Q2.

When the system controller 18 determines that the actual purchased power Qm falls below the first reference purchased power Q1, resulting in a relatively slow decrease in demand below the minimum demand power D, it heteronomously causes each local controller 17 to execute the first output decrease control to increase the actual purchased power Qm to the second reference purchased power Q2. This allows the power supply to follow the decrease in demand while effectively preventing the occurrence of reverse power flow.

Furthermore, when the system controller 18 determines that demand is increasing because the actual purchased power Qm exceeds the second reference purchased power Q2, it causes each local controller 17 to execute output increase control heteronomously to reduce the actual purchased power Qm to within the range from the first reference purchased power Q1 to the second reference purchased power Q2. This makes it possible to adjust the power supply to follow the increase in demand while aiming to return each power generating unit 100 to full load operation.

Furthermore, the system controller 18 causes each of the local controllers 17 to execute the first output decrease control with an equally allocated output decrease range, while also executing the output increase control with an equally allocated output increase range. This allows the output power of each power generation unit 101-104 to be constantly equalized during partial load operation.

(3) In the power supply system 1000 of (2), each local controller 17 calculates the actual purchased power Qm from the detection information of the current sensor 200 as the first information. If the actual purchased power Qm is lower than the third reference purchased power Q3, which is lower than the first reference purchased power Q1, the local controller 17 executes the second output reduction control so that the actual purchased power Qm becomes approximately equal to the third reference purchased power Q3. After the second output reduction control is executed, the system controller 18 executes the third output reduction control by the output reduction amount individually assigned to each local controller 17 so that the actual purchased power Qm becomes approximately equal to the second reference purchased power.

When each local controller 17 determines that actual purchased power Qm has fallen below the third reference purchased power Q3, resulting in a relatively sudden decrease in demand below the minimum demand power D, it autonomously executes second output decrease control to restore actual purchased power Qm to the third reference purchased power Q3. The system controller 18 then heteronomously causes each local controller 17 to execute third output decrease control to increase actual purchased power Qm to the second reference purchased power Q2. This makes it possible to reliably prevent reverse power flow from occurring even in the event of a sudden decrease in demand.

The system controller 18 also causes each local controller 17 to execute the third output reduction control using the individually assigned output reduction amount. This allows the uneven output power of each unit to be returned to an equalized state at the end of the second output reduction control, allowing partial load operation to continue.

(4) In the power supply system 1000 of (2) or (3), the multiple power generation units 100 have the same rated output power, and the first reference purchased power Q1 is a predetermined positive value that is less than the difference obtained by subtracting the maximum supplyable power calculated by multiplying the number N of installed power generation units by the rated output power A from the minimum demand power D for a predetermined period in the power demand facility 600.

When the first standard purchased power Q1 is set in this way, during periods of high demand when factories and other facilities are operating, all power generating units 100 will operate at their rated output power. This allows you to enjoy the benefits of private power generation, such as minimizing purchased power costs.

Furthermore, since each power generation unit 101-104 operates based on full-load operation, executing the first output decrease control and output increase control with an equally allocated output adjustment range keeps the output power during partial-load operation in an equalized state. This allows the maintenance cycles of each unit to be matched after the power supply system 1000 has been commissioned.

(5) In the power supply system 1000 of (2) or (3), each local controller 17 continuously transmits its own current output information (sweep current value for the cell stack 1, output power of the grid-connected inverter 16d, etc.) to the system controller 18, and the system controller 18 uses the output information received from each device to oversee heteronomous output adjustment control (constant-speed output decrease control A, constant-speed output decrease control C, constant-speed output increase control) and autonomous output adjustment control (constant-speed output decrease control B).

When the local controller 17 is executing constant-speed output decrease controls A to C and constant-speed output increase control, the system controller 18 continually acquires output information from each unit and monitors the progress of output adjustments. If output information cannot be acquired, there is a risk that demand changes cannot be accommodated and reverse power flow will occur, but this risk can be determined early.

Furthermore, when the local controller 17 completes constant-speed output decrease control A, C and constant-speed output increase control, it acquires output information from each unit as needed and calculates the output allocation amount for each power generation unit 101-104. This allows the output power of each power generation unit 101-104 to be quickly equalized.

(6) In the power supply system 1000 of (2) or (3), each of the local controllers 17 has a system control unit that can function as a system controller 18, and the multiple power generation units 100 are divided into one parent unit and the remaining child units, and the system control unit in the power generation unit 101 designated as the parent unit is enabled as the system controller 18, and the system control units in the power generation units 102 to 104 designated as child units are disabled as the system controller 18.

The multiple power generation units 101-104 are configured so that the system control unit built into the local controller 17 can be switched between enabled and disabled. By enabling only the system control unit of the power generation unit 101 designated as the parent unit as the system controller 18, there is no need to install a standalone system controller. This minimizes the introduction costs (equipment costs, construction costs, etc.) of the power supply system 1000.

(7) In the power supply system 1000 of (6), the current sensor 200 includes a plurality of first current sensors 201-204 (first current sensors) associated with each of the local controllers 17 of the parent and child devices, and a single second current sensor associated with the system controller 18 of the parent device, and it is possible to select whether or not to install the second current sensor.

Multiple first current sensors 201-204 are provided in correspondence with multiple power generation units 101-104. This allows the local controller 17 of each unit to grasp the actual purchased power Qm in real time. This allows the local controller 17 to execute second output reduction control without delay in response to a sudden decrease in demand.

Furthermore, if an additional second current sensor is installed, the system controller 18 will be able to independently calculate the monitor value of actual purchased power Qm. As a result, the system controller 18 can generate highly accurate allocated power decrease width information when having each of the local controllers 17 execute the first output decrease control and the third output decrease control. Similarly, the system controller 18 can generate highly accurate allocated power decrease width information when having each of the local controllers 17 execute the output increase control.

(8) In the power supply system 1000 of (1) to (3), each local controller 17 is further configured to be able to execute autonomous output adjustment control based on any of second information regarding the cooperative state between itself and the commercial power system 500, third information regarding the internal temperature of the power conditioner 16 exclusively owned by itself, and fourth information regarding the thermal balance of the power generation module 20 exclusively owned by itself, and the system controller 18 classifies the remaining power generation units 100, excluding the power generation units 100 currently executing autonomous output adjustment control based on any of the second information, third information, and fourth information, into groups of output adjusters that execute heteronomous output adjustment control (constant-speed output decrease control A, constant-speed output decrease control C, constant-speed output increase control) and autonomous output adjustment control (constant-speed output decrease control B) based on the first information.

Each local controller 17 autonomously executes output adjustment control based on the second information, third information, and fourth information, prioritizing it over output adjustment control based on the first information. By prioritizing output adjustment control based on the second information, unexpected reverse power flow is avoided. As a result, adverse effects on the commercial power grid 500 operated by the electric power utility can be prevented. By prioritizing output adjustment control based on the third information, switching elements such as IGBTs that constitute the power module of the grid-connected inverter 16d are prevented from being damaged by overheating. As a result, the frequency of shutting down the power generation module 100 due to abnormalities other than scheduled maintenance can be reduced. By prioritizing output adjustment control based on the fourth information, water independence of the power generation module 20 is maintained and deterioration of the fuel utilization rate and degradation of the power generation cells are prevented. As a result, highly efficient power generation operation can be continued.

Furthermore, if there are power generation units 100 that are executing autonomous output adjustment control based on any of the second, third, and fourth information, the system controller 18 classifies the remaining power generation units 100 excluding these into an output adjuster group. This makes it possible to make the power supply follow changes in demand while utilizing the output adjuster.

(9) In the power supply system 1000 of (1) to (3), each of the power generation modules 20 in the multiple power generation units 100 includes a cell stack 1 that integrates solid oxide fuel cell cells.

The power supply system 1000 generates electricity privately using a power generation unit 100 that uses an SOFC, and supplies the privately generated electricity to consumers. Because SOFCs have higher primary energy efficiency than thermally generated electricity, consumers can reduce carbon dioxide emissions by switching some of the commercial electricity they purchase from power companies to privately generated electricity.

Furthermore, multiple power generation units 100 can switch from grid-connected operation mode to independent operation mode in the event of a power outage in the commercial power system 500. By realizing a system that can independently maintain power supply in the event of a power outage caused by a natural disaster, etc., it is possible to reduce the adverse impact on social life and economic activity.

Although the above describes an embodiment of the present invention, the configuration of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention. In other words, the above embodiment is illustrative in all respects and should be considered not to be limiting. The technical scope of the present invention is defined by the claims, not the description of the above embodiment, and should be understood to include all modifications that fall within the meaning and scope of the claims.

[Contributing to the United Nations-led Sustainable Development Goals (SDGs)]
The power generation unit and power supply system according to the present disclosure reduce carbon dioxide emissions by improving primary energy efficiency, and can contribute to the realization of SDG Goal 13, "Take urgent action to combat climate change." Furthermore, the power generation unit and power supply system according to the present disclosure can independently maintain power supply in the event of a power outage caused by a natural disaster, and can contribute to the realization of SDG Goal 11, "Make cities and towns inclusive and sustainable."

REFERENCE SIGNS LIST 1 Cell stack 2 Reformer 3 Burner 4 Evaporator 5 Air preheater 6 Anode off-gas cooler 7 Anode off-gas condenser 7a Fan 8 CO oxidizer (carbon monoxide oxidizer)
9 Condensed water recovery tank 10 First raw fuel blower 11 First air blower 12 Water pump 13 Second raw fuel blower 14 Second air blower 15 Third air blower 16 Power conditioner 16a, 16b DC/DC converter 16c Smoothing capacitor 16d Grid-connected inverter 16e, 16f Switch 16g, 16h Control circuit 17 Local controller 17a Communication unit 18 System controller 20 Power generation module 30 Auxiliary equipment 40 Load module 41 Electric heater 42 Heat dissipation fan 100 Power generation unit 101 First power generation unit 102 Second power generation unit 103 Third power generation unit 104 Fourth power generation unit 200 Current sensor 201 First current sensor 202 Second current sensor 203 Third current sensor 204 Fourth current sensor 300 Stand-alone outlet 500 Commercial power supply system 600 Power demand facility 610 Distribution panel 1000 Power supply system Aa, Ab, Ac Air Ad Cooling air B1 First bellows type expansion joint B2 Second bellows type expansion joint B3 Third bellows type expansion joint B4 Fourth bellows type expansion joint E1, E2 Fuel inlet E3, E4, E5 Air inlet E6 Gas outlet Ga, Gf Raw fuel gas Gb Mixed gas Gc Reformed gas Gd Anode off-gas Ge Cathode off-gas Gg Combustion gas La Raw fuel line Lb Mixed gas line Lc Anode fuel line Ld Anode off-gas line Le Cathode air line Lf Cathode off-gas line Lg Combustion gas line Lh Burner cooling air line Li Reforming water line Lj Start-up air line Lk Cooling air line Lk1 Collection pipe Lw Condensed water recovery line Ma First distribution manifold Mb Second distribution manifold Mc First collection manifold Md Second collection manifold R1 First region R2 Second region Sa Air-water separator Sb Water level detector Sc Drain valve Wa Reforming water Wb Condensed water Za Heat radiation tube Zb Combustion gas pipe Zc Cooling pipe

Claims (9)

a plurality of power generation units operated in parallel with a commercial power system;
a system controller that controls the control state of the plurality of power generating units,
Each of the plurality of power generation units comprises:
a power generation module;
a power conditioner that converts the power generated by the power generation module into output power equivalent to AC power of the commercial power supply system;
a local controller that controls the output power by controlling the power generated by the power generation module,
In the plurality of power generating units, each of the local controllers is configured to be able to execute output adjustment control to adjust the output power within a range not exceeding a rated output power and not less than a minimum output power,
The output adjustment control includes:
a heteronomous output adjustment control for heteronomously adjusting the output power;
an autonomous output adjustment control that autonomously adjusts the output power;
The system controller
Dividing all of the plurality of power generating units into groups of output adjusters that execute the output adjustment control;
A power supply system that controls the heteronomous output adjustment control and the autonomous output adjustment control so as to approximately equalize the output power of each of the output adjusters based on first information regarding power purchased from the commercial power system. a current sensor for detecting a forward flow current flowing from the commercial power supply system to the power demand facility;
The system controller
calculating an actual purchased power from the detection information of the current sensor as the first information;
When the actual purchased power is lower than a first reference purchased power, a first output decrease control is executed with an output decrease width equally allocated to each of the local controllers so that the actual purchased power becomes substantially equal to a second reference purchased power that is higher than the first reference purchased power;
2. The power supply system of claim 1, wherein when the actual purchased power exceeds the second reference purchased power, each of the local controllers is caused to perform output increase control with an output increase amount equally allocated to each of the local controllers until the actual purchased power falls within a range from the first reference purchased power to the second reference purchased power. Each of the local controllers
calculating an actual purchased power from the detection information of the current sensor as the first information;
When the actual purchased power is lower than a third reference purchased power that is lower than the first reference purchased power, a second output decrease control is executed so that the actual purchased power becomes substantially equal to the third reference purchased power;
The system controller
3. The power supply system of claim 2, wherein after the second output decrease control is executed, a third output decrease control is executed with an output decrease width individually assigned to each of the local controllers so that the actual purchased power becomes approximately equal to the second reference purchased power. the plurality of power generating units have the same rated output power;
The power supply system described in claim 2 or 3, wherein the first standard purchased power is a predetermined positive value that is less than the difference value obtained by subtracting the maximum supplyable power obtained by multiplying the number of installed power generation units by the rated output power from the minimum demand power for a predetermined period in the power demand facility. each of the local controllers continuously transmits its own current output information to the system controller;
4. The power supply system according to claim 2, wherein the system controller uses the output information received from each device to control the heteronomous output adjustment control and the autonomous output adjustment control. each of the local controllers has a system control unit capable of functioning as the system controller;
The plurality of power generating units are divided into one parent unit and the remaining child units,
The system control unit in the power generating unit designated as the parent unit is enabled as the system controller,
4. The power supply system according to claim 2, wherein the system control unit in the power generating unit designated as the slave unit is disabled as the system controller. The current sensor
a plurality of first current sensors associated with the local controllers of the parent device and the child device;
a single second current sensor associated with the system controller of the parent device;
The power supply system according to claim 6, wherein the second current sensor can be selected whether or not to be provided. each of the local controllers is further configured to be able to execute the autonomous output adjustment control based on any of second information regarding a cooperative state between the local controller and the commercial power system, third information regarding an internal temperature of the power conditioner exclusively owned by the local controller, and fourth information regarding a thermal balance of the power generation module exclusively owned by the local controller;
The power supply system according to any one of claims 1 to 3, wherein the system controller classifies the remaining power generation units, excluding the power generation units currently executing the autonomous output adjustment control based on any one of the second information, the third information, and the fourth information, into a group of output adjusters that execute the heteronomous output adjustment control and the autonomous output adjustment control based on the first information. 4. The power supply system according to claim 1, wherein each of the power generation modules in the plurality of power generation units includes a cell stack in which solid oxide fuel cells are integrated.