JP2006147588A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system and an operation method of the same capable of securing a stable operation of a fuel cell even at a start-up time wherein a load of the fuel cell increases from zero, or at transition state wherein electric load amount of the fuel cell rapidly changes from stable operation state. <P>SOLUTION: The system includes a fuel cell 6 and a secondary battery 74 connected to a load 70 to which power generated from the fuel cell 6 is supplied to supply the power to the load 70. The method takes out power consistent with a power generation capacity of the fuel cell 6 and heats up the fuel cell 6 by the heat generated from the power generation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system comprising a fuel cell and devices for operating the fuel cell, for example, gas pumps, liquid pumps, or electrical devices such as control devices and control valves (hereinafter referred to as auxiliaries). In particular, the present invention relates to a fuel cell system in which electric power is supplied to the auxiliary machine from a commercial power source or a fuel cell system to supply hydrogen to the fuel cell, manage the temperature of the fuel cell, or control them.

  A polymer electrolyte fuel cell (hereinafter simply referred to as a fuel cell) using hydrogen as a fuel gas and oxygen in the air as an oxidant has a feature that it has a long life without fear of corrosion due to acid or alkali. Such an auxiliary machine used in the fuel cell system is supplied with electric power from a commercial power source or a fuel cell system to supply hydrogen gas or reaction air to the fuel cell, cooling the fuel cell, or raw fuel gas or hydrogen gas. The supply amount is controlled. In addition, in a fuel cell system connected so that the power generated by the fuel cell can be supplied to an external grid load, when the commercial power supply that supplies power to this grid load fails, a breaker is activated. The fuel cell system cannot output power to the system load.

When the commercial power source is out of power, the electric output from the fuel cell system to the external load is not only zero, but correspondingly, it is necessary to control the associated stop process in order to stop the fuel cell system. Furthermore, in a fuel cell system that uses a reformer to supply hydrogen (battery fuel) gas, the electrical output and the supply of raw fuel to be supplied to the reformer are linked. At the same time as the output stops, the raw fuel gas supplied to the reformer etc. stops and the operation of the fuel cell system stops, or the amount of raw fuel gas is reduced to the standby operation. Configured to migrate automatically. Shifting to standby operation to reduce the amount of raw fuel gas to the reformer means that all the related equipment, for example, the control valve that controls the supply of water vapor and the flow of gas, the combustion air, and the reaction air Control and adjustment of devices such as a gas pump to send or a pump to send water vapor or water are also performed in parallel.
Japanese Patent Laid-Open No. 08-148173 Japanese Patent Laid-Open No. 06-274233

  When an electric load connected to such a fuel cell system has a sudden increase in power consumption, the current in the circuit between the fuel cell and the load increases, and the control senses this increase. The device operates to increase the output from the fuel cell. However, even if such an increase in current is detected and the raw fuel gas supplied to the reformer increases, the amount of power generation does not increase immediately. When the amount of power used in the electric load suddenly increases beyond the capacity of the fuel cell, the fuel cell may be put into an overload operation state.

  The present invention solves such problems of the prior art, and an object of the present invention is to provide a fuel cell system configured to be able to supply electric power generated in the fuel cell to an electric load whose load varies. When the amount of power used by the electric load suddenly increases beyond the current power generation amount (limit capability) of the fuel cell or the rated output of the fuel cell, electricity from the fuel cell exceeds the limit capability or rated output of the fuel cell. It is possible to supply electric power required on the electric load side to the load while restraining it from being output, such as suddenly starting from the start when the load of the fuel cell increases from zero or from a stable operating state It is to provide a fuel fuel cell system and an operation method thereof that can ensure stable operation of the fuel cell even in a transition state in which the amount of load changes.

  A fuel cell system according to the present invention includes a fuel cell and a secondary battery connected to a load to which electric power generated by the fuel cell is supplied and supplying electric power to the load. Thus, stable fuel cell operation can be ensured even in a transition state in which the electrical load suddenly changes from the stable operation state. According to a second aspect of the present invention, in the fuel cell system according to the first aspect, the load is an auxiliary device for operating the fuel cell.

  According to a third aspect of the present invention, there is provided the fuel cell system according to the first or second aspect, wherein, after the fuel is supplied to the fuel cell, the power generated by the fuel cell is stabilized until the secondary battery is stabilized. The power is supplied to the load. Thus, if control is performed so that a part of the power supply to the load is supplied from the secondary battery until the fuel cell is supplied to the fuel electrode of the fuel cell and the fuel cell is in a stable output state, Can prevent damage to the fuel cell.

  According to a fourth aspect of the present invention, in the fuel cell system according to any one of the first to third aspects, when the power used by the load exceeds a predetermined threshold, the secondary battery transmits power to the load. It is characterized by supplying. Further, the invention according to claim 5 is the fuel cell system according to any one of claims 1 to 4, wherein when the electric power generated by the fuel cell is equal to or less than a predetermined threshold, Power is supplied to the load. As a result, when there is a sudden increase in power consumption on the load side connected to the fuel cell system, a sudden increase in electrical load can be achieved by temporarily supplementing the insufficient power with a secondary battery. This is a function to protect the fuel cell from overload.

  A sixth aspect of the present invention is the fuel cell system according to any one of the first to fifth aspects, wherein the fuel cell and the secondary battery are connected via a DC / DC converter. . As a result, the DC / DC converter that connects the fuel cell system and the load side also serves as a charging circuit for the secondary battery, so that the configuration of the apparatus is simplified.

  The fuel cell system operating method according to claim 7 is the fuel cell system according to any one of claims 1 to 6, wherein electric power corresponding to the power generation capacity of the fuel cell is extracted, and the fuel is generated by heat generated by power generation. The temperature of the battery is raised, and the invention according to claim 8 is the operation method of the fuel cell system according to claim 7, wherein the electric power taken out from the fuel cell is changed according to the temperature of the fuel cell. It is characterized by. Thereby, the operation of the fuel cell system can be promptly shifted to a steady operation state.

  According to the present invention, when the amount of electric power used in the electric load suddenly increases beyond the capacity of the fuel cell, the power generation state according to the increased electric load amount is reached until the operation of the fuel cell is stabilized. In the meantime, a part of the power supply to the load is also controlled from the secondary battery to prevent damage to the fuel cell due to overload, ensuring stable operation in the transition state of the fuel cell. An improved fuel cell system can be provided.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a fuel cell 6 such as a polymer electrolyte light fuel cell called a polymer electrolite fuel cell, a reformer 3 for supplying hydrogen gas to the fuel cell 6, a burner 12, and a control device 95. Gas pumps 10, 11, 14, 37 such as blowers that are auxiliary devices for operating these devices, liquid pumps 22, 23, 24, 48 such as water pumps, and control valves and on-off valves 36, 40, 41, 42, The fuel cell system provided with 92, 93 etc. is shown.

  The reformer 3 has a burner 12 for heating the reformer 3. The reformer 3 receives raw fuel gas from the raw fuel pipe 1 and steam from the heat exchanger 17 that is a steam source, and from the raw fuel. It is a device that generates high concentration hydrogen gas (reformed gas) and supplies it to the fuel electrode 6a. The raw fuel gas such as natural gas, city gas, methanol, LPG and butane supplied to the fuel cell system via the raw fuel pipe 1 and the fuel supply control valve 41 first flows into the desulfurizer 2 where the sulfur component is generated. Next, the pressure is boosted by the booster pump 10 together with the steam supplied from the heat exchanger 17 and supplied to the reformer 3.

  The heat exchanger 17 is provided, for example, in the exhaust system 31 of the reformer 3 and has a structure in which water is heated by the combustion gas discharged from the reformer 3, and is supplied from the water tank 21 via the pump 22. The supplied water is heated by the heat exchanger 17 to be steamed. The raw fuel gas and water vapor supplied to the reformer 3 obtain heat of chemical reaction from the burner 12 and are reformed into reformed gas containing hydrogen, carbon dioxide and carbon monoxide. The reformed gas leaving the reformer 3 is supplied to a CO converter 4 where carbon monoxide contained in the fuel gas is converted into carbon dioxide. The gas that has passed through the CO converter 4 is supplied to the CO remover 5 and unconverted carbon monoxide in the gas is oxidized into carbon dioxide.

  In the CO remover 5, a gas with high hydrogen concentration (reformed gas) whose carbon monoxide concentration is reduced to 10 ppm or less is supplied to the fuel electrode 6a of the fuel cell. Since the chemical reaction performed in the CO converter 4 and the CO remover 5 is an exothermic reaction, for example, the CO remover 5 burns a burner (not shown) only when the system is started, and the heat of the combustion gas generated at this time. Then, the temperature of the CO remover 5 is raised to the reaction temperature, and thereafter the reaction temperature is maintained by the heat of its own exothermic reaction. From the outside, cooling control (not shown) is performed as necessary so that the CO converter 4 and the CO remover 5 do not rise above the reaction temperature.

  The fuel cell 6 includes a fuel electrode 6a, an air electrode 6k, and a cooling unit 6c. The reformed gas introduced into the fuel electrode 6a is used for power generation here, while surplus hydrogen that has not reacted at the fuel electrode 6a is discharged as an off-gas through the off-gas control valve 92 to the conduit 15. Reaction air as an oxidant is supplied to the air electrode 6k, and electric power is generated by an electrochemical reaction between this and the reformed gas. On the other hand, the air after the electrochemical reaction is discharged to the atmosphere via the pipe line 27. The reaction air supplied to the air electrode 6k is sent out to the gas phase portion 53 while being bubbled into the water in the water tank 21 by the air pump 11, and is humidified. The reaction air is supplied with moisture so that the electrochemical reaction in the fuel cell 6 is appropriately maintained as described above, and then supplied to the air electrode 6k of the fuel cell via the pipe line 16. In the fuel cell 6, the cell itself generates reaction heat due to the activation overvoltage, concentration overvoltage, and resistance overvoltage during the electrochemical reaction, and the temperature necessary for the operation of the fuel cell 6 is maintained.

  The cooling unit 6c of the fuel cell is a cooling device provided to cool the fuel cell 6 so that the fuel cell 6 is not overheated by reaction heat or the like after the fuel cell 6 has shifted to a steady operating state. 6a and the air electrode 6k are juxtaposed. Water in the water tank 21 is circulated in the cooling unit 6c by a pump 48, and the temperature in the fuel cell 6 is maintained at an operating temperature suitable for power generation, for example, 70 ° C. to 80 ° C. by this cooling water. As a result, the fuel cell 6 is controlled so that the temperature in the cell is not excessively increased by the reaction heat to deteriorate the function of the constituent material of the cell or damage the solid polymer membrane of the cell.

  In the fuel cell system of FIG. 1, heat exchangers 18 and 19 are connected between the reformer 3 and the CO converter 4, and between the CO converter 4 and the CO remover 5, respectively. Water is circulated from the water tank 21 to the heat exchangers 18 and 19 via the pumps 23 and 24, and the gas passed through the reformer 3 and the CO converter 4 is cooled. In this way, in the reformer 3, the CO converter 4, the CO remover 5, and the fuel cell 6, a predetermined chemical reaction (reforming reaction, electrochemical reaction) is continued and electric power is generated.

  Fuel gas is supplied to the reformer burner 12 through the fuel pipe 13 having the combustion control valve 42, and off-gas is supplied through the pipe line 15 having the off-gas control valve 92. On the other hand, the combustion air is supplied by the gas pump 14, whereby the combustion of the fuel gas and off-gas in the burner 12 is performed.

  At the start of the fuel cell system, the temperature of the reformer 3 and the fuel cell 6 is low and no off-gas is generated. Therefore, in the burner 12 of the reformer 3, the fuel supplied through the combustion control valve 42 and the fuel pipe 13 Only the gas is burned and the reformer 3 is heated. Thereafter, the temperature of the reformer 3 rises, reformed gas is generated, sent to the electrode 6a of the fuel cell, and when power generation in the fuel cell 6 starts, the temperature of the fuel cell 6 gradually rises due to the temperature rise of the load. Can be made. In this way, when the temperature of the reformer 3 and the fuel cell 6 rises to the operating temperature and stabilizes, and the fuel cell system shifts to a steady operating state, the off-gas is stabilized from the fuel electrode 6a of the fuel cell. It will be discharged.

  After the fuel cell system shifts to a steady operation state, the combustion control valve 42 is closed, the supply of the fuel gas via the fuel pipe 13 is cut off, and the heating of the reformer 3 by the burner 12 is performed by the off-gas control valve 92. It switches so that it may be performed by combustion of the off gas supplied via.

  Next, startup control of this fuel cell system will be described. 1 in FIG. 1 is a control device of the fuel cell system. The combustion control of the burner 12 by the control device 95 after the fuel cell system has shifted to the steady operating state is performed by supplying the off gas discharged from the fuel electrode 6a to the burner 12 via the conduit 15 and Reaction hydrogen gas is combusted and the reformer 3 is controlled to be heated by off-gas combustion. Further, the control device 95 monitors the temperature of the reformer 3 and the fuel cell 6 by the temperature sensor 44 of the reformer 3 and the temperature sensor 45 of the fuel cell 6, and supplies the raw fuel supplied to the reformer 3. In addition, the flow of the fuel gas supplied to the burner 12 is controlled, and at the same time, the electric power generated by the fuel cell 6 is supplied to the electric loads 70, 71 and 72. Reference numeral 49 denotes an ammeter that detects the amount of electricity supplied from the fuel cell 6 to the electric loads 70, 71, 72.

  Control of the flow of the reformed gas and the fuel gas by the control device 95 is performed by controlling the combustion control valve 42 provided in the fuel pipe 13 and the control valve 93 and the opening / closing valve 36 provided in the pipes 64 and 35 through which the reformed gas flows. Further, the control is performed by opening / closing control of the control valve 40 and the off-gas control valve 92 provided in the pipelines 38 and 15 through which the off-gas flows. That is, since the temperature is low and the reforming reaction is not sufficient when the fuel cell system is started, the controller 95 causes the reformed gas having a stable composition when the temperature of each reactor such as the reformer 3 reaches the operating temperature. Until it is generated, the control valve 93 is closed and the on-off valve 36 is opened. As a result, the reformed gas having an unstable composition is not supplied to the electrode 6a of the fuel cell, but is led to the PG burner 34 via the pipe 35 and burned there.

  After starting the reformer 3 of the fuel cell system and the temperature and operation of each reactor including the reformer 3 are stabilized, the control device 95 closes the open / close valve 36 and opens the open / close valve 40 and the control valve 93. Then, the reformed gas is supplied to the fuel electrode 6a of the fuel cell, and power generation in the fuel cell 6 is started. When the reformed gas is introduced, the temperature of the fuel electrode 6a is low, and almost no power generation is performed. Even if power generation is gradually started, it does not immediately become a stable operating state. While the temperature of the fuel cell is low and the amount of power generation is small, the control device 95 controls the DC / DC converter 107 and the system linkage inverter 108 to apply a load corresponding to the power generation capacity of the fuel cell 6 to the fuel cell 6. Then, the fuel cell 6 is controlled so that the temperature of the fuel cell 6 increases due to the heat generated by the fuel cell 6 itself (load temperature increase).

  For example, when the power generation by the fuel cell 6 is started and the open voltage is confirmed, the control device 95 immediately connects the open voltage to the power system via the grid connection inverter 108, and the power generation capacity is low. Then, an electric load is applied to the fuel cell 6. In this process, the control device 95 monitors the temperature of the fuel cell 6 with the temperature sensor 45 and gradually increases the amount of electric load applied to the fuel cell 6 by increasing the extraction current value according to the cell temperature at that time. By increasing the load temperature, the temperature of the fuel cell is raised to a stable operating temperature as soon as possible, and control is performed so that the operation of the fuel cell system can immediately shift to a steady operating state.

  Unreacted gas that has not been used for power generation in the fuel cell 6 is guided to the PG burner 34 via the pipe line 38 and the control valve 40, and is burned there. After the temperature of the fuel cell 6 rises due to the temperature rise of the load and reaches an operating temperature (for example, 70 ° C. to 80 ° C.), the temperature stabilizes near this operating temperature and reaches the rated output state. The composition of the off-gas discharged becomes stable. After the fuel cell 6 is in a steady operating state, the control device 95 closes the control valve 40 and opens the offgas control valve 92 to switch the offgas flow from the pipe line 38 to the pipe line 15. The off-gas is burned by the burner 12. In this way, after the fuel cell system reaches a steady operating state, the reformer burner 12 burns the unreacted gas (hydrogen) in the off-gas introduced via the conduit 15 and reforms. The heating of the vessel 3 is continued.

  Thus, in the steady operation state of the fuel cell system, the off-gas control valve 92 and the control valve 93 are opened, and the valves 36 and 40 are closed. In the fuel cell 6, the fuel is cooled by the cooling unit 6c. The battery temperature is maintained at the operating temperature (70 ° C. to 80 ° C.), and rated power generation can be performed continuously. In the fuel cell system having such a configuration, the water pumps (liquid pumps) 22, 23, 24, 48 and gas pumps 10, 11, 14, 37, such as a blower, which are provided as auxiliary devices of the fuel cell system, and the control valve When viewed from the power source, the power supply for the operation of the valves 92 and 93, the on-off valves 36 and 40, the control device 95, etc. is a kind of electric load (hereinafter collectively referred to as an auxiliary load 71).

  Power supply to the auxiliary load 71 is performed by a commercial power source when the fuel cell system is started, and after the operation of the fuel cell 6 is stabilized, the fuel cell system is switched so that power is supplied from the fuel cell system. Can operate independently without receiving power from a commercial power source. Further, the power generated by the fuel cell 6 is not limited to the auxiliary load 71 and the system load 70 described above, but also the load of the home such as lighting equipment and electrical equipment in the home where the fuel cell system is installed (hereinafter referred to as the self load). 72). When it is necessary to increase or decrease the power generation amount of the fuel cell 6 by supplying power to the system load 70 or increasing or decreasing the amount of power used in the private load 72, the control device 95 causes the current sensor 49 to detect this change. The amount of raw fuel gas supplied to the reformer 3 is adjusted so that hydrogen gas corresponding to the changed load power amount can be supplied to the fuel electrode 6a.

  The amount of current (electric power) obtained in the fuel cell 6 and the amount of hydrogen (raw fuel) supplied to the fuel electrode 6a are substantially proportional to each other, and the raw fuel supplied to the fuel cell system via the raw fuel pipe 1 Since the relationship between the amount of gas and the reformed gas (hydrogen gas) is also approximately proportional, if the amount of raw fuel gas supplied to the reformer 3 is increased or decreased, the generated power (cell current value) of the fuel cell 6 is increased. ) Can also be increased or decreased proportionally. In the fuel cell 6 in a steady operating state, most of the obtained electric power is a load connected to the fuel cell system via the DC / DC converter 107, the grid interconnection inverter 108, and the distribution board 73 as described above. 70, 71, 72.

  The control device 95 calculates the amount of raw fuel gas supplied to the reformer 3 in order to supply the reformed gas corresponding to the load power amount to the fuel electrode 6a, and opens the fuel gas supply control valve 41. While adjusting the degree, the pump 22 is controlled to adjust the amount of water vapor corresponding to the amount of raw fuel gas to be supplied to the reformer 3. Thereby, the fuel electrode 6a of the fuel cell can generate electric power according to the change in the electric load. Further, the gas pumps 14 and 37 provided in the burner 12 and the PG burner 34 are controlled so that air corresponding to the amount of fuel gas supplied to the respective burners 12 and 34 is supplied to the burner to burn the gas. It is what is done.

  It should be noted that the opening / closing control of the control valve 40, the combustion control valve 42, the off-gas control valve 92, etc. used in the above description is simpler than the opening / closing valve. For example, the control valve 40 provided in the pipe 38 is used. The combustion control valve 42 provided in the pipeline 13 and the off-gas control valve 92 provided in the pipeline 15 are both valves whose opening degree can be changed steplessly, and the reformer is controlled by the control of these valves 42 and 92. The temperature of 3 may be controlled so as to always maintain a constant operating temperature. Further, the reformer burner 12 is supplied with and simultaneously burned off-gas via the off-gas control valve 92 and fuel gas via the combustion control valve 42, and after the fuel cell system has reached a stable operating state. Alternatively, the combustion control valve 42 may be closed to switch to combustion with only off gas. Furthermore, even after the fuel cell system reaches a stable operating state, the off-gas control valve 92 controls the amount of off-gas supplied to the burner 12 as needed to stabilize the temperature of the reformer 3, If there is a surplus, excess off-gas may be introduced to the PG burner 34 via the pipe line 38 and the control valve 40 and burned.

  Next, control when the commercial power supply is interrupted before the fuel cell system supplies power to the auxiliary machine, such as before the fuel cell system reaches a stable operation state, will be described. FIGS. 2 and 3 are diagrams each showing a configuration of a main part of the control device of the fuel cell system according to the present invention, and a secondary battery (chargeable / dischargeable battery) 74 that backs up the operating power of the auxiliary load 71. 1 shows an embodiment of an apparatus having

  In FIG. 2, reference numeral 74 denotes a secondary battery capable of supplying power to the auxiliary load 71, and the secondary battery 74 is connected via a bidirectional DC / DC converter (charge / discharge circuit) 78 and a diode 75. Are connected to the electrical output side of the fuel cell 6 and are connected to a commercial power source via an AC / DC converter (a charger using a commercial power source) 77.

  76 is a converter for supplying power from the secondary battery 74 to the auxiliary load 71, 107 is a DC / DC converter shown in FIG. 1, and 108 is a grid-connected inverter such as a DC / AC inverter. , 70 is a system load. When the commercial power supply is interrupted before the power supply from the fuel cell 6 to the auxiliary load 71 is performed and the power supply to the auxiliary load 71 is stopped, the secondary battery 74 supplies the auxiliary load 71 to the auxiliary load 71. The control device 95 controls the devices so that the start-up operation of these fuel cell systems does not hinder the operation of the fuel cell system by switching the circuits so that the operating power is supplied.

  Similarly, in FIG. 3 showing the second embodiment of the present invention, reference numeral 74 denotes a secondary battery capable of supplying power to the auxiliary load 71, and the secondary battery 74 is connected via the DC / DC converter 107. In addition to being connected to the output side of the fuel cell 6, it is connected to the system load 70 and the commercial power source side via the aforementioned AC / DC converter (charger to the secondary battery 74 using the commercial power source) 77. .

  As in FIG. 2, 76 is a converter for supplying power from the secondary battery 74 to the auxiliary load 71, and 108 is the grid interconnection inverter described above. Also in the control device of FIG. 3, before the operation of the fuel cell 6 reaches a certain operating state and power is supplied from the fuel cell 6 to the auxiliary load 71, the commercial power supply fails and the auxiliary load 71 When the power supply to the engine stops, the operating power is supplied from the secondary battery 74 to the auxiliary machine, and the control device 95 keeps the start-up operation of these fuel cell systems without hindrance and enters a steady operation state. These devices are controlled. In the embodiment of FIG. 3, the configuration of the control device is greater than that of the embodiment of FIG. 2 in that the DC / DC converter 107 that connects the fuel cell system and the system load side also serves as a charging circuit for the secondary battery 74. Has been simplified.

  By using such a control device for the fuel cell system, power is supplied from the fuel cell 6 to the auxiliary load 71 and the commercial power supply is cut off before the combustion cell system operates to supply the auxiliary power by itself. When the power failure is detected, the control device 95 that has detected the power failure immediately switches to the secondary battery 74 side to supply power to the auxiliary load 71, and the fuel cell 6 and the reformer 3 that constitute the fuel cell system are substantially affected by the power failure. Thus, the power to the auxiliary machine or the like can be supplied from the secondary battery 74 so that the operation of the fuel cell system can be shifted to a steady state without any trouble.

  Further, as another control function of the control device for the fuel cell system of the present invention, if the control device for the fuel cell system of FIG. 2 or FIG. 3 is used, for example, an earthquake occurs and is attached to the fuel cell system. When the operation of the fuel cell 6 is stopped by the seismic detector, and then the power supply from the commercial power source does not start, the secondary battery 74 supplies power to the auxiliary load 71 to start the fuel cell system. Can do. If the electric capacity of the secondary battery 74 is sufficiently large, the power supply to the auxiliary machine 71 can be provided by the secondary battery 74 as an auxiliary power source from the start of the fuel cell 6 by itself. Thus, even during such an earthquake, the control device 95 can control the device to bring the fuel cell system into an independent operation state.

  Another function of the control device of the fuel cell system of the present invention is a function of protecting the fuel cell against a sudden increase in load. This is because, for example, when there is a sudden increase in power usage on the side of the electric loads 70, 71, 72 connected to the fuel cell system, the insufficient power is temporarily supplemented by the secondary battery. This serves to alleviate the rapid increase in the electrical load and protect the fuel cell from overload. When the amount of the electrical load supplying power from the fuel cell 6 increases, the current in the circuit between the fuel cell 6 and the load increases, and the controller 95 that senses this increase with the ammeter 49 The control valve 41 is opened so as to increase the output from the fuel cell 6.

  However, even if the fuel supply control valve 41 is opened upon sensing such an increase in current and the amount of raw fuel gas supplied to the reformer 3 increases, the amount of power generation does not increase immediately. There is a time delay of at least about 1 minute before the raw fuel gas is generated in the reformer 3 and supplied to the fuel electrode 6a of the battery. When the amount of power used in the electric loads 70, 71, 72 suddenly increases beyond the capacity of the fuel cell 6, the fuel cell 6 may be put into an overload operation state. In this way, when the electric load is suddenly increased, the control device until hydrogen gas corresponding to the increased electric load is supplied to the fuel electrode 6a of the fuel cell and the fuel cell 6 reaches a stable output state. If 95 controls to supply a part of the power supply to the load from the secondary battery 74, damage to the fuel cell 6 due to overload can be prevented.

  In addition, the fuel cell 6 is overloaded when a use state of power exceeding the rated output of the fuel cell 6 occurs on the side of the electric loads 70, 71, 72 to which power is supplied from the fuel cell 6. There is a risk of entering a state. In such a case, since the maximum operating current value of the fuel cell 6 has been exceeded, a safety device (not shown) such as a breaker normally works to stop the power supply to the load. Safety devices do not work immediately. In such a case, if the control device 95 controls the output of the fuel cell 6 to be within the rated output and the secondary battery 74 performs control to supplement a part of the power supply to the electric loads 70, 71, 72, Even when the use of electric power exceeding the rated output is temporarily on the load side, the necessary electric power can be continuously supplied to the load while protecting the fuel cell 6 for a short time.

  According to the control device of the present invention, not only when a stopped fuel cell is started, but also when a sudden change in electrical load occurs in a fuel cell system in a stable operation state. In other words, during the time delay of the operation of the fuel cell with respect to such a rapid increase in load, the secondary battery 74 appropriately supplies power for the increased load to the fuel cell 6. It is also possible to alleviate overload.

  In the above-described embodiments, the solid polymer fuel cell system has been mainly described as the fuel cell system. However, the fuel cell system to which the present invention can be used has a fuel cell and an auxiliary device for operating the fuel cell. It can also be used for other fuel cell systems.

It is a figure which shows the whole structure of the fuel cell system using the starting method by this invention. It is a block diagram which shows the principal part structure of 1st embodiment of the control apparatus by this invention. It is a block diagram which shows the principal part structure of 2nd embodiment of the control apparatus by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Raw fuel pipe 3 Reformer 6 Fuel cell 6a Fuel electrode 6k Air electrode 12 Burner for reformer heating 13 Fuel pipe 15, 35, 38 Pipe line 21 Water tank 34 PG burner 36, 40 Open / close valve 41 Raw fuel supply Control valve 42 Combustion control valve 44, 45 Temperature sensor 49 Ammeter 70 System load 71 Auxiliary load 72 Private load 74 Secondary battery 75 Diode 76 Converter 77 AC / DC converter 92 Off-gas control valve 95 Controller 107 DC / DC converter 108 Grid interconnection inverter

Claims (8)

A fuel cell;
A secondary battery connected to a load to which power generated by the fuel cell is supplied, and supplying power to the load;
A fuel cell system comprising: The fuel cell system according to claim 1, wherein
The fuel cell system according to claim 1, wherein the load is an auxiliary machine for operating the fuel cell. The fuel cell system according to claim 1 or 2,
After the fuel is supplied to the fuel cell, until the power generated by the fuel cell is stabilized,
The fuel cell system, wherein the secondary battery supplies power to the load. The fuel cell system according to any one of claims 1 to 3,
When the power used by the load exceeds a predetermined threshold,
The fuel cell system, wherein the secondary battery supplies power to the load. The fuel cell system according to any one of claims 1 to 4,
When the electric power generated by the fuel cell is below a predetermined threshold,
The fuel cell system, wherein the secondary battery supplies power to the load. The fuel cell system according to any one of claims 1 to 5,
The fuel cell system, wherein the fuel cell and the secondary battery are connected via a DC / DC converter. The fuel cell system according to any one of claims 1 to 6,
A method of operating a fuel cell system, comprising: taking out electric power corresponding to the power generation capacity of the fuel cell and raising the temperature of the fuel cell by heat generated by power generation. The operation method of the fuel cell system according to claim 7,
An operation method of a fuel cell system, wherein electric power taken out from the fuel cell is changed according to a temperature of the fuel cell.

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