Fuel cell system for a vehicle

Abstract

comprising a fuel cell system (10) to be mounted on a vehicle: a fuel cell (100) configured to generate electrical power using reaction gas; a secondary battery (120) which is configured to be able to charge and discharge this electrical power; a secondary battery converter (130) which is electrically connected between a drive motor (220) for driving the vehicle and the secondary battery (120), wherein the secondary battery converter (130) is configured to perform a voltage conversion between the drive motor (220) and the secondary battery (120); a control device (160) configured to control the fuel cell system (10); and a fuel cell converter (110) configured to perform an amplification process to increase the output voltage of the fuel cell (100) to a target voltage and electrically connected to a motor inverter (150) which is electrically connected to the drive motor (220), wherein the control device (160) is configured such that it applies control such that electrical power is supplied by the secondary battery (120) during a period of reduced torque during power driving operation of the drive motor (220) before the drive motor (220) enters regenerative operation, starting from the receipt of a deceleration instruction by an accelerator pedal (210) to receive a speed control instruction for the vehicle under a condition that the charge level of the secondary battery (120) is greater than or equal to a preset value, or starting from the receipt of a deceleration instruction by the accelerator pedal (210) under a condition that the chargeable electrical power of the secondary battery (120) is less than or equal to a preset value, and the control device (160) is configured such that it controls the fuel cell converter (110) in response to the delay instruction in order to reduce the level of the output power of the fuel cell (100) by a decrease or more, so that the secondary battery (120) supplies the proportion of electrical power which is reduced to an extent beyond the decrease in the output power of the fuel cell (100) in response to the delay instruction.

Description

Background area

[0001] The present disclosure relates to a fuel cell system. Relevant state of the art

[0002] Of the conventional fuel cell systems intended for vehicle mounting, one exists in which a secondary battery is charged with renewable electrical power generated by the regenerative operation of a drive motor. There is also a known technology in which, with limitations regarding charging the secondary battery, auxiliary equipment is operated to utilize the renewable power.

[0003] Regarding the control device of JP 2013-150388 A, with limitations concerning the charging of the secondary battery, the situation would be that regenerative electrical power is consumed by exploiting power losses due to the circulation of electrical power generated by two motor-generators. However, a problem suffered by such a control device is that insufficient consumption of regenerative power would lead to auxiliary equipment for regenerative power consumption operating more frequently, resulting in increased vibration and noise generated by these auxiliary devices. To solve such problems, a technology is desirable that allows for the suppression of an increase in the operating frequency of auxiliary equipment involved in regenerative power consumption.

[0004] Furthermore, DE 10 2015 118 112 A1 discloses a vehicle powered by an engine, comprising: a secondary battery configured to supply an electric current to the engine; an energy recovery section configured to supply recovered electric current, obtained during braking, to the secondary battery; an energy storage quantity sensing section configured to detect the energy storage quantity of the secondary battery; and a control section configured to control the charging and discharging of the secondary battery. The control section estimates the recovered electric current and an expected energy storage quantity in order to calculate a virtual energy storage quantity from the sum of the expected energy storage quantity and the actual energy storage quantity.The control section executes the charging and discharging of the secondary battery based on the virtual amount of electricity stored.

[0005] Furthermore, DE 10 2013 009 732 A1 discloses that the following steps are carried out to distribute a recuperation power for a vehicle: Determining the recuperation power; Recording a respective target power of at least one energy consumer; Distributing the recuperation power to electrical energy sinks, which include an energy storage device and the at least one energy consumer, depending on the respective target power of the at least one energy consumer, such that an average actual power of the at least one energy consumer corresponds to the respective target power of the at least one energy consumer. Summary

[0006] The foregoing problem is solved by the subject matter of claim 1. Advantageous embodiments of the invention are the subject matter of the dependent claims that follow. (1) An explanatory aspect of the present disclosure provides for a fuel cell system. The fuel cell system, which is to be mounted on a vehicle, comprises: a fuel cell for generating electrical power or current using reaction gas; a secondary battery capable of charging and discharging electrical power; a converter electrically connected between a drive motor for propelling the vehicle and the secondary battery to perform a voltage conversion between the drive motor and the secondary battery; and a control device for controlling the fuel cell system, the control device applying such control that electrical power is supplied from the secondary battery during a period of power driving operation, which lasts until the drive motor switches to regenerative operation with reduced torque.If the accelerator pedal receives a deceleration instruction to receive a speed control command for the vehicle under a condition that the secondary battery's charge rate is greater than or equal to a preset value, or if the accelerator pedal receives a deceleration instruction under a condition that the secondary battery's chargeable electrical power is less than or equal to a preset value, then, according to this aspect, if the accelerator pedal has received a deceleration instruction, electrical power can be supplied by the secondary battery during a period of reduced-torque driving operation. In this case, a voltage drop in the secondary battery due to discharge causes a voltage differential to widen between the secondary battery side and the drive motor side of the converter, leading to an increase in power loss in the converter.which increases the electrical power supplied by the secondary battery. Therefore, in cases where the drive motor is located in objects to which electrical power is supplied by the secondary battery, the amount of power consumption due to the discharge of the secondary battery can increase to a level corresponding to the increase in power loss in the converter. Since the discharge or supply of electrical power from the secondary battery allows the charge level of the secondary battery to decrease and an increase in unused capacity, which enables regenerative power to be charged into the secondary battery, it becomes possible to suppress an increase in the frequency with which auxiliary equipment is operated to consume the regenerative power. (2) In the fuel cell system of the aspect described above, when the accelerator pedal has received a delay instruction under a condition that the charging rate of the secondary battery is greater than or equal to a preset value, or when the accelerator pedal has received a delay instruction under a condition that the chargeable electrical power of the secondary battery is less than or equal to a preset value, the control device may apply such control that the amount of electrical power to be delivered or discharged from the secondary battery to the drive motor is increased to an extent corresponding to an increase in power loss in the converter due to the discharge of electrical power from the secondary battery that has continued since the delay instruction was received.According to this aspect, the charge level of the secondary battery decreases, while its internal resistance increases as it continues to discharge, causing the secondary battery voltage to drop. This leads to an expansion of the voltage difference between the secondary battery side and the drive motor side of the converter. Therefore, due to an increase in power loss in the converter, which increases the electrical power supplied by the secondary battery, the amount of power consumed due to the secondary battery discharge can be further increased to a degree corresponding to the increase in power loss in the converter. (3) In the aspects described above, the fuel cell system may further comprise an auxiliary device connected to a DC line linking the secondary battery and the converter, and which operates by consuming electrical power, the control device being such that, when the operation of the drive motor is switched from power driving operation, which is carried out with reduced torque, to regenerative operation, following the receipt of a deceleration instruction from the accelerator pedal under a condition that the charging rate of the secondary battery is greater than or equal to a preset value, or following the receipt of a deceleration instruction from the accelerator pedal under a condition that the chargeable electrical power of the secondary battery is less than or equal to a preset value,that electrical power is continuously discharged from the secondary battery during operation under power driving mode, and that electrical power supplied by the secondary battery, as well as regenerative power generated by regenerative operation, is fed to the auxiliary system until regenerative operation is complete. Accordingly, the charge level of the secondary battery decreases, while its internal resistance increases as the secondary battery is continuously discharged, leading to a decrease in the secondary battery voltage. This results in an expansion of the voltage difference between the secondary battery side and the drive motor side of the converter. Therefore, the power loss in the converter, which reduces the regenerative power, increases.This means that the ratio or proportion of renewable energy in the electrical power supplied to the auxiliary equipment decreases over time. Consequently, it becomes possible to increase the amount of power consumed due to the discharge of the secondary battery. Therefore, while the auxiliary equipment is operating to consume renewable energy, the charge level of the secondary battery can be reduced, and the unused capacity, which allows renewable energy to be added to the secondary battery, can be increased. Accordingly, it becomes possible to suppress an increase in the frequency with which the auxiliary equipment is operated to consume renewable energy. (4) The fuel cell system of the aspect described above may further include an auxiliary device connected to a DC line connecting the secondary battery and the converter, and which operates by consuming electrical power, wherein the control device can supply electrical power from the secondary battery to the drive motor and / or the auxiliary device.

[0007] The embodiment of the present disclosure is not limited to the fuel cell system and can be applied to various modes, such as a fuel cell system intended for installation on vehicles or ships that can be powered by electrical energy as a power source, as well as the vehicles or ships themselves. The disclosure can also be implemented in a mode of a computer program or the like, which enables the implementation of the aforementioned modes. Furthermore, without any limitation to the modes described above, the disclosure can, of course, be implemented in various other modes, provided that these modes do not deviate from the fundamental concept of the disclosure. Brief description of the illustrations Fig. Figure 1 is a block diagram showing a sketched configuration of a fuel cell system according to a first embodiment; and Fig. Figure 2 is a time diagram showing exemplary status transitions during a period of time, starting from the receipt of a delay instruction from the accelerator pedal to the end of a regenerative operation of a drive motor. Detailed description A. First embodiment:

[0008] Fig. Figure 1 is a block diagram showing an outlined configuration of a fuel cell system 10 according to a first embodiment of the disclosure. The fuel cell system 10 is mounted as a power source for a vehicle driven by a drive motor 220. The fuel cell system 10 comprises a fuel cell 100, a fuel cell converter 110, a secondary battery 120, a secondary battery converter 130, auxiliary equipment 140, a motor inverter 150, and a control device 160.

[0009] The Fuel Cell 100 is a unit that generates electrical power through electrochemical reactions of hydrogen and oxygen. The Fuel Cell 100 is constructed by stacking multiple unit cells in layers. Each unit cell is a power generation element capable of generating power itself, comprising a MEGA (membrane electrode gas diffusion layer assembly) in which gas diffusion layers are provided on both sides of an MEA (membrane electrode assembly) with an electrolyte membrane, and separators arranged on the two outer sides of the MEGA. The electrolyte membrane is made of a thin, solid polymer film that exhibits successful proton conductivity in a wet state with internal moisture content.Regarding the fuel cell 100, a solid polymer type is used in this embodiment, although various types are applicable. The fuel cell 100 is electrically connected to the fuel cell converter 110.

[0010] The fuel cell converter 110 is a boost-type converter device that performs a boosting process to increase the output voltage of the fuel cell 100 to a target voltage. The fuel cell converter 110, including a reactor and a switching device (not shown), controls the electrical connection to the reactor using the switching device. Magnetic energy collected in the reactor by the switching device when it is in the "on" state is converted into an induced voltage by the switching device when it is in the "off" state. This induced voltage is output because it is superimposed on the output voltage of the fuel cell 100, thus increasing the voltage. In this way, the fuel cell converter 110 performs a switching operation to convert the output voltage of the fuel cell 100.The fuel cell converter 110 is electrically connected to the motor inverter 150 via a high-voltage DC line DCH.

[0011] The secondary battery 120, together with the fuel cell 101, serves as a power source for the fuel cell system 10. In this embodiment, the secondary battery 120 is configured with a lithium-ion battery. In other embodiments, the secondary battery 120 can be a battery of other types, such as a lead-acid battery, a nickel-cadmium battery, or a nickel-hydrogen battery. The secondary battery 120 is electrically connected to the secondary battery converter 130 via a low-voltage DC line DCL.

[0012] The secondary battery converter 130 is a step-up / step-down converter device, similar in configuration to the fuel cell converter 110. The secondary battery converter 130 is electrically connected to the fuel cell converter 110 and the motor inverter 150 via the high-voltage DC line DHC. The secondary battery converter 130 regulates the voltage in the high-voltage DC line DHC, i.e., an input voltage to the motor inverter 150, to control the charging / discharging of the secondary battery 120.

[0013] The secondary battery converter 130 initiates a discharge of the secondary battery 120 if the output power from the fuel cell converter 110 is insufficient to meet a target output power. Conversely, when regenerative power is generated in the drive motor 220, the secondary battery converter 130 converts this regenerative power and feeds it to the low-voltage DC line (DCL). The secondary battery converter 130 can also convert the output power of the fuel cell 100 and feed it to the low-voltage DC line (DCL). Additionally, the configuration of the secondary battery converter 130 may differ from that of the fuel cell converter 110.

[0014] The auxiliary equipment 140 corresponds to that required for the operation of the fuel cell 100. The auxiliary equipment 140 operates by consuming electrical power. The auxiliary equipment 140 includes, for example, an air compressor for supplying air as the cathode gas to the fuel cell 100, a hydrogen circulation pump for circulating hydrogen as the anode gas, a cooling device for cooling the fuel cell 100, a humidification device for humidifying the gas supplied to the fuel cell 100, and the like. The auxiliary equipment 140 is electrically connected to the low-voltage DC line DCL.

[0015] The motor inverter 150 converts electrical power supplied as direct current via the high-voltage DC line DCH from the fuel cell 100 and the secondary battery 120 into three-phase AC power. The motor inverter 150 is electrically connected to the drive motor 220 to supply three-phase AC power to the drive motor 220. The motor inverter 150 also converts regenerative power generated in the drive motor 220 into DC power and supplies this power to the high-voltage DC line DCH.

[0016] The control device 160 receives signals output by various types of sensors provided in the fuel cell system 10 and controls the operation of individual parts in the fuel cell system 10 using the received signals. The control device 160 comprises a PM-ECU 162 and an MG-ECU 164.

[0017] The PM-ECU 162 corresponds to an administrative control device for the administrative control of the operation of various control components (not shown), including the MG-ECU 164. The PM-ECU 162 transmits a signal to the MG-ECU 164, which indicates a vehicle speed control instruction received by an accelerator pedal 210, described later.

[0018] The MG-ECU 164 is a high-voltage control unit. The MG-ECU 164 controls the operation of the secondary battery converter 130 and the motor inverter 150 in response to a signal received from the PM-ECU 162, which indicates a vehicle speed control instruction.

[0019] The vehicle with the mounted fuel cell system 10 comprises an accelerator pedal 210 and a drive motor 220. The accelerator pedal 210 receives a vehicle speed control instruction from a driver of the vehicle with the mounted fuel cell system 10. The control device 160 receives a signal indicating a control instruction supplied by the accelerator pedal 210, and this controls the propulsion of the vehicle by the drive motor 220.

[0020] The drive motor 220 is an electric motor driven by electrical power supplied by the fuel cell 100 and the secondary battery 120. When the accelerator pedal 210 receives a deceleration instruction, the drive motor 220 causes a reduction in torque level until the transition to regenerative operation. In this embodiment, the drive motor 220 switches from power driving mode to regenerative operation when a certain time has elapsed since the accelerator pedal opening reaches zero after receiving the deceleration instruction from the accelerator pedal 210. The term "accelerator pedal opening" refers to a percentage of the degree of actual actuation relative to the total movable range of the accelerator pedal 210.In other embodiments, the drive motor 220 can switch from power driving mode to regenerative operation at a time when the torque reaches a set value or less.

[0021] Fig. Figure 2 is a time diagram showing exemplary state transitions in a vehicle with the fuel cell system 10 mounted on it during a period of time from the receipt of a deceleration instruction by the accelerator pedal 210 until the end of a regenerative operation by the drive motor 220. Fig. Figure 2 shows time series variations of the accelerator pedal opening at accelerator pedal 210, the engine torque at drive motor 220, the output power delivered by fuel cell 100, the output power delivered by secondary battery 120, the voltage of secondary battery 120, the power loss at secondary battery converter 130 and the charge level of secondary battery 120.

[0022] In this embodiment, the power loss in the secondary battery converter 130 is calculated using characteristic values ​​that are stored in advance in the control device 160. In other embodiments, the power loss in the secondary battery converter 130 can be calculated based on an estimated equation determined by experiment.

[0023] The charge level of the secondary battery 120 refers to a ratio of the remaining charge level to a fully charged capacity of the secondary battery 120.

[0024] During a period of time from time t0 to time t1 in Fig. 2. The driver of the vehicle with the mounted fuel cell system 10 keeps the accelerator pedal opening constant. Therefore, the engine torque and the output power of the fuel cell 100 are kept constant. Since no electrical power is discharged or delivered from the secondary battery 120, there is no change in the voltage or state of charge of the secondary battery 120. During the time period from time t0 to time t1 in Fig. 2. The charge level of the secondary battery 120 remains at a preset value or higher. In this embodiment, the preset value for the charge level of the secondary battery 120 is 70%. In other embodiments, the preset value for the charge level of the secondary battery 120 can be higher or lower than 70%.

[0025] During a period of time starting from time t1 towards time t2 in Fig. 2. The engine torque decreases because the accelerator pedal 210 receives a deceleration instruction from the driver of the vehicle with the fuel cell system 10 mounted on it. The deceleration instruction from the driver to the accelerator pedal 210 is executed by the driver reducing the accelerator pedal opening. In this case, the control device 160 controls the fuel cell converter 110 in response to the deceleration instruction to reduce the level of the output power of the fuel cell 100 by one decrease or reduction step or more. A dashed line from time t1 to time t2 at the fuel cell output power in Fig. Figure 2 shows a decrease in the output power of fuel cell 100 in response to the delay instruction.

[0026] In the case where the accelerator pedal 210 receives a deceleration instruction from the driver of the vehicle with the fuel cell system 10 mounted on it at time t1 in Fig. Upon receiving a signal from time t1, the control device 160 controls the secondary battery converter 130, so that electrical power is discharged from the secondary battery 120 to the drive motor 220, since the charge level of the secondary battery 120 is greater than or equal to a preset value. During the time period from time t1 to time t2 in Fig. 2. A portion of the electrical power that was reduced beyond the output power decrease of the fuel cell 100 in response to the delay instruction is compensated for by a total decrease in the output power of the fuel cell 100 due to a discharge from the secondary battery 120. Therefore, the electrical power delivered by the secondary battery 120 decreases during the time period from time t1 to time t2. Fig. 2. Since the secondary battery 120 delivers electrical power, its voltage decreases, while its state of charge also decreases. Additionally, the secondary battery 120 can be affected during the period from time t1 to time t2. Fig. 2 electrical power to the auxiliary equipment 140 and to the drive motor 220.

[0027] Even during the period from time t1 to time t2 in Fig. 2. The voltage drop of the secondary battery 120 causes an increase in the power loss in the secondary battery converter 130. This is because a voltage drop in the secondary battery 120 causes a voltage difference to expand between the low-voltage DC line (DCL) and the high-voltage DC line (DCH) of the secondary battery converter 130. The power loss in the converter increases with an increasing voltage difference between the input and output sides of the converter.

[0028] At time t2 in Fig. 2. The electrical power output from the fuel cell 100 to the drive motor 220 becomes zero. In this state, the electrical power supplied to the drive motor 220, which is operating in power mode, corresponds entirely to the electrical power supplied by the secondary battery 120.

[0029] At time t3 in Fig. 2. The driver of the vehicle with the mounted fuel cell system 10 sets the accelerator pedal opening to zero. At time t4, which corresponds to a point in time after a certain time has elapsed since time t3, the operation of the drive motor 220 switches from power driving mode to regenerative operation.

[0030] During a period of time from time t1 to time t4 in Fig. 2. The control device 160 performs such control that the amount of electrical power to be delivered by the secondary battery 120 to the drive motor 220 is increased to an extent corresponding to an increase in power loss in the secondary battery converter 130 due to the discharge of electrical power from the secondary battery 120, which has continued since receiving a deceleration instruction from the accelerator pedal 210. A secondary battery has the characteristic that its internal resistance increases with continuous electrical discharge. Therefore, the state of charge of the secondary battery 120 decreases when the secondary battery 120 is continuously discharged, while its internal resistance increases, which in turn causes the voltage of the secondary battery 120 to decrease.This leads to an expansion of the voltage difference between the low-voltage DC line side (DCL) and the high-voltage DC line side (DCH) of the secondary battery converter 130. Accordingly, due to an increase in power loss in the secondary battery converter 130, which increases the electrical power delivered by the secondary battery 120, the amount of power consumed due to the discharge of the secondary battery 120 may also be increased to an extent corresponding to the increase in power loss in the secondary battery converter 130.

[0031] At time t4 in Fig. 2. The control device 160 controls the motor inverter 150 to switch the drive motor 220 from power operation to regenerative operation. The control device 160 then instructs the auxiliary equipment 140 to commence operation, directing electrical power supplied by the secondary battery 120 and regenerative power generated by the drive motor 220 during regenerative operation to the auxiliary equipment 140 until the regenerative operation is terminated. At this point, the control device 160 causes the secondary battery 120 to continuously discharge the electrical power accumulated during power operation. Furthermore, the control device 160 controls the secondary battery converter 130 so that regenerative power is directed from the drive motor 220 to the auxiliary equipment 140.

[0032] After or starting from time t4 in Fig. 2. The power loss in the secondary battery converter 130 increases. Regarding the reason for this, it can be stated that the state of charge of the secondary battery 120 decreases, while its internal resistance increases, as the secondary battery 120 maintains continuous discharge from the power driving operation, which leads to a decrease in the voltage of the secondary battery 120. This results in an expansion of the voltage difference between the secondary battery 120 side and the drive motor 220 side of the secondary battery converter 130. Consequently, the power loss in the secondary battery converter 130 increases, reducing the regenerative power and diverting power to the low-voltage DC line side (DCL).

[0033] With a constant electrical power, which is determined by the power at time t4 in Fig. Since the auxiliary equipment 140 is required for the operation of two systems, the power loss in the secondary battery converter 130 increases as the voltage of the secondary battery 120 decreases over time. This results in a decrease in the proportion of regenerative power supplied to the auxiliary equipment 140, so that the amount of power consumed due to the discharge of the secondary battery 120 can be increased to an extent corresponding to the decrease in the proportion of regenerative power.

[0034] After or starting from time t4 in Fig. 2. At the end of the regenerative operation of the drive motor 220, the control device 160 stops the operation of the auxiliary equipment 140 in order to terminate the power supply from the secondary battery 120. Additionally, the control device 160 terminates the operation of the auxiliary equipment 140 if it receives an acceleration command from the driver of the vehicle with the fuel cell system 10 mounted on it, while a Fig. The sequence of processes described in section 2 is executed, the sequence of which is described in Fig. The processes described in point 2 will also necessarily occur during the execution of these steps.

[0035] According to the embodiment described above, when the accelerator pedal 210 has received a deceleration instruction, electrical power can be supplied by the secondary battery 120 during power driving operation, which lasts until a transition to regenerative operation, while the torque is reduced. In this case, the voltage of the secondary battery 120 decreases due to the discharge of the secondary battery 120, which causes an expansion of the voltage difference between the low-voltage DC line side DCL and the high-voltage DC line side DCH of the secondary battery converter 130, resulting in increased power loss in the secondary battery converter 130.Therefore, in the first embodiment with the drive motor 220 as an object to which electrical power is supplied from the secondary battery 120, the amount of power consumed due to the discharge of the secondary battery 120 can be increased to an extent corresponding to the increase in power loss in the secondary battery converter 130. Since the discharge of electrical power from the secondary battery 120 makes it possible to reduce the state of charge of the secondary battery 120 and increase unused capacity, which allows regenerative power to be charged into the secondary battery 120, it is therefore possible to suppress the increase in the frequency with which the auxiliary devices 140 are operated to consume the regenerative power.During the performance driving mode, which is carried out while the torque is reduced after receiving a deceleration instruction from the accelerator pedal 210, the amount of electrical power required by the drive motor 220 can only be met by the electrical power output of the fuel cell 100. In this embodiment, the amount of output power from the fuel cell 100 is significantly reduced beyond the reduction in response to the deceleration instruction, so that the portion of the electrical power that is reduced beyond the reduction in output power from the fuel cell 100 in response to the deceleration instruction is supplied by the secondary battery 120. Therefore, opportunities for discharging the secondary battery 120 are increased.

[0036] In the first embodiment, the control device 160 also performs such a control that the amount of electrical power to be delivered from the secondary battery 120 to the drive motor 220 is increased to an extent corresponding to an increase in the power loss in the secondary battery converter 130 in connection with, or due to, the electrical power output from the secondary battery 120 that has continued since the accelerator pedal 210 received the deceleration instruction. Therefore, the state of charge of the secondary battery 120 decreases, while its internal resistance increases as the secondary battery 120 continues to discharge, causing its voltage to decrease. This results in an expansion of the voltage difference between the low-voltage DC line (DCL) and the high-voltage DC line (DCH) of the secondary battery converter 130.Therefore, due to an increase in power loss in the secondary battery converter 130, which increases the electrical power delivered by the secondary battery 120, the amount of power consumption due to the discharge of the secondary battery 120 can be further increased to an extent corresponding to the increase in power loss in the secondary battery converter 130.

[0037] When the operation of the drive motor 220 has switched from power driving mode to regenerative operation, the control device 160, in the first embodiment, also performs such a control that a discharge of electrical power from the secondary battery 120 is carried out continuously until the end of the regenerative operation, starting from operation during power driving mode, while electrical power supplied by the secondary battery 120 and regenerative power generated by the regenerative operation of the drive motor 220 are directed to the auxiliary equipment 140. As a result, the state of charge of the secondary battery 120 decreases, while the internal resistance of the secondary battery 120 increases as the discharge continues, which leads to a decrease in the voltage of the secondary battery 120.This leads to an increase in the voltage difference between the low-voltage DC line (DCL) and the high-voltage DC line (DCH) of the secondary battery converter 130. Consequently, there is an increase in power loss in the secondary battery converter 130, which reduces the regenerative power output. As a result, the proportion of regenerative power supplied to the auxiliary equipment 140 decreases over time. This allows for an increase in the amount of power consumed by the secondary battery 120. Therefore, while the auxiliary equipment 140 is operating to consume regenerative power, the charge level of the secondary battery 120 can be reduced, and the unused capacity available for charging the secondary battery 120 with regenerative power can be increased.Accordingly, it becomes possible to suppress increases in the frequency with which the auxiliary equipment 140 is operated to consume the regenerative power. In other words, opportunities are provided for the discharge of the secondary battery 120 while the auxiliary equipment 140 is operated to consume the regenerative power, thereby increasing opportunities to provide unused capacity that allows regenerative power to be charged into the secondary battery 120. Consequently, based on the ability to increase the frequency with which the secondary battery 120 is charged with regenerative power, it becomes possible to suppress increases in the frequency with which the auxiliary equipment 140 is operated to consume the regenerative power. B. Modifications: B1. Modification 1:

[0038] In the fuel cell system 10 of the first embodiment, a discharge from the secondary battery 120 is carried out during both regenerative and power driving operation, starting from the receipt of a deceleration instruction by the accelerator pedal 210 until the transition to regenerative operation. However, the present disclosure is not limited to this. The fuel cell system 10 can, for example, also be arranged such that the secondary battery 120 is only permitted to discharge while the drive motor 220, whose torque is reduced, continues to perform power driving operation from the moment a deceleration instruction is received by the accelerator pedal 210, and that the secondary battery 120, which is prevented from discharging, is charged with regenerative power while the drive motor 220 performs regenerative operation. B2. Modification 2:

[0039] In the fuel cell system 10 of the first embodiment, the secondary battery 120 outputs power before receiving a delay instruction from the accelerator pedal 210 at time t1. Fig. 2. No electrical power is supplied to the drive motor 220. However, the present disclosure is not limited to this. The secondary battery 120 can, for example, also be arranged such that this electrical power is supplied to the drive motor 220 even before the accelerator pedal 210 receives a deceleration instruction. In this case, discharge from the secondary battery 120 continues both before and after the accelerator pedal 210 receives a deceleration instruction. In this case as well, the secondary battery 120 can supply electrical power to the auxiliary equipment 140 in addition to the drive motor 220. B3. Modification 3:

[0040] In the fuel cell system 10 of the first embodiment, regenerative power generated by the regenerative operation of the drive motor 220 is supplied to the auxiliary equipment 140. However, the present disclosure is not limited to this. For example, in a fuel cell system with an air compressor that is electrically connected to a line linking the secondary battery converter 130 and the motor inverter 150, regenerative power can likewise be supplied to the air compressor and the auxiliary equipment 140 and thereby consumed.

[0041] In the fuel cell system 10 of the first embodiment, the control device 160 causes electrical power to be delivered from the secondary battery 120 when the accelerator pedal 210 has received a delay instruction under the condition that the charge level of the secondary battery 120 is greater than or equal to a preset value. However, the present disclosure is not limited to this. The fuel cell system 10 can, for example, also be arranged such that electrical power is delivered from the secondary battery 120 when the accelerator pedal 210 has received a delay instruction under the condition that the chargeable electrical power of the secondary battery 120 is less than or equal to a preset value. The term "chargeable electrical power of the secondary battery 120" refers to a ratio of the chargeable quantity to the charge capacity of the secondary battery 120.For example, if the charge level of the secondary battery 120 is 70%, the chargeable electrical power of the secondary battery 120 is 30%.

[0042] The technical features of any of the foregoing embodiments and their modifications according to the technical features of each of the aspects described in the summary can be suitably substituted or combined to solve some or all of the problems described above or to achieve some or all of the advantageous effects described above.

Claims

[1] Fuel cell system (10) which is to be mounted on a vehicle comprising: a fuel cell (100) configured to generate electrical power using reaction gas; a secondary battery (120) which is configured to be able to charge and discharge this electrical power; a secondary battery converter (130) which is electrically connected between a drive motor (220) for driving the vehicle and the secondary battery (120), wherein the secondary battery converter (130) is configured to perform a voltage conversion between the drive motor (220) and the secondary battery (120); a control device (160) configured to control the fuel cell system (10); and a fuel cell converter (110) configured to perform an amplification process to increase the output voltage of the fuel cell (100) to a target voltage and electrically connected to a motor inverter (150) which is electrically connected to the drive motor (220), wherein the control device (160) is configured such that it applies control such that electrical power is supplied by the secondary battery (120) during a period of reduced torque during power driving operation of the drive motor (220) before the drive motor (220) enters regenerative operation, starting from the receipt of a deceleration instruction by an accelerator pedal (210) to receive a speed control instruction for the vehicle under a condition that the charge level of the secondary battery (120) is greater than or equal to a preset value, or starting from the receipt of a deceleration instruction by the accelerator pedal (210) under a condition that the chargeable electrical power of the secondary battery (120) is less than or equal to a preset value, and the control device (160) is configured such that it controls the fuel cell converter (110) in response to the delay instruction in order to reduce the level of the output power of the fuel cell (100) by a decrease or more, so that the secondary battery (120) supplies the proportion of electrical power which is reduced to an extent beyond the decrease in the output power of the fuel cell (100) in response to the delay instruction. [2] Fuel cell system (10) according to claim 1, wherein the control device (160) is configured such that, when the accelerator pedal (210) has received the delay instruction under the condition that the charge level of the secondary battery (120) is greater than or equal to the preset value, or when the accelerator pedal (210) has received the delay instruction under the condition that the chargeable electrical power of the secondary battery (120) is less than or equal to the preset value, it applies such control that the amount of electrical power to be delivered from the secondary battery (120) to the drive motor (220) is increased to an extent corresponding to an increase in power loss in the secondary battery converter (130) due to the discharge of electrical power from the secondary battery (120) that has continued since the delay instruction was received. [3] Fuel cell system (10) according to claim 1 or 2, further comprising an auxiliary device (140) connected to a DC line (DCL) connecting the secondary battery (120) and the secondary battery converter (130), wherein the auxiliary device (140) is configured to operate by consuming electrical power, wherein the control device (160) is configured to operate the drive motor (220) from the power driving mode performed with reduced torque, when the drive motor (220) is operated after receiving a deceleration instruction from the accelerator pedal (210) under the condition that the charge level of the secondary battery (120) is greater than or equal to the preset value, or after receiving a deceleration instruction from the accelerator pedal (210) under the condition that the chargeable electrical power of the secondary battery (120) is less than or equal to the preset value.When switching to regenerative operation, such a control is applied that a discharge of electrical power from the secondary battery (120) is carried out continuously from operation under power driving mode, and furthermore, electrical power supplied by the secondary battery (120), as well as regenerative power generated by the regenerative operation, are directed to the auxiliary device (140) until the regenerative operation is completed. [4] Fuel cell system (10) according to claim 1, further comprising an auxiliary device (140) connected to a DC line (DCL) connecting the secondary battery (120) and the secondary battery converter (130), wherein the auxiliary device (140) is configured to operate by consuming electrical power, wherein the control device (160) is configured to cause the drive motor (220) and / or the auxiliary device (140) to consume electrical power supplied by the secondary battery (120).

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