JP2009153295A - Control method of hybrid power supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To smoothly drive a hybrid power supply system that is structured by combining an electricity-storing device with a fuel cell system and is systematically connected to a commercial power supply in normal power supply. <P>SOLUTION: If a power failure occurs at the commercial power supply, power supply from the fuel cell system 1 and the electricity-storing device 2 to an emergency load 11 is continued and power distribution systems 12-15 connected to normal loads 7-10 are subjected to interruption control according to the outputs of the fuel cell system 1 and the electricity-storing device 2. When the charge capacity of the electricity-storing device 2 decreases to a target value, interruption control is further performed within a range of the rated output of the fuel cell system 1 and the output capacity of the fuel cell system 1 is changed gradually so as to be balanced with load. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for controlling a hybrid power supply system configured by connecting a power feeding means including a fuel cell to a commercial power source. In normal times, the fuel cell system is linked to a commercial power source, and at the commercial power source side. The present invention relates to a control method for a hybrid power supply system that causes a fuel cell system to operate independently and supplies power from a fuel cell system and a power storage device to a load during a power failure.

A fuel cell is a kind of power generation device that generates electricity by electrochemically reacting hydrogen (H ₂ ) and oxygen (O ₂ ), for example, and has high power generation efficiency and as a cogeneration (combination of thermoelectric) system If exhaust heat is also used, a higher overall energy efficiency can be achieved. At the same time, fuel cells produce less harmful substances such as nitrogen oxides (NO _x ) and sulfur oxides (SO _x ) during power generation, and emit carbon dioxide (CO ₂ ), which causes global warming. The noise and vibrations associated with driving are also small. For this reason, in recent years, fuel cells have attracted social attention as environmentally friendly and highly efficient power generation devices.

  Typical types of fuel cells include phosphoric acid fuel cells (PAFC), polymer electrolyte fuel cells (PEFC), solid oxide fuel cells (SOFC). oxide fuel cell) and molten carbonate fuel cell (MCFC). Among these, phosphoric acid fuel cells have been commercialized earliest, and a system with a rated output capacity of 50 to 200 kW has been introduced as a cogeneration system in schools, hotels, office buildings, hospitals, factories and the like. In addition, polymer electrolyte fuel cells are currently in the early stages of practical use, mainly for applications such as residential cogeneration systems, automobiles, portable devices, and commercial power backups. Research and development is ongoing, and some are already commercialized. Solid oxide fuel cells are being researched and developed for use in a wide range of output capacities, from residential and office buildings to power plant-scale applications.

A fuel cell generally uses hydrogen as a fuel, and is generally configured as a fuel cell system in combination with a reformer or the like for generating hydrogen. In a fuel cell system of about 1 kW to several hundred kW class used for generating electricity by installing in a customer's house, usually, hydrogen is produced from hydrocarbons such as city gas (natural gas) using a reformer, This is supplied to a cell which is a power generation unit of the fuel cell system to generate power. In the reaction for producing hydrogen using a reformer, generally, a steam reforming reaction in which hydrogen (such as methane (CH ₄ )) and steam (H ₂ O) are reacted at a high temperature to generate hydrogen. Is used. For the reformer, according to the power demanded by the load connected to the fuel cell system, there is no excess or shortage of hydrocarbons to generate the hydrogen gas necessary for the fuel cell system to generate the power. And water vapor are supplied.

  Here, when the power required by the load increases or decreases, it is necessary to increase or decrease the amount of hydrocarbons supplied to the reformer, and to adjust the amount of hydrogen produced in the reformer accordingly. . However, the steam reforming reaction in the reformer is not so fast that the amount of hydrogen generation can be instantaneously changed following the sudden change in the load power. Therefore, when the load power increases rapidly, the amount of hydrogen gas required in the power generation cell is insufficient, and the fuel cell system cannot supply the necessary power to the load. On the other hand, when the load power is suddenly reduced, the hydrogen gas produced by the reformer is surplus, and the balance relationship with the amount of hydrocarbons supplied to the reformer is lost. Here, in the operation of the fuel cell system, if the reformer cannot follow the load fluctuation or if it is forced to perform an operation in which the produced hydrogen gas is excessive, the protection function in the fuel cell system is activated. As a result, the operation of the fuel cell system is stopped. From this point of view, the fuel cell system has an allowable output change rate indicating how much the output can be changed per unit time for the stable operation. In the operation of the fuel cell system, it is important that a large load fluctuation on the output side is not directly burdened on the fuel cell system.

  By the way, in the actual operation of the fuel cell system, the power is connected to the commercial power source, and the power supplied from the commercial power source and the power generated by the fuel cell system are combined to supply power to the load through the same distribution line. Such a power distribution configuration is often used. In this case, it is common to continuously operate the fuel cell system at the rated output so as to cover a part of the entire load, and to cope with the load fluctuation by changing the power supply amount from the commercial power source ( Non-patent document 1). That is, if there is a load fluctuation, this is absorbed on the commercial power supply side. Also, from the viewpoint of economy, for example, when performing partial load operation by reducing the output of the fuel cell system at night, the speed at which the reformer can follow, that is, the output change allowed in the fuel cell system If the output is gradually reduced within the range of the rate and maintained at the specified output, and then returned to the rated output again during the day, the output to the reformer is increased by gradually increasing the output to the specified value. The balance between the amount of hydrocarbons supplied and the amount of hydrogen produced, and the balance between the amount of hydrogen generated and the amount of hydrogen consumed are maintained.

  The operation of the fuel cell system interconnected with the commercial power source has been described above. Here, when the commercial power supply stops due to a disaster or the like, that is, when a power failure occurs, the fuel cell system is operated independently and used to supply power to the load. However, since the reaction of the reformer is not so fast in the fuel cell system, if a large load fluctuation is directly imposed on the fuel cell system, the fuel cell system will stop operating.

  Conventionally, as a method of operating a fuel cell system during a power failure of a commercial power source, an emergency power generator such as an engine power generator or a turbine power generator is started and the fuel cell system is connected in parallel to these emergency power generators. Thus, there is a method of suppressing the fluctuation of the portion of the load electric power borne by the fuel cell system and sharing the fluctuation with the engine power generator or the turbine power generator for a large load fluctuation. There is also a method of sharing such load fluctuations in the storage battery by combining the storage battery (power storage equipment) such as a lead storage battery and sodium sulfur battery with the fuel cell system, and charging / discharging the storage battery with the fluctuation due to the large load fluctuation. is there.

In the event of a commercial power failure, the power from the fuel cell system, emergency power generator, and storage battery takes precedence over the power distribution system that includes the load to which power should be supplied even during a power failure (hereinafter referred to as an emergency load). In this case, if the power supplied from the fuel cell system, emergency power generator, or storage battery is less than the power required for the entire load, a load other than the emergency load (hereinafter referred to as the normal load) A part or all of the power supply to the distribution system is called off. In order to ensure the power supply to the emergency load, the power supply to the normal load is generally cut off simultaneously with the detection of the occurrence of a power failure at the commercial power source.
“Fuel Cell Introduction Guidebook”, New Energy and Industrial Technology Development Organization (NEDO), pages 48-49

  In the above-described configuration, the fuel cell system is connected to the commercial power supply during normal operation, and the fuel system is operated independently in the event of a power failure, and the power is supplied to at least the emergency load in combination with the emergency power generator or storage battery. There are problems as described below.

In a configuration in which an engine power generator, a turbine power generator, or the like is started and a fuel cell system is operated in parallel therewith, even if there is no problem in terms of power supply capacity with respect to the load, the engine power generator and the turbine power generator As a result, harmful substances such as nitrogen oxides (NO _x ) and sulfur oxides (SO _x ) are generated, and carbon dioxide (CO ₂ ), which is a cause of global warming, is also emitted, and noise and vibration are also generated. Because of its large size, environmental friendliness is impaired.

  In addition, in a configuration in which a storage battery such as a lead storage battery or a sodium-sulfur battery is combined with the fuel cell system, the capacity of the storage battery can be increased so that the fuel cell system can cope with a large load fluctuation without burdening the load fluctuation. It is necessary to increase the size, which leads to an increase in equipment size and economic efficiency.

  An object of the present invention is to solve these problems, and is a control method for a hybrid power supply system that is configured by combining a power storage device with a fuel cell system, and normally the fuel cell system is grid-connected to a commercial power source. It is an object of the present invention to provide a control method that can cope with load fluctuations even during a power failure of a commercial power source without increasing the size of the facility or reducing the economic efficiency.

  A control method for a hybrid power supply system according to the present invention includes a hybrid power that includes a power supply unit having a fuel cell and a power storage device, and a grid interconnection device that grid-connects the power supply unit to a commercial power source, and supplies power to a load. In the control method of the supply system, the power distribution system for supplying power to the load is at least one to which the emergency power distribution system to which the emergency load is connected and the normal load that is a load other than the emergency load are respectively connected. When there is no power outage in the commercial power supply, power is supplied to both the emergency power distribution system and each normal power distribution system, and a power outage occurs in the commercial power supply. In this case, the power supply to the emergency distribution system is continued by supplying power from the fuel cell and the power storage device, and the total load capacity including the emergency load is determined by the fuel cell. If the output is greater than or equal to the sum of the discharge output of the power storage device, the load capacity is normally removed from the distribution system so that the total load capacity is less than the sum of the rated output of the fuel cell and the discharge output of the power storage device. When power supply to the normal power distribution system is cut off in descending order of capacity, and it is detected that the charge amount of the power storage device has decreased to the target value, the emergency load is applied to the normal power distribution system that is not cut off at that time. Find the combination whose total load capacity is less than the rated output of the fuel cell and is closest to the rated output, stop supplying power to the normal distribution system other than the one that belongs to the requested combination, and then load the emergency load Reduce the output capacity of the fuel cell within the allowable output change rate range of the fuel cell to a value corresponding to the sum of the load capacity with the normal load of the normal distribution system belonging to the combination. And features.

  In the present invention, when the commercial power supply recovers from the power failure, the power supply from the commercial power supply and the power from the fuel cell are resumed to the normal distribution system where the power supply is stopped at that time, and the fuel cell It is preferable to increase the output capacity to the rated output of the fuel cell within the range of the allowable output change rate in the fuel cell. Further, it is preferable that the sum of the capacity of the emergency load and the capacity of the normal load connected to any one of the normal load wirings is less than the rated capacity of the fuel cell.

  In the present invention, when the commercial power supply is not interrupted, it is preferable to control so that the charge amount of the power storage device is maintained at the maximum capacity value that can be stored. In this case, the target value is set to a value that is less than the maximum capacity value and is half or more of the maximum capacity value, for example.

  In carrying out the control method of the hybrid power supply system of the present invention, for example, a first measuring means for measuring the charge / discharge amount of the power storage device, a second measuring means for measuring the capacity of the emergency power distribution system, Third measuring means for measuring the capacity of each normal power distribution system is provided, and the controller determines the output capacity of the fuel cell, the charge / discharge of the power storage device based on the measured values in the first to third measuring means, and The supply / cutoff of power to the normal distribution system may be controlled.

  In the present invention, as the power storage device, all types of storage batteries (secondary batteries) such as lead storage batteries, nickel cadmium storage batteries, nickel hydride storage batteries, lithium ion storage batteries, sodium sulfur storage batteries, electric double layer capacitors, and the like are used. it can. The amount of charge of the power storage device can be obtained by measuring the charge / discharge current for the power storage device and integrating the time.

  In the present invention, the fuel cell preferably constitutes a fuel cell system together with a reformer that generates hydrogen, and generates power using the hydrogen generated by the reformer as fuel. In such a fuel cell system, all types of fuel cells such as phosphoric acid type, solid polymer type, molten carbonate type, solid oxide type and the like can be applied. In the reformer, hydrogen supplied to the fuel cell can be produced from hydrocarbons such as city gas, liquefied petroleum gas (LPG), butane gas, methanol, ethanol, kerosene, and gasoline.

  The present invention provides a hybrid power supply system having a configuration in which a power storage device is combined with a fuel cell system by performing a timed shut-off control of a power distribution system and a remaining capacity control of a storage battery, and when the load suddenly changes during a self-sustaining operation However, there is an effect that the fuel cell system can be smoothly operated.

  Next, a preferred embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a configuration of a distribution facility to which a control method for a hybrid power supply system according to an embodiment of the present invention is applied.

  1 includes a fuel cell system 1, a power storage device 2 connected to the fuel cell system 1 through a power line 24, and a grid interconnection device 6 that grids at least the fuel cell system 1 to a commercial power source 5. And a hybrid power supply system composed of the controller 26. The commercial power source 5 is, for example, an AC 100V. The grid interconnection device 6 is inserted between the commercial power supply 5 and the load side, and the fuel cell system 1 is connected thereto by a power line 24. The power line 24 extending from the grid interconnection device 6 to the load side branches to the distribution systems 12 to 16, and the normal loads 7 to 10 are connected to the distribution systems 12 to 15 via the switches 17 to 20, respectively. The emergency load 11 is directly connected to. Therefore, AC 100V power sent from the grid interconnection device 6 branches to the distribution systems 12 to 16 and is fed to the normal loads 7 to 10 and the emergency load 11. The operating power of the grid interconnection device 6 is supplied by the fuel cell system 1. Opening and closing of the switches 17 to 20 can be controlled by a controller 26 via a signal / control line 25.

  This distribution facility supplies power from the fuel cell system 1 and the commercial power source 5 to the load via the grid interconnection device 6 when the commercial power source 5 is operating normally. 1 is operated independently, and electric power is supplied from the fuel cell system 1 and the power storage device 2 to the load.

  In each of the distribution systems 12 to 15, a current / voltmeter 23 is inserted in order to detect the power supplied to the normal loads 7 to 10, and the distribution system 16 is supplied to the emergency load 11. An ammeter / voltmeter 23 is inserted to detect the power. A current / voltmeter 21 is also inserted into the power line connecting the grid interconnection device 6 and the fuel cell system 1, and the charge / discharge current of the power storage device 2 is also connected to the line connecting the fuel cell system 1 and the power storage device 2. An ammeter / voltmeter 22 is inserted to detect. The detection results of the current / voltmeters 21 to 23 are sent to the controller 26 via the signal / control line 25.

  The fuel cell system 1 is a polymer electrolyte fuel cell system having a DC output and a rated output of 5 kW. The power storage device 2 includes a storage battery 3 and a charger / discharger 4 that charges and discharges the storage battery 3. Here, the storage battery 3 is a lead storage battery having a capacity (1.75 kWh) capable of supplying power of 3.5 kW to an AC load connected to the distribution system via the power line 24 for 30 minutes. Of course, if power smaller than 3.5 kW is fed, power can be fed for a time longer than 30 minutes. However, in the following explanation, the discharge output of the power storage device 2, that is, the load side supply from the power storage device 2 It is assumed that the maximum power that can be generated is 3.5 kW.

  Here, for the sake of explanation, as an example, the normal loads 7 to 10 connected to the distribution systems 12 to 15 have capacities of 4 kW, 4 kW, 3 kW, and 2 kW when the normal loads operate at the maximum power consumption, respectively. It is assumed that the emergency load 11 connected to the power distribution system 16 has a capacity of 4 kW when operated with the maximum power consumption. The capacities of the distribution systems 14 and 15 are 3 kW and 2 kW, respectively, which are smaller than the capacities of the other distribution systems, because the fuel cell system 1 is operated when the fuel cell system 1 is operated independently during a power failure of the commercial power supply 5. This is because if the power is supplied to the emergency load 11 and there is still room to supply the normal load, the normal load can be supplied.

  The fuel cell system 1 and the power storage device 2 are connected to a controller 26 through a signal / control line 25 and are configured to be able to control the operations of the fuel cell system 1 and the power storage device 2 according to a command from the controller 26. The controller 26 constantly monitors the generated power of the fuel cell system 1, the charge / discharge capacity of the power storage device 2, and the power supplied to the load side in each distribution system by the current / voltmeters 21 to 23, and the load power (normally It has a function of calculating the total value of the power consumption of the loads 7 to 10 and the emergency load 11) and also has a function of operating the switches 17 to 20 from a remote location. Electric power necessary for operating the controller 26 is supplied from the fuel cell system 1.

  Next, assuming that the power distribution facility is configured as described above, refer to the flowchart of FIG. 2 and the time chart of FIG. 3 for the entire process in the control method of the hybrid power supply system according to the embodiment of the present invention. This will be described in detail.

  During normal times (period before time T1 in FIG. 3), that is, when no power failure has occurred in the commercial power source 5 and AC power is supplied from the commercial power source 5, the fuel cell system 1 is operated at its rated output. The fuel cell system 1 is continuously operated for 24 hours at a certain 5 kW, and the fuel cell system 1 is connected to the commercial power source 5 to supply power to each load (step S1). At this time, the switches 17 to 20 are normally closed to the normal loads 7 to 10, that is, are brought into conduction. In the following, the measured values of the load power measured by each current / voltmeter 23 are 3 kW, 2.5 kW, 2 kW, and 1 kW for the normal loads 7 to 10, respectively, and 3.5 kW for the emergency load 11. The case will be described. In this case, the total capacity of the load is 12 kW, and the output of 5 kW from the fuel cell system 1 is insufficient. Therefore, the shortage of 7 kW is covered by the commercial power source 5. When a lead storage battery is used as the storage battery 3, it is a case where power is not supplied to the load, and the amount of charge is reduced by self-discharge. Therefore, a part of the output from the fuel cell system 1 is charged to the storage battery 3. Allocate electricity and keep lead-acid batteries fully charged.

  As shown in step S <b> 2, the grid interconnection device 6 constantly monitors the occurrence of a power failure on the commercial power supply 5 side and outputs the result to the controller 26. If it is not a power failure, the operation in step S1 described above is executed permanently.

  Next, when a power failure occurs in the commercial power source 5 at time T1 (see FIG. 3), the grid interconnection device 6 detects it and disconnects the fuel cell system 1 from the commercial power source 5 side, and the fuel cell system 1 To operate independently. At this time, the fuel cell system 1 continues the operation at 5 kW which is the rated output. In step S3, the controller 26 has a total capacity of the emergency load and the normal load of 5 kW or more which is the rated capacity of the fuel cell system 1 and supplies the rated capacity 5 kW of the fuel cell system 1 from the storage battery 3. The power supply to at least a part of the normal load is stopped so that the capacity is less than 8.5 kW which is a capacity obtained by adding 3.5 kW. Here, the power supply to the normal load is stopped so that the fuel cell system 1 can supply power to the normal load if there is still room to supply power to the normal load even if power is supplied to the emergency load 11. Perform in order of load power. That is, power supply is stopped from the one with a large load power, and it is determined whether or not the total load capacity at that time is less than the sum of the rated output of the fuel cell and the discharge output of the storage battery (step S4). In that case, the process returns to step S3 to stop the power supply to the normal load having the next largest load capacity.

  Since the measured value of the load power for each load is always sent from each current / voltmeter 23 to the controller 26, if the measured value of the load power is as described above, specifically, the controller 26 The power consumption of the normal load 7 is determined to be the largest at 3 kW, and the power supply to the normal load 7 is stopped by remotely operating the switch 17. Although the total load capacity is 9 kW due to the power supply stop to the normal load 7, the controller 26 determines from the load power measurement value that the total load power is still 8.5 kW or more, and then the switch 18. Is remotely controlled to stop power supply to the normal load 8 having the next largest load power. The total load capacity is further reduced by 2.5 kW to 6.5 kW due to the stoppage of power supply to the normal load 8, and the controller 26 determines that the total load power is less than 8.5 kW. If the total load power is less than 8.5 kW, power can be supplied by the fuel cell system 1 and the storage battery 3, so the fuel cell system 1 operates with a rated output of 5 kW, and the storage battery 3 has a load of 1.5 kW. The power supply is shared (step S5).

  The controller 26 constantly monitors the charge amount (current capacity) of the storage battery 3 from the measurement value of the current / voltmeter 22, and determines whether the charge amount has dropped to 70% of the fully charged capacity. Determination is made (step S6). 70% here is a target value of the charge amount of the storage battery when the full charge capacity is 100% and the fuel cell system 1 is operating independently. If the current charge amount is 70% or more with respect to the fully charged capacity, the state in which the load capacity exceeding the rated output of the fuel cell in step S5 is shared by the discharge of the storage battery is maintained. As a result, the lead storage battery 3 is discharged until the capacity reaches 70% of the fully charged capacity, that is, the target value. The discharge time during that time is about 21 minutes when calculated with the above-mentioned numerical values. Here, the reason for discharging the storage battery 3 is that, in order to continuously operate the fuel cell system 1 at its rated output of 5 kW, when the load decreases, the surplus power from the fuel cell system 1 corresponding to the decrease is obtained. This is because the storage battery 3 needs to be absorbed, but cannot be absorbed when the storage battery 3 is in a fully charged state or close to it.

When the lead storage battery 3 reaches a capacity of about 70% of the fully charged capacity at time T2, the controller 26 next stops the power supply to the normal load having the largest capacity and not stopped. The total value P ₁ of the remaining load capacity in the case where it is assumed that it has been calculated is calculated (step S7), and it is determined whether this total value P ₁ is less than the rated output of the fuel cell system 1 (step S8). If P ₁ is greater than or equal to the rated output of the fuel cell system 1, the capacitance among the load is not stopped feeding stops power supply to the normal load is the maximum (step S9), and returns to step S7. If P ₁ is less than the rated output of the fuel cell system 1, then the controller 26 sets N as an integer equal to or greater than 2, and then shifts to a normal load having the Nth largest capacity among the loads that have not stopped feeding. The total value P _N of the remaining load capacities when it is assumed that the power supply is stopped is calculated (step S10). The controller has a value that is less than the rated output of the fuel cell system 1 and is closest to the value of the rated output among the total values P ₁ , P ₂ , P ₃ ,. And the power supply to the mth normal load is actually stopped (step S11), assuming that the selected value has stopped the power supply to the mth normal load. Thereafter, as shown in step S12, the surplus fuel cell system 1 will continue to operate at its rated output, represented by the difference between the rated output of the surplus power (fuel cell system 1 which is generated when the P _m Power) is used to charge the storage battery 3. In addition, when the total value of the power consumption of the load hardly changes, the time width that the reformer can follow from the rated output to the total value of the power consumption of the load (that is, the fuel) The charging amount of the storage battery 3 is maintained so as to be about 70% of the target value, that is, the fully charged capacity.

In the above-described example, the controller 26 determines the remaining load capacity when the power supply to the normal load with the third largest power consumption (in this case, the normal load 9 with a capacity of 2 kW) is stopped in step S7. The total value P ₁ is calculated (because the power supply to the first and second largest normal loads has already been stopped, the normal load with the third largest power consumption is one of the normal loads being fed. Therefore, 4.5 kW is calculated as the value P ₁ . Since this 4.5 kW is 5 kW or less of the rated capacity of the fuel cell system 1, the controller 26 further remains in the case where power supply to the normal load 10 with the fourth largest power consumption is stopped in step S10. The total value P ₂ of the load capacities is calculated (at this time, the power supply to the normal load with the third largest power consumption is assumed to be continued). In this case, the value P ₂ obtained as a calculation result is 5.5 kW, and does not fall below 5 kW which is the rated output of the fuel cell system 1. Therefore, the total value of the remaining load capacity is 5 kW or less, which is the rated output of the fuel cell system 1, and the capacity closer to 5 kW is when the power supply to the normal load 9 is stopped, This is not the case when power supply to the normal load 10 is stopped.

  From the above determination, the controller 26 stops the power supply to the normal load 9 in step S11. At this time, the total load capacity is 4.5 kW, but all this power is provided by the output of the fuel cell system 1. The output of the fuel cell system 1 remains at 5 kW, and surplus power of 0.5 kW is generated. This amount is used as charging power for the lead storage battery 3. Here, since the surplus power is not so large as 0.5 kW, the charging current does not become so large, and the storage battery 3 is hardly deteriorated and its life is not shortened. The reason why the amount of surplus power can be reduced in this way is the effect that the capacities of some distribution systems are initially set to be small.

  When the power consumption of the load is stable and the total load capacity is almost unchanged at 4.5 kW even when time elapses, the output of the fuel cell system 1 is set within the range of the output change rate allowed for the fuel cell system 1 In this case, it gradually decreases from 5 kW which is the rated output to 4.5 kW which is the total value of the load capacity, and when it reaches 4.5 kW, the charging of the lead storage battery 3 is completed (time T3 in FIG. 3). ). Here, when the storage battery 3 is charged, the controller 26 calculates the amount of charging power by measuring the current value with the current / voltmeter 22, and the capacity of the storage battery 3 is 70% of the fully charged capacity with a large amount of charging power. When the value exceeds the value, the power supply to a part of the normal load is resumed, so that the power supply to the load is also performed by discharging from the lead storage battery 3, and the charge amount of the storage battery 3 is fully charged. The capacity is reduced to about 70% of the capacity. The reason why the charge amount of the storage battery 3 is reduced to about 70% of the fully charged capacity as a target value is that load fluctuations that cannot be followed by the fuel cell system 1, particularly a sudden decrease in load capacity, occur. This is because the storage battery 3 can be easily absorbed.

  In addition, although the case where the total load capacity was stabilized at 4.5 kW for the fuel cell system 1 with the rated power of 5 kW was described here, the case where the power consumption on the load side is stabilized with other capacities is also described above. The output of the fuel cell system 1 may be gradually lowered to its stable capacity by the same procedure as described above. When the load fluctuates at short time intervals, the fluctuation can be absorbed by charging / discharging of the storage battery 3 to stably supply power to the load.

  The system power supply device 6 constantly monitors whether the commercial power supply 5 has been restored (recovered from a power failure) (step S13), and the commercial power supply 5 is restored at time T4 so that the commercial power supply 5 can be used. Then, in Step S14, the controller 26 closes all the switches 17 to 20 by remote operation and returns the power to the normal loads 7 to 10 by the commercial power source 5 (system power), and the output of the fuel cell system 1 is rated. The output is gradually increased to 5 kW, which is an output, within the range of the output change rate allowed for the fuel cell system 1. After the fuel cell system 1 establishes an output of 5 kW, which is a rated output, the storage battery 3 is charged with the output of the fuel cell system 1 and the storage battery 3 is maintained in a fully charged state. As a result, the state before the time T1 when the power failure occurs is restored. For safety, the operation of closing the switches 17 to 20 to resume the power supply to the normal loads 7 to 10 may be performed manually instead of the remote operation from the controller 26.

  In the control method of the present embodiment described above, the output capacity of the fuel cell cannot be changed suddenly due to the response of the reformer of the fuel cell. This is compensated by stopping the power supply to the load for a while, and the power supply to the emergency load is continued.

  As mentioned above, as an embodiment of the present invention, the fuel cell constituting the fuel cell system is a solid polymer fuel cell and the system capacity (rated output) is 5 kW. Even when a battery is applied or when the capacity is several tens to several hundreds kW, the control method according to the present invention can be similarly implemented. Moreover, in the above, in order to make the storage battery 3 made of a lead storage battery easily absorb the load fluctuation, the case where the storage battery 3 is maintained at a charge amount of 70% with respect to the full charge capacity as the target value has been described. Depending on the rated capacity and load capacity of the system, and the rated capacity of the storage battery, the target value of the storage battery charge can be set appropriately within a range of capacity smaller than the full charge capacity and more than half of the full charge capacity. . The reason for setting the target value to be half or more of the fully charged capacity value is to prevent the storage battery from being overdischarged due to load fluctuation. Although the case where a lead storage battery is used as the storage battery 3 has been described here, other types of storage batteries may be used.

  In any case, by adopting the above-described control method, in the hybrid power supply system in which the power storage device is combined with the fuel cell system, the environmental friendliness is not impaired, and the facility size and economy are reduced. Even if the load suddenly changes during the independent operation, smooth operation is possible without causing a decrease in performance.

It is a figure explaining an example of composition of distribution equipment to which a control method of a hybrid power supply system of an embodiment of the invention is applied. It is a flowchart explaining the control method of the hybrid electric power supply system of one Embodiment of this invention. It is a time chart explaining the control method shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 2 Electric power storage apparatus 3 Storage battery 4 Charger / discharger 5 Commercial power supply 6 System interconnection apparatus 7-10 Normal load 11 Emergency load 12-16 Distribution system 17-20 Switch 21-23 Current / voltmeter 24 Power line 25 Signal / control line

Claims (6)

In a control method of a hybrid power supply system that includes a power supply unit including a fuel cell and a power storage device, and a grid interconnection device that grid-connects the power supply unit to a commercial power source, and supplies power to a load.
The power distribution system for supplying power to the load includes an emergency power distribution system to which an emergency load is connected and at least one normal power distribution system to which a normal load that is a load other than the emergency load is connected. Divided,
When no power failure occurs in the commercial power supply, power is supplied to both the emergency power distribution system and each of the normal power distribution systems,
When a power failure occurs in the commercial power supply,
The power supply to the emergency power distribution system is continued by supplying power from the fuel cell and the power storage device, and the total load capacity including the emergency load is the rated output of the fuel cell and the discharge of the power storage device. If it is greater than or equal to the sum of the output, the power supply to the normal power distribution system is cut off from the normal power distribution system in descending order so that the total load capacity is less than the sum,
When it is detected that the amount of charge of the power storage device has decreased to a target value, the sum of load capacities including the emergency load is less than the rated output of the fuel cell with respect to a normal distribution system that is not cut off at that time And obtaining a combination that is closest to the rated output, and stopping power supply to the normal distribution system other than that belonging to the obtained combination,
Thereafter, the output capacity of the fuel cell is reduced to a value corresponding to the sum of the load capacities of the emergency load and the normal load of the normal distribution system belonging to the combination. A control method for a hybrid power supply system, wherein   When the commercial power supply recovers from a power failure, the power supply from the commercial power supply and the power from the fuel cell are resumed to the normal power distribution system where power supply is stopped at that time, and the fuel cell The method for controlling a hybrid power supply system according to claim 1, wherein the output capacity is increased to a rated output of the fuel cell within a range of an allowable output change rate in the fuel cell.   The hybrid power according to claim 1 or 2, wherein a sum of a capacity of the emergency load and a capacity of the normal load connected to any one of the normal load wirings is less than a rated capacity of the fuel cell. Supply system control method.   The control of the hybrid power supply system according to any one of claims 1 to 3, wherein when the commercial power source is not out of power, the charge amount of the power storage device is controlled to be maintained at a maximum capacity value capable of storing power. Method.   The method for controlling a hybrid power supply system according to claim 4, wherein the target value is set to a value that is less than the maximum capacity value and is not less than half of the maximum capacity value.   First measuring means for measuring the charge / discharge amount of the power storage device, second measuring means for measuring the capacity of the emergency power distribution system, and third measuring means for measuring the capacity of each normal power distribution system And the controller controls output / capacity of the fuel cell, charge / discharge of the power storage device, and supply / cut-off of power to each of the normal power distribution systems based on the measurement values obtained by the first to third measurement means. The method for controlling a hybrid power supply system according to claim 1, wherein the hybrid power supply system is controlled.

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