JPH0626131B2 - Load control device for fuel cell system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load control device for a fuel cell system, and in particular, avoids a fuel cell overpotential region at the time of starting and stopping the fuel cell and at the time of low load operation, and at the time of operation. The present invention relates to a load control device for a fuel cell system that facilitates output control of the fuel cell system.

BACKGROUND OF THE INVENTION A fuel cell system of this type includes a fuel cell in which a fuel is taken into a fuel electrode through a fuel reforming device, an oxidizing gas is taken into an oxidizing electrode, and these react to generate electric power. An inverter output control device that includes an inverter DC / AC converter that converts electric power generated from a battery into AC, and a coolant circulation system that circulates a coolant to cool the fuel cell. Steam separator that generates steam by the heat obtained from the heat and the heat supplied from the heater, a turbo compressor that takes in the waste gas discharged from the fuel cell and recovers the power, and from the turbo compressor It is composed of an exhaust tower that releases waste gas to the atmosphere.

The fuel cell system configured as described above (hereinafter "FC
In the fuel cell operation output control system by the fuel reformer (hereinafter referred to as “reformer”) that supplies hydrogen-rich reformed fuel to the inverter output control device and the fuel cell. When an output change occurs, the inverter output control device changes the output on the power transmission end side and, at the same time, adjusts the fuel supplied to the reaction part of the reformer and the auxiliary fuel supplied to the reformer fuel part to improve the supply to the battery. Change the amount of quality fuel and change the battery output. At that time, the pressure / temperature balance of the FCS is temporarily disrupted, and a rib composed of an oxidation electrode (oxygen electrode or cathode) and a fuel electrode (hydrogen electrode or anode) of the unit cell (hereinafter, cell) shown in FIG. 1 is provided. An event occurs in which the differential pressure of the electrode 2 exceeds the limit value (0.1 kgf / cm ² ) and the catalyst layer 3 and the electrolyte layer 4 are destroyed. Incidentally, reference numeral 1 is a separator.

Further, conventionally, when a low load operation of 25% output (low load output point PLOW) with respect to the rated point P _N is performed, the operation is performed in the cell excess potential region A _0V shown in FIG. Platinum catalyst 6 which is uniform with respect to carbon powder 5
As shown in FIG. 3, the state of the distribution becomes uneven, the capacity of the battery deteriorates, the output decreases, and the life of the battery becomes short.

More specifically, the excess potential region A _0V on the VA characteristic in FIG. 4 occurs when the cell voltage exceeds 0.8V. When the power generation state of the battery once enters this region, the power generation capacity of the cell decreases by about ten and several mW, and when power generation is continued in this region A _0V for a long time, as shown in FIG. It is possible that the distribution of the catalyst becomes non-uniform, the power generation efficiency of the battery decreases, and finally the power generation becomes impossible. However, the conventional method has a drawback that when the low-load operation is performed, power must be generated in the excess potential region A _0V of the cell voltage of 0.8 V or more, that is, the minimum output point P _min or less.

[Object of the Invention]

An object of the present invention is to protect the battery by reducing the battery load at the time of starting and stopping the FCS, and avoiding the battery overpotential region at the time of low load operation, to prolong the battery life and to further balance the system. An object of the present invention is to provide a load control device for a fuel cell system that can smoothly and safely follow a load without breaking.

[Outline of Invention]

The present invention achieves the above object by
The output of the CS at the power transmission end is set to the minimum output point P _min or less, the output of the power generation end of the fuel cell is set to the minimum output point P _min , the excess potential region A _{0 V} is avoided, and the difference is provided between the fuel cell and the inverter. It is designed to be consumed under load. That is, the fuel gas supplied to the fuel electrode through the fuel reforming device and the oxidizing gas supplied to the oxidizing electrode react to generate electric power, and the DC power generated in the fuel cell is converted into alternating current. A power system including an inverter output control device including an inverter for converting to electric power and controlled by a fuel cell output control device, and a cooling circulation system for circulating cooling water for cooling the fuel cell, and a heater. And a fuel cell comprising a steam separator that generates steam by the heat obtained from the cooling water circulation system and the heat of the heater, and an exhaust tower that discharges the waste gas discharged from the fuel reformer to the atmosphere. In the power generation system, a path connecting the steam separator and the exhaust tower via a control valve and the heater are connected to each other. -A switch that can be connected to the battery power generation end as a load and a heater power supply control device that controls the switch are provided, and the heater power supply control device controls the fuel consumption when the fuel cell is started or stopped, when the load is low, or when the power transmission end is abnormal. While connecting the heater and the battery power generation end based on a signal from the battery output control device,
This is achieved by opening the control valve.

Example of Invention

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

FIG. 5 is a system diagram showing an embodiment of the load control device of the fuel cell system according to the present invention.

In FIG. 5, the fuel cell system takes fuel into the fuel electrode 7a via a fuel reforming device (not shown), and
A fuel cell 7 that takes in an oxidizing gas into the oxidizing electrode 7k to generate electric power by reacting with them, and an inverter direct current alternating current converter that converts the electric power generated from the fuel cell 7 into alternating current are included. Steam is generated by heat obtained from a coolant circulation system including an inverter output control device 14 for controlling and a circulation pump 11 that circulates a coolant for cooling the fuel cell 7 and heat supplied from a heater 12. With steam separator 8
It is composed of a turbo compressor 9 that takes in the waste gas discharged from the fuel cell 7 and recovers the power, and an exhaust tower 10 that discharges the waste gas from the turbo compressor 9 to the atmosphere. Reference numeral 17 is a heater power source for heating the heater 12.

In such a fuel cell system, in order to remove heat generated when oxygen and hydrogen react to generate power, cooling water as a coolant is cooled by the steam separator 8, and then the fuel cell is pumped through the cooling water circulation pump 11. It is sent into the inside of the fuel cell 7, where the fuel cell 7 is cooled and the cooling water which has reached a high temperature is returned to the steam separator 8 again for cooling. In the steam separator 8, water is evaporated by the heater 12 equipped with the heater power source 17,
It supplies the steam necessary for the reformer's fuel reforming reaction. On the other hand, the exhaust gas of the reformer is discharged to the atmosphere by the exhaust tower 10 after the power is recovered by the turbo compressor 9.

In the present embodiment, the heater 12 for the steam separator 8 is used as a dummy load in the above fuel cell system, and the heater 12 as the dummy load is used as the output end of the fuel cell 7 (the input end of the inverter output control device 14). ) ・ Heater power supply 1 via switch box 16
7 are connected in parallel. Further, the steam separator 8 and the exhaust tower 10 are connected by a pipe, and a control valve 18 is provided to temporarily discharge excess steam generated by the excess power from the exhaust tower 10 when the excess power is consumed. Constitutes a means. Further, the control means for controlling these devices at the time of starting and stopping the battery, at the time of low load operation, and at the time of abnormalities at the power transmission end include the fuel cell output control device 13 and the heater power supply control device 15. The above is the configuration of the embodiment of the load control device.

Next, the configuration of the load control device used in the above embodiment will be described in more detail.

The load control device includes a fuel cell output control device 13, a heater power supply control device 15, a switch box 16 and a control valve 18. The fuel cell output control device 13 aims at coordinating the inverter output control device 14 and the fuel cell 7, and provides pattern control when the fuel cell is started and stopped, information necessary for low load operation and control commands of the lower controller. It is given to the heater power supply controller 15 and the inverter output controller 14. The load setting signal 28 sent from the inverter output controller 14 is the main controller 19
Is taken into. On the other hand, the cell output signal 29 is also taken into the fuel cell output control device 13, passes through the filter 21 and the sensitivity corrector 22, and is deviated from the output signal of the main controller 19 described above. When this deviation is zero, the fuel cell output control device 13 does not operate. The fuel cell output control device 1
In FIG. 3, 23 is the difference limiter, and 24 is a lead / lag compensator.

Further, in the heater power supply device 15, 25 is an automatic / manual control switching device, and 26 is a controller.

Next, the low load operation method, the FCS stop method, and the operation method at the time of abnormalities at the power transmission end according to the present invention will be described with reference to FIGS.

In Fig. 7, when switching from the rated operation state to the rated 25% output operation, as described above, the fuel sent to the reformer is reduced, the reformed fuel supplied to the battery is reduced, and the power generation amount is reduced. fixing the amount of fuel sent to Rihoma at time t ₂ the end output 33 becomes minimum output point.
On the other hand, the fuel cell output control device 13 receives the load setting signal 28 from the inverter output control device 14 at the time t ₁ , and the dummy load power consumption and the dummy load switching time t ₂ and the power generation end power from the time t ₁ to t _2. To set the output request signal 30 to the inverter output control device 14
And to the heater power controller 15. Here, the heater power supply controller 15 sends a signal to the switch box 16 at time t ₂ , disconnects the heater power supply 17, connects the heater 12 as a dummy load between the battery inverters, and at the same time sends the control valve control signal 34. , The control valve 18 is opened. Ie -75
When the deviation of% output appears, the deviation signal is the error limiter 2
3 and the lead / lag compensator 24, output request signal 30
Then, the inverter output control device 14 and the fuel supply are adjusted. It is sent to another FCS control system and heater power supply controller 15. At this time, when the battery output reaches 35% of the rated value, the controller 26 sends a switch switching signal to the switch box 16 to apply a dummy load, and at the same time, open the control valve 18 to generate excess steam generated in the steam separator. Is to prepare to escape.

In this way, in the steam separator 8, excess steam is generated by the heater 12 and is discharged to the atmosphere from the exhaust tower 10.

In FIG. 8, when stopping the FCS, the fuel cell output control device 13 calculates the dummy load power consumption and the battery output 35% arrival time t ₂ and the FCS stop time t ₃ according to a preset pattern. , And the output request signal 30 during that time is sent to the inverter output control device 14 and the heater power supply control device 15. On the other hand, the heater power supply control device 15 connects the dummy load and opens the control valve 18 at the stop start time t ₁ . The power transmission end output 32 and the power generation end output 33 each decrease due to the difference in dummy load power consumption, the power transmission end output 32 becomes zero at time t ₃ , and only the dummy load is present between times t ₃ and t _4. Therefore, the battery output is consumed, and the FCS stops power generation at time t ₄ .

In FIG. 9, when activating the FCS, the fuel cell output control device 13 sends the output request signal 30 to the inverter output control device 14 and the heater power supply control device 15 at the activation start time t ₀ , and at the same time supplies the output from the reformer. Increase quality fuel and gradually increase battery output. On the other hand, the heater power control device 15 divides several resistors of the heater 12 into two types, one for the heater power source 17 and one for consuming the dummy load power in the switch box 16, and transmits a switch switching signal 35 to connect each. Then, the control valve 18 is opened. From time t ₀ to t _1, that is, the battery output reaches the low load output point, the battery output is consumed by the dummy load, and the power transmission end side is left open. Time t
_{In No. 1} , the inverter output control device 14 connects the power transmission end and starts power transmission. On the other hand, the fuel cell 7 has time t
_In a few minutes from ₁ to t ₂ , the output is increased from the low load output point to the rated output point and the rated operation state is reached. During this period, the dummy load is delayed by Δt seconds from the time t ₁ by the heater power control device 15. Then, the battery is disconnected at the time when the battery output does not exceed the minimum output point.

The FCS start / stop operation described with reference to FIGS. 8 and 9 is the start or stop signal 36 in the case of the embodiment of FIG.
Thus, it is possible to automatically start and stop according to the start / stop pattern stored in the main controller 19. in this case,
It is also possible to manually start or stop by operating the main automatic / manual switch 20.

As described above, the load on the battery at the time of starting and stopping the FCS is reduced by using the dummy load and making the change in output at the power generation end gentler than the change in output at the transmission end.

In FIGS. 10 (I) and (II), when an abnormality occurs on the power transmission end side, the inverter output control device 14 sends an output side abnormality signal 31 to the heater power supply control device 15 and connects a dummy load by the switch box 16. And lower the output at the power transmission end. If the output error signal in this case the time t ₂ is released, disconnecting the dummy load, but again returning the output, if has failed is canceled, time as Fig. 11 t
_{At 2} , the battery output is reduced, the voltage at the power transmission end becomes zero at time t ₃ , and the voltage at the power generation end becomes zero at time t ₄ . Here, by decreasing the power transmission end output only by the dummy load from time t ₁ to time t ₂ , it is possible to prevent the fuel cell from being unnecessarily started up and shut down due to an erroneous abnormal signal.

When the above operation is applied to FIG. 6, when an abnormality such as a short circuit accident occurs on the power transmission side and it is necessary to immediately disconnect the FCS from the power transmission system, the inverter output control device 14 outputs the output side abnormality signal 31. To the controller 26, the dummy load is immediately turned on, and the output of the FCS power transmission end is lowered. On the other hand, the main controller 19 determines whether or not the output-side abnormality signal is an erroneous signal based on the load setting signal 28 sent at the same time. If it is an erroneous signal, a signal for releasing the dummy load is sent to the controller 26, but if an output abnormality is confirmed, the main controller automatically stops the FCS according to the stop pattern.

〔The invention's effect〕

As described above, the load control device of the present invention enables the FC
In S, the inverter output control system and the other FCS control systems that regulate the fuel supply, temperature, pressure, etc. are closely linked, and FCS without imposing an excessive burden on each control system.
The output can be controlled.

Further, according to the present invention, when the FCS is started and stopped, a large amount of steam is generated by the dummy load, which has the effect of facilitating temperature rise and heat retention of the battery.

Further, according to the present invention, there is an effect that it is possible to utilize waste heat such as heating of a building by utilizing the surplus steam when the dummy load is input.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of a unit cell (cell) of a fuel cell, FIG. 2 is an explanatory view showing a distribution state of platinum catalyst during normal operation, and FIG. 3 is a case where the cell is at a high potential. FIG. 4 is an explanatory view showing a distribution state of the platinum catalyst, FIG. 4 is a V-A characteristic diagram showing a relation between cell voltage and current density, and FIG. 5 is a load control device embodiment of the fuel cell power generation system according to the present invention. System diagram, FIG. 6 is a block diagram showing a specific example of the load control device used in the same embodiment, FIG. 7 is a diagram shown for explaining the fuel cell low load operation operation according to this embodiment, and FIG. The figure shown in order to explain the fuel cell stop operation by the example,
The figure is a diagram for explaining the fuel cell starting operation according to the present embodiment, and FIGS. 10 (I) and (II) are for explaining the fuel cell power generation system operation control operation at the time of output side abnormality according to the present embodiment. FIG. 11 and FIG. 11 are views for explaining the fuel cell power generation control operation when the output side is abnormal according to the present embodiment. 1 ... separator, 2 ... ribbed electrode, 3 ... catalyst,
4 ... Electrolyte, 5 ... Carbon powder, 6 ... Platinum, 7 ...
... Fuel cell, 8 ... Steam separator, 9 ... Turbo compressor, 10 ... Exhaust tower, 11 ... Cooling water circulation pump, 12 ... Heater, 13 ... Fuel cell output control device, 14 ... Inverter output Controller, 15 ...
Heater power controller, 16 ... Switch box, 1
7 ... Heater power supply, 18 ... Control valve, 19
...... Main controller, 20 ...... Main automatic / manual control switching device, 21
...... Filter, 22 …… Sensitivity corrector, 23 …… Error limiter, 24 …… Advance / delay compensator, 25 …… Automatic / manual control switching device, 26 …… Controller, 27 …… Inverter output control device automatic・ Manual control switch, 28 ... Load setting signal, 29 ... Battery output signal, 30 ... Output request signal, 3
1 ... Output side abnormal signal, 32 ... Fuel cell power generation system output, 33 ... Fuel cell output, 34 ... Control valve control signal, 35 ... Switch switching signal.

Claims (1)

[Claims] 1. A fuel cell for generating electric power by reacting a fuel gas supplied to a fuel electrode through a fuel reformer with an oxidizing gas supplied to an oxidizing electrode, and a fuel cell generated by the fuel cell. A power system having an inverter output control device that is controlled by a fuel cell output control device, including an inverter that converts DC power into AC power,
A steam separator that is provided in a cooling circulation system that circulates cooling water for cooling the fuel cell, and is provided with a heater, and that generates steam by the heat obtained from the cooling water circulation system and the heat of the heater. ,
In a fuel cell power generation system including an exhaust tower that discharges waste gas discharged from the fuel reformer to the atmosphere, a path connecting the steam separator and the exhaust tower via a control valve, and the heater as a dummy. A switch that can be connected to the battery power generation end as a load and a heater power supply control device that controls the switch are provided, and the heater power supply control device is configured to operate the fuel cell when the fuel cell is stopped or started, when the load is low, or when the power transmission end is abnormal. A fuel cell power generation system characterized in that the heater is connected to the battery power generation end based on a signal from an output control device or an inverter control device, and the control valve is opened.