JP4502985B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system including a fuel cell and a capacitor connected in parallel to a motor drive circuit, for example, a fuel cell system suitable for an electric vehicle.

  Conventionally, a fuel cell system used in an electric vehicle or the like has been proposed in which a fuel cell and a capacitor are connected in parallel, and regenerative power generated during braking by a regenerative brake is stored by the capacitor. Thus, it is possible to make up for the shortage of electric energy supplied from the fuel cell only at the time of high load such as acceleration by the electric energy stored in the capacitor.

  Such a capacitor is usually a large-capacity electric double layer capacitor or the like, and is connected to the fuel cell or the motor drive circuit in parallel via a switch or the like.

JP 2001-325977 A

  However, when a large-capacity capacitor is connected in parallel to the fuel cell or the motor drive circuit as described above, the following problems occur.

  Since the fuel cell and the motor drive circuit are connected in parallel to the capacitor, when surplus power from the fuel cell or regenerative power from the motor drive circuit is generated, the electrical energy can be supplied to the capacitor. In such a case, there is a problem that if the supply is continued beyond the expected charging capacity of the capacitor, the charge / discharge characteristics of the capacitor may be affected, for example, the electrolyte in the capacitor is decomposed.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel cell system that hardly adversely affects the charge / discharge characteristics of a capacitor.

  In order to achieve the above object, the fuel cell system of claim 1 according to claim 1 is a fuel cell system including a fuel cell and a capacitor respectively connected in parallel to a motor drive circuit, the terminal of the capacitor When the voltage between the terminals of the capacitor is higher than a predetermined voltage value, it is determined that there is a risk of exceeding the maximum allowable voltage value of the capacitor, and the regenerative current flowing into the capacitor from the motor drive circuit It is technically characterized by comprising current control means for suppressing the value to a predetermined current value that is set as a current value that fluctuates based on the voltage across the capacitor within a range in which the electrolyte in the capacitor is not decomposed. .

  The fuel cell system according to claim 2 according to the claim is characterized in that, in the fuel cell system according to claim 1, the current control means is composed of a semiconductor element.

  According to the first aspect of the present invention, the voltage between the terminals of the capacitor is detected, and when the voltage between the terminals of the capacitor is higher than the first predetermined voltage value, it is determined that there is a risk of exceeding the maximum allowable voltage value of the capacitor, and the motor The regenerative current value that flows into the capacitor from the drive circuit is suppressed to a predetermined current value that is set as a current value that varies based on the voltage across the terminals of the capacitor within a range where the electrolyte in the capacitor does not decompose. As a result, even if a fuel cell and a capacitor are connected in parallel to the motor drive circuit, the regenerative current value that flows from the motor drive circuit to the capacitor does not affect the charge / discharge characteristics of the capacitor. It is suppressed to a predetermined current value that is set as a current value that varies based on the voltage. Therefore, for example, even if surplus power generated by the fuel cell or regenerative power generated by the motor drive circuit is supplied to the capacitor, the regenerative current that flows into the capacitor within the range of the capacitor's scheduled charging capacity is reduced. Can be suppressed. Therefore, there is an effect that it is difficult to adversely affect the charge / discharge characteristics of the capacitor.

  In the invention of claim 2, since the current control means is made of a semiconductor element, energy loss in current control can be suppressed more than that made of a passive element such as a resistor. As a result, the current can be controlled efficiently, so that the electric energy generated in the fuel cell or the like can be stored in the capacitor as much as possible without waste. Therefore, in addition to the effect of hardly adversely affecting the charge / discharge characteristics of the capacitor, there is also an effect of suppressing wasteful consumption of clean energy.

  Hereinafter, embodiments of the fuel cell system of the present invention will be described with reference to the drawings. In the following embodiment, an example in which the fuel cell system of the present invention is applied to an electric vehicle will be described. First, before describing the embodiment according to the present invention, a fuel cell system 20 positioned as a technique related to the present invention will be described as a reference example of the present invention.

  FIG. 1 is a functional block diagram showing a main functional configuration of a fuel cell system 20 according to a reference example. As shown in the figure, the fuel cell system 20 mainly includes a fuel cell 21, an output control current adjustment unit 23, a capacitor (capacitor) 25, a protection current adjustment unit 28, a load 29, a system controller 31, and the like. The fuel cell 21 and the capacitor 25 are connected to the load 29 in parallel. Therefore, a configuration such as the fuel cell system 20 is also referred to as a hybrid circuit. In addition, the broken line shown in FIG. 1 has shown the flow of the information signal transmitted / received between each functional block.

  FIG. 2 is a circuit diagram showing an electrical configuration of the fuel cell system 20, and the configuration contents of the fuel cell system 20 are shown in more detail than the functional block diagram of FIG. Hereinafter, the configuration of the fuel cell system 20 will be described with reference to FIG. 2 indicate the flow of information signals exchanged between the functional blocks or functional components.

  The fuel cell 21 can extract electric energy by reacting hydrogen and oxygen, and is one of the energy sources of an electric vehicle that drives wheels by a motor. For this reason, hydrogen and oxygen (or air) are supplied to the fuel cell 21, and the supply amount thereof is controlled by a fuel cell / motor controller (hereinafter referred to as “FC / M controller”) 35 described later, Output power is controlled. The fuel cell 21 is generally classified into various types according to a method such as hydrogen storage or a reforming catalyst. However, any fuel cell system according to the present invention can be used as long as it generates electricity by reacting hydrogen and oxygen. Can be applied.

  In the fuel cell 21, the voltage between the terminals (hereinafter referred to as “FC voltage”) Vfc is detected by the voltage sensor 22. That is, the voltage sensor 22 is connected between the output terminals of the fuel cell 21, and the FC voltage Vfc detected by the voltage sensor 22 is output to the FC / M controller 35. As a result, the FC / M controller 35 can appropriately monitor the output voltage (FC voltage Vfc) of the fuel cell 21, thereby enabling output control of the fuel cell 21 based on this.

  Further, contactors CN-a and CN-b are connected to the output terminal of the fuel cell 21. That is, the contactor CN-a is connected to the positive electrode terminal side of the fuel cell 21, and the contactor CN-b is connected to the negative electrode terminal side of the fuel cell 21. These contactors CN-a and CN-b have a mechanical switch circuit such as a relay. For example, the switch circuit is turned on / off by a control signal input from the outside of the system controller 31 such as an ignition switch. It is comprised so that it can control to each state.

  As a result, either one of the contactors CN-a and CN-b operates to shut off the switch circuit, so that the input / output of the fuel cell 21 can be shut off. Since the contactor is connected, even if one of the contactors CN-a (or contactor CN-b) fails, the other contactor CN-b (or contactor CN-a) cuts off the input / output of the fuel cell 21. be able to. Therefore, the fuel cell 21 can be electrically disconnected from the external circuit when an abnormality occurs in the fuel cell 21 or when a vehicle equipped with the fuel cell system 20 detects a large impact due to a collision or the like.

  The output control current adjusting unit 23 controls the amount of current output from the fuel cell 21, and is represented as a switching element 23A in FIG. For this, a power semiconductor switching element such as an IGBT (insulated gate bipolar transistor) is used, and its base terminal or gate terminal is connected to the FC / M controller 35.

  Thus, the switching control by the FC / M controller 35 is performed on the switching element 23A based on the fuel cell current (hereinafter referred to as “FC current”) Ifc detected by the current sensor 24 that can measure the input / output current of the fuel cell 21. Can be done. Therefore, the FC current Ifc of the fuel cell 21 output via the switching element 23A is detected by the current sensor 24 and input to the FC / M controller 35, and the switching of the switching element 23A is performed based on the value of the FC current Ifc. Control is performed. That is, a closed loop negative feedback control system including the switching element 23A, the current sensor 24, and the FC / M controller 35 can be configured, so that the output control of the fuel cell 21 with a predetermined current value as a target can be performed.

  The capacitor 25 is a large-capacity capacitor that can store electric charge of several F to several hundred F. For example, an electric double layer capacitor is used. The fuel cell 21 is connected in parallel to the fuel cell 21 and the motor drive circuit 29A via the protective current adjusting unit 28. Therefore, electric energy (charging current) due to electric power generated by the fuel cell 21 and electric energy (regenerative current) due to regenerative electric power generated by the motor drive circuit 29A can be stored, that is, charged.

  Similarly to the fuel cell 21, the capacitor 25 also detects a voltage Vec between its terminals (hereinafter referred to as “capacitor voltage”) Vec by a voltage sensor 26. That is, a voltage sensor 26 is connected between the output terminals of the capacitor 25, and the capacitor voltage Vec detected by the voltage sensor 26 is output to a hybrid circuit controller (hereinafter referred to as “HBC controller”) 33 described later. Yes. Thereby, the output voltage (capacitor voltage Vec) of the capacitor 25 is appropriately monitored by the HBC controller 33.

  Further, contactors CN-c and CN-d similar to the above-described contactor CN-a and the like are connected to the output terminal of the capacitor 25. That is, the contactor CN-c is connected to the positive electrode terminal side of the capacitor 25, and the contactor CN-d is connected to the negative electrode terminal side of the capacitor 25. These contactors CN-c and CN-d are also configured so that the switch circuit can be controlled to each of the conductive / shut off states by a control signal input from the outside of the system controller 31 such as an ignition switch.

  As a result, one of the contactors CN-c and CN-d operates to shut off the switch circuit, so that the input / output of the capacitor 25 can be shut off. In addition, contactors are connected to both terminals of the capacitor 25. Since it is connected, even if one of the contactors CN-c (or contactor CN-d) fails, the other contactor CN-d (or contactor CN-c) can shut off the input / output of the capacitor 25. . Therefore, the capacitor 25 can be electrically disconnected from the external circuit when an abnormality occurs in the capacitor 25 or when a vehicle having the fuel cell system 20 detects a large impact due to a collision or the like.

  A current sensor 27 is connected to the contactor CN-c. The current sensor 27 detects the current input to the capacitor 25, that is, the amount of charge current and regenerative current flowing into the capacitor 25, and the amount of discharge current output from the capacitor 25 and detects it. The capacitor current Iec is output to the HBC controller 33.

  The protective current adjusting unit 28 controls the charging current flowing from the fuel cell 21 to the capacitor 25 and also controls the regenerative current flowing from the motor drive circuit 29A to the capacitor 25, and is represented as a switching element 28A in FIG. Yes. Similar to the switching element 23A described above, a power semiconductor switching element such as an IGBT is used for this, and its base terminal or gate terminal is connected to the HBC controller 33. The switching element 28 </ b> A is subjected to current control according to the capacitor current Iec of the current sensor 27 by the capacitor management control processing by the HBC controller 33.

  The protective current adjusting unit 28 (switching element 28A) constitutes a functional element corresponding to the “current control means” described in the claims together with the HBC controller 33 described later.

  The motor drive circuit 29A constitutes a part of a load connected in parallel to the fuel cell 21 and the capacitor 25, and includes, for example, an inverter circuit that drives an AC motor M for a vehicle. As the load 29, in addition to the vehicle AC motor M driven by the motor drive circuit 29A, electric components such as a pump and a fan (not shown) that supply hydrogen and oxygen (air) to the fuel cell 21 are also included in the load 29. Can be included.

  The system controller 31 is a control device including a microprocessor, a memory, an input / output interface, and the like (not shown), and is connected to the HBC controller 33 and the FC / M controller 35, and includes the contactors CN-a, CN- It is also connected to b, CN-c, and CN-d. As a result, it is possible to control the entire fuel cell system 20 such as various controls and processes by the HBC controller 33 and the FC / M controller 35, and based on information input from the HBC controller 33 and the FC / M controller 35. Thus, it is also possible to output a conduction / shut-off control signal for the contactors CN-a to CN-d.

  Similarly to the system controller 31, the HBC controller 33 is a control device including a microprocessor, a memory, an input / output interface, and the like (not shown). The HBC controller 33 is connected to the system controller 31, the voltage sensor 26, the current sensor 27, and the switching element 28A. It is connected. As a result, it is possible to deliver predetermined information to the system controller 31 and to be described later based on information on the capacitor voltage Vec input from the voltage sensor 26 and information on the capacitor current Iec input from the current sensor 27. Capacitor management control processing, that is, switching control of the switching element 28A can be executed.

  Similarly to the system controller 31, the FC / M controller 35 is a control device including a microprocessor, a memory, and an input / output interface (not shown). The system controller 31, the fuel cell 21, the voltage sensor 22, the switching element 23A, the current The sensor 24 and the motor drive circuit 29A are connected to each other. Thereby, delivery of predetermined information to the system controller 31, control of the supply amount of hydrogen or the like supplied to the fuel cell 21, or control of the motor drive circuit 29A can be performed. The switching control of the switching element 23A can also be performed based on the information on the FC voltage Vfc input from the voltage sensor 22 and the information on the FC current Ifc input from the current sensor 24.

  By configuring the fuel cell system 20 in this way, even if the fuel cell 21 and the capacitor 25 are connected in parallel to the motor drive circuit 29A, the charging current that flows into the capacitor 25 from the fuel cell 21 and the motor drive circuit 29A. And the regenerative current can be limited. Therefore, for example, even when the amount of charge stored in the capacitor 25 is extremely reduced so as to be close to 0%, the charging current flowing from the fuel cell 21 to the capacitor 25 can be suppressed, Even when the surplus power generated by the fuel cell 21 or the regenerative power generated by the motor drive circuit 29A is supplied to the capacitor 25, the charging current flowing into the capacitor 25 within the range of the scheduled charging capacity of the capacitor 25 and Regenerative current can be suppressed. Therefore, there is an effect that the power generation characteristics of the fuel cell 21 and the charge / discharge characteristics of the capacitor 25 are hardly adversely affected.

  Further, even if the contactor CN-a shown in FIG. 2 is deleted and the fuel cell 21 and the switching element 23A are directly connected, the function of the contactor CN-a is replaced with the switching element 23A, so that the number of parts can be reduced. Can be reduced. That is, by performing the control to cut off the conduction by the gate control of the switching element 23A, the switching function of the circuit by the contactor CN-a can be replaced by the switching element 23A, so even without the contactor CN-a. The fuel cell 21 can be electrically disconnected from the external circuit when an abnormality occurs in the fuel cell 21 or when a vehicle equipped with the fuel cell system 20 detects a large impact due to a collision or the like. It is also possible to replace the contactor CN-b with a switching element similar to the switching element 23A.

  Next, the HBC when starting an electric vehicle equipped with the fuel cell system 20 or when supplying the electric energy stored in the capacitor 25 mainly to the AC motor M when the output demand by the AC motor M is low. The flow of the capacitor management control process by the controller 33 will be described with reference to FIGS.

  As shown in FIG. 3, the capacitor management control process at the time of starting the electric vehicle or the like first performs a process of reading the capacitor voltage Vec from the voltage sensor 26 in step S101. Then, it is determined whether or not the capacitor voltage Vec read from the voltage sensor 26 in step S103 is lower than a preset first predetermined voltage value C_LV0.

  That is, in step S103, it is determined from the capacitor voltage Vec which is the voltage across the terminals of the capacitor 25 whether or not the amount of charge stored in the capacitor 25 is extremely reduced so as to be close to 0%. Process.

  If it is determined in step S103 that the capacitor voltage Vec is lower than the first predetermined voltage value C_LV0 (Yes in S103), the amount of charge stored in the capacitor 25 is extremely small, and the power generation of the fuel cell 21 is performed. May adversely affect properties. That is, by connecting the fuel cell 21 directly to the capacitor 25 in which the input impedance is extremely low, more electric energy can be extracted from the fuel cell 21 than expected, so that the subsequent power generation characteristics of the fuel cell 21 are improved. May have adverse effects. Accordingly, a predetermined charging current value (first predetermined current value) that does not adversely affect the power generation characteristics of the fuel cell 21 is set corresponding to the capacitor voltage Vec read by the voltage sensor 26. The setting of the charging current value is determined by the map in the next step S105.

  In step S105, for example, a process of reading a predetermined charging current value is performed according to a map as shown in FIG. In the map, predetermined charging current values are mapped in advance corresponding to the range of the capacitor voltage detected by the voltage sensor 26 (C_LV0> C_LV1> C_LV2> C_LV3, C_CC1 <C_CC2 <C_CC3). For example, if the range of the capacitor voltage C_LV is C_LV0 (for example, 290V) ≧ C_LV ≧ C_LV1 (for example, 210V), the charging current is set to C_CC1 (for example, 75A), and C_LV1 (for example, 210V)> C_LV ≧ C_LV2 (for example, 190V) If so, the charging current is set to C_CC2 (for example, 240 A). Further, if the range of the capacitor voltage C_LV is C_LV2 (for example, 190V)> C_LV ≧ C_LV3 (for example, 0V), the charging current is set to C_CC3 (for example, 270A).

  When a predetermined charging current value is set in step S105, a process of reading the capacitor current Iec from the current sensor 27 is performed in subsequent step S107. In other words, the charging current flowing into the current capacitor 25 is detected as the capacitor current Iec, and based on this, the process of reading the capacitor current Iec is performed in order to perform the control process of the switching element 28A in the next step S109.

  In step S109, a current control process for the switching element 28A is performed. That is, the capacitor current Iec read in step S107 is compared with the charging current set in step S105, and the gate control of the switching element 28A is performed so that they match. Then, when this process ends, the process returns to step S101 again.

  On the other hand, if it cannot be determined in step S103 that the capacitor voltage Vec is lower than the first predetermined voltage value C_LV0 (No in S103), there is a high possibility that a certain amount of charge is stored in the capacitor 25. Then, the process proceeds to step S111 to control the switching element 28A to the continuous conduction state. That is, electric energy that can be supplied from the fuel cell 21 is supplied to the capacitor 25 without controlling the current to the capacitor 25. Then, steady operation control is started in step S113, and a series of capacitor management control processing at the time of starting the electric vehicle is ended.

  As described above, according to the fuel cell system 20 according to this reference example, when the capacitor voltage Vec of the capacitor 25 is lower than the first predetermined voltage value C_LV0 by the switching element 28A and the HBC controller 33 (Yes in S103), the fuel cell. The charging current flowing from the capacitor 21 into the capacitor 25 is suppressed to the first predetermined current value C_CC1 or less (S105, S107, S109). As a result, when the conditions that can adversely affect the power generation characteristics of the fuel cell 21 are met based on the capacitor voltage Vec of the capacitor 25 (Yes in S103), the charging current flowing from the fuel cell 21 into the capacitor 25 is suppressed ( In other cases (S105, S107, S109) and in other cases (No in S103), the current control according to the storage state of the capacitor 25, that is, not suppressed (S111), can be performed. Therefore, there is an effect that the power generation characteristics of the fuel cell 21 are hardly adversely affected.

  Next, the flow of capacitor management control processing by the HBC controller 33 during steady operation of an electric vehicle equipped with the fuel cell system 20 will be described with reference to FIGS. 5 and 6.

  As shown in FIG. 5, the capacitor management control process at the time of steady operation of the electric vehicle is a modification of the flow of the capacitor management control process at the time of start-up described with reference to FIG. Note that steps S101, S107, S109, and S111 shown in FIG. 3 correspond to steps S201, S207, S209, and S211 shown in FIG. 5, respectively, and the same processing is performed.

  In the capacitor management control process at the time of steady operation or the like, first, the capacitor voltage Vec is read from the voltage sensor 26 in step S201, and then the read capacitor voltage Vec is higher than a preset second predetermined voltage value C_HV0. This determination process is performed in step S203. The second predetermined voltage value C_HV0 can correspond to a “predetermined voltage value” recited in the claims.

  That is, in step S203, processing is performed to determine whether or not the charge is stored in the capacitor 25 to the vicinity of the predetermined charging capacity, based on the capacitor voltage Vec that is the voltage across the terminals of the capacitor 25.

  If it is determined in this step S203 that the capacitor voltage Vec is higher than the second predetermined voltage value C_HV0 (Yes in S203), the capacitor 25 has already stored an electric charge that is close to its charging capability. The charging / discharging characteristics of the capacitor 25 may be adversely affected by passing a normal charging current. Therefore, a predetermined charging current value (second predetermined current value) that does not adversely affect the charge / discharge characteristics of the capacitor 25 is set corresponding to the capacitor voltage Vec read by the voltage sensor 26. The setting of the charging current value is determined by the map in the next step S205. The second predetermined current value can correspond to a “predetermined current value” recited in the claims.

  In step S205, for example, a process of reading a predetermined charging current value is performed according to a map as shown in FIG. In the map, predetermined charging current values are mapped in advance corresponding to the capacitor voltage range detected by the voltage sensor 26 (C_HV0 <C_HV1, C_CC4 <C_CC5). For example, if the range of the capacitor voltage C_HV is C_HV0 (eg, 369V) ≦ C_HV <C_HV1 (eg, 410V), the charging current is set to C_CC4 (eg, 5A), and if C_HV1 (eg, 410V) ≦ C_HV, the charging current is C_CC5 (for example, 0A) is set.

  In the above description, the basis of specific numerical examples is as follows. The maximum allowable voltage value of a capacitor having a single cell laminated structure was set to 410 V, and this was set as C_HV1. The maximum allowable voltage of the capacitor is usually determined by the maximum allowable voltage of a single cell (the maximum value at which the electrolyte in the cell does not decompose due to the voltage) × the number of stacked layers. C_HV0 is the maximum allowable value of the capacitor as a value that may cause the voltage of a specific single cell in the capacitor to exceed the maximum allowable voltage value due to a temporary local bias of the voltage due to a rapid inflow of current into the capacitor. The value was 90% of the voltage value (C_HV1). Further, under this voltage of C_HV0, the value of C_CC4 is set to 5A as a current inflow that does not cause a temporary local bias of voltage between cells in the capacitor. When the voltage of the capacitor is more than the maximum allowable voltage value C_HV1, if the capacitor is further charged, the electrolyte begins to be decomposed in all the cells in the capacitor, which may cause serious damage to the capacitor. It was set to 0A.

  When a predetermined charging current value is set in step S205, a process of reading capacitor current Iec from current sensor 27 is performed in subsequent step S207, and the read capacitor current Iec is compared with the charging current set in step S205. The gate control of the switching element 28A is performed in step S209 so that the two coincide.

  On the other hand, if it cannot be determined in step S203 that the capacitor voltage Vec is higher than the second predetermined voltage value C_HV0 (No in S203), there is a high possibility that the capacitor 25 still has room for storing the charge amount. The process proceeds to step S211, and the switching element 28A is controlled to be in a continuous conduction state. That is, electric energy that can be supplied from the fuel cell 21 or the motor drive circuit 29A during regenerative braking is supplied to the capacitor 25 without controlling the current of the capacitor 25.

  When the process in step S209 or step S211 is completed, a series of capacitor management control processes are terminated.

  Thus, according to the fuel cell system 20 according to the present reference example, when the capacitor voltage Vec of the capacitor 25 is higher than the second predetermined voltage value C_HV0 by the switching element 28A and the HBC controller 33 (Yes in S203), the fuel cell. The charging current flowing from the capacitor 21 into the capacitor 25 and / or the regenerative current flowing into the capacitor 25 from the motor drive circuit 29A are suppressed to the second predetermined current value C_CC3 or less. As a result, when conditions that can adversely affect the charge / discharge characteristics of the capacitor 25 are obtained based on the capacitor voltage Vec of the capacitor 25 (Yes in S203), the fuel cell 21 and / or the motor drive circuit 29A changes the capacitor 25 to the capacitor 25. The charging current and / or regenerative current flowing in can be suppressed, and in other cases (No in S203), current control according to the storage state of the capacitor 25 can be performed. Therefore, there is an effect that the charge / discharge characteristics of the capacitor 25 are hardly adversely affected.

Note that it is also preferable that the circuit configuration described in this reference example is a circuit in which the following changes are made, for example.
(1) A diode for preventing current backflow is added to the output side of the fuel cell 21. In this case, the direction of the diode is arranged so that the current output from the fuel cell 21 passes (the anode on the fuel cell 21 side, the capacitor 25, and the cathode on the motor drive circuit 29A side). This arrangement location is preferably arranged directly on any terminal of the switching element 23A or between the contactor CN-a and the fuel cell 21 in the circuit of FIG. By the arrangement of the diode, it is possible to prevent the current from flowing from the capacitor 25 or the motor drive circuit 29A to the fuel cell 21.
(2) A current adjusting unit for controlling the discharge current from the capacitor 25 is installed. For example, in the circuit of FIG. 2, the arrangement location is connected in series to any terminal of the switching element 28A. More specifically, a semiconductor element equivalent to the switching element 28A is arranged in series with one of the terminals of the switching element 28A in a direction to control a current in the direction opposite to that of the switching element 28A.
(3) It is also preferable not to arrange the switching element 23A in FIG. By doing in this way, a circuit structure can be simplified and there exists an effect which reduces the cost of the fuel cell system 20 whole.

  Next, the fuel cell system 40 according to the embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a circuit diagram showing an electrical configuration of a fuel cell system 40 according to an embodiment of the present invention. The fuel cell system 20 according to the above-described reference example has substantially the same components. Are given the same reference numerals. Note that the broken lines shown in FIG. 7 indicate the flow of information signals exchanged between the functional blocks.

The fuel cell system 40 according to the present embodiment is characterized by control when the regenerative power from the motor drive circuit 29A during braking of the electric vehicle is supplied to the capacitor 25, that is, regenerative braking control.
Therefore, as can be seen by comparing FIG. 2 and FIG. 7, in the fuel cell system 40 according to the present embodiment, the circuit element in which the discharge resistor 41 and the switching element 42 are connected in series is connected in parallel with the motor drive circuit 29A. Furthermore, the brake mechanism 53 provided in the AC motor M is controlled by the brake controller 51, which is different from the fuel cell system 20 according to the reference example described above. Therefore, hereinafter, the configuration and operation of the fuel cell system 40 will be described focusing on these differences.

  As shown in FIG. 7, the fuel cell system 40 has a circuit element in which a discharge resistor 41 and a switching element 42 are connected in series in parallel to the motor drive circuit 29A, and is connected to the motor drive circuit 29A. The input / output voltage (inverter voltage) Viv of the motor drive circuit 29A can be detected by the voltage sensor 43 connected in parallel. The brake mechanism 53 is provided in the motor drive circuit 29 </ b> A, and the brake mechanism 53 can be controlled by the brake controller 51 connected to the system controller 31. The brake controller 51 is configured so that brake depression amount information can be input from the outside.

Next, regenerative braking control processing in the fuel cell system 40 configured as described above will be described based on the flowcharts shown in FIGS. 8 and 9. The regenerative braking control process is performed by the system controller 31.
This regenerative braking control process is a process that is started as an interrupt process by generating an interrupt signal to the system controller 31 when the depression amount sensor detects the depression of the brake pedal. Therefore, the regenerative braking control process is repeatedly executed while the brake pedal is depressed, and the required braking force Brq described below is updated according to the change in the depression amount. Further, the regenerative braking force Bre is also updated at any time according to the rotational speed of the AC motor M that changes as the vehicle speed decreases.

  As shown in FIG. 8, in the regenerative braking control process by the system controller 31, first, in step S301, it is determined whether or not the brake pedal is depressed based on the brake depression amount information input from the outside. The brake depression amount information is detected by a depression amount sensor (not shown) attached to the brake pedal.

  If it is determined in step S301 that the brake pedal is depressed (Yes in S301), a process for detecting the depression amount from the input brake depression amount information is performed in the subsequent step S303. On the other hand, if it is not determined in step S301 that the brake pedal has been depressed (No in S301), the brake is not generated by the brake, and the regenerative braking control process is terminated (RETURN).

  When the stepping amount is detected in step S303, a process of calculating a braking force to be realized, that is, a required braking force Brq, from the stepping amount of the brake pedal is performed in step S305. The required braking force Brq may be a value proportional to the amount of depression of the brake pedal, or may be obtained by a predetermined function or map using the amount of depression of the brake pedal as an input and the required braking force Brq as an output. For example, when the amount of depression (input) is large, the required braking force Brq is output according to the proportional relationship. Further, it may be based on the depression speed of the brake pedal.

Subsequently, in step S307, the braking force that can be achieved with the regenerative power generated at the current motor speed, that is, the regenerative braking force Bre, is calculated from the characteristics of the AC motor M and the motor drive circuit 29A.
Here, “regenerative power” refers to a counter electromotive force generated from the electric motor when the output shaft of the electric motor is forcibly rotated by an external force. Also, the regenerative braking force is the sum of the torque generated by the counter electromotive force and the viscous resistance of the electric motor. Further, these can be calculated from various characteristics of the electric motor and its drive circuit (inverter circuit or the like).

  In step S309, a process of calculating a braking force to be achieved by the mechanical brake, that is, a mechanical braking force Bme is performed. The mechanical braking force Bme corresponds to a value obtained by removing the regenerative braking force Bre from the required braking force Brq (Bme = Brq−Bre).

  Then, the mechanical braking force Bme calculated in step S309 is output from the system controller 31 to the brake controller 51 in step S311 as an output command value to the brake controller 51, and the series of regenerative braking control processing is terminated. Thus, the brake mechanism 53 that has received the output command value Bme from the brake controller 51 executes mechanical braking based on the command value.

On the other hand, almost simultaneously with this, the capacitor management control process during regenerative braking shown in FIG. 9 is executed by the HBC controller 33. This capacitor management control process will be described with reference to FIG.
The capacitor management control process at the time of regenerative braking is always executed by the HBC controller 33 in parallel with the above-described regenerative braking control process. First, as shown in FIG. Call. That is, the capacitor management control process in the steady operation described with reference to FIG.

  In step S403, during regeneration, it is monitored whether or not the inverter voltage Viv of the motor drive circuit 29A detected by the voltage sensor 43 is greater than or equal to an allowable value. If the inverter voltage Viv is equal to or higher than the allowable value (Yes in S403), the process proceeds to step S405, and the switching element 42 is turned on so that the discharge resistor 41 consumes the excess regenerative power. That is, a process of giving a trigger signal to the gate or base of the switching element 42 is performed.

  On the other hand, if it is not determined in step S403 that the inverter voltage Viv is greater than or equal to the allowable value (No in S403), the series of capacitor management control processing ends, and the process waits until it is activated again.

  As described above, according to the fuel cell system 40 according to the present embodiment, it is monitored whether or not the inverter voltage Viv of the motor drive circuit 29A detected by the voltage sensor 43 is equal to or higher than the allowable value, and the inverter voltage Viv is equal to or higher than the allowable value. If there is (Yes in S403), the process proceeds to step S405, and the discharge resistor 41 is made to consume the surplus regenerative power. As a result, surplus regenerative power that cannot be charged by the capacitor 25 is consumed by the discharge resistor 41, so that it is possible to prevent electric energy from being supplied to the capacitor 25 beyond the planned charging capacity of the capacitor 25. Therefore, there is an effect that the charge / discharge characteristics of the capacitor 25 are hardly adversely affected.

It is a functional block diagram which shows the main functional structures of the fuel cell system which concerns on the reference example of this invention. It is a circuit diagram which shows the electrical constitution of the fuel cell system by this reference example. It is a flowchart which shows the flow of the capacitor management control process at the time of starting of the electric vehicle etc. which mount the fuel cell system of this reference example. It is explanatory drawing which shows the example of the "capacitor voltage-charging current map" used for the capacitor management control process shown in FIG. It is a flowchart which shows the flow of the capacitor management control processing at the time of the steady operation of the electric vehicle carrying the fuel cell system of this reference example. It is explanatory drawing which shows the example of the "capacitor voltage-charging current map" used for the capacitor management control process shown in FIG. 1 is a circuit diagram showing an electrical configuration of a fuel cell system according to an embodiment of the present invention. It is a flowchart which shows the flow of the regenerative braking control process by the fuel cell system of this embodiment. It is a flowchart which shows the flow of the capacitor management control process by the fuel cell system of this embodiment.

Explanation of symbols

20, 40 Fuel cell system 21 Fuel cell 23 Current control unit for output control 23A Switching element 25 Capacitor
28 Current adjuster for protection (Current control means)
28A switching element (current control means)
29 Load 29A Motor drive circuit 31 System controller 33 HBC controller (current control means)
35 FC / M Controller M Motor Vec Capacitor voltage (Capacitor terminal voltage)
Vfc FC voltage C_LV0 first predetermined voltage value C_CC1 first predetermined current value C_HV0 second predetermined voltage value (predetermined voltage value)
C_CC4 Second predetermined current value (predetermined current value)

Claims (2)

A fuel cell system comprising a fuel cell and a capacitor respectively connected in parallel to a motor drive circuit,
The voltage between the terminals of the capacitor is detected, and when the voltage between the terminals of the capacitor is higher than a predetermined voltage value, it is determined that there is a risk of exceeding the maximum allowable voltage value of the capacitor, and the capacitor from the motor drive circuit It is characterized by comprising current control means for suppressing the regenerative current value that flows into a predetermined current value that is set as a current value that varies based on the voltage across the capacitor within a range in which the electrolyte in the capacitor is not decomposed. Fuel cell system.   2. The fuel cell system according to claim 1, wherein the current control means is made of a semiconductor element.

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