System for controlling the electrical power supply of a vehicle, as well as vehicle

Abstract

System for controlling the electrical power supply of a vehicle (1) in a vehicle (1) comprising a motor (3) to provide torque to wheels (4), a battery (21) to store electrical current and to supply the stored electrical current to the motor (3), and fuel cells (11) to generate electrical current and to supply the generated electrical current to the motor (3) and the battery (21), to control the supply of electrical current from the fuel cells (11), wherein the system for controlling the electrical power supply comprises: a battery charge level determination module (31) to determine a battery charge level of the battery (21); a switching unit (14) configured to provide a connection between the fuel cells (11) and the motor (3) and the battery (21) or to disconnect the fuel cells (11) from the motor (3) and the battery (21); and a control unit (30) configured to not only cause the switching unit (14) to disconnect the fuel cells (11) from the motor (3) and the battery (21), but also to cause the fuel cells (11) to continue generating electricity in the disconnected state from the motor (3) and the battery (21) when the battery charge level determined by the battery charge level determination module (31) is equal to or greater than a first predetermined threshold (SOC). H ) is.

Description

TECHNICAL AREA

[0001] The present invention relates to a technology for charging a battery using electric current provided by fuel cells and for driving a motor. GENERAL STATE OF THE ART

[0002] Currently known conventional fuel cell electric vehicles are those with a hybrid system that includes a battery (i.e., a secondary battery) to improve system efficiency or to compensate for an immediate load requirement during acceleration.

[0003] In order to regulate the voltage between the fuel cells (or FCs, fuel cells) and the battery, most fuel cell vehicles of the above type also have a DC / DC converter at a junction for the fuel cells or the battery.

[0004] However, since DC / DC converters are generally large and heavy components, it is desirable to eliminate the DC / DC converter and connect the fuel cells electrically and directly to a battery and further to a motor (or an inverter).

[0005] Therefore, JP 2005 - 151 643 A discloses a configuration in which fuel cells and a battery are directly connected in parallel by means of a relay box, without voltage conversion between the fuel cells and the battery by means of a DC / DC converter. Furthermore, JP 2008 - 538 650 A also discloses a configuration that does not require a DC / DC converter between fuel cells and a battery. STATE OF THE ART

[0006] The publication US 2010 / 0068577A1 discloses a fuel cell system that reduces the output voltage of a fuel cell to perform a catalyst activation process. The fuel cell system includes a control device that changes the rate of change of the fuel cell's output voltage for the catalyst activation process according to the absorption capacity of a receiving device for excess power generated by the fuel cell.

[0007] German patent application DE 11 2005 003 300 T5 discloses a fuel cell system comprising a fuel cell stack, a supplementary power source coupled to the fuel cell stack, and a power controller. The power controller regulates a power output of the fuel cell stack and the supplementary power source by using the power source as a load on the fuel cell stack to maintain a voltage on the fuel cell stack below a predetermined oxidation threshold. Brief description of the problem the invention is intended to solve.

[0008] Incidentally, in most systems where fuel cells and a battery are directly connected, the battery is charged with electricity generated by the fuel cells when there is no load demand to supply power to a motor or when the load demand is low. Furthermore, the battery will enter a state of overcharging if this charging state persists.

[0009] However, JP 2005 - 151 643 A contains no disclosure regarding measures to be taken to prevent a battery from entering a state of overcharging.

[0010] And although JP 2008 - 538 650 A discloses such measures, these are simple measures of stopping power generation by fuel cells or disconnecting the fuel cells from the battery when the output voltage from the fuel cells is higher than an allowable upper limit voltage (i.e., a voltage level that defines an upper limit of battery voltage levels at which the battery is not in a state of overcharging).

[0011] However, if the voltage of the fuel cells is at an open-circuit voltage level during the start-up and shutdown processes, the deterioration of the catalyst at the electrodes of the fuel cells will be accelerated.

[0012] One object of the present invention is to limit the deterioration of fuel cells while preventing battery overcharging. MEANS TO SOLVENT THE PROBLEM

[0013] (1) To achieve the objective, according to one aspect of the present invention, a system for controlling the electrical power supply of a vehicle is provided in order to control the supply of electrical power from the fuel cells in a vehicle comprising a motor to supply torque to the wheels, a battery to store electrical current and supply the stored electrical current to the motor, and fuel cells to generate electrical current and supply the generated electrical current to the motor and the battery, wherein the system for controlling the electrical power supply comprises: a battery charge level determination module to determine a battery charge level of the battery; a switching unit configured to provide a connection of the fuel cells to the motor and the battery or to disconnect the fuel cells from the motor and the battery;and a control unit configured to not only cause the switching unit to disconnect the fuel cells from the engine and battery, but also to cause the fuel cells to continue generating power when disconnected from the engine and battery if the battery charge level determined by the battery charge level determination module is equal to or greater than a first predetermined threshold.

[0014] (2) According to one aspect of the present invention, it is desirable that the control unit no longer enables the generation of electricity by the fuel cells after a predetermined period of time has elapsed since the connection of the fuel cells to the motor and the battery has been disconnected by the switching unit.

[0015] (3) According to one aspect of the present invention, it is desirable that the control unit no longer enables the fuel cells to generate electricity when the battery charge level determined by the battery charge level determination module is equal to or greater than a second predetermined threshold, which is lower than the first predetermined threshold, after a predetermined period of time since the switching unit disconnected the fuel cells from the engine and the battery, but causes the switching unit to reconnect the fuel cells to the engine and the battery when the battery charge level determined by the battery charge level determination module is lower than the second predetermined threshold.

[0016] (4) According to one aspect of the present invention, it is desirable that the switching unit be a field-effect transistor.

[0017] (5) According to one aspect of the present invention, a vehicle is provided comprising a motor to provide torque to wheels, a battery to store electrical current and to supply the stored electrical current to the motor, and fuel cells to generate electrical current and to supply the generated current to the motor and the battery, characterized in that it comprises: a battery charge level determination module to determine a battery charge level of the battery; a switching unit configured to provide a connection of the fuel cells to the motor and the battery or to disconnect the fuel cells from the motor and the battery;and a control unit configured to not only cause the switching unit to disconnect the fuel cells from the engine and the battery, but also to cause the fuel cells to continue generating electricity when the battery charge level determined by the battery charge level determination module is equal to or greater than a first predetermined threshold. EFFECT OF INVENTION

[0018] According to aspects (1) and (5) of the present invention, the vehicle or the electrical power supply control system of a vehicle, even in the case of a configuration where the fuel cells and the battery are connected without any DC / DC converter, can prevent a state of battery overcharging by disconnecting the fuel cell stack from the engine and the battery when the battery charge level is equal to or greater than the predetermined threshold. Furthermore, according to aspect (1) of the present invention, the vehicle or the electrical power supply control system of a vehicle can reduce the frequency of fuel cell start-up and shutdown in order to limit fuel cell degradation by allowing the fuel cells to continue generating power when the battery charge level is equal to or greater than the predetermined threshold.

[0019] According to aspect (2) of the present invention, the system for controlling the electrical power supply of a vehicle can limit the deterioration of the fuel cells caused by the fact that the fuel cells continue to generate electricity.

[0020] According to aspect (3) of the present invention, the deterioration is limited because the fuel cells do not enter the start-up and shutdown process by continuing to generate electricity when the battery charge level is less than a second predetermined threshold after the predetermined time period since the fuel cells were disconnected from the motor and the battery.

[0021] According to aspect (4) of the present invention, the system for controlling the electrical power supply of a vehicle can prevent the occurrence of an overcurrent caused by a difference between the connection voltages of the switching unit when the fuel cells are connected to the engine and the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Fig. Figure 1 is a schematic diagram showing an exemplary configuration of the present embodiment of a fuel cell vehicle. Fig. Figure 2 is a state diagram used to describe an example of the state transition between operating modes in which a control unit can operate. Fig. Figure 3 is a flowchart illustrating an example of an algorithm followed by the control unit. Fig. Figure 4 is a schematic view illustrating an example of the construction of a hydrogen fuel cell. Fig. Figure 5 is a view illustrating a relationship between the voltage and power of a typical fuel cell. DESCRIPTION OF ONE (OF) FORM(S)

[0023] With reference to the drawings, an embodiment of the present invention is described.

[0024] The present embodiment relates to a fuel cell vehicle with a control system for the vehicle's electrical power supply.

[0025] Fig. Figure 1 is a figure showing an exemplary configuration of a fuel cell vehicle 1.

[0026] As in Fig. As shown in Figure 1, the fuel cell vehicle 1 has a fuel cell or FC system 10, a battery pack 20, an inverter 2, a motor 3 and a control unit 30.

[0027] The FC system 10 supplies power to the battery pack 20 and the inverter 2. This FC system 10 comprises a fuel cell stack, hereinafter referred to as the FC stack, 11, a blower drive 12, a blower 13, and a field-effect transistor or FET 14.

[0028] In the FC system 10, the blower drive 12 and the FET 14 are electrically connected to an output stage of the FC stack 11. The blower drive 12 and the FET 14 are electrically connected to the output stage of the FC stack 11 in this order.

[0029] The blower 13 is provided to cause the FC stack 11 to generate electricity (by introducing air for power generation) and to cool the system. The blower drive 12 powers this blower 13 by supplying power from the FC stack 11.

[0030] The FET 14 is a switching unit that allows either the connection of the inverter 2 (which also includes the motor 3) and the battery pack 20 to the FC system 10 or the disconnection of the connection.

[0031] Inverter 2 and battery pack 20 are electrically coupled to the output stage of FC system 10. Specifically, inverter 2 and battery pack 20 are connected in parallel with respect to a power supply circuit for FC system 10. This results, for example, in FET 14 being located between blower drive 12 and battery pack 20, and between blower drive 12 and inverter 2, since blower drive 12 and FET 14, as previously mentioned, are coupled to the output stage of FC stack 11 in FC system 10 in that order.

[0032] The battery pack 20 has several relays 22 that allow a connection of a battery 21 to a circuit to which the FC system 10 can supply power, and a disconnection of the connection.

[0033] Inverter 2, controlled by control unit 30, causes motor 3 to provide torque to drive wheels 4 using power supplied by FC system 10 or battery pack 20. The torque provided by this motor 3 propels the vehicle.

[0034] The control unit 30 is configured within an ECU (electronic control unit), which includes, for example, a microcomputer and its peripheral circuitry. Therefore, the control unit 30 comprises a CPU, a ROM, and a RAM. The ROM stores one or more programs for executing various types of processing. The CPU executes these different types of processing according to the stored two or more programs.

[0035] With reference to Fig. The control unit 30 comprises a battery charge level determination module 31 and a timer 32. The battery charge level determination module 31 determines, in particular, the battery charge level or SOC (State of Charge) of the battery 21 in the battery pack 20. The timer 32 is used to measure the duration for which the operation continues in an idle mode described later.

[0036] Furthermore, this control unit 30 controls the FC system 10, the battery pack 20, and the inverter 2. Specifically, the control unit 30 causes the system to operate differently depending on various operating modes, such as a start-up mode, a fuel cell shutdown mode, a normal mode, and an idle mode, based on the battery state of charge (SOC) determined by the battery charge level determination module 31. The different operating modes are described below.

[0037] The start-up mode is an operating mode that the system enters immediately after the FC system 10 is started up. The fuel cell shutdown mode is an operating mode in which the FC stack 11 is prevented from generating power. The normal mode is an operating mode in which the FC stack 11 is caused to generate power (or in which the FC stack 11 is in an operating state). The idle mode is an operating mode in which the FC stack is caused to generate power in a state where the FC system 10 is disconnected from the battery pack 20 and the inverter 2.

[0038] Fig. Figure 2 is a diagram (or state diagram) used to describe an example of the state transition between these operating modes. Referring to this state diagram, the following paragraphs describe in more detail how the system operates in each mode, while also describing the transition to each mode.

[0039] As in Fig. As shown in Figure 2, in start-up mode M1, the fuel cell stack 11 is switched off and the FET (or "fuel cell FET") 14 is switched off. In normal mode M2, the fuel cell stack 11 is in the operating state and the FET 14 is switched on. In fuel cell shutdown mode M3, the fuel cell stack 11 is switched off and the FET 14 is switched off. In idle mode M4, the fuel cell stack 11 is in the operating state and the FET 14 is switched off.

[0040] First, the control unit 30, which can control the system in each of these operating modes, initiates the commissioning of the FC system 10, so that it operates in the initial mode M1. In this initial mode, the control unit 30 continues to determine the battery state of charge, which is represented by a detection value determined by a battery state of charge determination module 31, and causes the system to transition to the fuel cell shutdown mode M3 when the battery state of charge is equal to or greater than a threshold value. L To determine a low level, (battery SOC ≧ SOC) L ). At this point, the control unit 30 causes the system to perform the transition from the start mode M1 to the fuel cell shutdown mode M3 by keeping the FC stack 11 in the off state and the FET 14 in the off state.

[0041] Furthermore, the control unit 30 then initiates the system if the battery SOC is lower than the threshold SOC during operation in the initial mode. L To determine a low level, (battery SOC < SOC L ), to transition to normal mode M2. At this point, the control unit causes the system to perform the transition from the initial mode M1 to normal mode M2 ​​by activating the FC stack 11 and turning on the FET 14 to connect the FC stack 11 to the battery pack 20 and the inverter 2.

[0042] It should be noted here that the threshold SOC L For determining a low level, a predetermined value is used, which can be determined in advance experimentally, empirically, or theoretically.

[0043] After transitioning to normal mode M2, the control unit 30 then initiates the system if the battery SOC during this normal mode is equal to or greater than a threshold SOC. H To determine a high level, (battery SOC ≧ SOC) L ), to transition to idle mode M4. At this point, the control unit 30 causes the system to perform the transition from normal mode M2 ​​to idle mode M4 by keeping the FC stack 11 in the operating state and switching off the FET 14 to disconnect the FC stack 11 from the battery pack 20 and the inverter 2.

[0044] It should be noted here that the threshold SOC H The high level used to determine a threshold value is used to determine whether battery 21 is overcharged or not. This threshold value is called SOC (State of Charge). L The threshold value SOC is greater than the threshold value for determining a high level. Lfor determining a low level (SOC) H > SOC L For example, the threshold SOC H To determine a high level, a predetermined value is used, which can be determined in advance experimentally, empirically, or theoretically.

[0045] Furthermore, after transitioning to fuel cell shutdown mode M3, the control unit 30 then instructs the system if the battery SOC during this fuel cell shutdown mode is lower than the SOC threshold. L To determine a low level, (battery SOC < SOC L ), to transition to normal mode M2. At this point, the control unit 30 causes the system to perform the transition from the fuel cell shutdown mode M3 to normal mode M2 ​​by activating the FC stack 11 and switching on the FET 14 to connect the FC stack 11 to the battery pack 20 and the inverter 2.

[0046] Furthermore, when transitioning to idle mode M4, the control unit 30 activates the timer 32 at the start of this idle mode M4. Since the FC stack 11 generates power in this idle mode M4, the control unit 30 causes the blower drive 12 to activate the blower 13, which is provided to force the FC stack 11 to generate power (by introducing air for power generation) and to cool the system. The blower 13 then operates using power supplied by the FC stack 11.

[0047] If the battery SOC is lower than the threshold SOC during this idle mode L To determine a low level, (battery SOC < SOC L ) or if the timer value becomes greater than a threshold t1 for determining the elapsed time and the battery SOC is lower than a threshold SOC MTo determine an average level, (timer value > t1 and battery SOC < SOC) M ), the control unit 30 causes the system to transition to normal mode M2. At this point, the control unit 30 causes the system to perform the transition from idle mode M4 to normal mode M2 ​​by keeping the FC stack 11 in the operating state and turning on the FET 14 to connect the FC stack 11 to the battery pack 20 and the inverter 2.

[0048] Furthermore, the control unit 30 initiates the system when the timer value becomes greater than the threshold t1 for determining the elapsed time and the battery SOC is equal to or greater than the threshold SOC M To determine an average level, (timer value > t1 and battery SOC ≧ SOC) M), to transition to fuel cell shutdown mode M3. At this point, the control unit 30 causes the system to transition from idle mode M4 to fuel cell shutdown mode M3 by switching off FC stack 11 while keeping FET 14 in the off state.

[0049] It should be noted here that the threshold SOC M for determining an average level smaller than the SOC threshold H for determining a high level, but greater than the SOC threshold L for determining a low level (SOC) H > SOC M > SOC L For example, the threshold SOC L For determining an average level, a predetermined value is used, which can be determined in advance experimentally, empirically, or theoretically.

[0050] The threshold t1 for determining the elapsed time represents a period of time for which the degree of deterioration of the FC stack 11 resulting from the operation of the FC stack 11 during the period represented by the threshold t1 for determining the elapsed time is equal to or less than the degree of deterioration of the FC stack 11 resulting from a cycle of shutting down the FC stack 11 and its subsequent restarting.

[0051] Fig. Figure 3 is a flowchart diagram illustrating an example of the execution of previously described transitions between operating modes.

[0052] As in Fig. As shown in Figure 3, the control unit 30 first determines in step S1 whether the battery SOC is lower than the threshold SOC. L for determining a low level. If it determines that the battery SOC is lower than the SOC threshold. Lfor determining a low level (SOC < SOC L ), the control unit 30 instructs the algorithm to transition to step S5. And if it determines that the battery SOC is equal to or greater than the SOC threshold L for determining a low level (SOC ≧ SOC L ), the control unit 30 initiates the algorithm to transition to step S2.

[0053] In step S2, control unit 30 determines whether the vehicle's power supply is switched on. If it determines that the vehicle's power supply is switched on, control unit 30 initiates the algorithm to transition to step S3. And if it determines that the vehicle's power supply is not switched on, control unit 30 initiates the algorithm in Fig. 3 illustrated algorithm for exiting processing.

[0054] In step S3, control unit 30 causes FC stack 11 to be switched off and causes FET 14 to be switched off. In the next step S4, control unit 30 determines whether the battery state of charge (SOC) is lower than the threshold SOC. L for determining a low level. If it determines that the battery SOC is lower than the SOC threshold. L for determining a low level (SOC < SOC L ), the control unit 30 instructs the algorithm to transition to step S5. And if it determines that the battery SOC is equal to or greater than the SOC threshold L for determining a low level (SOC ≧ SOC L ), causes the control unit 30 to start the algorithm again with step S2.

[0055] The algorithm in steps S3 and S4 corresponds to the processing in start mode M1 and in fuel cell shutdown mode M3.

[0056] In step S5, control unit 30 determines whether the vehicle's power supply is switched on. If it determines that the vehicle's power supply is switched on, control unit 30 initiates the algorithm to transition to step S6. And if it determines that the vehicle's power supply is not switched on, control unit 30 initiates the algorithm in Fig. 3 illustrated algorithm for exiting processing.

[0057] In step S6, the control unit 30 causes the FC stack 11 to enter its operating state and causes the FET 14 to be switched on. In the next step S7, the control unit 30 determines whether the battery state of charge (SOC) is equal to or greater than the threshold SOC value. H for determining a high level. If it determines that the battery SOC is equal to or greater than the threshold SOC L For determining a high level, (battery SOC ≧ SOC L), the control unit 30 instructs the algorithm to transition to step S8. And if it determines that the battery SOC is lower than the SOC threshold L for determining a high level (battery SOC < SOC L ), causes the control unit 30 to start the algorithm again with step S5.

[0058] The algorithm used in steps S6 and S7 corresponds to the processing in normal mode M2.

[0059] In step S8, control unit 30 determines whether the vehicle's power supply is switched on. If it determines that the vehicle's power supply is switched on, control unit 30 initiates the algorithm to proceed to step S9. And if it determines that the vehicle's power supply is not switched on, it initiates the algorithm in Fig. 3 illustrated algorithm for exiting processing.

[0060] In step S9, the control unit 30 causes the FC stack 11 to enter its operating state and causes the FET 14 to be switched off. Additionally, the control unit 30 causes the timer 32 to begin its measurement. In the next step, S10, the control unit 30 determines whether the battery state of charge (SOC) is below the threshold value. L for determining a low level. If it determines that the battery SOC is lower than the threshold SOC L for determining a low level (battery SOC < SOC L ), the control unit 30 instructs the algorithm to transition to step S5. And if it determines that the battery SOC is equal to or greater than the SOC threshold L For determining a low level, (battery SOC ≧ SOC L ), the control unit 30 initiates the algorithm to transition to step S11.

[0061] In step S11, the control unit 30 determines whether the timer value, the measurement of which began in step S9, is greater than the threshold t1 for determining the elapsed time. If it determines that the timer value is greater than the threshold t1 for determining the elapsed time (timer value > t1), the control unit 30 instructs the algorithm to proceed to step S12. If it determines that the timer value is equal to or less than the threshold t1 for determining the elapsed time (timer value ≤ t1), the control unit 30 instructs the algorithm to restart with step S8.

[0062] In step S12, the control unit 30 determines whether the battery SOC is lower than the SOC threshold. M for determining an average level. If it determines that the battery SOC is lower than the threshold SOC M for determining an average level (battery SOC < SOC M), the control unit 30 instructs the algorithm to transition to step S5. And if it determines that the battery SOC is equal to or greater than the SOC threshold M for determining an average level (battery SOC ≧ SOC M ), the control unit 30 initiates the algorithm to transition to step S2.

[0063] The algorithm in steps S9 to S12 corresponds to the processing in idle mode M4. OPERATION AND FUNCTION

[0064] Next, the operation and function of the vehicle will be described.

[0065] If the battery SOC in start-up mode is lower than the SOC threshold L To determine a low level, (battery SOC < SOC) L), the control unit 30 causes the system to perform a transition to normal mode M2 ​​by activating the FC stack 11 and switching on the FET 14 to electrically connect the FC stack 11 to the battery pack 20 and the inverter 2.

[0066] In normal mode M2, the control unit 30 allows current to be supplied from the FC stack 11 to charge the battery pack 20 and to drive the motor 3 as required.

[0067] Furthermore, the control unit 30 then initiates the system when, in this normal mode, the battery SOC is equal to or greater than the SOC threshold. L To determine a high level, (SOC ≧ SOC) L ), to perform the transition to idle mode M4 by causing the FC stack 11 to remain in the operating state and switching off the FET 14 to electrically disconnect the FC stack 11 from the battery pack 20 and the inverter 2.

[0068] Since the supply of power from the FC stack 11 to the battery pack 20 and the motor 3 (especially the inverter 2) is interrupted in the idle mode M4, the inverter 2 operates the motor 3 by supplying power from the battery pack 20.

[0069] If the battery SOC falls below the threshold SOC during this idle mode due to power consumption by the motor drive L To determine a low level, (battery SOC < SOC L ) or if the battery SOC is lower than the SOC threshold M for determining an average level, while the timer value counted since the start of idle mode becomes greater than the threshold t1 for determining the elapsed time (timer value > t1 and battery SOC < SOC M), the control unit 30 causes the system to perform the transition to normal mode M2 ​​by switching on the FET 14 to electrically connect the FEC stack 11 to the battery pack 20 and the inverter 2, while the FC stack 11 remains in operating mode.

[0070] Furthermore, the control unit 30 then initiates the system if, during this idle mode, the battery SOC is equal to or greater than the SOC threshold despite the power consumption by the motor drive. M for determining an average level, while the timer value counted since the start of the idle mode becomes greater than the threshold t1 for determining the elapsed time, to perform the transition to the fuel cell shutdown mode M3 by switching off the FC stack 11 while the FET 14 remains in the off state.

[0071] Since the supply of current from the FC stack 11 to the battery pack 20 and the motor 3 (especially the inverter 2) is interrupted in this fuel cell shutdown mode M3 as in the idle mode M4, the inverter 2 operates the motor 3 by supplying current from the battery pack 20.

[0072] Since in this fuel cell shutdown mode M3 the FC stack 11 is brought to a standstill and the FC stack 11 is disconnected from the battery pack 20 and the inverter 2 to avoid being under load, the voltage of the FC stack 11 will also be as high as an open-circuit voltage at its highest potential. It will be discussed later that the voltage of the FC stack 11 will be as high as an open-circuit voltage at its highest potential.

[0073] If, during this fuel cell shutdown mode, the battery SOC falls below the threshold SOC due to power consumption resulting from the engine's operation, LTo determine a low level, (battery SOC < SOC L ), the control unit 30 causes the system to perform the transition to normal mode M2 ​​by activating the FC stack 11 and switching on the FET 14 to electrically connect the FC stack 11 to the battery pack 20 and the inverter 2. EFFECTS OF THE PRESENT FORM OF EXECUTION

[0074] According to the present embodiment, in the fuel cell vehicle 1, despite the fact that the FC stack 11 and the battery pack 20 are connected without a DC / DC converter, the connection of the FC stack 11 with the battery pack 20 and the motor 3, in particular the inverter 2, is interrupted in idle mode M4 when the battery SOC is equal to or greater than the threshold value SOC Lfor determining a high level. This prevents the battery 21 in the fuel cell vehicle 1 according to the present embodiment from being overcharged.

[0075] Furthermore, the present embodiment uses the FET 14 as a switching unit configured to establish and disconnect a connection between the fuel cell stack 11 and the battery pack 20 and the motor 3 (in particular, the inverter 2). This prevents overcurrent caused by a difference between the terminal voltages of the FET 14, since, in the fuel cell vehicle 1 according to the present embodiment, the FET 14 limits the electrical current by switching during the electrical connection of the fuel cell stack 11 to the battery pack 20 and the motor 3, in particular the inverter 2.

[0076] Moreover, in the fuel cell vehicle 1 according to the present embodiment, the FC stack 11 continues to generate electricity by selecting idle mode M4 even when the battery SOC is equal to or greater than the threshold SOC L for determining a high level. This reduces the frequency of starting up / shutting down the FC stack 11 in the fuel cell vehicle 1 according to the present embodiment, thereby limiting the deterioration of the FC stack 11.

[0077] Now, with reference to Fig. 4 and Fig. 5 additionally describes why a reduction in the frequency with which a start-up / shutdown of the FC stack 11 occurs leads to a deterioration of the FC stack 11.

[0078] Fig. Figure 4 is a schematic view illustrating an example of the construction of a hydrogen fuel cell. Fig. Figure 5 is a view illustrating the relationship between the voltage and power of a typical fuel cell.

[0079] First, the electrochemical reaction that takes place in a fuel cell system and the associated production of water are described.

[0080] A fuel cell system is configured as a stack by laminating a large number of minimal units, commonly referred to as cells. As in Fig. As shown in Figure 4, in each cell of a typical proton exchange membrane fuel cell system, diffusion layers 53, an anode and a cathode catalyst layer 54, and an electrolyte membrane 55 are arranged between an anode 51 and a cathode 52, to which air (or oxygen) and hydrogen are supplied. Each catalyst layer 54 is a layer for increasing the reaction rate. Furthermore, the electrolyte membrane 55 is a membrane designed to allow hydrogen ions, but not electrons, to pass through.

[0081] In this configuration, the anode catalyst layer 54 on the side of the anode 51 facing the electrolyte causes the hydrogen supplied to the anode 51 to be activated to convert into hydrogen ions, thereby releasing electrons. Fig. 4 The reaction given by (1) is represented by the following chemical equation (1): H2 → 2H ++ 2e - (1)

[0082] The hydrogen ions originating from the reaction according to equation (1) above, along with moisture contained in the electrolyte membrane 55, pass from the anode side 51 through the electrolyte membrane 55 to the cathode side 52. The released electrons move through an external circuit to the cathode 52. Oxygen molecules from the air, which are directed to the cathode 52 on the other side of the membrane, combine at the cathode catalyst layer 54 with the electrons from the external circuit to form oxygen ions and react with the hydrogen ions that have passed through the electrolyte membrane 55 to form water. Fig. 4 The reaction given by (2) is represented by the following chemical equation (2): ½O2 + 2H + + 2e - → H2O (2).

[0083] Some of the moisture generated in this way moves from the cathode 52 to the anode 51 via concentration diffusion.

[0084] Fuel cells exhibit properties that cause a decrease in the terminal voltage with increasing electric current and power, due to various losses resulting from the aforementioned chemical reactions inside the fuel cell, such as losses caused by a resistance overvoltage originating from the resistances of the electrolyte 55 and the terminals, an activation overvoltage to cause an electrochemical reaction between the hydrogen and the oxygen, and a diffusion overvoltage to cause the hydrogen and oxygen to pass through the diffusion layers 53.

[0085] With reference to Fig.5, which describes fuel cell properties, states that during shutdown the load is disconnected from a fuel cell and the potentials to which the fuel cell is exposed are reduced to an open-circuit voltage V. OCV , i.e., the maximum voltage. Afterwards, the hydrogen anode pressure gradually decreases through the electrolyte membrane 55, which accordingly leads to a decrease in the potentials to which the fuel cell is exposed. Thus, it is a well-known fact that the potentials to which fuel cells are exposed should not be kept at high potentials as far as possible in order to limit fuel cell degradation.

[0086] As mentioned above, shutting down a fuel cell exposed to higher potentials significantly affects its degradation. Therefore, it is desirable to minimize the start / stop cycle (or frequency) to limit fuel cell degradation.

[0087] Therefore, the present embodiment does not perform a direct transition from normal mode M2 ​​to fuel cell shutdown mode M3, but rather an indirect transition from normal mode M2 ​​to fuel cell shutdown mode M3 after a transition to idle mode M4. This first activates the blower 13; instead of immediately disconnecting the load, such as the battery pack 20, from the power supply line, the power supply line is subjected to a voltage (V IDL ) for the no-load condition, which is lower than the no-load voltage (V) OCV) is, and reduces the number of shutdown events of the FC stack 11 as much as possible, resulting in a reduction in the number of start-up events, thereby limiting the deterioration of the fuel cells.

[0088] Furthermore, in a system configuration such as the present embodiment, if the motor 3, which represents the load, is disconnected from the FC stack 11 while the FC system 10 remains in operation, the power generated by the FC stack 11 in the idle state is reduced to the extent of P IDL The power is consumed by the blower 13, which is one of the auxiliary devices. This leads to a reduction in the level of power generated by the FC stack 11 to a voltage V. IDL , which are lower than the open-circuit voltage V OCV is.

[0089] Despite the fact that the potential to which the FC stack 11 is exposed exhibits a voltage V at idle IDLis lower than the open-circuit voltage V OCV Even if the potential remains high, a noticeable effect on fuel cell degradation persists. Therefore, it cannot be said that remaining in an idle state for an extended period is desirable.

[0090] Therefore, the present embodiment enters the shutdown process to shut down the FC stack 11 and stop power generation during a transition from idle mode M4 to fuel cell shutdown mode M3, which occurs when the battery SOC is equal to or greater than the threshold SOC M for the criterion of the mean level and a time period has elapsed which is equal to the threshold value t1 for the criterion of the elapsed time since the FET 14 was switched off in order to separate the FC stack 11 from the battery pack 20 and the motor 3 or in particular the inverter 2.

[0091] According to the present embodiment, this prevents deterioration of the FC stack 11 caused by remaining in idle mode M4 for a long period of time.

[0092] In the preceding description of the present embodiment, the FET 14 and the control unit 30 including the battery charge level determination module 31 form, for example, a system for controlling the electrical power supply of a vehicle. ADAPTED FORMS

[0093] A relay can be used instead of the FET 14 of the present embodiment.

[0094] Furthermore, instead of the battery SOC, the battery voltage can be used as the representative battery charge level of battery 21 in the present embodiment. DESCRIPTION OF REFERENCE MARKS

[0095] 1 Fuel cell vehicle, 2 Inverter, 3 Motor, 10 Fuel cell system, 11 FC stack, 12 Blower drive, 13 Blower, 14 FET, 20 Battery pack, 21 Battery, 30 Control unit, 31 Battery charge level determination module, 32 Timer.

Claims

[1] System for controlling the electrical power supply of a vehicle (1) in a vehicle (1) comprising a motor (3) to provide torque to wheels (4), a battery (21) to store electrical current and to supply the stored electrical current to the motor (3), and fuel cells (11) to generate electrical current and to supply the generated electrical current to the motor (3) and the battery (21), to control the supply of electrical current from the fuel cells (11), wherein the system for controlling the electrical power supply comprises: a battery charge level determination module (31) to determine a battery charge level of the battery (21); a switching unit (14) configured to provide a connection between the fuel cells (11) and the motor (3) and the battery (21) or to disconnect the fuel cells (11) from the motor (3) and the battery (21); and a control unit (30) configured to not only cause the switching unit (14) to disconnect the fuel cells (11) from the motor (3) and the battery (21), but also to cause the fuel cells (11) to continue generating electricity in the disconnected state from the motor (3) and the battery (21) when the battery charge level determined by the battery charge level determination module (31) is equal to or greater than a first predetermined threshold (SOC). H ) is. [2] System for controlling the electrical power supply of a vehicle (1) according to claim 1, characterized by , that the control unit (30) no longer enables the generation of electricity by the fuel cells (11) after a predetermined period of time (t1) has elapsed since the fuel cells (11) were disconnected from the motor (3) and the battery (21) by the switching unit (14). [3] System for controlling the electrical power supply of a vehicle (1) according to claim 1, characterized by , that the control unit (30) no longer enables power generation by the fuel cells (11) if the battery charge level determined by the battery charge level determination module (31) is equal to or greater than a second predetermined threshold (SOC) after a predetermined time period (t1) since the fuel cells (11) were disconnected from the motor (3) and the battery (21) by the switching unit (14). M ) which is lower than the first predetermined threshold (SOC) H ) but causes the switching unit (14) to reconnect the fuel cells (11) to the motor (3) and the battery (21) if the battery charge level determined by the battery charge level determination module (31) is lower than the second predetermined threshold (SOC) after the predetermined time period (t1) since the switching unit (14) disconnected the fuel cells (11) from the motor (3) and the battery (21). M ) is. [4] System for controlling the electrical power supply of a vehicle (1) according to claim 1, characterized by , that the switching unit (14) is a field-effect transistor. [5] Vehicle (1) comprising a motor (3) to provide torque to wheels (4), a battery (21) to store electrical current and to supply the stored electrical current to the motor (3), and fuel cells (11) to generate electrical current and to supply the generated current to the motor (3) and the battery (21), characterized by , that it includes: a battery charge level determination module (31) to determine a battery charge level of the battery (21); a switching unit (14) configured to provide a connection between the fuel cells (11) and the motor (3) and the battery (21) or to disconnect the fuel cells (11) from the motor (3) and the battery (21); and a control unit (30) configured to not only cause the switching unit (14) to disconnect the fuel cells (11) from the motor (3) and the battery (21), but also to cause the fuel cells (11) to continue generating electricity when the battery charge level determined by the battery charge level determination module (31) is equal to or greater than a first predetermined threshold (SOC). H ) is.

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