JP5837957B2 - FUEL CELL SYSTEM AND METHOD FOR OPERATING FUEL CELL SYSTEM - Google Patents

Description

  The present invention relates to a fuel cell system and a method for operating the fuel cell system, and particularly to quickly return the power supplied outside the fuel cell system to the required power when the abnormality of the system power supply is instantaneous. The present invention relates to a fuel cell system capable of performing the same and a method for operating the fuel cell system.

  When installing a fuel cell that generates electricity by introducing a hydrogen-containing gas and an oxygen-containing gas, in view of the lack of infrastructure to obtain the hydrogen-containing gas, the hydrocarbon-based raw material is reformed to produce a hydrogen-containing gas. In many cases, a reformer is attached. Some fuel cells are connected to a system power supply in preparation for the case where the power generated by the fuel cell is less than the demand power of a power load such as an electric device (see, for example, Patent Document 1). On the other hand, as an operation method when the load of the fuel cell system including the fuel cell and the reformer is increased, the target power generation amount of the fuel cell module is set, the oxidant gas supplied to the fuel cell module is increased, and then the fuel Whether the water supplied to the battery module is increased, the fuel gas supplied to the fuel cell module is increased, and then the power generation amount of the fuel cell module is increased, and then the power generation amount of the fuel cell module has reached the target power generation amount or more There is one that detects whether or not (see, for example, Patent Document 2).

JP 2011-192419 A (paragraph 0015) JP 2009-104886 A (paragraph 0012)

  In the future, if distributed power sources such as fuel cells become widespread, and fuel cells are connected to a large amount and a large amount of power to the system power source, the proportion of the power generation output by the distributed power source to the total power generation output will increase. If the distributed power supply is disconnected from the system power supply all at once due to the disturbance of the power supply, the supply and demand balance in the system may be disrupted and there may be a power outage over a wide area. In order to avoid such problems due to the simultaneous disconnection of distributed power sources, the establishment of performance requirements (FRT requirements) for fuel cells to continue operation without disconnecting the fuel cells from the system power source when the system is disturbed Is underway. In the FRT requirement, when the abnormality (voltage drop) of the system power supply is instantaneous, it is required to quickly restore the power generation output of the fuel cell to the state before the occurrence of the abnormality. However, when the operation method described in Patent Document 2 is applied to FRT requirements by analogy, the amount of fuel treated in the reformer is reduced in accordance with a decrease in the target power output when an abnormality occurs in the system power supply. If the abnormality is determined to be instantaneous, the fuel throughput will be increased, and then the power generation output will be increased, so it will be slow to restore the power output of the fuel cell to the state before the abnormality occurred. End up.

  In view of the above-described problems, the present invention provides a fuel cell system and a fuel that can quickly return the power supplied to the outside of the fuel cell system to the required power when the abnormality of the system power supply is instantaneous. It aims at providing the operating method of a battery system.

  In order to achieve the above object, a fuel cell system according to a first aspect of the present invention is a fuel cell system 1 linked to a system power supply PS, for example, as shown in FIG. A fuel cell 13 for generating electric power to be supplied to the outside; a reformer 11 for reforming the introduced raw material D into a fuel gas E to be supplied to the fuel cell 13; and an abnormality detection unit for detecting an abnormality in the system power supply PS 35; when the abnormality detection unit 35 detects an abnormality of the system power supply PS, the generated power of the fuel cell 13 is reduced while the generation flow rate of the fuel gas E in the reformer 11 is reduced by the abnormality of the system power supply PS. A control unit that adjusts the return request output, which is the power required to be supplied to the outside of the fuel cell system 1 when it is eliminated, to a flow rate necessary to generate power in the fuel cell 13 and maintains it for a predetermined time. 40 Equipped with a. Here, the return request output is typically determined by an agreement between electric utilities. Further, adjusting the generation flow rate of the fuel gas E to the flow rate required for generating the return request output by the fuel cell 13 includes maintaining the flow rate immediately before the detection of the abnormality of the system power supply PS.

  With this configuration, the generation power of the fuel cell is reduced when an abnormality in the system power supply is detected, while the generation flow rate of the fuel gas in the reformer is necessary to generate the return request output with the fuel cell. Since the flow rate is adjusted and maintained for a predetermined time, the power supplied to the outside of the fuel cell system can be quickly made a return request output when the abnormality of the system power supply is instantaneous.

  Moreover, when the fuel cell system according to the second aspect of the present invention is shown with reference to FIG. 1, for example, in the fuel cell system 1 according to the first aspect of the present invention, the control unit 40 includes an abnormality detection unit. When the abnormality of the system power source PS is not resolved even after a predetermined time has elapsed since the detection of the abnormality of the system power source PS 35, the supply of power to the outside of the fuel cell system 1 is stopped and the reformer 11 The control is performed so as to reduce the generation flow rate of the fuel gas E.

  With this configuration, it is possible to avoid the continuation of the state in which the return request output can be generated by the fuel cell in a state where there is no possibility of eliminating the abnormality of the system power supply, and it is possible to suppress the raw material consumption. The fuel cell system can be protected.

  Further, when the fuel cell system according to the third aspect of the present invention is shown with reference to FIG. 4, for example, in the fuel cell system according to the first aspect of the present invention, the fuel cell system 1A is the fuel cell 13. An in-system load 51 that can use the power generated in the fuel cell 13 when the generated power is not supplied to the outside is provided; after the control unit 40 detects an abnormality in the system power supply PS When the abnormality of the system power source PS is not resolved even after a predetermined time has elapsed, control is performed to recover the power generated by the fuel cell 13 and supply the power generated in the fuel cell 13 to the in-system load 51. Has been.

  With this configuration, even if the abnormality of the system power supply is not resolved even after a predetermined time has elapsed after the abnormality detection unit detects the abnormality of the system power supply, the power generation before the abnormality of the system power supply is detected. The operation of the fuel cell can be continued with electric power, and the generation flow rate of the fuel gas in the reformer can be maintained without being reduced, and the electric power generated in the fuel cell can be reduced when the system power supply abnormality is resolved. It becomes possible to supply the fuel cell system quickly.

  Further, the fuel cell system according to the fourth aspect of the present invention is, for example, as shown in FIG. 1, in the fuel cell system 1 according to any one of the first to third aspects of the present invention. The fuel cell 13 is composed of a solid oxide fuel cell that generates power by introducing the oxidant gas A and the fuel gas E; the gas that has not been used for power generation among the fuel gas E supplied to the fuel cell 13 And a combustion section 15 for introducing the fuel off-gas Fe and the oxidant off-gas Fa, which is the gas not used for power generation among the oxidant gas A supplied to the fuel cell 13, to burn the fuel off-gas Fe. Provided: When the abnormality detection unit 35 detects an abnormality in the system power supply PS, the control unit 40 uses the fuel cell 13 to generate the flow of the oxidant gas A supplied to the fuel cell 13 and the return request output. Necessary flow It was adjusted to, and is configured to perform control for maintaining for a predetermined time.

  If comprised in this way, when the abnormality of a system | strain power supply is instantaneous, the electric power supplied out of a fuel cell system can be rapidly made into a return request | requirement output.

  In order to achieve the above object, the operation method of the fuel cell system linked to the system power source PS according to the fifth aspect of the present invention is shown in FIG. 1 and FIG. 1. Power generation step (S2) for generating electric power to be supplied to the outside with the fuel cell 13; Fuel gas generation step (S1) for generating the fuel gas E to be supplied to the fuel cell 13; Monitoring whether there is an abnormality in the system power supply PS The abnormality monitoring step (S3) to be performed; when the abnormality of the system power supply PS is detected in the abnormality monitoring step (S3), the generated power of the fuel cell 13 is reduced, while the fuel gas E in the fuel gas generation step (S1) The generation request flow rate is adjusted to a flow rate required to generate power by the fuel cell 13, which is a power required to be supplied to the outside of the fuel cell system 1 when the abnormality of the system power supply PS is resolved, of And maintained for between, and a standby step of waiting for a resolution of the system power supply PS abnormal (S4-S6).

  With this configuration, when an abnormality in the system power supply is detected, the generated power of the fuel cell is reduced, while the fuel gas generation flow rate in the fuel gas generation process is used to generate the return request output with the fuel cell. Since the flow rate is adjusted to the required flow rate and maintained for a predetermined time, the power supplied to the outside of the fuel cell system can be quickly made a return request output when the abnormality of the system power supply is instantaneous.

  According to the present invention, when the abnormality of the system power supply is instantaneous, the power supplied to the outside of the fuel cell system can be quickly made a return request output.

1 is a schematic system diagram of a fuel cell system according to an embodiment of the present invention. It is a flowchart explaining the operating method of the fuel cell system which concerns on embodiment of this invention. It is a time chart explaining the operating method of the fuel cell system concerning an embodiment of the invention. It is a typical systematic diagram of the fuel cell system which concerns on the modification of embodiment of this invention. It is a time chart explaining the driving | running method of the fuel cell system which concerns on the modification of embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or similar members are denoted by the same or similar reference numerals, and redundant description is omitted.

  First, a fuel cell system 1 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic system diagram of the fuel cell system 1. The fuel cell system 1 includes a reformer 11 that reforms a raw material D into a fuel gas E rich in hydrogen, a fuel cell 13, a combustion unit 15, and an abnormality detection unit that detects an abnormality of the system power supply PS. And a control device 40 as a control unit.

  The raw material D can be made into a gas rich in hydrogen (hydrogen-rich gas) that can be used for power generation in the fuel cell 13 by reforming, and typically a hydrocarbon-based fuel is used. Specific examples include hydrocarbons, alcohols, ethers, biofuels, and these hydrocarbon fuels are derived from fossil fuels such as petroleum and coal, those derived from synthetic fuels such as synthesis gas, Those derived from biomass can be used as appropriate. Examples of hydrocarbons include methane, ethane, propane, butane, natural gas, LPG, city gas, town gas, gasoline, naphtha, kerosene, and light oil. Examples of alcohols include methanol and ethanol. Examples of ethers include dimethyl ether. Examples of biofuels include biogas, bioethanol, biodiesel, and biojet.

  The reformer 11 has a reforming catalyst that promotes reforming of the raw material D inside. As the reforming catalyst, for example, a partial oxidation reforming catalyst, a steam reforming catalyst, an autothermal reforming catalyst, or the like can be used alone or in combination. In the present embodiment, the steam reforming catalyst is accommodated in the reformer 11. Since the steam reforming catalyst is a reforming catalyst in which the endothermic reaction is dominant, in the present embodiment, the steam reforming catalyst is configured so that the heat necessary for the endothermic reaction can be obtained also from the combustion unit 15. ing. A raw material pipe 21 as a raw material flow path for introducing the raw material D and a reforming water pipe 23 as a reforming water flow path for introducing the reforming water W used for steam reforming are connected to the reformer 11. Yes. A raw material blower 22 as a raw material supply device for pumping the raw material D toward the reformer 11 is inserted and disposed in the raw material pipe 21. In the reforming water pipe 23, a reforming water pump 24 is inserted and disposed as a reforming water supply device that pumps the reforming water W toward the reformer 11. The reformer 11 is configured to introduce the raw material D and the reformed water W to generate the fuel gas E. The reformer 11 is also connected with a fuel gas pipe 25 as a fuel gas flow path for deriving the generated fuel gas E.

  The fuel cell 13 is connected to the reformer 11 via a fuel gas pipe 25. The fuel cell 13 is also connected with an oxidant gas pipe 26 as an oxidant gas flow channel for introducing an oxidant gas A containing oxygen. The oxidant gas A is typically air. An oxidant gas blower 27 serving as an oxidant gas supply device that pumps the oxidant gas A toward the fuel cell 13 is inserted into the oxidant gas pipe 26. The fuel cell 13 is configured to introduce a fuel gas E and an oxidant gas A, and to generate DC power by an electrochemical reaction between hydrogen or the like in the fuel gas E and oxygen in the oxidant gas A. Yes. As the fuel cell 13, a cylindrical type (including a flat plate cylindrical type) solid oxide fuel cell (SOFC) is used in the present embodiment. The fuel gas E and the oxidant gas A supplied to the fuel cell 13 for power generation in the fuel cell 13 are not all used for power generation, but the amount corresponding to the power generation current of the fuel cell 13 is used. The Of the fuel gas E supplied to the fuel cell 13 for power generation in the fuel cell 13, the portion not used for power generation is derived as fuel off-gas Fe. Further, of the oxidant gas A supplied to the fuel cell 13 for power generation in the fuel cell 13, the portion not used for power generation is derived as the oxidant off-gas Fa. Hereinafter, the fuel off-gas Fe and the oxidant off-gas Fa are sometimes collectively referred to as off-gas F.

  The combustion unit 15 communicates with the fuel cell 13 via the off gas flow path 28 and is configured to burn off gas F. The combustion unit 15 is mainly for purifying unburned components in the offgas F, but is disposed adjacent to the reformer 11 so that heat is applied to the reforming catalyst in the reformer 11. It is preferable to be configured so that it can be given. For example, in a casing (not shown) in which the reformer 11 and the fuel cell 13 are accommodated, the reformer 11 is disposed above a portion from which the fuel off-gas Fe is derived, and the reformer 11 and the fuel cell 13 are arranged. It is good also as a structure which burns off gas F in the space between. In this case, the space between the reformer 11 and the fuel cell 13 corresponds to the combustion unit 15, and the off-gas flow path 28 and the combustion unit 15 are very close to each other. The combustion unit 15 is configured to burn off gas F in which the fuel off gas Fe and the oxidant off gas Fa are mixed, and to discharge exhaust gas G generated by the combustion of the off gas F. An exhaust gas pipe 29 is connected to the combustion unit 15 as an exhaust gas flow path through which the exhaust gas G flows.

  The fuel cell system 1 is linked to the system power supply PS via the power conditioner 30. The system power source PS is a power source supplied from a commercial distribution line network owned by an electric power company. The power conditioner 30 is a device that adjusts the electric power generated by the fuel cell 13 to a stable output. The power conditioner 30 includes a converter 31 that boosts the voltage generated by the fuel cell 13, an inverter 32 that converts DC power boosted by the converter 31 to AC, and an abnormality detector that detects an abnormality in the system power supply PS. 35. The inverter 32 includes a switching element such as an IGBT, and by electrically turning off all the switching elements, the connection between the fuel cell system 1 and the system power supply PS can be electrically disconnected (performs a gate block). It is configured to be able to. The fuel cell system 1 connected to the system power supply PS via the power conditioner 30 is electrically connected to a load L such as a home appliance disposed outside the fuel cell system 1, and the fuel cell 13 generates power. It is configured so that the generated power can be supplied to the load L.

  The control device 40 is a device that controls the operation of the fuel cell system 1. The control device 40 is connected to the raw material blower 22, the reforming water pump 24, and the oxidant gas blower 27 through signal cables, respectively, and the flow rate of the raw material D supplied to the reformer 11 and the reforming supplied to the reformer 11. The flow rate of the water W and the flow rate of the oxidant gas A supplied to the fuel cell 13 can be adjusted. Further, the control device 40 is connected to the power conditioner 30 through a signal cable, can adjust the generated power in the fuel cell 13, and the abnormality detector 35 detects that the abnormality of the system power supply PS has been detected. It is configured to be able to receive information.

  With continued reference to FIG. 2, the operation of the fuel cell system 1 will be described. FIG. 2 is a flowchart for explaining the operating state of the fuel cell system 1. In addition, about the structure of the fuel cell system 1 mentioned in the following description of an effect | action, suppose that FIG. 1 is referred suitably. In the fuel cell system 1, the raw material D and the reforming water W are supplied to the reformer 11, whereby the reformer 11 performs steam reforming of the raw material D and generates fuel gas E (fuel gas) Generation process: S1). The generated fuel gas E is supplied to the fuel electrode (not shown) of the fuel cell 13. Further, the oxidant gas A is supplied to the oxidant electrode (not shown) of the fuel cell 13.

  In the fuel cell 13 into which the fuel gas E and the oxidant gas A are introduced, power generation is performed by an electrochemical reaction between hydrogen or the like in the fuel gas E and oxygen in the oxidant gas A (power generation step: S2). The fuel gas E and the oxidant gas A introduced into the fuel cell 13 are derived as off-gas F after being used for power generation and reach the combustion unit 15. The offgas F is combusted in the combustion unit 15, and the combustion heat generated at this time is used for the steam reforming reaction in the reformer 11. The exhaust gas G generated by the combustion of the off-gas F in the combustion unit 15 flows through the exhaust gas pipe 29, and is appropriately recovered by a heat exchanger (not shown), and then discharged outside the fuel cell system 1. The

  In the fuel cell 13 during the steady operation, the electric power requested by the power conditioner 30 is generated. Here, the steady operation is a state in which desired generated power can be generated in the fuel cell 13 (at this time, the reformer 11 is in a state in which the fuel gas E having a desired flow rate can be generated). The operation is typically an operation when the fuel cell system 1 is in a state other than the starting process and the stopping process. In general, the fuel cell is supplied with hydrogen and oxygen at a flow rate higher than the flow rates of hydrogen and oxygen used when the requested power is generated by the fuel cell. The control device 40 modifies the flow rate of the fuel gas E that can supply the fuel cell 13 with a flow rate of hydrogen that is higher by a predetermined ratio than the flow rate of hydrogen used when the fuel cell 13 generates the required power. The rotational speed of the raw material blower 22 is adjusted so that it can be generated by the mass device 11. Further, the control device 40 adjusts the rotational speed of the reforming water pump 24 so as to supply the reforming water W with the reforming water W corresponding to the flow rate of the fuel gas E generated in the reformer 11. Further, the control device 40 has a flow rate of oxidant gas that can supply the fuel cell 13 with a flow rate of oxygen that is higher by a predetermined ratio than the flow rate of oxygen used when the fuel cell 13 generates the required power. The rotational speed of the oxidant gas blower 27 is adjusted so that A is supplied to the fuel cell 13. The DC power generated by the fuel cell 13 is boosted by the converter 31 in the power conditioner 30, converted to AC power by the inverter 32, and supplied to the load L. When the power supplied to the load L is insufficient with only the power generated by the fuel cell 13, the insufficient power is supplied from the system power supply PS to the load L.

  As described above, while the fuel cell system 1 is connected to the system power source PS, the system power source PS may cause an abnormality such as a disturbance while the fuel cell system 1 is performing steady operation. When the system power supply PS fails, it is generally required to disconnect the distributed power supply such as the fuel cell system 1 from the system power supply PS from the viewpoint of ensuring the safety of the public and workers. However, if the power failure of the system power supply PS is instantaneous, if the system power supply PS is restored to the state before the instantaneous power failure with the distributed power sources disconnected from the system power supply PS all at once, Therefore, the power supply of the system power supply PS is insufficient, and there is a possibility that a power outage that would not have occurred unless the distributed power supply was disconnected was caused in a wide range. Considering such circumstances, the FRT requirements are examined so that the distributed power supply can be quickly connected to the system power supply PS when the power failure of the system power supply PS is instantaneous. Is underway. Therefore, in the fuel cell system 1, the following control is performed during steady operation in order to satisfy the FRT requirement.

  From here, the time chart shown in FIG. 3 is also referred to in conjunction with FIG. 2 and FIG. During steady operation of the fuel cell system 1, the control device 40, for example, during the period P1 from time t1 to time t2 in FIG. The flow rates of the raw material D and the reforming water W supplied to the reformer 11 related to the flow rate of the agent gas A and the flow rate of the fuel gas E supplied to the fuel cell 13 are also gradually increased. Further, for example, during the period P2 from time t3 to time t4 in FIG. 3, when the generated power of the fuel cell 13 is gradually reduced, the raw material D and the reforming related to the flow rate of the oxidant gas A and the flow rate of the fuel gas E The flow rate of water W is also gradually reduced. By doing in this way, the production | generation flow volume of the fuel gas E can be increased / decreased according to increase / decrease in the electric power generation of the fuel cell 13, and the appropriate utilization rate of hydrogen and oxygen (the flow rate used for the electric power generation in the fuel cell) It is possible to supply the fuel cell 13 with the fuel gas E and the oxidant gas A at a flow rate capable of maintaining a ratio of the flow rate supplied to the fuel cell). The control device 40 monitors whether or not an abnormality has occurred in the system power supply PS during the steady operation of the fuel cell system 1 (abnormality monitoring step: S3).

  In the abnormality monitoring step (S3), when the abnormality detector 35 does not detect the presence or absence of abnormality of the system power supply PS, the process returns to the abnormality monitoring step (S3) again. On the other hand, when the abnormality detector 35 detects an abnormality in the system power supply PS (time t5 or time t8 in FIG. 3), the control device 40 prevents the fuel cell system 1 from supplying power to the fuel cell system 1. The generated power of 13 is reduced (S4). Note that the gate block may be instantaneously performed when a phase change occurs due to an abnormality in the system power supply PS. In the step (S4) of reducing the generated power of the fuel cell 13, the control device 40 reduces the generated power of the fuel cell 13 until the generated power becomes a level that does not cause any inconvenience in the system power supply PS in which an abnormality has occurred. The generated power that does not cause inconvenience here is, for example, power that is consumed in an auxiliary device (raw material blower 22, reforming water pump 24, oxidant gas blower 27, etc.) provided in the fuel cell system 1. Can be reduced. In the present embodiment, the generated power of the fuel cell 13 is reduced to 20% of the generated power of the fuel cell 13 immediately before the abnormality of the system power supply PS is detected.

  As the generated power of the fuel cell 13 is reduced, the control device 40 adjusts the flow rates of the fuel gas E and the oxidant gas A supplied to the fuel cell 13 so as to satisfy the following conditions ( S5). The condition to be satisfied here is that the electric power supplied to the outside of the fuel cell system 1 within the return request time is set to a flow rate necessary for generating power by the fuel cell 13 to become a return request output. is there. Here, the “return request output” is electric power required to be supplied to the outside of the fuel cell system 1 when the abnormality of the system power supply PS is resolved. Further, the “return request time” is the time from the power recovery of the system power supply PS to the time limit for recovering the distributed power supply following this, in order to maintain the supply and demand balance in the system. The return request time in the present embodiment corresponds to a period P4 from time t6 to time t7 in FIG. In this embodiment, the return request output reached within the return request time P4 is 80% of the generated power of the fuel cell 13 immediately before the abnormality of the system power supply PS is detected. The return request output and the return request time are typically determined by an agreement (an agreement between electric utilities) between an operator that supplies the system power PS and an operator that supplies the distributed power source such as the fuel cell system 1. It is what Further, in the present embodiment, even after the return request time has elapsed, the fuel gas E and the oxidant are supplied in order to supply the power immediately before the abnormality of the system power supply PS is detected to the outside of the fuel cell system 1. In the step (S5) of adjusting the flow rate of the gas A, the flow rates of the fuel gas E and the oxidant gas A supplied to the fuel cell 13 are maintained at the flow rates immediately before the abnormality of the system power supply PS is detected. Yes. Thus, in order to adjust the flow rates of the fuel gas E and the oxidant gas A supplied to the fuel cell 13 so as to satisfy the above-described conditions, the flow rate just before the abnormality detection of the system power supply PS is maintained. included. Along with maintaining the flow rate of the fuel gas E supplied to the fuel cell 13 at the level immediately before the abnormality of the system power supply PS is detected, the flow rates of the raw material D and reformed water W supplied to the reformer 11 Also, the flow rate immediately before the abnormality of the system power supply PS is detected is maintained.

  The abnormality detector 35 detects the abnormality of the system power supply PS and reduces the generated power of the fuel cell 13 (S4), while the abnormality of the system power supply PS detects the flow rate of the fuel gas E supplied to the fuel cell 13. If the flow rate immediately before being maintained is maintained, the utilization rate of hydrogen in the fuel cell 13 decreases, the combustible component (hydrogen) contained in the fuel off-gas Fe increases, and the combustion state in the combustion section 15 may change. There is. However, when the generated power of the fuel cell 13 is reduced (S4), the flow rate of the oxidant gas A is maintained at the flow rate immediately before the abnormality of the system power supply PS is detected. The rate is also reduced, the amount of oxygen contained in the oxidant offgas Fa is increased, and the balance between the combustible component in the fuel offgas Fe and the amount of oxygen in the oxidant offgas Fa can be suppressed. In the fuel cell system 1, since both the fuel off-gas Fe and the oxidant off-gas Fa are guided to the combustion section 15 and burned, special control for off-gas F combustion is performed even if the composition of the off-gas F varies. Without this, combustion of the offgas F can be stabilized.

  The controller 40 decreases the generated power of the fuel cell 13 (S4) and adjusts the flow rates of the fuel gas E and the oxidant gas A (S5), and determines whether or not a predetermined time has passed (S6). . The predetermined time here is a time during which it is possible to determine whether or not the abnormality of the system power supply PS is instantaneous, and corresponds to the period P3 from time t5 to time t6 or from time t8 to t9 in FIG. In the step of determining whether or not the predetermined time has passed (S6), if the predetermined time has not elapsed, the step of determining whether or not the predetermined time has elapsed (S6) is continued. On the other hand, when a predetermined time has elapsed, it is determined whether or not the abnormality of the system power supply PS has been resolved (S7). The control device 40 determines whether or not the abnormality of the system power supply PS has been resolved based on a signal from the abnormality detector 35. It should be noted that the period from when the abnormality of the system power supply PS is detected until a predetermined time elapses corresponds to the standby process.

  In the step of determining whether or not the abnormality of the system power supply PS has been resolved (S7), when the abnormality is resolved, the control device 40 restarts the supply of power to the outside of the fuel cell system 1 in order to resume the supply of power to the fuel cell 13. Is recovered toward the generated power immediately before the abnormality of the system power supply PS is detected (immediately before time t5 in FIG. 3) (S8). Note that the gate block may be performed when a phase change occurs due to power recovery of the system power supply PS. At this time, the fuel cell 13 is supplied with the fuel gas E and the oxidant gas A at a flow rate suitable for generating the power immediately before the abnormality of the system power supply PS is detected. The power recovers quickly, and the power supplied to the outside of the fuel cell system 1 within the recovery request time P4 is the recovery request output (in this embodiment, 80% of the generated power immediately before the abnormality of the system power supply PS is detected). It recovers to 100% of the generated power immediately before the abnormality of the system power supply PS is detected shortly thereafter. As shown by a one-dot chain line Qc in FIG. 3, the flow rate of the fuel gas E or the like supplied to the fuel cell 13 is reduced from the time t5 when the abnormality of the system power source PS is detected to decrease the generated power in the fuel cell 13. In the case of a corresponding decrease, even if an attempt is made to increase the flow rate of the fuel gas E or the like supplied to the fuel cell 13 in order to recover the generated power of the fuel cell 13 from the time t6 when the abnormality of the system power supply PS is resolved, The flow rate of the fuel gas E and the like supplied to the fuel cell 13 does not increase immediately due to a delay in the response of the increase in the flow rate of the fuel gas E generation in the reformer 11, but returns as shown by a one-dot chain line Rc in FIG. The power supplied to the outside of the fuel cell system 1 within the requested time P4 cannot be recovered to the return request output, making it difficult to satisfy the FRT requirement. In contrast, in the fuel cell system 1 according to the present embodiment, the generated power of the fuel cell 13 is recovered so that the power supplied to the outside of the fuel cell system 1 becomes the return request output within the return request time P4. Can meet the FRT requirements. When the control device 40 recovers the power generated by the fuel cell 13, it returns to the abnormality monitoring step (S3) again.

  In the step of determining whether or not the abnormality of the system power supply PS has been resolved (S7), if the abnormality has not been resolved (see time t9 in FIG. 3), the control device 40 stops the output of the inverter 32. The supply of electric power to the outside of the fuel cell system 1 is stopped (S9), the flow rate of the fuel gas E supplied to the fuel cell 13 is reduced by reducing the amount of fuel gas E generated in the reformer 11, and The flow rate of the oxidant gas A supplied to the fuel cell 13 is decreased (S10). At this time, if the production of the fuel gas E in the reformer 11 is continued as a small amount, the start-up can be accelerated when the steady operation of the reformer 11 is resumed. Note that reducing the amount of fuel gas E generated in the reformer 11 includes reducing the amount of fuel gas E generated to 0, and in this case, the reformer 11 is stopped. At this time, the generation amount of the fuel gas E in the reformer 11 is set to 0, and the power generation of the fuel cell 13 itself is stopped. Alternatively, the production amount of the fuel gas E in the reformer 11 is reduced to a level that can be consumed in auxiliary equipment (such as the raw material blower 22, the reforming water pump 24, and the oxidant gas blower 27) provided in the fuel cell system 1. It is possible to wait until the abnormality of the system power supply PS is solved while continuing the power generation by the fuel cell 13 only for the power of the power. Thereafter, when the power generation in the fuel cell 13 is resumed, the flow shown in FIG. 2 is performed from the fuel gas generation step (S1).

  As described above, according to the fuel cell system 1 according to the present embodiment, when the abnormality of the system power supply PS is detected, the generated power of the fuel cell 13 is reduced while being supplied to the fuel cell 13. Since the flow rates of the fuel gas E (fuel gas E generated by the reformer 11) and the oxidant gas A are maintained at the flow rates just before the abnormality of the system power supply PS is detected, the abnormality of the system power supply PS is instantaneous. In the case of the target, the generated power of the fuel cell 13 can be restored to the power required for the power supplied to the outside of the fuel cell system 1 to become the return request output within the return request time P4. Can be satisfied. In addition, since both the fuel off-gas Fe and the oxidant off-gas Fa are burned in the combustion unit 15, when the abnormality of the system power supply PS is detected, the generated power of the fuel cell 13 is reduced while being supplied to the fuel cell 13. Even if the flow rates of the fuel gas E and the oxidant gas A are maintained as they were immediately before the abnormality of the system power supply PS is detected, the combustion of the off gas F in the combustion section 15 can be stably maintained. In particular, when the combustion heat of the offgas F is used for heating the reformer 11, the reformer 11 is stably heated and the generation of the fuel gas E is also stably continued. It is possible to prepare for the recovery of the generated power of the fuel cell 13 while maintaining the generation state of the gas E.

  Next, a fuel cell system 1A according to a modification of the embodiment of the present invention will be described with reference to FIG. FIG. 4 is a schematic system diagram of the fuel cell system 1A. The fuel cell system 1A is different from the fuel cell system 1 (see FIG. 1) in that an in-system load 51 is provided. As the in-system load 51, a battery (storage battery), a heater, an electric appliance in the home, and the like can be applied. Among them, when the battery is applied, the degree of freedom in using the electric power generated in the fuel cell 13 is improved. It is. In the present modification, the in-system load 51 is electrically connected between the inverter 32 and the abnormality detector 35 via a cable 59. As indicated by a dotted line, the converter 31 may be connected between the inverter 32 and the upstream of the converter 31 (between the fuel cell 13 and the converter 31). When the in-system load 51 is a battery, if it is connected upstream of the inverter 32, there is an advantage that it is not necessary to rectify to direct current. The cable 59 is provided with a relay 55. As the relay 55, an electromagnetic relay is typically used. The relay 55 is connected to the control device 40 via a signal cable, and is configured to receive a signal from the control device 40 and open and close the circuit. In the following description, when the relay 55 is open, the circuit is open and power is not supplied to the system load 51. When the relay 55 is closed, the circuit is closed and power is supplied to the system load 51. Is in a state of being supplied. The other configuration of the fuel cell system 1A is the same as that of the fuel cell system 1 (see FIG. 1).

  The operation of the fuel cell system 1A configured as described above is based on the power generation just before the abnormality of the system power supply PS is detected from the fuel gas generation step (S1) in the flow shown in FIG. The process up to power recovery (S8) is the same as that of the fuel cell system 1 (see FIG. 1). However, unlike the fuel cell system 1 (see FIG. 1), when the abnormality is not resolved in the step (S7) of determining whether or not the abnormality of the system power supply PS of the flow shown in FIG. Instead of the step of stopping the supply of power outside the system (S9) and the step of reducing the flow rate of the fuel gas E and the like supplied to the fuel cell 13 (S10), the operation is as follows.

  Hereinafter, description will be made with reference to the time chart shown in FIG. The time chart shown in FIG. 5 explains the operation method of the fuel cell system 1A, and the time chart from time t1 to time t8 is the same as the time chart shown in FIG. In the fuel cell system 1A, during normal operation in which no abnormality of the system power supply PS is detected and within a predetermined time after the abnormality of the system power supply PS is detected, the abnormality is resolved and the generated power of the fuel cell 13 is recovered. When performing the operation to be performed, the relay 55 is opened. When the abnormality has not been resolved in the step (S7) of determining whether or not the abnormality of the system power supply PS in the flow shown in FIG. 2 has been resolved (see time t9 ′ in FIG. 5), the control device 40 turns on the relay 55. The system is closed so that the power generated by the fuel cell 13 can be supplied to the in-system load 51, and the generated power of the fuel cell 13 is set just before the abnormality of the system power supply PS is detected (immediately before time t8 in FIG. 5). Recover toward the generated power. At this time, the fuel cell 13 is supplied with the fuel gas E and the oxidant gas A at a flow rate suitable for generating the power immediately before the abnormality of the system power supply PS is detected. Electricity will recover quickly. That is, in the fuel cell system 1A, the amount of fuel gas E generated in the reformer 11, and thus the fuel, even if the abnormality is not resolved even after a predetermined time has elapsed since the abnormality of the system power supply PS is detected. Power generation in the fuel cell 13 is continued without decreasing the flow rate of the fuel gas E supplied to the battery 13 and the flow rate of the oxidant gas A supplied to the fuel cell 13. When the power generated in the fuel cell 13 is supplied to the in-system load 51 and the abnormality of the system power supply PS is resolved, the control device 40 opens the relay 55 and uses the power generated in the fuel cell 13 as fuel. Supply outside battery system 1A. Since the power supplied to the outside of the fuel cell system 1A at this time is equivalent to the generated power immediately before the abnormality of the system power supply PS is detected, it can be quickly performed in a time shorter than or equal to that required by the FRT requirement. In addition, the supply of power to the outside of the fuel cell system 1A can be resumed. Note that when the abnormality of the system power supply PS is resolved and power is supplied to the outside of the fuel cell system 1A, the process may return to the flow abnormality monitoring step (S3) shown in FIG.

  As described above, according to the fuel cell system 1A according to the present modification, the fuel cell system 1A supplies the fuel cell 13 when the abnormality is not resolved even after a predetermined time has elapsed since the abnormality of the system power supply PS is detected. The generated power of the fuel cell 13 is recovered without reducing the flow rates of the fuel gas E and the oxidant gas A, so that the abnormality of the system power supply PS can be detected regardless of whether or not the abnormality of the system power supply PS has been resolved. The operation of the fuel cell 13 can be continued with the output before the detection, and when the abnormality of the system power source PS is resolved, the fuel cell system generates power equivalent to the generated power immediately before the abnormality of the system power source PS is detected. 1A can be supplied to the outside, and the supply of power to the outside of the fuel cell system 1A can be promptly restarted.

  In the above description, the reformer 11 performs the steam reforming reaction. However, the reformer 11 may be configured to perform the partial oxidation reforming reaction. In the case where the reformer 11 is configured to perform the partial oxidation reforming reaction, the reformer 11 is supplied with the reforming oxidant instead of the reforming water W. Instead of the reforming water pipe 23 provided, a reforming oxidant gas pipe provided with a reforming oxidant blower is connected to the reformer 11.

  In the above description, the fuel cell 13 is a cylindrical SOFC, but it may be a plate type (flat type). In addition, the combustion unit 15 has a structure formed in the space between the reformer 11 and the fuel cell 13, but the combustion unit 15 is configured as a combustion device having a burner that burns off-gas F. It may be. Further, the reformer 11 and the fuel cell 13 are configured to be accommodated in the casing, but the reformer 11 may be configured to be installed outside the casing. In this case, the heat of the exhaust gas can be used for heating the reformer 11 by supplying the exhaust gas generated by the combustion in the combustion unit 15 to the vicinity of the reformer 11. When a reforming catalyst that does not require heating is used in the reformer 11, it is not necessary to consider the heat transfer between the exhaust gas generated by the combustion in the combustion unit 15 and the reformer 11.

  In the above description, when the abnormality detector 35 detects an abnormality of the system power supply PS in the abnormality monitoring step (S3), the fuel gas E supplied to the fuel cell 13 is reduced while the generated power of the fuel cell 13 is reduced. The flow rate (including the production flow rate of the fuel gas E in the reformer 11) and the flow rate of the oxidant gas A are maintained at the flow rate immediately before the abnormality of the system power supply PS is detected for a predetermined time. The flow rates of the fuel gas E and the oxidant gas A supplied to the fuel cell 13 may be maintained at the flow rates just before the abnormality of the system power supply PS is detected for a predetermined time. Maintaining the flow rate substantially immediately before the abnormality of the system power supply PS is detected means that, when the abnormality of the system power supply PS is instantaneous, the abnormality is immediately after the abnormality is resolved (within the return request time P4). The flow rate of the fuel gas E supplied to the fuel cell 13 (to this) within a range in which the generated power of the fuel cell 13 can be recovered to the power necessary to output the power supplied to the outside of the fuel cell system 1 before the detection. This also means that the flow rate of the oxidant gas A and the flow rate of the raw material D and the reforming water W supplied to the accompanying reformer 11 are allowed.

  In the above description, when the abnormality detector 35 detects an abnormality of the system power supply PS in the abnormality monitoring step (S3), the fuel gas E supplied to the fuel cell 13 is reduced while the generated power of the fuel cell 13 is reduced. The flow rate (including the production flow rate of the fuel gas E in the reformer 11) and the flow rate of the oxidant gas A are maintained at the flow rate immediately before the abnormality of the system power supply PS is detected for a predetermined time. As described above, it is sufficient that the electric power supplied to the outside of the fuel cell system 1 within the return request time is a flow rate required to generate the power required for the fuel cell 13 to generate the return request output. If the return request output is relatively small, the flow rate of the fuel gas E and the oxidant gas A is adjusted in the step (S5) of adjusting the flow rate of the fuel gas E and the oxidant gas A, thereby reducing the raw material consumption and auxiliary equipment The amount of power consumption that can be reduced is relatively large. On the other hand, while reducing the generated power of the fuel cell 13, the flow rate of the fuel gas E supplied to the fuel cell 13 (including the generation flow rate of the fuel gas E in the reformer 11) and the flow rate of the oxidant gas A are When it is decided to maintain the flow rate immediately before the abnormality of the system power supply PS is detected, the step (S5) of adjusting the flow rates of the fuel gas E and the oxidant gas A in the flow shown in FIG. 2 can be omitted. Thus, the control can be simplified.

DESCRIPTION OF SYMBOLS 1 Fuel cell system 11 Reformer 13 Fuel cell 15 Combustion part 35 Abnormality detector 40 Control apparatus A Oxidant gas D Raw material E Fuel gas F Off gas Fe Fuel off gas Fa Oxidant off gas PS System power supply

Claims (5)

A fuel cell system linked to a grid power source;
A fuel cell for generating electric power to be supplied to the outside of the fuel cell system;
A reformer for reforming the introduced raw material into a fuel gas supplied to the fuel cell;
An abnormality detection unit for detecting an abnormality of the system power supply;
When the abnormality detection unit detects an abnormality in the system power supply, the generated power of the fuel cell is reduced while the generation flow rate of the fuel gas in the reformer is resolved. And a control unit for adjusting a return request output, which is electric power required to be supplied to the outside of the fuel cell system, to a flow rate necessary for power generation by the fuel cell and maintaining it for a predetermined time. Huh;
The fuel cell comprises a solid oxide fuel cell that generates electricity by introducing an oxidant gas and the fuel gas;
Of the fuel gas supplied to the fuel cell, a fuel off gas which is a gas not used for power generation, and among the oxidant gas supplied to the fuel cell, an oxidant off gas which is a gas not used for power generation And further comprising a combustion part for burning the fuel off gas by introducing
When the abnormality detection unit detects an abnormality in the system power supply, the control unit generates a flow rate of the fuel gas and the oxidant gas supplied to the fuel cell, and generates a return request output by the fuel cell. Configured to adjust to the flow rate necessary to maintain and maintain for a predetermined time;
Fuel cell system. Supplying power to the outside of the fuel cell system when the abnormality of the system power source is not resolved even after the predetermined time has elapsed after the abnormality detection unit detects the abnormality of the system power source. And a control for reducing the flow rate of the fuel gas generated in the reformer;
The fuel cell system according to claim 1. An in-system load that can use the power generated in the fuel cell when the fuel cell system is not supplying the power generated in the fuel cell to the outside;
The control unit restores the generated power of the fuel cell when the abnormality of the system power source is not resolved even after the predetermined time has elapsed after the abnormality detection unit detects the abnormality of the system power source. Configured to perform control to supply power generated in the fuel cell to the in-system load;
The fuel cell system according to claim 1.   The reformer is disposed above a portion where the fuel off gas is led out from the fuel cell, and a space between the fuel cell and the reformer is formed in the combustion unit;
  The fuel cell system according to any one of claims 1 to 3. A method of operating a fuel cell system linked to a grid power source;
A power generation step of generating electric power to be supplied outside the fuel cell system with a solid oxide fuel cell that generates power by introducing an oxidant gas and a fuel gas ;
A fuel gas generating step of generating the fuel gas supplied to the fuel cell;
Of the fuel gas supplied to the fuel cell, a fuel off gas which is a gas not used for power generation, and among the oxidant gas supplied to the fuel cell, an oxidant off gas which is a gas not used for power generation And a combustion step of burning the fuel off gas by introducing into the combustion section;
An abnormality monitoring step of monitoring the presence or absence of abnormality of the system power supply;
When the abnormality of the system power supply is detected in the abnormality monitoring step, the generated power of the fuel cell is reduced, while the generation flow rate of the fuel gas in the fuel gas generation step is solved by the abnormality of the system power supply. In this case, a return request output, which is power required to be supplied to the outside of the fuel cell system, is adjusted to a flow rate necessary for generating power by the fuel cell , and the fuel gas supplied to the fuel cell and the fuel cell A standby step of adjusting the flow rate of the oxidant gas to a flow rate required for generating the return request output by the fuel cell, maintaining the output for a predetermined time, and waiting for resolution of the abnormality of the system power supply. ;
Operation method of fuel cell system.

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