Fuel cell system

Abstract

This specification provides a technique for shortening the startup time in an FC system that has multiple FC stacks. [Solution] The FC system disclosed herein comprises a first / second FC stack, shared equipment, and a first / second controller. The shared equipment is shared by the first / second FC stack. The first controller performs a first FC first preparation process, a shared equipment operation to operate the shared equipment, and a first FC second preparation process. The second controller performs a second FC first preparation process and a second FC second preparation process. The first / second FC first preparation process is a process that can be executed even without a shared equipment operation, while the first / second FC second preparation process is a process that cannot be executed until a shared equipment operation has been performed. After the first controller has executed a shared equipment operation, it sends a completion signal for the shared equipment operation to the second controller, and after the second controller receives the completion signal, it executes the second FC second preparation process.

Description

Technical Field

[0005]

[0001] The technology disclosed in this specification relates to a fuel cell system including a plurality of fuel cell stacks.

Background Art

[0002] In a fuel cell system, it is necessary to execute a preparation process prior to the start of power generation of the fuel cell stack. In Patent Document 1, as a preparation process, a controller measures the voltage of each cell of the fuel cell stack and checks whether the voltage of each cell is within a normal range. If the voltage of each cell is within the normal range, the controller closes the relay at the output terminal of the fuel cell stack, and the state becomes ready for power supply. Hereinafter, for convenience of explanation, the "fuel cell" may be abbreviated as "FC". The "fuel cell system" may be abbreviated as "FC system", and the "fuel cell stack" may be abbreviated as "FC stack". "FC" is an abbreviation of "Fuel Cell".

[0003] In an FC system, in order to increase the output power, there may be a case where a plurality of FC stacks are provided (Patent Documents 2-4). In this case, it is necessary to perform a preparation process for each FC stack.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] In FC systems with multiple FC stacks, a single piece of equipment may be shared among multiple FC stacks. Furthermore, prior to the start of power generation in an FC stack, there are shared equipment operations to be performed, as well as FC preparation processes that must be carried out in each individual FC stack. If the FC preparation processes are performed in each FC stack only after the shared equipment operations are completed, the time until power generation can begin (i.e., the startup time) may be prolonged. This specification provides a technology that can shorten the startup time in an FC system with multiple FC stacks. [Means for solving the problem]

[0006] The FC system disclosed herein comprises a first FC stack, a second FC stack, shared equipment, a first controller, and a second controller. The shared equipment is equipment shared by the first FC stack and the second FC stack. Prior to the start of power generation of the first FC stack, the first controller performs the first FC preparation process, the shared equipment operation, and the second FC preparation process in this order. Prior to the start of power generation of the second FC stack, the second controller performs the second FC preparation process and the second FC preparation process in this order. The first FC preparation process and the second FC preparation process can be performed without the shared equipment operation, while the second FC preparation process and the second FC preparation process cannot be performed without the shared equipment operation. After performing the shared equipment operation, the first controller sends a completion signal to the second controller indicating that the shared equipment operation is complete. The second controller performs the second FC preparation process before receiving the completion signal, and performs the second FC preparation process after receiving the completion signal.

[0007] In the technology disclosed herein, the preparation process of the second controller is divided into a second FC first preparation process that does not require shared equipment operation and a second FC second preparation process that requires shared equipment operation. The second controller executes the second FC first preparation process without waiting for a completion signal. This process allows the FC system disclosed herein to shorten the startup time.

[0008] Details of the technology disclosed herein and further improvements are described in the following "Modes for Carrying Out the Invention". [Brief explanation of the drawing]

[0009] [Figure 1] This is a block diagram of the FC system in the embodiment. [Figure 2] This diagram illustrates the coordinated operation of the first and second controllers. [Figure 3] This diagram illustrates a modified example of the coordinated operation of the first and second controllers. [Modes for carrying out the invention]

[0010] The FC system 2 of this embodiment will be described with reference to the drawings. As mentioned earlier, "FC" is an abbreviation for "fuel cell". Figure 1 shows a block diagram of the FC system 2. The FC system 2 comprises two FC stacks (first FC stack 10a and second FC stack 10b). The output terminal of the first FC stack 10a is connected to the system output terminal 6 via a voltage converter 21a and an FC relay 22a, and the output terminal of the second FC stack 10b is connected to the system output terminal 6 via a voltage converter 21b and an FC relay 22b. In other words, the output terminals of the first FC stack 10a and the second FC stack 10b are connected in parallel to the system output terminal 6. The letters "CNTLR" in Figure 1 mean "controller".

[0011] The FC system 2 also includes a battery 3, the output terminal of which is connected to the system output terminal 6 via a voltage converter 4 and a battery relay 5. A device 100 that receives power from the FC system 2 is connected to the system output terminal 6.

[0012] The first FC stack 10a is accompanied by several auxiliary devices. In this specification, "auxiliary devices" means devices necessary for the operation of the FC stack (power generation by the FC stack). The first FC stack 10a is accompanied by a compressor 13a and pressure regulating valves 14a, 15a, 18a, and 19a as auxiliary devices. The compressor 13a is provided on the oxygen supply pipe 11a, which is connected to the oxygen inlet of the first FC stack 10a. The pressure regulating valve 14a is also provided on the oxygen supply pipe 11a. The pressure regulating valve 15a is provided on the oxygen exhaust pipe 12a, which is connected to the oxygen outlet of the first FC stack 10a. The other end of the oxygen exhaust pipe 12a is open to the atmosphere.

[0013] Compressor 13a compresses outside air and pumps oxygen (air) to the oxygen supply pipe 11a. Pressure regulating valve 14a adjusts the pressure of the oxygen (air) sent to the oxygen inlet of the first FC stack 10a. Pressure regulating valve 15a adjusts the pressure of the residual oxygen (residual air) discharged from the first FC stack 10a. Residual oxygen refers to the oxygen that was not used in the reaction in the FC stack. Compressor 13a, pressure regulating valves 14a and 15a are controlled by the first controller 20a. The first controller 20a controls these auxiliary devices and adjusts the amount of oxygen (air) supplied to the first FC stack 10a.

[0014] A pressure regulating valve 18a is provided on the hydrogen supply pipe 16a, one end of which is connected to the hydrogen inlet of the first FC stack 10a, and the other end of which is connected to the hydrogen tank 30. A pressure regulating valve 19a is provided on the hydrogen discharge pipe 17a, one end of which is connected to the hydrogen outlet of the first FC stack 10a. The other end of the hydrogen discharge pipe 17a is open to the atmosphere via a gas-liquid separator and muffler (not shown). The pressure regulating valve 18a regulates the pressure of the hydrogen supplied to the first FC stack 10a, and the pressure regulating valve 19a regulates the pressure of the residual hydrogen discharged from the first FC stack 10a. Residual hydrogen refers to hydrogen that was not used in the reaction in the FC stack. The pressure regulating valves 18a and 19a are controlled by a first controller 20a. The first controller 20a controls these auxiliary devices and adjusts the amount of hydrogen supplied to the first FC stack 10a. The pressure regulating valves 14a, 15a, 18a, and 19a can also completely close the flow path. When the first FC stack 10a is not in use, the first controller 20a closes the pressure regulating valves 14a, 15a, 18a, and 19a.

[0015] The auxiliary equipment associated with the second FC stack 10b is the same as that associated with the first FC stack 10a. That is, the second FC stack 10b is equipped with a compressor 13b and pressure regulating valves 14b, 15b, 18b, and 19b as auxiliary equipment. The compressor 13b and pressure regulating valve 14b are connected to the oxygen supply pipe 11b, and the pressure regulating valve 15b is connected to the oxygen discharge pipe 12b. The pressure regulating valve 18b is connected to the hydrogen supply pipe 16b, and the pressure regulating valve 19b is connected to the hydrogen discharge pipe 17b. The roles of these auxiliary equipment are the same as those of the auxiliary equipment in the first FC stack 10a.

[0016] Voltage converters 21a and 21b, and FC relays 22a and 22b are also considered auxiliary equipment. The first FC stack 10a and the second FC stack 10b are each associated with various other auxiliary equipment such as injectors, temperature sensors, and pressure sensors, but their illustrations and explanations are omitted.

[0017] The FC system 2 includes a first controller 20a that controls the auxiliary equipment of the first FC stack 10a and a second controller 20b that controls the auxiliary equipment of the second FC stack 10b. In addition to these two controllers, the FC system 2 includes a management controller 7. The management controller 7 monitors the state of the system main switch 8 and controls the opening and closing of the battery relay 5. Further, the management controller 7 communicates with a device 100 that receives power supply from the FC system 2 and obtains information on the power required by the device 100.

[0018] As is clear from FIG. 1, both the hydrogen supply pipes 16a and 16b are connected to the hydrogen tank 30. The hydrogen tank 30 is provided with a main stop valve 9, and by opening the main stop valve 9, hydrogen supply to the plurality of FC stacks 10a and 10b becomes possible. The main stop valve 9 is auxiliary equipment necessary for the power generation of the plurality of FC stacks 10a and 10b and is equipment shared by the plurality of FC stacks 10a and 10b. Equipment that is shared by the first FC stack 10a and the second FC stack 10b and is necessary for the power generation of each FC stack (auxiliary equipment) may hereinafter be referred to as shared equipment. The main stop valve 9 corresponds to the shared equipment.

[0019] In FIG. 1, the equipment with the symbol "a" attached is the exclusive auxiliary equipment of the first FC stack 10a, and the equipment with the symbol "b" attached is the exclusive auxiliary equipment of the second FC stack 10b. Hereinafter, when indicating one of the first FC stack 10a and the accompanying equipment (such as the compressor 13a and the oxygen supply pipe 11a) and the second FC stack 10b and the accompanying equipment (such as the compressor 13b and the oxygen supply pipe 11b) without distinction, the subscript "a" or "b" is removed and denoted as FC stack 10, compressor 13, oxygen supply pipe 11, etc.

[0020] In the FC system 2, several preparatory processes need to be executed before each FC stack 10 generates electricity. For example, the controller 20 closes the FC relay 22 to connect the output terminal of the FC stack 10 and the system output terminal 6. Also, the controller 20 operates the compressor 13, opens the pressure regulating valves 14 and 15 when the pressure upstream of the pressure regulating valve 14 reaches a predetermined threshold pressure, and vigorously blows oxygen into the cathode of the FC stack 10. By this process, the impurities remaining during the previous operation of the FC stack 10 are discharged from the FC stack 10. The process of vigorously blowing gas into the FC stack 10 to discharge impurities (or moisture) is called scavenging. The scavenging process is also performed on the hydrogen supply side (anode side). However, to blow hydrogen into the anode of the FC stack 10, it is necessary to open the main stop valve 9 of the hydrogen tank 30. In the FC system 2, each controller 20 controls the auxiliary equipment associated with each FC stack. The first controller 20a controls the shared equipment (main stop valve 9), and the second controller 20b cannot control it. In this case, the second controller 20b cannot perform the scavenging process of the anode until it knows that the main stop valve 9 has been opened. On the other hand, the scavenging process of the cathode can be executed by each individual controller 20 regardless of the state of the shared equipment (main stop valve 9).

[0021] Fig. 2 shows a flowchart of the preparatory processes executed by the first controller 20a and the second controller 20b (and the management controller 7). Fig. 2 also shows the cooperative operation of the first controller 20a, the second controller 20b, and the management controller 7.

[0022] When the management controller 7 detects that the system main switch 8 is turned ON, it sends a startup command to each of the first controller 20a and the second controller 20b (steps S32, S33). Although not shown in the figure, when the management controller 7 detects that the system main switch 8 is turned ON, it closes the battery relay 5.

[0023] Upon receiving a start command, the first controller 20a executes the first FC first preparation process (step S12). The first FC first preparation process is a preparation process that can be executed without operating the main shut-off valve 9 (shared equipment). In the system configuration shown in Figure 1, the first FC first preparation process consists of closing the FC relay 22a and scavenging the cathode electrode. As mentioned earlier, the first controller 20a drives the compressor 13a, and when the pressure upstream of the pressure regulating valve 14a exceeds a predetermined threshold pressure, it opens the pressure regulating valves 14a and 15a. Oxygen (air) flows vigorously to the cathode electrode of the first FC stack 10a, and impurities on the cathode electrode are discharged.

[0024] The start command is also sent to the second controller 20b. Upon receiving the start command, the second controller 20b executes the second FC first preparation process (step S22). The second FC first preparation process is the same as the first FC first preparation process, and the second controller 20b closes the FC relay 22b and performs scavenging of the cathode electrode of the second FC stack 10b. That is, the second controller 20b drives the compressor 13b, and when the pressure upstream of the pressure regulating valve 14b exceeds a predetermined threshold pressure, it opens the pressure regulating valves 14b and 15b. Oxygen (air) flows vigorously to the cathode electrode of the second FC stack 10b, and impurities on the cathode electrode are discharged.

[0025] Prior to performing anode scavenging, the main shut-off valve 9 of the hydrogen tank 30 must be opened. Since the second controller 20b cannot control the main shut-off valve 9 (shared equipment), it waits until it receives an operation completion signal indicating that the process of opening the main shut-off valve 9 (shared equipment operation) is complete (step S23).

[0026] Meanwhile, after completing the first FC first preparation process, the first controller 20a performs a shared equipment operation (step S13). The shared equipment operation is the process of operating equipment (auxiliary equipment) shared by the first FC stack 10a and the second FC stack 10b in preparation for power generation. In this embodiment, the shared equipment operation is the process of opening the main shut-off valve 9. The main shut-off valve 9 is controlled only by the first controller 20a. When the first controller 20a opens the main shut-off valve 9, it sends a signal to the management controller 7 notifying that the main shut-off valve 9 has been opened, that is, a signal indicating the completion of the shared equipment operation (operation completion signal) (step S14). Upon receiving the operation completion signal, the management controller 7 sends the same signal to the second controller 20b (step S34).

[0027] Upon receiving the operation completion signal, the second controller 20b executes the second FC second preparation process (step S24). The second FC second preparation process is a preparatory process that requires opening the main shut-off valve 9 (i.e., operating the shared equipment) in advance, and in this embodiment, it is the scavenging of the anode electrode. As the first controller 20a opened the main shut-off valve 9 in the shared equipment operation in step S13, the upstream side of the pressure regulating valves 18a and 18b is the same as the internal pressure of the hydrogen tank 30. The second controller 20b opens the pressure regulating valves 18b and 19b. Hydrogen in the hydrogen tank 30 flows vigorously through the second FC stack 10b, and impurities at the anode electrode of the second FC stack 10b are exhausted.

[0028] Having transmitted an operation completion signal, the first controller 20a then performs the first FC second preparation process (step S15). The first FC second preparation process, like the second FC second preparation process, is the scavenging of the anode electrode. The first controller 20a opens the pressure regulating valves 18a and 19a. Hydrogen in the hydrogen tank 30 flows vigorously through the first FC stack 10a, and impurities at the anode electrode of the first FC stack 10a are exhausted.

[0029] The first controller 20a sends a signal (ready signal) to the management controller 7 indicating that all preparation work is complete and the first FC stack 10a is ready to generate power (step S16). Similarly, the second controller 20b, after completing the second preparation process for the second FC, also notifies the management controller 7 of a signal (ready signal) indicating that the second FC stack 10b is ready to generate power (step S25). Having received ready signals from both controllers 20a and 20b, the management controller 7 determines the target output for each FC stack based on the power request of the device 100 and notifies the respective controllers 20a and 20b (step S35). The first controller 20a controls the auxiliary equipment of the first FC stack 10a (i.e., the compressor 13a, pressure regulating valves 14a, 15a, 18a, 19a, and voltage converter 21a) so that the output of the first FC stack 10a follows the target output (step S17). Similarly, the second controller 20b controls the auxiliary equipment of the second FC stack 10b (i.e., the compressor 13b, pressure regulating valves 14b, 15b, 18b, 19b, and voltage converter 21b) so that the output of the second FC stack 10b follows the target output (step S26). Steps S35 and S17 / S26 are repeated until the system main switch 8 is turned OFF or until device 100 sends a power supply stop command to the management controller 7.

[0030] The advantages of the preparation process for FC system 2 are explained. FC system 2 is equipped with multiple FC stacks 10a and 10b, and the hydrogen tank 30 and main shut-off valve 9 are shared by the multiple FC stacks 10a and 10b. The main shut-off valve 9 can be controlled by the first controller 20a, but not by the second controller 20b. The second controller 20b cannot complete the preparation process for the second FC stack 10b unless the first controller 20a opens the main shut-off valve 9.

[0031] In FC system 2, the preparation process is divided into first preparation process (first FC first preparation process, second FC first preparation process) and second preparation process (first FC second preparation process, second FC second preparation process). The first FC (second FC) first preparation process is a process that is executed prior to the start of power generation of the first FC (second FC) stack 10a (10b), and can be executed regardless of the state of the shared equipment (main shut-off valve 9). On the other hand, the first (second) FC second preparation process is a process that is executed prior to the start of power generation of the first FC (second FC) stack 10a (10b), and cannot be executed unless the shared equipment (main shut-off valve 9) is operated to a predetermined state in advance.

[0032] If the first controller 20a opens the main shut-off valve 9 and then the second controller 20b starts a series of preparation processes for the second FC stack 10b, the time required for the second FC stack 10b to become capable of generating power (i.e., the startup time) will be longer. Therefore, in the FC system 2, the preparation process is divided into a first preparation process and a second preparation process. The second controller 20b then executes the first preparation process (second FC first preparation process) regardless of shared equipment operation. When the first controller 20a performs a shared equipment operation, it sends an operation completion signal to the second controller 20b indicating that the operation of the shared equipment has been completed. The second controller 20b waits for the operation completion signal and then executes the second preparation process (second FC second preparation process).

[0033] The FC system 2 disclosed herein divides the preparation process into two stages (a first preparation process that does not require shared equipment operation and a second preparation process that requires shared equipment operation), and each controller executes the first preparation process before the shared equipment operation. Since the preparation processes that each of the multiple FC controllers can execute are executed in parallel, the startup time can be shortened.

[0034] In addition, in the flowchart of Figure 2, the ready signal transmitted by the first controller 20a may be sent directly to the second controller 20b without going through the management controller 7.

[0035] (Modified Example) A modified example of the coordinated operation of the first / second controllers 20a / 20b is described. Figure 3 shows a flowchart of the preparation process in the modified example. In this modified example, the first controller 20a also functions as the management controller 7. When the first controller 20a detects that the system main switch 8 is ON, it sends a start command to the second controller 20b (steps S112, S113). After that, the first controller 20a executes the first FC first preparation process (step S12). The second controller 20b, having received the start command, executes the second FC first preparation process (step S22). The second controller 20b waits until it receives an operation completion signal (a signal indicating that the operation of the shared equipment has been completed) (step S23).

[0036] Meanwhile, the first controller 20a, having completed the first FC first preparation process, performs shared equipment operation (step S13). The first controller 20a, having performed the shared equipment operation, sends an operation completion signal to the second controller 20b (step S14). Then, the first controller 20a performs the first FC second preparation process (step S15). Having completed all preparation processes, the first controller 20a waits for a readiness completion signal from the second controller 20b (step S114).

[0037] Upon receiving the operation completion signal, the second controller 20b executes the second FC second preparation process (step S24). The second controller 20b sends a ready signal to the first controller 20a indicating that all preparation processes are complete and the second FC stack 10b is ready to generate power (step S25). Upon receiving the ready signal, the first controller 20a determines the target output of each FC stack based on the power request of the device 100 (step S115). The first controller 20a transmits the target output to the second controller 20b and controls the auxiliary equipment of the first FC stack 10a so that its output follows the target output (step S17). Upon receiving the target output, the second controller 20b controls the auxiliary equipment of the second FC stack 10b so that its output follows the target output (step S26).

[0038] The modified flowchart also shows that the FC system 2 can shorten its startup time.

[0039] The following points concern the technology described in the embodiment. In the FC system 2 of the embodiment, the main shut-off valve 9 of the hydrogen tank 30 corresponds to a shared piece of equipment, and the operation of opening the main shut-off valve 9 corresponds to a shared piece of equipment operation. The shared piece of equipment is not limited to the main shut-off valve 9. For example, when one compressor is shared by multiple FC stacks, the compressor corresponds to a shared piece of equipment, and the operation of driving the compressor for cathode scavenging corresponds to a shared piece of equipment operation. In this case, the cathode scavenging process, which involves opening the cathode-side pressure regulating valves 14a, 15a (14b, 15b), corresponds to the second preparation process of the first FC (second FC).

[0040] Alternatively, if one battery supplies power to the compressors of multiple FC stacks, the relay between the battery and the multiple compressors corresponds to a shared device, and the operation of closing the relay corresponds to the operation of the shared device. In this case, the cathode scavenging process using the compressor corresponds to the second preparation process of the first FC (second FC).

[0041] The first controller 20a and the second controller 20b (and the management controller 7) may be implemented in separate computers, or they may be implemented as tasks (programs) on a single computer. In other words, the first controller 20a and the second controller 20b (and the management controller 7) may be implemented as independent programs on a single multitasking computer.

[0042] The technology disclosed herein may be applied to an FC system comprising three or more FC stacks.

[0043] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness. [Explanation of Symbols]

[0044] 2: FC system 3: Battery 4: Voltage converter 5: Battery relay 6: System output terminal 7: Management controller 8: System main switch 9: Main shut-off valve 10: FC stack 11: Oxygen supply pipe 12: Oxygen exhaust pipe 13: Compressor 14, 15, 18, 19: Pressure regulating valve 16: Hydrogen supply pipe 17: Hydrogen exhaust pipe 20: Controller 21: Voltage converter 22: FC relay 30: Hydrogen tank 100: Device

Claims

[Claim 1] First fuel cell stack and second fuel cell stack, The shared equipment used by the first fuel cell stack and the second fuel cell stack, Prior to the start of power generation of the first fuel cell stack, a first controller executes the first FC first preparation process, the shared equipment operation for operating the shared equipment, and the first FC second preparation process in this order, Prior to the start of power generation of the second fuel cell stack, a second controller executes the second FC first preparation process and the second FC second preparation process in this order, It is equipped with, The first FC first preparation process and the second FC first preparation process are processes that do not require the operation of the shared equipment. The first FC second preparation process and the second FC second preparation process are processes that require the operation of the shared equipment. When the first controller has performed the shared equipment operation, it sends a completion signal to the second controller indicating that the shared equipment operation has been completed. A fuel cell system in which the second controller performs the second FC first preparation process before receiving the completion signal, and performs the second FC second preparation process after receiving the completion signal.

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