Fuel cell system and control method thereof

Abstract

A fuel cell system (110) includes a fuel cell unit (120) and a control device (130). The fuel cell unit (120) includes a plurality of fuel cells (125). Each fuel cell (125) has an output power range. An upper limit of the output power range is rated output power. Here, output power of the fuel cell unit (120) is referred to as unit output power. The control device (130) controls the unit output power. The control device (130) controls output power of each fuel cell (125) such that the number of fuel cells (125) outputting the rated output power takes a maximum value according to the unit output power and the output power range of each fuel cell (125).

Description

FUEL CELL SYSTEM AND CONTROL METHOD THEREOF

[0001] The present disclosure relates to a fuel cell system and a control method thereof.

[0002] Patent Literature 1 discloses a fuel cell system including a plurality of fuel cells. In this system, fuel cells to be activated and fuel cells to be deactivated are determined based on the number of activations of each fuel cell. Patent Literature 1 states an effect that it is possible to inhibit some fuel cells from being degraded earlier than the other fuel cells.

[0003] JP 2023-047079 A

[0004] The present disclosure provides a technology suitable for reducing the cost per power generation of a fuel cell system.

[0005] The present disclosure provides a fuel cell system including: a fuel cell unit including a plurality of fuel cells, each fuel cell having an output power range whose upper limit is rated output power; and a control device that controls unit output power that is output power of the fuel cell unit, the control device controlling output power of each fuel cell such that the number of fuel cells outputting the rated output power takes a maximum value according to the unit output power and the output power range of each fuel cell.

[0006] In another aspect, the present disclosure provides a control method for a fuel cell system including a fuel cell unit including a plurality of fuel cells, each fuel cell having an output power range whose upper limit is rated output power, when it is assumed that output power of the fuel cell unit is referred to as unit output power, the method including controlling output power of each fuel cell such that the number of fuel cells outputting the rated output power takes a maximum value according to the unit output power and the output power range of each fuel cell, thereby controlling the unit output power.

[0007] The technology according to the present disclosure is suitable for reducing the cost per power generation of the fuel cell system.

[0008] Fig. 1 illustrates a configuration of a fuel cell system according to Embodiment 1.Fig. 2 is a time chart illustrating a control by a control device.

[0009] (Findings and the like on which the present disclosure is based) In Patent Literature 1, the fuel cell is operated so as to output power that is 40% to 60% of the maximum output power of the fuel cell. Studies by the present inventors revealed that the operation method of Patent Literature 1 is not suitable for reducing the cost per power generation of the fuel cell system. The reason is as follows. That is, a lifetime operation period of the fuel cell is consumed by an operation in which generated power of the fuel cell is low, so that it is difficult to obtain a sufficient amount of generated power. Thus, the present inventors have studied the technology suitable for reducing the cost per power generation of the fuel cell system.

[0010] An embodiment will be described in detail below with reference to the drawings. However, an unnecessarily detailed description may be omitted. For example, a detailed description of the matters already well known and a repeated description of substantially the same configuration may be omitted.

[0011] The accompanying drawings and the following description are provided for those skilled in the art to fully understand the present disclosure, and thus are not intended to limit the subject matters recited in the claims to these.

[0012] (Embodiment 1) [1-1. Configuration] Fig. 1 illustrates a configuration of a fuel cell system 110 according to Embodiment 1. The fuel cell system 110 includes a fuel cell unit 120 and a control device 130. The fuel cell unit 120 includes a plurality of fuel cells 125.

[0013] The fuel cell system 110 supplies power to a load 140. The load 140 is, for example, a factory, a hospital, a school, a commercial facility, an office building, or the like.

[0014] Each fuel cell 125 is capable of performing rated power generation and partial-load power generation. The rated power generation generates rated generation power. Hereinafter, the output power at the time of rated power generation is sometimes referred to as rated output power. The partial-load power generation generates power less than the rated generation power. The output power at the time of partial-load power generation is less than the rated output power. The fuel cell 125 is, for example, a polymer electrolyte fuel cell (PEFC), a solid oxide fuel cell (SOFC), or the like.

[0015] The fuel cell 125 reaches the end of service life through operation. Here, it is assumed that operating the fuel cells 125 is accompanied by power generation. Specifically, a lifetime operation period and the number of lifetime activations are provided for each fuel cell 125.

[0016] The lifetime operation period of the fuel cell 125 is a cumulative period in which the fuel cell 125 is operable, counted from when the fuel cell 125 is new. In the fuel cell system 110, a fuel cell 125, whose cumulative operation period counted from when it was new has reached the lifetime operation period, is not operated anymore.

[0017] The number of lifetime activations of the fuel cell 125 is a cumulative number of times the fuel cell 125 can be activated, counted from when the fuel cell 125 is new. In the fuel cell system 110, a fuel cell 125, whose cumulative number of activations counted from when it was new has reached the number of lifetime activations, is not operated anymore.

[0018] In Embodiment 1, the fuel cells 125 have the same specification. The fuel cells 125 have the same lifetime operation period, and the same number of lifetime activations. The fuel cells 125 may be degraded at the same speed if being used in the same manner.

[0019] The control device 130 is, for example, a computer including a memory and a processor. Programs required for control are stored in the memory. The processor reads out a program from the memory and executes the program.

[0020] The control device 130 controls output power of the fuel cell unit 120 (hereinafter referred to as unit output power). Specifically, the control device 130 controls the unit output power so as to follow request power requested by the load 140 connected to the fuel cell system 110. More specifically, the control device 130 controls the output powers of the fuel cells 125 such that the unit output power follows the request power of the load 140.

[0021] In a typical example, the fuel cell unit 120 includes a plurality of power converters (not shown). The power converters are one-to-one corresponding to the fuel cells 125. The output power of each fuel cell 125 is DC output power. The DC output power of a fuel cell 125 is converted to AC power by a power converter corresponding to the fuel cell 125. Thus, the AC power is outputted by the combination of the fuel cell 125 and the power converter. AC powers from one or a plurality of the combinations are supplied to the load 140 as the unit output power.

[0022] [1-2. Operation] Each of the fuel cells 125 in the fuel cell unit 120 has an output power range. In Embodiment 1, the output power ranges of the fuel cells 125 are based on the specification of the fuel cells 125. The output power ranges of the fuel cells 125 may be nominal values. The output power ranges of the fuel cells 125 are described in, for example, the specification of the fuel cells 125. The output power range of each of the fuel cells 125 is stored in the memory of the control device 130.

[0023] An upper limit of the output power range of each fuel cell 125 is the rated output power of the fuel cell 125. In Embodiment 1, a lower limit of the output power range of each fuel cell 125 is not defined, and the control device 130 can transmit, to each fuel cell 125, an instruction for causing the fuel cell 125 to output very small (e.g., almost zero) power. In Embodiment 1, the fuel cells 125 have the same rated output power.

[0024] The control device 130 controls the output power of each fuel cell 125 such that the number of fuel cells 125 outputting the rated output power takes a maximum value according to the unit output power and the output power range of each fuel cell 125. In this configuration, a situation in which the lifetime operation period of the fuel cell 125 is consumed by an operation in which the generated power of the fuel cell 125 is low, hardly occurs. This is advantageous in terms of increasing the lifetime power generation of each fuel cell 125, reducing the cost per power generation of the fuel cell system 110, and realizing inexpensive power supply.

[0025] Here, the lifetime power generation of each fuel cell 125 is, specifically, the total amount of power (“amount of power” is also referred to as “electrical energy”) that the fuel cell 125 generates from when it is new to when it is discarded. The cost per power generation (“cost per power generation” is also referred to as “unit price of power generation”) of the fuel cell system 110 is, specifically, a value obtained by dividing the total of equipment costs of the fuel cells 125 in the fuel cell unit 120 by the total lifetime power generation of the fuel cells 125 in the fuel cell unit 120.

[0026] Hereinafter, the control by the control device 130 will be further described with reference to Fig. 2. Fig. 2 is a time chart illustrating the control by the control device 130. In Fig. 2, the horizontal axis represents time, and the vertical axis represents power. A solid line 171 represents the unit output power. A diagonal line hatching 175 schematically represents the output power of a fuel cell 125 performing rated power generation. A dotted hatching 176 schematically represents the output power of a fuel cell 125 performing partial-load power generation.

[0027] In the example shown in FIG. 2, the control device 130 controls the output power of each fuel cell 125 such that, in each control cycle CS, the number of fuel cells 125 outputting the rated output power takes the maximum value according to the unit output power and the output power range of each fuel cell 125. Thus, the control device 130 controls the unit output power in each control cycle CS.

[0028] Specifically, the control device 130 creates an operation plan for the fuel cell unit 120. The operation plan indicates the unit output power and the output power of each fuel cell 125 for each control cycle CS. The output power of each fuel cell 125 in the operation plan is set such that the number of fuel cells 125 outputting the rated output power takes the maximum value according to the unit output power and the output power range of each fuel cell 125. The control device 130 controls the unit output power and the output power of each fuel cell 125 according to the operation plan.

[0029] In a typical example, the control device 130 repeatedly executes a set of creation of an operation plan and control according to the created operation plan. The operation plan represents a plan of operation of the fuel cell unit 120 for a predetermined period. In the example shown in Fig. 2, the predetermined period is 24 hours.

[0030] Creating the operation plan is not essential. For example, the control device 130 may be caused to perform a control for sequentially changing the unit output power and the output power of each fuel cell 125 while monitoring the request power of the load 140.

[0031] In Embodiment 1, in the case of increasing the unit output power so as to satisfy a first increase condition, the control device 130 executes a first increase control. Hereinafter, the first increase condition and the first increase control will be described. In the following description, ・ The rated output power of the fuel cell 125 is expressed as WRAT. ・ The number of operating fuel cells 125 before the increase in the unit output power is expressed as MA1. Here, MA1is an integer not less than 0. ・ The unit output power after the increase in the unit output power is expressed as WA2. ・ A value for X1that satisfies WA2=X1×WRATis expressed as MA2. Here, X1is a natural number not less than 1. ・ |MA2-MA1| is expressed as ΔMA. Here, ΔMAis an integer not less than 0. Note that |z| represents an absolute value of z.

[0032] The first increase condition includes conditions that ・ WA2＞MA1×WRAT, and ・ WA2is divisible by WRAT.

[0033] The first increase control controls the output power of each fuel cell 125 such that ・ ΔMAfuel cells 125 are activated and thereby the number of operating fuel cells 125 becomes MA2, and ・ the output powers of the MA2fuel cells 125 become WRAT.

[0034] An example of numerical values in the first increase condition and the first increase control according to Embodiment 1 is as follows. ・ WRAT=5 kW, ・ MA1=10, ・ WA2=55 kW, ・ MA2=11, and ・ ΔMA=1.

[0035] In Embodiment 1, in the case of decreasing the unit output power so as to satisfy a first decrease condition, the control device 130 executes a first decrease control. Hereinafter, the first decrease condition and the first decrease control will be described. In the following description, ・ The rated output power of the fuel cell 125 is expressed as WRAT. ・ The number of operating fuel cells 125 before the decrease in the unit output power is expressed as MB1. Here, MB1is a natural number not less than 2. ・ The unit output power after the decrease in the unit output power is expressed as WB2. ・ A value for X2that satisfies WB2=X2×WRATis expressed as MB2. Here, X2is a natural number not less than 1. ・ |MB2-MB1| is expressed as ΔMB. Here, ΔMBis an integer not less than 0.

[0036] The first decrease condition includes conditions that ・ WB2＜MB1×WRAT, and ・ WB2is divisible by WRAT.

[0037] The first decrease control controls the output power of each fuel cell 125 such that ・ ΔMBfuel cells 125 are deactivated and thereby the number of operating fuel cells 125 becomes MB2, and ・ the output powers of MB2fuel cells 125 become WRAT.

[0038] An example of numerical values in the first decrease condition and the first decrease control according Embodiment 1 is as follows. ・ WRAT=5 kW, ・ MB1=10, ・ WB2=40 kW, ・ MB2=8, and ・ ΔMB=2.

[0039] In Embodiment 1, in the case of increasing the unit output power so as to satisfy a second increase condition, the control device 130 executes a second increase control. Hereinafter, the second increase condition and the second increase control will be described. In the following description, ・ The rated output power of the fuel cell 125 is expressed as WRAT. ・ The number of operating fuel cells 125 before the increase in the unit output power is expressed as MC1. Here, MC1is an integer not less than 0. ・ The unit output power after the increase in the unit output power is expressed as WC2. ・ A value for X3that satisfies (X3-1)×WRAT＜WC2＜X3×WRATis expressed as MC2. Here, X3is a natural number not less than 1. ・ |MC2-MC1| is expressed as ΔMC. Here, ΔMCis an integer not less than 0. ・ MC2-1 is expressed as MCRAT. ・ WC2-MCRAT×WRATis expressed as δWC.

[0040] The second increase condition includes conditions that ・ WC2＞MC1×WRAT, and ・ WC2is not divisible by WRAT.

[0041] The second increase control controls the output power of each fuel cell 125 such that ・ ΔMCfuel cells 125 are activated and thereby the number of operating fuel cells 125 becomes MC2, ・ the output powers of MCRATfuel cells 125 become WRAT, ・ the output power of one fuel cell 125 becomes δWC, and ・ the total of the output powers of the MC2fuel cells 125 becomes WC2. Here, the expression “such that ... the total of the output powers of the MC2fuel cells 125 becomes WC2” does not intend to limit the value of MC2. As understood from the above explanation, MC2can be one, and MC2can be two or more. This can be applied to other similar expressions.

[0042] An example of numerical values in the second increase condition and the second increase control according to Embodiment 1 is as follows. ・ WRAT=5 kW, ・ MC1=10, ・ WC2=56 kW, ・ MC2=12, ・ ΔMC=2, ・ MCRAT=11, and ・ δWC=1 kW.

[0043] In Embodiment 1, in the case of decreasing the unit output power so as to satisfy a second decrease condition, the control device 130 executes a second decrease control. Hereinafter, the second decrease condition and the second decrease control will be described. In the following description, ・ The rated output power of the fuel cell 125 is expressed as WRAT. ・ The number of operating fuel cells 125 before the decrease in the unit output power is expressed as MD1. Here, MD1is a natural number not less than 1. ・ The unit output power after the decrease in the unit output power is expressed as WD2. ・ A value for X4that satisfies (X4-1)×WRAT＜WD2＜X4×WRATis expressed as MD2. Here, X4is a natural number not less than 1. ・ |MD2-MD1| is expressed as ΔMD. Here, ΔMDis an integer not less than 0. ・ MD2-1 is expressed as MDRAT. ・ WD2-MDRAT×WRATis expressed as δWD.

[0044] The second decrease condition includes conditions that ・ WD2＜MD1×WRAT, and ・ WD2is not divisible by WRAT.

[0045] The second decrease control controls the output power of each fuel cell 125 such that ・ ΔMDfuel cells 125 are deactivated and thereby the number of operating fuel cells 125 becomes MD2, ・ the output powers of MDRATfuel cells 125 become WRAT, ・ the output power of one fuel cell 125 becomes δWD, and ・ the total of the output powers of the MD2fuel cells 125 becomes WD2.

[0046] An example of numerical values in the second decrease condition and the second decrease control according to Embodiment 1 is as follows. ・ WRAT=5 kW, ・ MD1=10, ・ WD2=41 kW, ・ MD2=9, ・ ΔMD=1, ・ MDRAT=8, and ・ δWD=1 kW.

[0047] Some other embodiments will be described below. In the following description, elements common to the already described embodiment and embodiments described below are denoted by the same reference characters, and the description thereof may be omitted. The descriptions for the respective embodiments may be applied to each other as long as there is no technical contradiction. The embodiments can be combined with each other as long as there is no technical contradiction.

[0048] (Embodiment 2) In Embodiment 2, a lower limit of the output power range of each fuel cell 125 is defined. Hereinafter, the lower limit is referred to as a minimum output power. That is, in Embodiment 2, the output power range of each fuel cell 125 is a range from the minimum output power of the fuel cell 125 to the rated output power of the fuel cell 125.

[0049] The minimum output power is larger than zero. The minimum output power of each fuel cell 125 is, for example, a value of 10% or more and 90% or less of the rated output power of the fuel cell 125. The minimum output power may be a value of 20% or more and 60% or less of the rated output power, or a value of 30% or more and less than 50% of the rated output power.

[0050] In Embodiment 2, the fuel cells 125 have the same minimum output power. The fuel cells 125 have the same rated output power.

[0051] In Embodiment 2, in the case of increasing the unit output power so as to satisfy a third increase condition, the control device 130 executes a third increase control. Hereinafter, the third increase condition and the third increase control will be described. In the following description, ・ The rated output power of the fuel cell 125 is expressed as WRAT. ・ The minimum output power of the fuel cell 125 is expressed as WMIN. ・ The number of operating fuel cells 125 before the increase in the unit output power is expressed as ME1. Here, ME1is an integer not less than 0. ・ The unit output power after the increase in the unit output power is expressed as WE2. ・ A value for X5that satisfies (X5-1)×WRAT＜WE2＜X5×WRATis expressed as ME2. Here, X5is a natural number not less than 1. ・ ME2-1 is expressed as METEM. ・ WE2-METEM×WRATis expressed as δWE. ・ |ME2-ME1| is expressed as ΔME. Here, ΔMEis an integer not less than 0. ・ A minimum value for X6that satisfies (X6-1)×WRAT+δWE≧X6×WMINis expressed as MEPAR. Here, X6is a natural number not less than 1. ・ ME2-MEPARis expressed as MERAT.

[0052] The third increase condition includes conditions that ・ WE2＞ME1×WRAT, ・ WE2is not divisible by WRAT, and ・ δWE＜WMIN.

[0053] The third increase control controls the output power of each fuel cell 125 such that ・ ΔMEfuel cells 125 are activated and thereby the number of operating fuel cells 125 becomes ME2, ・ the output powers of MERATfuel cells 125 become WRAT, ・ the output powers of MEPARfuel cells 125 become less than WRAT, and ・ the total of the output powers of the ME2fuel cells 125 becomes WE2.

[0054] An example of numerical values in the third increase condition and the third increase control according to Embodiment 2 is as follows. ・ WRAT=5 kW, ・ WMIN=4 kW, ・ ME1=10, ・ WE2=56 kW, ・ ME2=12, ・ METEM=11, ・ δWE=1 kW, ・ ΔME=2, ・ MEPAR=4, and ・ MERAT=8.

[0055] In Embodiment 2, in the case of decreasing the unit output power so as to satisfy a third decrease condition, the control device 130 executes a third decrease control. Hereinafter, the third decrease condition and the third decrease control will be described. In the following description, ・ The rated output power of the fuel cell 125 is expressed as WRAT. ・ The minimum output power of the fuel cell 125 is expressed as WMIN. ・ The number of operating fuel cells 125 before the decrease in the unit output power is expressed as MF1. Here, MF1is a natural number not less than 2. ・ The unit output power after the decrease in the unit output power is expressed as WF2. ・ A value for X7that satisfies (X7-1)×WRAT＜WF2＜X7×WRATis expressed as MF2. Here, X7is a natural number not less than 1. ・ MF2-1 is expressed as MFTEM. ・ WF2-MFTEM×WRATis expressed as δWF. ・ |MF2-MF1| is expressed as ΔMF. Here, ΔMFis an integer not less than 0. ・ A minimum value for X8that satisfies (X8-1)×WRAT+δWF≧X8×WMINis expressed as MFPAR. Here, X8is a natural number not less than 1. ・ MF2-MFPARis expressed as MFRAT.

[0056] The third decrease condition includes conditions that ・ WF2＜MF1×WRAT, ・ WF2is not divisible by WRAT, and ・ δWF＜WMIN.

[0057] The third decrease control controls the output power of each fuel cell 125 such that ・ ΔMFfuel cells 125 are deactivated and thereby the number of operating fuel cells 125 becomes MF2, ・ the output powers of MFRATfuel cells 125 become WRAT, ・ the output powers of MFPARfuel cells 125 become less than WRAT, and ・ the total of the output powers of the MF2fuel cells 125 becomes WF2.

[0058] An example of numerical values in the third decrease condition and the third decrease control according to Embodiment 2 is as follows. ・ WRAT=5 kW, ・ WMIN=4 kW, ・ MF1=10, ・ WF2=41 kW, ・ MF2=9, ・ MFTEM=8, ・ δWF=1 kW, ・ ΔMF=1, ・ MFPAR=4, and ・ MFRAT=5.

[0059] In the case of increasing the unit output power so as to satisfy a fourth increase condition, the control device 130 executes a fourth increase control. Hereinafter, the fourth increase condition and the fourth increase control will be described. In the following description, ・ The rated output power of the fuel cell 125 is expressed as WRAT. ・ The minimum output power of the fuel cell 125 is expressed as WMIN. ・ The number of operating fuel cells 125 before the increase in the unit output power is expressed as MG1. Here, MG1is an integer not less than 0. ・ The unit output power after the increase in the unit output power is expressed as WG2. ・ A value for X9that satisfies (X9-1)×WRAT＜WG2＜X9×WRATis expressed as MG2. Here, X9is a natural number not less than 1. ・ MG2-1 is expressed as MGRAT. ・ WG2-MGRAT×WRATis expressed as δWG. ・ |MG2-MG1| is expressed as ΔMG. Here, ΔMGis an integer not less than 0.

[0060] The fourth increase condition includes conditions that ・ WG2＞MG1×WRAT, ・ WG2is not divisible by WRAT, and ・ δWG=WMIN.

[0061] The fourth increase control controls the output power of each fuel cell 125 such that ・ ΔMGfuel cells 125 are activated and thereby the number of operating fuel cells 125 becomes MG2, ・ the output powers of MGRATfuel cells 125 become WRAT, and ・ the output power of one fuel cell 125 becomes WMIN.

[0062] An example of numerical values in the fourth increase condition and the fourth increase control according to Embodiment 2 is as follows. ・ WRAT=5 kW, ・ WMIN=4 kW, ・ MG1=10, ・ WG2=54 kW, ・ MG2=11, ・ MGRAT=10, ・ δWG=4 kW, and ・ ΔMG=1.

[0063] In the case of decreasing the unit output power so as to satisfy a fourth decrease condition, the control device 130 executes a fourth decrease control. Hereinafter, the fourth decrease condition and the fourth decrease control will be described. In the following description, ・ The rated output power of the fuel cell 125 is expressed as WRAT. ・ The minimum output power of the fuel cell 125 is expressed as WMIN. ・ The number of operating fuel cells 125 before the decrease in the unit output power is expressed as MH1. Here, MH1is a natural number not less than 1. ・ The unit output power after the decrease in the unit output power is expressed as WH2. ・ A value for X10that satisfies (X10-1)×WRAT＜WH2＜X10×WRATis expressed as MH2. Here, X10is a natural number not less than 1. ・ MH2-1 is expressed as MHRAT. ・ WH2-MHRAT×WRATis expressed as δWH. ・ |MH2-MH1| is expressed as ΔMH. Here, ΔMHis an integer not less than 0.

[0064] The fourth decrease condition includes conditions that ・ WH2＜MH1×WRAT, ・ WH2is not divisible by WRAT, and ・ δWH=WMIN.

[0065] The fourth decrease control controls the output power of each fuel cell 125 such that ・ ΔMHfuel cells 125 are deactivated and thereby the number of operating fuel cells 125 becomes MH2, ・ the output powers of MHRATfuel cells 125 become WRAT, and ・ the output power of one fuel cell 125 becomes WMIN.

[0066] An example of numerical values in the fourth decrease condition and the fourth decrease control according to Embodiment 2 is as follows. ・ WRAT=5 kW, ・ WMIN=4 kW, ・ MH1=10, ・ WH2=44 kW, ・ MH2=9, ・ MHRAT=8, ・ δWH=4 kW, and ・ ΔMH=1.

[0067] The first increase condition and the first decrease control can also be executed in Embodiment 2.

[0068] [1-3. Effects and the like] The fuel cell system 110 according to one example of the present disclosure includes the fuel cell unit 120 and the control device 130. The fuel cell unit 120 includes a plurality of fuel cells 125. Each fuel cell 125 has an output power range. The upper limit of the output power range of each fuel cell 125 is the rated output power of the fuel cell 125. Here, the output power of the fuel cell unit 120 is referred to as unit output power. The control device 130 controls the unit output power. The control device 130 controls the output power of each fuel cell 125 such that the number of fuel cells 125 outputting the rated output power takes a maximum value according to the unit output power and the output power range of each fuel cell 125. This configuration is suitable for reducing the cost per power generation of the fuel cell system 110.

[0069] A control method according to one example of the present disclosure is a method for controlling the fuel cell system 110. The fuel cell system 110 includes the fuel cell unit 120. The fuel cell unit 120 includes a plurality of fuel cells 125. Each fuel cell 125 has an output power range. The upper limit of the output power range of each fuel cell 125 is the rated output power of the fuel cell 125. Here, the output power of the fuel cell unit 120 is referred to as unit output power. The control method includes a first step. In the first step, the output power of each fuel cell 125 is controlled such that the number of fuel cells 125 outputting the rated output power takes a maximum value according to the unit output power and the output power range of each fuel cell 125, thereby controlling the unit output power.

[0070] A program according to one example of the present disclosure, when being executed by a processor, includes an instruction that causes the processor to execute the above control method. A storage medium according to one example of the present disclosure is a computer-readable storage medium in which the above program is stored. In one example, the program is installed in the fuel cell system 110. Specifically, the program is installed in the control device 130. The processor is, for example, a central processing unit (CPU), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like. The storage medium is, for example, a semiconductor storage medium, a magnetic storage medium, a magneto-optical storage medium, an optical storage medium, or the like. The semiconductor storage medium is, for example, a secure digital (SD) card, a universal serial bus (USB) memory, a solid state drive (SSD), or the like. The magnetic storage medium is, for example, a hard disk drive (HDD), a flexible disk, or the like. The magneto-optical storage medium is, for example, a magneto-optical (MO) disk or the like. The optical storage medium is, for example, a compact disc (CD), a digital versatile disc (DVD), or the like.

[0071] The technology according to the present disclosure is applicable to factories and the like.

Claims

1. A fuel cell system comprising: a fuel cell unit including a plurality of fuel cells, each fuel cell having an output power range whose upper limit is rated output power; and a control device that controls unit output power that is output power of the fuel cell unit, the control device controlling output power of each fuel cell such that the number of fuel cells outputting the rated output power takes a maximum value according to the unit output power and the output power range of each fuel cell.

2. The fuel cell system according to claim 1, wherein the plurality of fuel cells have the same rated output power.

3. The fuel cell system according to claim 2, wherein in a case of increasing the unit output power so as to satisfy a first increase condition, the control device executes a first increase control, when it is assumed that the rated output power of the fuel cell is expressed as WRAT, the number of operating fuel cells before the increase in the unit output power is expressed as MA1, and the unit output power after the increase in the unit output power is expressed as WA2, the first increase condition includes conditions that WA2＞MA1×WRAT, and WA2is divisible by WRAT, and when it is assumed that a natural number X1that satisfies WA2=X1×WRATis expressed as MA2, and |MA2-MA1| is expressed as ΔMA, the first increase control controls the output power of each fuel cell such that the ΔMAfuel cells are activated and thereby the number of operating fuel cells becomes MA2, and the output powers of the MA2fuel cells become WRAT.

4. The fuel cell system according to claim 2 or 3, wherein in a case of decreasing the unit output power so as to satisfy a first decrease condition, the control device executes a first decrease control, when it is assumed that the rated output power of the fuel cell is expressed as WRAT, the number of operating fuel cells before the decrease in the unit output power is expressed as MB1, and the unit output power after the decrease in the unit output power is expressed as WB2, the first decrease condition includes conditions that WB2＜MB1×WRAT, and WB2is divisible by WRAT, and when it is assumed that a natural number X2that satisfies WB2=X2×WRATis expressed as MB2, and |MB2-MB1| is expressed as ΔMB, the first decrease control controls the output power of each fuel cell such that the ΔMBfuel cells are deactivated and thereby the number of operating fuel cells becomes MB2, and the output powers of the MB2fuel cells become WRAT.

5. The fuel cell system according to any one of claims 2 to 4, wherein in a case of increasing the unit output power so as to satisfy a second increase condition, the control device executes a second increase control, when it is assumed that the rated output power of the fuel cell is expressed as WRAT, the number of operating fuel cells before the increase in the unit output power is expressed as MC1, and the unit output power after the increase in the unit output power is expressed as WC2, the second increase condition includes conditions that WC2＞MC1×WRAT, and WC2is not divisible by WRAT, and when it is assumed that a natural number X3that satisfies (X3-1)×WRAT＜WC2＜X3×WRATis expressed as MC2, |MC2-MC1| is expressed as ΔMC, MC2-1 is expressed as MCRAT, and WC2-MCRAT×WRATis expressed as δWC, the second increase control controls the output power of each fuel cell such that the ΔMCfuel cells are activated and thereby the number of operating fuel cells becomes MC2, the output powers of the MCRATfuel cells become WRAT, and the output power of one fuel cell becomes δWC.

6. The fuel cell system according to any one of claims 2 to 5, wherein in a case of decreasing the unit output power so as to satisfy a second decrease condition, the control device executes a second decrease control, when it is assumed that the rated output power of the fuel cell is expressed as WRAT, the number of operating fuel cells before the decrease in the unit output power is expressed as MD1, and the unit output power after the decrease in the unit output power is expressed as WD2, the second decrease condition includes conditions that WD2＜MD1×WRAT, and WD2is not divisible by WRAT, and when it is assumed that a natural number X4that satisfies (X4-1)×WRAT＜WD2＜X4×WRATis expressed as MD2, |MD2-MD1| is expressed as ΔMD, MD2-1 is expressed as MDRAT, and WD2-MDRAT×WRATis expressed as δWD, the second decrease control controls the output power of each fuel cell such that the ΔMDfuel cells are deactivated and thereby the number of operating fuel cells becomes MD2, the output powers of the MDRATfuel cells become WRAT, and the output power of one fuel cell becomes δWD.

7. The fuel cell system according to any one of claims 1 to 4, wherein minimum output power that is a lower limit of the output power range is larger than zero.

8. The fuel cell system according to claim 7, wherein the plurality of fuel cells have the same minimum output power, and the plurality of fuel cells have the same rated output power.

9. The fuel cell system according to claim 8, wherein in a case of increasing the unit output power so as to satisfy a third increase condition, the control device executes a third increase control, when it is assumed that the rated output power of the fuel cell is expressed as WRAT, the minimum output power of the fuel cell is expressed as WMIN, the number of operating fuel cells before the increase in the unit output power is expressed as ME1, the unit output power after the increase in the unit output power is expressed as WE2, a natural number X5that satisfies (X5-1)×WRAT＜WE2＜X5×WRATis expressed as ME2, ME2-1 is expressed as METEM, and WE2-METEM×WRATis expressed as δWE, the third increase condition includes conditions that WE2＞ME1×WRAT, WE2is not divisible by WRAT, and δWE＜WMIN, and when it is assumed that |ME2-ME1| is expressed as ΔME, a minimum natural number X6that satisfies (X6-1)×WRAT+δWE≧X6×WMINis expressed as MEPAR, and ME2-MEPARis expressed as MERAT, the third increase control controls the output power of each fuel cell such that the ΔMEfuel cells are activated and thereby the number of operating fuel cells becomes ME2, the output powers of the MERATfuel cells become WRAT, and the output powers of the MEPARfuel cells become less than WRAT.

10. The fuel cell system according to claim 8 or 9, wherein in a case of decreasing the unit output power so as to satisfy a third decrease condition, the control device executes a third decrease control, when it is assumed that the rated output power of the fuel cell is expressed as WRAT, the minimum output power of the fuel cell is expressed as WMIN, the number of operating fuel cells before the decrease in the unit output power is expressed as MF1, the unit output power after the decrease in the unit output power is expressed as WF2, a natural number X7that satisfies (X7-1)×WRAT＜WF2＜X7×WRATis expressed as MF2, MF2-1 is expressed as MFTEM, and WF2-MFTEM×WRATis expressed as δWF, the third decrease condition includes conditions that WF2＜MF1×WRAT, WF2is not divisible by WRAT, and δWF＜WMIN, and when it is assumed that |MF2-MF1| is expressed as ΔMF, a minimum natural number X8that satisfies (X8-1)×WRAT+δWF≧X8×WMINis expressed as MFPAR, and MF2-MFPARis expressed as MFRAT, the third decrease control controls the output power of each fuel cell such that the ΔMFfuel cells are deactivated and thereby the number of operating fuel cells becomes MF2, the output powers of the MFRATfuel cells become WRAT, and the output powers of the MFPARfuel cells become less than WRAT.

11. The fuel cell system according to any one of claims 8 to 10, wherein in a case of increasing the unit output power so as to satisfy a fourth increase condition, the control device executes a fourth increase control, when it is assumed that the rated output power of the fuel cell is expressed as WRAT, the minimum output power of the fuel cell is expressed as WMIN, the number of operating fuel cells before the increase in the unit output power is expressed as MG1, the unit output power after the increase in the unit output power is expressed as WG2, a natural number X9that satisfies (X9-1)×WRAT＜WG2＜X9×WRATis expressed as MG2, MG2-1 is expressed as MGRAT, and WG2-MGRAT×WRATis expressed as δWG, the fourth increase condition includes conditions that WG2＞MG1×WRAT, WG2is not divisible by WRAT, and δWG=WMIN, and when it is assumed that |MG2-MG1| is expressed as ΔMG, the fourth increase control controls the output power of each fuel cell such that the ΔMGfuel cells are activated and thereby the number of operating fuel cells becomes MG2, the output powers of the MGRATfuel cells become WRAT, and the output power of one fuel cell becomes WMIN.

12. The fuel cell system according to any one of claims 8 to 11, wherein in a case of decreasing the unit output power so as to satisfy a fourth decrease condition, the control device executes a fourth decrease control, when it is assumed that the rated output power of the fuel cell is expressed as WRAT, the minimum output power of the fuel cell is expressed as WMIN, the number of operating fuel cells before the decrease in the unit output power is expressed as MH1, the unit output power after the decrease in the unit output power is expressed as WH2, a natural number X10that satisfies (X10-1)×WRAT＜WH2＜X10×WRATis expressed as MH2, MH2-1 is expressed as MHRAT, and WH2-MHRAT×WRATis expressed as δWH, the fourth decrease condition includes conditions that WH2＜MH1×WRAT, WH2is not divisible by WRAT, and δWH=WMIN, and when it is assumed that |MH2-MH1| is expressed as ΔMH, the fourth decrease control controls the output power of each fuel cell such that the ΔMHfuel cells are deactivated and thereby the number of operating fuel cells becomes MH2, the output powers of the MHRATfuel cells become WRAT, and the output power of one fuel cell becomes WMIN.

13. The fuel cell system according to any one of claims 1 to 12, wherein the control device, in each control cycle, controls the output power of each fuel cell such that the number of the fuel cells outputting the rated output power takes a maximum value according to the unit output power and the output power range of each fuel cell, thereby controls the unit output power.

14. The fuel cell system according to any one of claims 1 to 13, wherein the control device controls the unit output power so as to follow a request power that a load connected to the fuel cell system requests.

15. A control method for a fuel cell system including a fuel cell unit including a plurality of fuel cells, each fuel cell having an output power range whose upper limit is rated output power, when it is assumed that output power of the fuel cell unit is referred to as unit output power, the method including controlling output power of each fuel cell such that the number of fuel cells outputting the rated output power takes a maximum value according to the unit output power and the output power range of each fuel cell, thereby controlling the unit output power.

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