JP2011181227A - Fuel battery system - Google Patents

Abstract

An object of the present invention is to provide a fuel cell system capable of quickly closing a FC relay and connecting a fuel cell and a rotating electric machine while suppressing an increase in voltage of a secondary battery.
The present invention relates to a chargeable / dischargeable secondary battery, a voltage converter for a secondary battery that performs voltage conversion of the secondary battery, and a fuel that generates electric power by an electrochemical reaction between a fuel gas and an oxidant gas. A battery, a voltage converter for a fuel cell that performs voltage conversion of the fuel cell, an FC relay that turns on and off the electrical connection between the fuel cell and the rotating electrical machine, opening and closing of the FC relay, and driving of the rotating electrical machine A control unit that controls the regenerative operation of the rotating electrical machine when the voltage of the secondary battery is equal to or higher than a predetermined voltage value, and the fuel cell system includes: The FC relay is opened until the difference between the output voltage of the battery voltage converter and the output voltage of the secondary battery voltage converter becomes a predetermined output voltage value or less.
[Selection] Figure 1

Description

  The present invention relates to control of relay connection in a fuel cell system.

  Some fuel cell systems mounted on electric vehicles are configured such that a fuel cell and a secondary battery are connected in parallel so that electric power can be supplied from each to a rotating electric machine mounted on the electric vehicle. . The fuel cell system is provided with an FC relay for turning on and off the connection between the fuel cell and the rotating electrical machine. When the fuel cell is stopped, the fuel cell is disconnected from the rotating electrical machine and the fuel cell is started. Then, the fuel cell is connected to the rotating electrical machine.

JP 2008-22640 A JP 2003-52103 A

  Usually, when the voltage of the secondary battery is high, the open voltage of the secondary battery becomes close to the open voltage of the fuel cell, and the voltage converter for the secondary battery cannot boost the voltage of the secondary battery. In this case, in order to avoid failure of the FC relay, the FC relay may be closed and the fuel cell and the rotating electric machine may not be connected. Conventionally, the secondary battery has reached a voltage at which the FC relay can be closed. By supplying electric power to the rotating electrical machine and driving the rotating electrical machine, the charge of the secondary battery is consumed and the voltage of the secondary battery is lowered.

  However, when power is supplied from the secondary battery to the rotating electrical machine to drive the rotating electrical machine, if the regenerative operation of the rotating electrical machine is performed, the secondary battery is charged and the voltage of the secondary battery remains high. As a result, the FC relay cannot be closed.

  Accordingly, an object of the present invention is to provide a fuel cell system capable of quickly closing the FC relay and connecting the fuel cell and the rotating electrical machine while suppressing the voltage increase of the secondary battery.

  The present invention provides a chargeable / dischargeable secondary battery, a secondary battery voltage converter that is provided between the secondary battery and the rotating electrical machine and performs voltage conversion of the secondary battery, a fuel gas, and an oxidant. A fuel cell that generates electricity by an electrochemical reaction with gas, a voltage converter for a fuel cell that is provided between the fuel cell and the rotating electrical machine and performs voltage conversion of the fuel cell, the fuel cell, and the rotating electrical machine And a control unit that controls opening and closing of the FC relay and driving of the rotating electric machine, wherein the control unit is configured to control the secondary battery. When the voltage is equal to or higher than a predetermined voltage value, the regenerative operation of the rotating electrical machine is prohibited, and a difference between the output voltage of the fuel cell voltage converter and the output voltage of the secondary battery voltage converter is predetermined. Until the output voltage is below the FC relay It is referred to as open.

  Further, in the fuel cell system, the control unit drives the rotating electric machine with electric power of the secondary battery, and outputs an output voltage of the fuel cell voltage converter and an output voltage of the secondary battery voltage converter. It is preferable that the difference between the two is not more than a predetermined output voltage value.

  Further, in the fuel cell system, the control unit is configured such that a difference between an output voltage of the fuel cell voltage converter and an output voltage of the secondary battery voltage converter is a predetermined output voltage value or less, It is preferable to set the regenerative power of the rotating electrical machine by rate processing after closing the FC relay and permitting the regenerative operation of the rotating electrical machine.

  According to the present invention, it is possible to quickly connect the fuel cell and the rotating electrical machine by closing the FC relay while suppressing the voltage increase of the secondary battery.

It is a mimetic diagram showing an example of composition of a fuel cell system concerning this embodiment. It is a time chart which shows the output voltage of a secondary battery and each buck-boost converter. It is a time chart of the regeneration power rate process in the fuel cell system concerning this embodiment. 5 is a flowchart for explaining the operation of the fuel cell system according to the present embodiment.

  Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing an example of the configuration of the fuel cell system according to the present embodiment. As shown in FIG. 1, a fuel cell system 1 mounted on an electric vehicle or the like includes a rechargeable secondary battery 10, a secondary battery step-up / down converter 12 that performs voltage conversion of the secondary battery 10, a fuel A battery 14, a fuel cell boost converter 16 that performs voltage conversion of the fuel cell 14, an inverter 18 that converts the DC power of each step-up / step-down converter into AC power, and supplies the AC power to the rotating electrical machine (MG1, MG2); 32.

  The secondary battery 10 is composed of a chargeable / dischargeable lithium ion battery or the like, and is connected to the inverter 18 via the secondary battery step-up / down converter 12. The secondary battery step-up / down converter 12 includes a plurality of switching elements, and converts a voltage supplied from the secondary battery 10 into a voltage driven by the rotating electrical machine (MG1, MG2) by an on / off operation of the switching elements. . In addition, a secondary battery 10 and a load system (rotating electrical machines (MG1, MG2), a fuel cell hydrogen pump, a cooling water pump, an air conditioner) are connected to an electric circuit between the secondary battery 10 and the secondary battery step-up / down converter 12. A system relay 20 is provided to turn on and off the electrical connection with a conditioner or the like.

  The fuel cell 14 is supplied with hydrogen gas, which is a fuel gas, and air, which is an oxidant gas, and generates electricity by an electrochemical reaction between the hydrogen gas and oxygen in the air. The inverter 18 is connected. The fuel cell boost converter 16 includes a plurality of switching elements, and converts a voltage supplied from the fuel cell 14 into a voltage driven by the rotating electrical machine (MG1, MG2) by an on / off operation of the switching elements. In addition, an FC relay 22 that turns on and off the electrical connection between the rotating electric machine (MG1, MG2) and the fuel cell 14 is provided on the electric path between the fuel cell 14 and the inverter 18.

  On the input side of the secondary battery step-up / down converter 12, a primary side capacitor 24 that smoothes the voltage output from the secondary battery 10 is provided. The primary side capacitor 26 for smoothing the voltage output from the fuel cell 14 is provided on the input side of the fuel cell boost converter 16, and the fuel cell boost converter 16 is provided on the output side of the fuel cell boost converter 16. Is provided with a secondary-side capacitor 28 for smoothing the voltage output by. A secondary side capacitor 30 is provided on the input side of the inverter 18 to smooth the voltage output by each step-up / down converter. Each capacitor is provided with a voltage sensor (not shown) for detecting the voltage of each capacitor.

  The inverter 18 converts the DC voltage supplied from each step-up / step-down converter into an AC voltage and outputs the AC voltage to the rotating electrical machine (MG1, MG2), or outputs the electric power generated by the rotating electrical machine (MG1, MG2) during the regenerative operation. The battery is returned to the secondary battery 10 side.

  The control unit 32 is a computer that includes a CPU that performs signal processing and a storage unit that stores programs and control data. The fuel cell boost converter 16, the secondary battery buck-boost converter 12, the inverter 18, the rotating electrical machines (MG 1 and MG 2), the FC relay 22, and the system relay 20 are connected to the control unit 32 and operate according to commands from the control unit 32. It is configured as follows. Each voltage sensor (not shown) is connected to the control unit 32, and a detection signal of each voltage sensor is input to the control unit 32.

  FIG. 2 is a time chart showing output voltages of the secondary battery and each buck-boost converter. As shown in FIG. 2, when the voltage of the secondary battery 10 is a high voltage exceeding a certain value, the open-circuit voltage of the secondary battery 10 becomes close to the open-circuit voltage of the fuel cell 14, so The voltage converter 12 cannot boost the voltage of the secondary battery 10. When the FC relay 22 is closed and the fuel cell 14 and the rotating electrical machine (MG1, MG2) are connected without boosting the voltage of the secondary battery 10, a large amount of current flows through the FC relay 22 or the like. May break down. Therefore, as shown in FIG. 2, the voltage of the secondary battery 10 needs to be boosted by the secondary battery step-up / down converter 12 after the voltage of the secondary battery 10 is set to a certain value or less. At this time, if there is a regenerative operation of the rotating electrical machine (MG1, MG2), it takes time until the secondary battery 10 is charged and the voltage of the secondary battery 10 is reduced to a certain value or less. It cannot be closed.

  Therefore, the control unit 32 of the present embodiment generates a drive instruction for converting the inverter 18 into an AC voltage for driving the rotating electrical machines (MG1, MG2) and the rotating electrical machines (MG1, MG2). A regenerative instruction for converting an AC voltage into a DC voltage and returning it to the secondary battery 10 side is output. The voltage value input from the voltage sensor for detecting the voltage of the secondary battery 10 is equal to or greater than a predetermined voltage value. In this case, an instruction to prohibit the regenerative operation of the rotating electrical machines (MG1, MG2) is output to the inverter 18. Here, since the open voltage of the secondary battery 10 becomes close to the open voltage of the fuel cell 14 when the voltage of the secondary battery 10 exceeds the set voltage value, the predetermined voltage value is a step-up / down converter for the secondary battery. 12 is set to a voltage value at which the voltage of the secondary battery 10 cannot be boosted or a voltage value at which the FC relay 22 is closed and the fuel cell 14 cannot be connected to the rotating electrical machine (MG1, MG2). That's fine.

  In addition, when an instruction to prohibit the regenerative operation is output, the control unit 32 outputs the output voltage value input from the voltage sensor that detects the output voltage of the fuel cell boost converter 16 and the secondary battery buck-boost converter. A difference from the output voltage value input from the voltage sensor that detects the output voltage of 12 is calculated, and an opening instruction is output to the FC relay 22 until the calculated value becomes equal to or less than a predetermined output voltage value. Here, the predetermined output voltage value may be set to an output voltage value that can connect the fuel cell 14 and the rotating electrical machine (MG1, MG2) with the FC relay 22 closed.

  By such operation of the control unit 32, the regenerative operation of the rotating electrical machines (MG1, MG2) is performed until the fuel cell 14 and the rotating electrical machines (MG1, MG2) can be connected by closing the FC relay 22. Since prohibiting, the voltage rise of the secondary battery 10 can be suppressed.

  When the difference between the output voltage of the fuel cell boost converter 16 and the output voltage of the secondary battery step-up / down converter 12 exceeds a predetermined output voltage value, the control unit 32 determines the power of the secondary battery 10. To drive the rotary electric machine (MG1, MG2) to the inverter 18 and the secondary battery step-up / down converter 12. Thereby, the voltage of the secondary battery 10 can be quickly reduced to a predetermined voltage value or less.

  Further, when the difference between the output voltage of the fuel cell boost converter 16 and the output voltage of the secondary battery step-up / down converter 12 is equal to or less than a predetermined output voltage value, the control unit 32 is closed to the FC relay 22. While outputting an instruction | indication, the instruction | indication of the regeneration permission which converts the alternating voltage generated with the rotary electric machine (MG1, MG2) into a DC voltage, and returns to the secondary battery 10 side is output. Generally, after the connection of the FC relay 22 and the regeneration of the electric power generated by the rotating electrical machines (MG1, MG2) are permitted, a regenerative torque is generated when a regenerative operation occurs. Will be given to the user (causes worsening of drivability). Therefore, in this embodiment, as shown in FIG. 3, after permitting the connection of the FC relay 22 and the regeneration of the electric power generated by the rotating electrical machines (MG1, MG2), the regenerative power is subjected to rate processing by the control unit 32. Set and gradually increase regenerative power. As a result, it is possible to suppress the deterioration of drivability that occurs when switching from the regeneration prohibited state to the regeneration permission. The regenerative power rate of the rate process is stored in the control unit 32 in advance.

  FIG. 4 is a flowchart for explaining the operation of the fuel cell system 1 according to this embodiment.

  As shown in FIG. 4, in step S <b> 10, the voltage of the secondary battery 10 is detected by a voltage sensor that detects the voltage of the secondary battery 10. Then, the control unit 32 determines whether or not the detected voltage value of the secondary battery 10 is equal to or greater than a predetermined voltage value. If the voltage value of the secondary battery 10 is equal to or higher than the predetermined voltage value, the process proceeds to step S12, where the control unit 32 instructs the inverter 18 to prohibit the regenerative operation of the rotating electrical machines (MG1, MG2) and the FC relay 22 When the opening instruction is output and the voltage of the secondary battery 10 is less than the predetermined voltage, the process returns to step S10. Next, in step S14, the control unit 32 outputs a drive instruction to the secondary battery step-up / down converter 12 and the fuel cell boost converter 16 to set the output voltage (target voltage) of each converter. Next, in step S16, the output voltage of each converter is detected by the voltage sensor that detects the output voltage of the secondary battery step-up / down converter 12 and the voltage sensor that detects the output voltage of the fuel cell boost converter 16. Then, the control unit 32 calculates the difference between the output voltage value of the fuel cell boost converter 16 and the output voltage value of the secondary battery step-up / down converter 12, and the calculated value is equal to or less than the predetermined output voltage value. It is determined whether or not.

  When the calculated value exceeds the predetermined output voltage value, the process proceeds to step S18, and the control unit 32 causes the inverter 18 to consume the electric charge of the secondary battery 10 by driving the rotating electrical machines (MG1, MG2). And a drive instruction | indication is output to the buck-boost converter 12 for secondary batteries.

  When the calculated value is less than or equal to the predetermined output voltage value, the process proceeds to step S20, where the control unit 32 outputs an opening instruction to the FC relay 22 and outputs an regeneration permission instruction to the inverter 18. Is done.

  After the regeneration permission instruction is output, in step S22, the control unit 32 sets the regenerative power subjected to rate processing so that the regenerative power gradually increases.

  As described above, in the present embodiment, the regenerative operation of the rotating electrical machine is prohibited until the FC relay is closed and the fuel cell and the rotating electrical machine can be connected. Can be suppressed. Moreover, since the power of the secondary battery is used to drive the rotating electrical machine, the voltage of the secondary battery can be quickly reduced. Furthermore, since the regenerative power that has been rate-processed so that the regenerative power gradually increases after switching from the prohibition of the regenerative operation to the regenerative permission, deterioration of drivability due to the generation of regenerative torque can be suppressed.

  DESCRIPTION OF SYMBOLS 1 Fuel cell system, 10 Secondary battery, 12 Buck-boost converter for secondary batteries, 14 Fuel cell, 16 Boost converter for fuel cells, 18 Inverter, 20 System relay, 22 FC relay, 24, 26 Primary side capacitor, 28 , 30 Secondary capacitor, 32 control unit.

Claims (3)

A rechargeable secondary battery;
A voltage converter for a secondary battery that is provided between the secondary battery and the rotating electrical machine and performs voltage conversion of the secondary battery;
A fuel cell that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas;
A voltage converter for a fuel cell, which is provided between the fuel cell and the rotating electrical machine and performs voltage conversion of the fuel cell;
An FC relay that turns on and off the electrical connection between the fuel cell and the rotating electrical machine;
A fuel cell system comprising: a controller that controls opening and closing of the FC relay and driving of the rotating electrical machine,
The control unit prohibits the regenerative operation of the rotating electrical machine when the voltage of the secondary battery is equal to or higher than a predetermined voltage value, and converts the output voltage of the fuel cell voltage converter and the voltage conversion of the secondary battery. The fuel cell system is characterized in that the FC relay is opened until the difference from the output voltage of the vessel becomes equal to or less than a predetermined output voltage value.   2. The fuel cell system according to claim 1, wherein the control unit drives the rotating electric machine with electric power of the secondary battery, and outputs an output voltage of the fuel cell voltage converter and the secondary battery voltage converter. 3. The fuel cell system is characterized in that the difference from the output voltage is less than or equal to a predetermined output voltage value.   2. The fuel cell system according to claim 1, wherein the control unit is configured such that a difference between an output voltage of the fuel cell voltage converter and an output voltage of the secondary battery voltage converter is equal to or less than a predetermined output voltage value. Thus, after the FC relay is closed and the regenerative operation of the rotating electrical machine is permitted, the regenerative power of the rotating electrical machine is set by rate processing.

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