Fuel Cell Systems

Abstract

To favorably implement efficient power generation control of a fuel cell.SOLUTION: A fuel cell system 10 comprises a power control unit 53 that controls, during external power supply in which power is supplied to an external load LD, power generation of an FC stack so as to generate power at predetermined power generation efficiency and supplies surplus power, which is not consumed, of power generated by the FC stack to a battery 41 to charge the battery 41. During the external power supply, the power control unit 53 stops the power generation of the FC stack when a charging rate of the battery 41 becomes equal to or larger than a first predetermined value, controls output of the battery 41 so that power of the battery 41 is supplied to the external load LD, and resumes the power generation of the FC stack when the charging rate becomes equal to or smaller than a second predetermined value that is smaller than the first predetermined value.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fuel cell system mounted on a vehicle driven by a motor. [Background technology]

[0002] 2. Description of the Related Art There is known an apparatus that supplies electric power from a fuel cell and a power storage device mounted on a fuel cell vehicle to an external load such as equipment outside the vehicle (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-56771 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, since the power generation efficiency of a fuel cell is maximized within a certain power generation range, when the power required by an external load is within the power generation range, it becomes difficult to efficiently control the power generation. On the other hand, if an attempt is made to generate power in excess of the required power by prioritizing power generation efficiency, there is a risk that the surplus generated power will flow excessively into the storage device when the required power suddenly decreases, causing the storage device to deteriorate. [Means for solving the problem]

[0005] A fuel cell system according to one aspect of the present invention has an external power supply function that supplies battery power and fuel cell power to an external load. The fuel cell system includes a power generation control unit that controls power generation by the fuel cell so as to generate power at a predetermined power generation efficiency during external power supply in which power is supplied to the external load, and supplies surplus power not consumed among the power generated by the fuel cell to the battery to charge the battery. During external power supply, the power generation control unit stops power generation by the fuel cell when the charging rate of the battery becomes equal to or greater than a first predetermined value, controls the output of the battery so that the power of the battery is supplied to the external load, and resumes power generation by the fuel cell when the charging rate of the battery becomes equal to or less than a second predetermined value that is smaller than the first predetermined value. The power generation control unit further determines an upper limit of the power generated by the fuel cell based on the power that can be consumed by an auxiliary device driven using at least one of the power of the battery and the power of the fuel cell and the charging rate of the battery. Effect of the Invention

[0006] According to the present invention, efficient power generation control of a fuel cell can be satisfactorily achieved. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic diagram showing an example of a vehicle system having a fuel cell system according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a diagram showing a connection relationship between the external power supply system and its peripheral devices. [Diagram 3] FIG. 4 is a diagram showing an example of the correspondence relationship between power generation efficiency and generated power of a fuel cell. [Figure 4] FIG. 4 is a diagram for explaining a method for determining a power generation target value. [Diagram 5] 4 is a flowchart showing an example of a process executed by a power control unit in FIG. [Figure 6A] 2 is a diagram for explaining the operation of the power control unit in FIG. 1; [Figure 6B] 2 is a diagram for explaining the operation of the power control unit in FIG. 1; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] <Summary> In a fuel cell vehicle equipped with a vehicle system according to an embodiment of the invention, a driving motor is driven using at least one of power (FC power) generated by a fuel cell (hereinafter sometimes referred to as FC) and power (battery power) stored in a secondary battery of the vehicle system. Also, power (regenerative power) generated from the driving motor during regeneration is stored in the secondary battery of the vehicle system. Furthermore, the vehicle system has an external power supply function that supplies at least one of the FC power and the battery power to an electrically-driven device (hereinafter referred to as an external load) connected to a power supply port provided on the fuel cell vehicle. Details of such a vehicle system will be described below with reference to the drawings.

[0009] <Fuel cell vehicle> FIG. 1 is a schematic diagram showing an example of a vehicle system having a fuel cell system 10 according to this embodiment. The vehicle system is mounted on a fuel cell vehicle, which is an example of an electric vehicle driven by a motor 11. The vehicle system includes at least a motor 11 for driving, drive wheels 12, a brake device 13, a vehicle sensor 20, a battery system (electricity storage device) 40, a control device 50, an external power supply system 60, an FC unit 100, a converter 102, and a BTVCU (Battery Voltage Control Unit) 103. A diode 101 is disposed between the FC unit 100 and the converter 102 and BTVCU 103 to prevent reverse current. The fuel cell system 10 constitutes a part of the vehicle system, and includes the battery system 40, the control device 50, the external power supply system 60, the FC unit 100, and the BTVCU 103. A solid line connecting the blocks indicates an electrical connection, and a dashed line connecting the control device 50 and the blocks illustrates a signal direction.

[0010] <Motor> The motor 11 is, for example, a three-phase AC motor. A rotor of the motor 11 is connected to the drive wheels 12. The motor 11 outputs drive force to the drive wheels 12 using at least one of the FC power generated by the FC unit 100 and the battery power stored in the battery system 40 (power running operation). The motor 11 also generates power using the kinetic energy of the fuel cell vehicle when the fuel cell vehicle is decelerating (regenerative operation).

[0011] <Brake device> As an example, the braking device 13 includes a brake caliper, a cylinder that transmits hydraulic pressure to the brake caliper, and an electric motor that generates hydraulic pressure in the cylinder (all of which are not shown). The braking device 13 may include a backup mechanism that transmits hydraulic pressure generated by operating the brake pedal to the cylinder via a master cylinder. Note that the braking device 13 is not limited to the above-mentioned configuration, and may be an electronically controlled hydraulic brake device that transmits hydraulic pressure from a master cylinder to the cylinder.

[0012] <Vehicle sensor> The vehicle sensor 20 includes, for example, an accelerator opening sensor, a vehicle speed sensor, and a brake depression sensor (all not shown). The accelerator opening sensor is attached to an accelerator pedal, which is an example of an operator that accepts an acceleration command from a driver, detects the amount of operation of the accelerator pedal, and outputs the accelerator opening to the control device 50. The vehicle speed sensor includes, for example, wheel speed sensors attached to each wheel and a speed calculator (all not shown), and combines the wheel speeds detected by the wheel speed sensors to derive the speed of the fuel cell vehicle (vehicle speed), which is output to the control device 50. The brake depression sensor is attached to the brake pedal, detects the amount of operation of the brake pedal, and outputs the brake depression to the control device 50.

[0013] <Converter> The converter 102 is, for example, a bidirectional DC voltage / AC voltage converter. A DC side terminal of the converter 102 is connected to a DC link DL. The battery system 40 is connected to the DC link DL via the BTVCU 103. The converter 102 converts a DC voltage boosted by the BTVCU 103 into a three-phase AC voltage and supplies the DC voltage to the motor 11. The converter 102 also converts an AC voltage generated by a regenerative operation of the motor 11 into a DC voltage and outputs the DC voltage to the DC link DL. The voltage obtained by the regenerative operation may be called a regenerative voltage.

[0014] <btvcu> The BTVCU 103 has, for example, a step-up / step-down type DC voltage converter. The BTVCU 103 steps up the DC voltage supplied from the battery system 40 and outputs the resulting DC voltage to the DC link DL. The BTVCU 103 also steps down the regenerative voltage from the motor 11 or the DC voltage output from the FC unit 100 and outputs the resulting DC voltage to the battery system 40. The voltage output from the FC unit 100 may be referred to as an FC voltage.

[0015] <Battery system> The battery system 40 includes, for example, a battery 41, a battery sensor 42, a temperature adjustment unit 43, and an SOC calculation unit 44.

[0016] The battery 41 is, for example, a secondary battery such as a lithium ion battery. As an example, the battery 41 stores (charges) regenerative power obtained by the regenerative operation of the motor 11 or FC power obtained by the power generation operation of the FC unit 100, and discharges the power to run the fuel cell vehicle and to operate auxiliary machinery described below.

[0017] The battery sensor 42 includes, for example, a current sensor, a voltage sensor, a temperature sensor, etc. (all not shown). The current sensor, the voltage sensor, and the temperature sensor respectively detect the current value, the voltage value, and the temperature of the battery 41. The battery sensor 42 outputs signals indicating the detected current value, voltage value, temperature, etc. to the control device 50.

[0018] The temperature adjustment unit 43 heats or cools the battery 41, for example, by using power supplied from the battery 41 via the BTVCU 103. As an example, the temperature adjustment unit 43 is controlled by a battery ECU (Electronic Control Unit) (not shown) so that the temperature of the battery 41 detected by the battery sensor 42 falls within a predetermined temperature range.

[0019] The SOC calculation unit 44 calculates the SOC (State Of Charge: battery charging rate) of the battery 41 based on the output of the battery sensor 42. The SOC calculation unit 44 outputs to the control device 50 a signal indicating the calculated SOC.

[0020] <FCユニット> The FC unit 100 includes a fuel cell. The fuel cell generates power by reacting hydrogen contained in the fuel gas as fuel with oxygen contained in the air as an oxidant. In this embodiment, FC power generated by the FC unit 100 is output to the DC link DL. As a result, the FC power from the FC unit 100 is supplied to the motor 11 via the converter 102, and to the battery system 40 via the BTVCU 103. The FC power supplied to the battery system 40 is stored in the battery 41.

[0021] <External power supply system> The external power supply system 60 includes a power supply port 61 for electrically connecting the external load LD and the fuel cell system 10. The external power supply system 60 receives FC power from the FC unit 100 and battery power from the battery system 40. The external power supply system 60 has an external power supply function for supplying at least one of FC power and battery power to the external load LD connected to the power supply port 61. When a connector (not shown) of the external load LD is connected to the power supply port 61, the external power supply system 60 outputs an external power supply request signal (described later) to the control device 50 (power control unit 53). The external power supply system 60 establishes communication with the external load LD connected to the power supply port 61 via the connector, and acquires device information (such as model information and rated power consumption (maximum power consumption)) of the external load LD via the communication. The external power supply system 60 stores the device information in a storage unit (not shown) of the control device 50. The external power supply system 60 may also have an external charging function of converting AC voltage supplied from an external power source (not shown) into DC voltage and supplying it to the battery system 40 to charge the battery 41. In this case, the power supply port 61 also functions as a charging port that electrically connects the external power source and the fuel cell system 10.

[0022] <Control device> The control device 50 includes a CPU (microprocessor) and storage units such as a ROM and a RAM, and has input / output interfaces such as a timer circuit, an A / D converter, a D / A converter, etc., as necessary. Note that the control device 50 is not limited to being composed of only one control unit, and may be composed of multiple control units included in the motor 11, the FC unit 100, the battery system 40, the external power supply system 60, the BTVCU 103, etc.

[0023] The control device 50 determines, while arbitrating, the allocation (sharing) of the load to be borne by the FC unit 100, the load to be borne by the battery system 40, and the load to be borne by the motor 11 as a regenerative power source, from the load required of the vehicle system of the fuel cell vehicle as a whole, which is determined based on the state of the FC unit 100, the state of the battery 41, the state of the external power supply system 60, and the state of the motor 11, as well as input (load requirements) from various switches and various sensors not shown, and sends commands to the motor 11, the converter 102, the FC unit 100, the battery system 40 and the BTVCU 103.

[0024] The control device 50 includes, for example, a motor control unit 51, a brake control unit 52, and a power control unit 53. As described above, the motor control unit 51, the brake control unit 52, and the power control unit 53 may be replaced with separate control units (for example, a motor ECU, a brake ECU, a battery ECU, etc.).

[0025] As an example, the motor control unit 51 calculates a driving force required of the motor 11 based on the output of the vehicle sensor 20, and controls the motor 11 to output the calculated driving force.

[0026] For example, the brake control unit 52 calculates a braking force required of the brake device 13 based on the output of the vehicle sensor 20, and controls the brake device 13 to output the calculated braking force.

[0027] As an example, the power control unit 53 calculates the total required power of the battery system 40 and the FC unit 100 based on the output of the vehicle sensor 20. For example, the power control unit 53 calculates the torque to be output by the motor 11 based on the accelerator opening and the vehicle speed, and calculates the total required power by adding up the drive shaft required power found from the torque and the rotation speed of the motor 11, the power required by the accessories, etc., and the external power supply required power. The accessories are driven using at least one of the battery power and the FC power. The accessories include, for example, an air pump (A / P) 30, which will be described later using FIG. 2.

[0028] Furthermore, the power control unit 53 calculates the charge / discharge required power of the battery 41 based on the SOC of the battery 41. Then, the power control unit 53 subtracts the charge / discharge required power of the battery 41 from the total required power (with the discharge side being positive), calculates the FC required power required of the FC unit 100, and causes the FC unit 100 to generate power equivalent to the calculated FC required power.

[0029] FIG. 2 is a diagram showing the connection relationship between the external power supply system 60 and its peripheral devices. The external power supply system 60 includes a power supply port 61 (AC power supply port 61a and DC power supply port 61d) and an inverter 62. Contactors 104, 106, and 107 in FIG. 2 electrically connect and disconnect the external power supply system 60 to and from the FC stack 110 and the battery 41 under the control of the control device 50. The FCVCU (Fuel Cell Voltage Control Unit) 105 includes, for example, a step-up type DC voltage converter. Under the control of the control device 50, the FCVCU 105 steps up the voltage of the primary side (input side) input from the FC stack 110 via the contactor 104 to a voltage corresponding to a power generation target value described later, and applies the voltage to the secondary side (output side). The air pump 30 is one of the auxiliary devices, includes a motor and the like that are driven and controlled by the FC unit 100, and supplies air, which is an oxidant gas (reactive gas) containing oxygen as an oxidant, to the FC stack 110.

[0030] When the connector of the external load LD is inserted into either the AC power feed port 61a or the DC power feed port 61d, the external load LD is electrically connected to the external power supply system 60. When the contactor 107 is on (connected state), the external load LD connected to the AC power feed port 61a or the DC power feed port 61d can be supplied with FC power from the FC unit 100 and battery power from the battery system 40. The AC power feed port 61a and the DC power feed port 61d detect connection or disconnection of the connector of the external load LD and output a detection signal to the control device 50. The inverter 62 is provided between the contactor 107 and the AC power feed port 61a, and converts the FC power and battery power input via the contactor 107 from direct current to alternating current.

[0031] Meanwhile, during external power feeding, it is necessary to perform efficient power generation control so that power can be fed for as long as possible to the external load LD connected to the power feeder. Fig. 3 is a diagram showing an example of the correspondence between the power generation efficiency and generated power of the FC unit 100 (FC stack 110). As shown in Fig. 3, the FC stack reaches its maximum power generation efficiency (hereinafter simply referred to as maximum efficiency) EM in the range from generated power P1 to generated power P2. Hereinafter, this range will be referred to as the maximum efficiency power generation range. Therefore, during external power feeding, it is preferable to generate power so that the generated power P of the FC stack falls within the maximum efficiency power generation range.

[0032] On the other hand, there is a case where the electrical connection between the external power supply system 60 and the external load LD is suddenly cut off when the user suddenly stops the operation of the external load LD during the external power supply. Hereinafter, such a sudden cut off of the electrical connection between the external power supply system 60 and the external load LD is referred to as load drop. When load drop occurs, the power that was originally supposed to be supplied to the external load LD has nowhere to go and flows into the battery system 40. The surplus power that has nowhere to go at the time of load drop (hereinafter, referred to as sudden surplus power) may deteriorate or break down the battery 41 of the battery system 40 depending on its magnitude. Therefore, during the external power supply, it is necessary to perform power generation control of the FC unit 100 so as to be within the maximum efficient power generation range and within the range in which the fuel cell system 10 can absorb (consume) the sudden surplus power at the time of load drop. In this embodiment, taking this point into consideration, the power control unit 53 is configured as follows. It should be noted that the external power supply function is normally used when the fuel cell vehicle is stopped (not running), so regenerative power is not input to the external power supply system 60 during external power supply.

[0033] During external power supply, the power control unit 53 controls the power generation of the fuel cell so that power is generated at a predetermined power generation efficiency (the above-mentioned maximum efficiency power generation range). The power control unit 53 also supplies surplus power that is not consumed in the fuel cell system 10 out of the power generated by the FC stack 110 to the battery 41 to charge the battery 41.

[0034] When the SOC of the battery 41 becomes equal to or higher than the charging limit value during external power supply, the power control unit 53 outputs a power generation stop command to the FC unit 100 to stop power generation by the FC stack 110. This starts power supply from the battery power. In other words, discharging of the battery 41 starts.

[0035] Thereafter, when the SOC of the battery 41 falls below the discharge limit value (<charge limit value), the power control unit 53 outputs a power generation start command to the FC unit 100 to start power generation in the FC stack 110. This causes the FC stack 110 to resume power generation.

[0036] The charge limit value is a threshold value for determining whether the battery 41 is fully charged. Full charge is, for example, a state in which the SOC is 100%. Note that, from the viewpoint of preventing deterioration of the battery 41, a value smaller than 100% (for example, 80%) is set as the charge limit value so as not to fully charge the battery 41 in practice. The discharge limit value is a threshold value for determining whether external power supply by the battery 41 alone is no longer possible. Note that, from the viewpoint of preventing deterioration of the battery 41, a value larger than 0% is set as the discharge limit value so as not to completely discharge the battery 41.

[0037] Furthermore, the power control unit 53 determines a power generation target value so as to be able to absorb sudden surplus power that occurs when a load drop occurs during external power feeding, and controls the power generation of the FC stack 110 based on the power generation target value. Fig. 4 is a diagram for explaining a method for determining the power generation target value (hereinafter also referred to as target power generation).

[0038] <Power generation upper limit> First, the power control unit 53 calculates the amount of power that can be charged to the battery 41 (hereinafter referred to as the BAT charge limit) and the amount of power that can be discharged from the battery 41 (hereinafter referred to as the BAT discharge limit) based on the SOC of the battery 41. The power control unit 53 determines the upper limit value of the power generation of the FC stack 110 (hereinafter referred to as the maximum power generation limit power or power generation upper limit value) based on the BAT charge limit and the total value of the power that can be consumed by the auxiliary equipment (hereinafter referred to as the auxiliary equipment power consumption). Specifically, the power control unit 53 calculates the power generation upper limit value by adding up the auxiliary equipment power consumption and the BAT charge limit. By suppressing the power generation of the FC stack 110 to or below this power generation upper limit value, sudden surplus power when the power supply load is lost can be absorbed (consumed) by the auxiliary equipment and the battery 41.

[0039] <Power generation lower limit> Next, the power control unit 53 determines a lower limit of the power generation of the FC stack 110 (hereinafter referred to as the minimum required power generation or power generation lower limit) based on the BAT discharge limit, the auxiliary power consumption, and the maximum power consumption of the external load LD (hereinafter referred to as the maximum power consumption of the external power supply). Specifically, the power control unit 53 calculates the power generation lower limit by subtracting the BAT discharge limit from the sum of the auxiliary power consumption and the maximum power consumption of the external power supply. If an amount of power equal to or greater than the BAT discharge limit is discharged from the battery 41, this may cause deterioration or failure of the battery 41. By controlling the power generation of the FC stack 110 so that it does not fall below this power generation lower limit, it is possible to prevent deterioration or failure of the battery 41 due to over-discharge as described above.

[0040] <Power generation target value> Next, the power control unit 53 determines a power generation target value for the FC stack 110 based on the power generation upper limit value, the power generation lower limit value, and the maximum efficiency power generation range. At this time, the power generation target value is determined so that its value is included in both the power generation limited range defined by the power generation upper limit value and the power generation lower limit value, and the maximum efficiency power generation range. For example, the power control unit 53 determines the maximum value within the range where the power generation limited range and the maximum efficiency power generation range overlap as the power generation target value.

[0041] Once the power generation target value has been determined, finally, the power control unit 53 outputs a control signal indicative of the power generation target value to the FC unit 100. Based on the control signal from the power control unit 53, the FC unit 100 controls the power generation of the FC stack 110 so that the generated power of the FC stack 110 becomes the power generation target value. The power obtained by subtracting the auxiliary power consumption from the sum of the power generated by the FC stack 110 based on the power generation target value and the BAT discharge limit becomes the power that the fuel cell system 10 can supply to an external load (hereinafter referred to as supplyable power).

[0042] FIG. 5 is a flowchart showing an example of processing executed by the power control unit 53 of the control device 50. The processing of FIG. 5 is repeatedly executed at a predetermined cycle when it is detected that the external load LD is connected via the AC power feed port 61a or the DC power feed port 61d of the external power supply system 60. First, in step S11, the SOC of the battery 41 is acquired. More specifically, the SOC calculated by the SOC calculation unit 44 is acquired from the battery system 40. In step S12, it is determined whether the SOC of the battery 41 is higher than the charging limit value TH. If the result in step S12 is affirmative, in step S13, a power generation stop command is output to the FC unit 100 to stop power generation of the FC stack 110. Note that if power generation of the FC stack 110 is completely stopped, it takes time to resume power generation, so that the power generation target value may be determined to be the minimum power generation power of the FC stack 110 and a signal indicating the power generation target value may be output to the FC unit 100. If the result in step S12 is negative, then in step S14 it is determined whether or not the SOC of the battery 41 is lower than the discharge limit value. If the result in step S14 is negative, then the process proceeds to step S16. If the result in step S14 is positive, then in step S15 a power generation start command is sent to the FC unit 100. In step S16 a power generation target value is determined, and in step S17 power generation control is performed based on the power generation target value. Specifically, a signal indicating the power generation target value is output to the FC unit 100.

[0043] 6A and 6B are diagrams for explaining the operation of the power control unit 53. FIG. 6A shows an example of the operation of the power control unit 53 during AC power supply, that is, when power is supplied to an external load LD connected to the AC power supply port 61a. When the ignition switch (not shown) of the fuel cell vehicle is turned on by the driver or the like in a state where an ignition switch is turned off (ACC (accessory) power supply is turned on) and an external load is connected to the AC power supply port 61a, the external power supply system 60 outputs an external power supply request signal to the control device 50 (power control unit 53). When the power control unit 53 receives the external power supply request signal, it outputs a power generation start command to the FC unit 100. Since the SOC of the battery 41 is equal to or lower than the charging limit value TH, the generated power of the FC unit 100 is supplied to the battery 41, and the battery 41 is charged (time point t11).

[0044] In the AC power supply, the rated power consumption of the external load is small, and the sum of the maximum power consumption of the external power supply and the auxiliary power consumption is below the minimum power P1 in the maximum efficiency power generation range. Therefore, as shown in FIG. 6A, when the FC stack 110 generates power at the maximum efficiency, surplus power is generated. The surplus power is supplied to the battery 41 via the BTVCU 103, and the battery 41 is charged. After that, when the SOC of the battery 41 reaches the charging limit value TH, a power generation stop command is output to the FC unit 100 (time t12). As a result, the power generation of the FC stack 110 stops, and the power supply from the battery 41 to the external load LD and the auxiliary starts. Therefore, after time t12, the SOC of the battery 41 gradually decreases. Note that in the example of FIG. 6A, the ignition switch is turned off at time t13, so the output power from the battery 41 decreases after time t13. When the SOC of the battery 41 reaches the discharge limit value TL, the power control unit 53 outputs a power generation start command to the FC unit 100 (time t14). This restarts power generation in the FC stack 110. Thereafter, the power control unit 53 repeats the same operation. Thereafter, when the driver or the like performs an operation to stop the external power supply, for example, when the ignition switch is turned off (the ACC power supply is also turned off), the external power supply system 60 outputs an external power supply stop signal to the control device 50 (power control unit 53). Upon receiving the external power supply stop signal, the power control unit 53 outputs a power generation stop command to the FC unit 100 (time point t15).

[0045] 6B shows an example of the operation of the power control unit 53 during DC power supply, i.e., when power is supplied to the external load LD connected to the DC power supply port 61d. When the ignition switch of the fuel cell vehicle is turned off (the ACC power supply is on) and the external load LD is connected to the DC power supply port 61d, and the ignition switch is turned on by the driver or the like, the external power supply system 60 outputs an external power supply request signal to the control device 50 (the power control unit 53). Upon receiving the external power supply request signal, the power control unit 53 outputs a power generation start command to the FC unit 100 (time point t21).

[0046] In the DC power supply, the rated power consumption of the external load LD is large, and the sum of the maximum power consumption of the external power supply and the auxiliary power consumption exceeds the maximum power P2 of the maximum efficient power generation range. Therefore, if the power generation of the FC stack 110 is limited to within the maximum efficient power generation range, power is drawn from the battery 41 whose SOC has reached the discharge limit value TL. In order to suppress such over-discharge of the battery 41, in the example shown in FIG. 6B, the power generated by the FC stack 110 is output beyond the maximum efficient power generation range after time t21. At this time, the power generated by the FC stack 110 is all consumed by the external load LD and the auxiliary, so no surplus power is generated. As a result, the battery 41 is not charged. When the ignition switch is turned off at time t22, the auxiliary power consumption decreases, and the sum of the maximum power consumption of the external power supply and the auxiliary power consumption falls below the minimum power P1 of the maximum efficient power generation range. Therefore, after time t22, power generation is performed at maximum efficiency in the FC stack 110, and part of the generated power (surplus power) is supplied to the battery 41 via the BTVCU 103, starting charging of the battery 41. The operation up until the driver or the like performs an operation to stop the external power supply at time t23 is similar to the operation of the AC power supply in Fig. 6A, and therefore a description thereof will be omitted.

[0047] According to the embodiment described above, the following advantageous effects are achieved. (1) The fuel cell system 10 has an external power supply function of supplying the power of the battery 41 and the power of the FC stack (fuel cell) 110 to the external load LD. When the external power supply is in progress in which power is supplied to the external load LD, the system includes a power control unit 53 as a power generation control unit that controls the power generation of the FC stack 110 so that power is generated at a predetermined power generation efficiency (more specifically, the maximum power generation efficiency) and supplies the surplus power that is not consumed among the power generated by the FC stack 110 to the battery 41 to charge the battery. When the charging rate of the battery 41 becomes equal to or higher than a first predetermined value (charging limit value) during the external power supply, the power control unit 53 stops the power generation of the FC stack 110, controls the output of the battery 41 so that the power of the battery 41 is supplied to the external load LD, and resumes the power generation of the FC stack 110 when the charging rate becomes equal to or lower than a second predetermined value (discharging limit value) that is smaller than the first predetermined value. This makes it possible to satisfactorily realize efficient power generation control of the fuel cell.

[0048] (2) The power control unit 53 determines the upper limit of the power generated by the FC stack 110 (power generation upper limit) based on the power that can be consumed by the auxiliaries such as the air pump 30 and the state of charge (SOC) of the battery 41. The power control unit 53 also determines the lower limit of the power generated by the FC stack 110 (power generation upper limit) based on the power that can be consumed by the auxiliaries and the maximum power consumption of the external load LD. under Furthermore, the power control unit 53 sets the power generation target value of the FC stack 110 between the power generation upper limit values. This makes it possible to perform efficient power generation control within a range that can absorb sudden surplus power.

[0049] The above embodiment can be modified in various ways. Modifications will be described below. In the above embodiment, the air pump 30 is given as an example of an auxiliary device, but the auxiliary device may include an air conditioner or an FC cooling device (not shown) mounted on a fuel cell vehicle. In the above embodiment, the external power supply system 60 acquires device information of the external load LD via communication, but the method of acquiring the device information is not limited to this.

[0050] The above description is merely an example, and the present invention is not limited to the above-mentioned embodiment and modifications, as long as the characteristics of the present invention are not impaired. One or more of the above-mentioned embodiment and modifications can be arbitrarily combined, and modifications can also be combined with each other. [Explanation of symbols]

[0051] 10 fuel cell system, 11 motor, 12 drive wheel, 13 brake device, 20 vehicle sensor, 102 converter, 103 BTVCU, 40 battery system, 50 control device, 53 power control unit, 60 external power supply system, 100 FC unit< / btvcu>

Claims

1. A fuel cell system having an external power supply function for supplying battery power and fuel cell power to an external load, a power generation control unit that controls power generation by the fuel cell so that power is generated at a predetermined power generation efficiency during external power feeding in which the power is supplied to the external load, and supplies surplus power that is not consumed out of the power generated by the fuel cell to the battery to charge the battery, the power generation control unit, during the external power supply, stops power generation by the fuel cell when the charging rate of the battery becomes equal to or greater than a first predetermined value, controls an output of the battery so that the power of the battery is supplied to the external load, and resumes power generation by the fuel cell when the charging rate of the battery becomes equal to or less than a second predetermined value that is smaller than the first predetermined value; The fuel cell system is further characterized in that the power generation control unit determines an upper limit of the power generation of the fuel cell based on the power that can be consumed by an auxiliary device driven using at least one of the power of the battery and the power of the fuel cell and the charging rate of the battery.

2. In the fuel cell system according to claim 1, A fuel cell system, wherein the power generation control unit determines a lower limit of the power generated by the fuel cell based on the power that can be consumed by the auxiliary device and the maximum power consumption of the external load.

3. In the fuel cell system according to claim 2, The fuel cell system according to claim 1, wherein the power generation control unit sets a power generation target value of the fuel cell between the upper limit value and the lower limit value.

4. A fuel cell system according to any one of claims 1 to 3, A fuel cell system, wherein the predetermined power generation efficiency is a maximum power generation efficiency of the fuel cell.

Images