JP2010288326A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress welding of a relay arranged on a power supply route. <P>SOLUTION: A fuel cell system is provided with a switch SW which changes over a limiting resistor presence circuit where a current limiting resistor LR is arranged between a first voltage converting part and an FC relay R1 which are included in an FC converter 3, and a limiting resistor absence circuit where the current limiting resistor LR is not arranged between the first voltage converting part and the FC relay R1. When a value obtained by subtracting an output voltage of a Bat converter 5 from an output voltage of the FC converter 3 is larger than a prescribed value, a control part 9 connects the switch SW to a limiting resistor presence circuit-side and turns ON the FC relays R1 and R2 when the fuel cell system 1 is started. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel cell system.

  Patent Document 1 below discloses a fuel cell system in which a load is driven by a fuel cell and a battery, and includes two converters for a fuel cell and a battery. In this fuel cell system, in order to supply power stably to a load, a fuel cell converter and a battery converter are operated in a coordinated manner. In addition, a relay as a connecting portion is provided on the power supply path that connects the battery and the load, and when the system is stopped, the relay is turned off, and the voltage supplied from the fuel cell to the load is activated by the system. When the voltage exceeds the voltage, the relay is turned on to connect the battery and the load. This prevents waste of battery power when the system is stopped, and prevents current from rushing from the battery side to the load side when the relay is connected.

JP 2006-340419 A

  By the way, in Patent Document 1, the relay is turned on when the voltage on the fuel cell side exceeds the voltage on the battery side. Thus, for example, if the fuel system ends abnormally when the output voltage of the fuel cell converter is higher than the open voltage of the fuel cell, the voltage on the fuel cell side is increased if the fuel cell system is started immediately after that. The relay is turned on in a state higher than the voltage on the battery side, that is, in a state where there is a potential difference between both ends of the relay. In such a case, the relay may be welded due to overcurrent.

  The present invention has been made to solve the above-described problems caused by the prior art, and an object of the present invention is to provide a fuel cell system capable of suppressing welding of a connecting portion provided on a power supply path. To do.

  In order to solve the above-described problems, a fuel cell system according to the present invention includes a fuel cell that receives supply of a fuel gas and an oxidant gas and generates power by an electrochemical reaction between the fuel gas and the oxidant gas, and a power generated by the fuel cell. An electric power unit that can charge the battery, an electric power consuming device that consumes electric power from the fuel cell and the electric power unit, and a first voltage conversion unit that is disposed between the fuel cell and the electric power consuming device A second voltage converter disposed between the livestock power unit and the power consuming device, and a path for supplying power from the first voltage converter to the power consuming device, A connection part for connecting or disconnecting the path connecting the voltage conversion part and the second voltage conversion part, and a part of the path between the first voltage conversion part and the connection part in parallel. A current limiting resistor disposed on the first A connection switching unit that switches whether or not to connect the voltage conversion unit and the connection unit via the current limiting resistor, and the connection switching unit that controls connection or disconnection of the path by the connection unit, and the switching by the connection switching unit. Control means for controlling the output voltage, and the control means subtracts the output voltage of the second voltage converter from the output voltage of the first voltage converter when the system is started up. In this case, the connection switching unit is controlled to connect the first voltage conversion unit and the connection unit via the current limiting resistor, and then the connection unit is controlled to connect the path. Features.

  According to this invention, even when an output voltage difference larger than a predetermined value occurs between the first voltage conversion unit and the second voltage conversion unit when connecting the power supply path at the time of system startup, the connection The current flowing into the part can be reduced by the current limiting resistor. In addition, since the output of the first voltage conversion unit can be consumed by the current limiting resistor, the output voltage difference between the first voltage conversion unit and the second voltage conversion unit can be reduced.

  In the fuel cell system, the control unit subtracts the output voltage of the second voltage conversion unit from the output voltage of the first voltage conversion unit after controlling the connection unit to connect the path. When the value decreases below a predetermined value, the connection switching unit may be controlled to connect the first voltage conversion unit and the connection unit without going through the current limiting resistor.

  In this way, after the output voltage difference between the first voltage converter and the second voltage converter is eliminated, the system can be operated without consuming power with the current limiting resistor. It becomes possible.

  In the fuel cell system, when the system is activated, when the value obtained by subtracting the output voltage of the second voltage converter from the output voltage of the first voltage converter is equal to or less than a predetermined value, The connection switching unit may be controlled to connect the first voltage conversion unit and the connection unit without passing through the current limiting resistor, and then the connection unit may be controlled to connect the path.

  In this way, when the power supply path is connected at the time of system startup, if the output voltage difference between the first voltage converter and the second voltage converter is less than or equal to a predetermined value, the current The system can be started up without consuming electric power by the limiting resistor.

  In the fuel cell system, the connection switching unit includes a circuit in which the current limiting resistor is disposed between the first voltage conversion unit and the connection unit, and the first voltage conversion unit and the connection unit. It is good also as a switch which switches the circuit in which the said current limiting resistance is not arrange | positioned between.

  In the fuel cell system, the connection switching unit includes a first switch that connects or disconnects a circuit in which the current limiting resistor is disposed between the first voltage conversion unit and the connection unit; A second switch that connects or disconnects a circuit in which the current limiting resistor is not disposed between one voltage conversion unit and the connection unit, and the first switch and the second switch, May be connected in parallel between the first voltage conversion unit and the connection unit.

  ADVANTAGE OF THE INVENTION According to this invention, welding of the connection part provided on the electric power supply path | route can be suppressed.

It is a figure which shows typically the structure of the fuel cell system in embodiment. It is a flowchart for demonstrating the flow of FC relay control processing. It is a figure which shows the structure of the switch vicinity in a modification.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a fuel cell system according to the invention will be described with reference to the accompanying drawings. In the embodiment, a case will be described in which the fuel cell system according to the present invention is used as an on-vehicle power generation system of a fuel cell vehicle (FCHV). The fuel cell system according to the present invention can also be applied to various mobile bodies (robots, ships, aircrafts, etc.) other than fuel cell vehicles, and further used as power generation equipment for buildings (housing, buildings, etc.). It can be applied to a stationary power generation system.

  First, with reference to FIG. 1, the structure of the fuel cell system in embodiment is demonstrated. FIG. 1 is a diagram schematically illustrating a fuel cell system according to an embodiment.

  As shown in FIG. 1, a fuel cell system 1 includes a fuel cell 2 that generates electric power by an electrochemical reaction between an oxidizing gas that is a reaction gas and a fuel gas, and an FC converter 3 that is a DC / DC converter for the fuel cell. A battery 4 (power storage unit) as a secondary battery, a Bat converter 5 (second voltage conversion unit) which is a DC / DC converter for the battery, a traction inverter 6 as a load, and a traction motor 7 (power consumption device) ) And auxiliary inverters 8a and 8b, and a control unit 9 (control means) for overall control of the entire system. The fuel cell 2 and the FC converter 3, the battery 4 and the Bat converter 5 are connected in parallel to the traction inverter 6 and the traction motor 7.

  The fuel cell 2 is, for example, a polymer electrolyte fuel cell, and has a stack structure in which a large number of single cells are stacked. The single cell has an air electrode on one surface of an electrolyte membrane made of an ion exchange membrane, a fuel electrode on the other surface, and a pair of separators so as to sandwich the air electrode and the fuel electrode from both sides. It has become. In this case, hydrogen gas is supplied to the hydrogen gas passage of one separator, the oxidizing gas is supplied to the oxidizing gas passage of the other separator, and electric power is generated by the chemical reaction of these reaction gases. The fuel cell 2 is provided with a voltage sensor V <b> 1 that detects the output voltage of the fuel cell 2.

  The FC converter 3 is a DC voltage converter and has a function of boosting the DC voltage input from the fuel cell 2 and outputting the boosted voltage to the traction inverter 6 and the traction motor 7. The output voltage of the fuel cell 2 is controlled by the FC converter 3.

  The FC converter 3 includes, for example, a capacitor C1 for smoothing the DC voltage input from the fuel cell 2, a coil L1 and a main switch S1 for boosting the DC voltage, a capacitor C2 and a coil L2 constituting a resonance circuit, The resonance switch S2 for turning on / off the resonance circuit and the capacitor C3 for smoothing the output voltage of the FC converter 3 are configured. Each of these components constitutes a first voltage converter that boosts the DC voltage input from the fuel cell 2 and outputs the boosted DC voltage to the traction inverter 6 and the traction motor 7.

  The FC converter 3 includes a voltage sensor V2 that detects an output voltage of the FC converter 3, FC relays R1 and R2 (connection portions) that connect or cut off a power supply path that supplies power to the traction inverter 6 and the traction motor 7. It has further. The FC relays R <b> 1 and R <b> 2 are also connection units that connect or block a path that connects the FC converter 3 and the Bat converter 5.

  The FC converter 3 includes a current limiting resistor LR disposed in parallel with a part of the power supply path between one end of the capacitor C3 and one end of the FC relay R1 included in the first voltage conversion unit, It further has a switch SW (connection switching unit) for switching whether or not to connect the voltage conversion unit and the FC relay R1 via the current limiting resistor LR.

  The switch SW is a switch that switches between two circuits. In the present embodiment, the switch SW includes a circuit in which a current limiting resistor LR is disposed between the first voltage conversion unit and the FC relay R1 (hereinafter referred to as “circuit having a limiting resistor”) and the first. The circuit in which the current limiting resistor LR is not disposed between the voltage converter and the FC relay R1 (hereinafter referred to as “circuit without limiting resistor”) is switched.

  Even if the FC relays R1 and R2 are turned ON when there is an output voltage difference between the FC converter 3 and the Bat converter 5, the FC relays R1 and R2 are welded due to overcurrent. A resistance value capable of reducing the current value is set in a range where the current is not applied. This resistance value can be obtained by experiments or the like.

  The battery 4 is configured such that battery cells are stacked and a constant high voltage is used as a terminal voltage, and the surplus power of the fuel cell 2 can be charged or supplementarily supplied by control of a battery computer (not shown). ing. The battery 4 is provided with a voltage sensor V3 that detects an output voltage of the battery 4, and Bat relays R3 and R4 that connect or cut off a path for supplying battery power to the traction inverter 6 and the traction motor 7. The Bat relays R3 and R4 are turned on when the fuel cell system 1 is started and turned off when the fuel cell system 1 is stopped.

  The Bat converter 5 is a DC voltage converter, which adjusts (boosts) the DC voltage output from the battery 4 and outputs it to the traction inverter 6 and the traction motor 7, and outputs from the fuel cell 2 or the traction motor 7. A function of adjusting (stepping down) the direct current voltage and outputting it to the battery 4. By such a function of the Bat converter 5, charging / discharging of the battery 4 is realized. The Bat converter 5 is provided with a voltage sensor V4 that detects the output voltage of the Bat converter 5.

  The traction inverter 6 converts a direct current into a three-phase alternating current and supplies it to the traction motor 7 and the compressor CP motor. The traction motor 7 is, for example, a three-phase AC motor, and constitutes a main power source of a fuel cell vehicle on which the fuel cell system 1 is mounted. Auxiliary machine inverters 8a and 8b are motor control units that control driving of motors included in auxiliary equipment such as hydrogen pump HP and cooling water pump WP, and convert DC current into three-phase AC and supply it to each motor. To do. Auxiliary machine inverters 8a and 8b are, for example, pulse width modulation type PWM inverters, which convert DC voltage output from battery 4 into three-phase AC voltage in accordance with a control command from control unit 9 and generate it in each motor. Controls rotational torque.

  The control unit 9 detects an operation amount of an acceleration operation member (for example, an accelerator) provided in the fuel cell vehicle, and controls an acceleration request value (for example, a required power generation amount from a power consuming device such as the traction motor 7). Receives information and controls the operation of various devices in the system. In addition to the traction motor 7, the power consuming device includes, for example, auxiliary devices required for operating the fuel cell 2 (for example, a compressor CP, a hydrogen pump HP, a cooling water pump WP motor, etc.), a vehicle This includes actuators used in various devices (transmissions, wheel control devices, steering devices, suspension devices, etc.) involved in traveling, air conditioning devices (air conditioners) for passenger spaces, lighting, audio, and the like.

  The control unit 9 physically includes, for example, a CPU, a memory, and an input / output interface. The memory includes a ROM that stores a control program and control data processed by the CPU, and a RAM that is mainly used as various work areas for control processing. These elements are connected to each other via a bus. Various sensors such as a voltage sensor are connected to the input / output interface, and various drivers for driving the traction motor 7 and the like are connected.

  The CPU receives the detection results of the various sensors via the input / output interface according to the control program stored in the ROM, and processes them using various data in the RAM, whereby various control processes in the fuel cell system 1 are performed. Execute. Further, the CPU controls the entire fuel cell system 1 by outputting control signals to various drivers via the input / output interface.

  For example, the controller 9 controls switching of the switch SW and ON / OFF of the FC relays R1 and R2. Specifically, the control is performed as follows.

  The controller 9 sets the output voltage of the Bat converter 5 to the open circuit voltage of the battery 4 and the output voltage of the FC converter 3 to the open voltage of the fuel cell 2 when the fuel cell system 1 is started. Subsequently, the control unit 9 subtracts the output voltage of the Bat converter 5 from the output voltage of the FC converter 3 to obtain an output voltage difference between the FC converter 3 and the Bat converter 5. The controller 9 determines whether or not the obtained output voltage difference is equal to or less than a predetermined value.

  As the predetermined value, for example, when the FC relays R1 and R2 are turned on, the FC relays R1 and R2 can be set within a range of potential differences that can be turned on without welding. Of these, it is desirable to set the upper limit. The range of this potential difference can be obtained by experiments or the like.

  When the output voltage difference is equal to or smaller than the predetermined value, the control unit 9 connects the switch SW to the circuit without the limiting resistor and then turns on the FC relays R1 and R2. Thus, when the power supply path is connected at the time of starting the system, if the output voltage difference between the FC converter 3 and the Bat converter 5 is equal to or less than a predetermined value, the current limiting resistor LR does not consume power. Since the fuel cell system can be activated, the operation efficiency can be improved.

  On the other hand, when the output voltage difference is larger than the predetermined value, the control unit 9 connects the switch SW to the circuit with the limiting resistance and then turns on the FC relays R1 and R2. Thereby, even if an output voltage difference larger than a predetermined value is generated between the FC converter 3 and the Bat converter 5, the current flowing into the FC relay R1 can be reduced by the current limiting resistor LR. Further, since the output power of the FC converter 3 can be consumed by the current limiting resistor LR, the output voltage difference between the FC converter 3 and the Bat converter 5 can be reduced.

  When the output voltage difference between the FC converter 3 and the Bat converter 5 decreases to a predetermined value or less, the control unit 9 connects the switch SW to the circuit without the limiting resistor. As a result, after the output voltage difference between the FC converter 3 and the Bat converter 5 is eliminated, the fuel cell system can be operated without consuming electric power with the current limiting resistor LR, thereby improving the operation efficiency. Can be made.

  Next, the FC relay control process in the embodiment will be described using the flowchart shown in FIG. This FC relay control process is started, for example, when an ignition key is turned on. Further, the FC relays R1, R2 and the switch SW are respectively OFF when the ignition key is ON.

  First, the control unit 9 drives the Bat converter 5 (Step S101), and sets the output voltage of the Bat converter 5 to the open voltage of the battery 4 (Step S102).

  Subsequently, the control unit 9 drives the FC converter 3 (step S103), and sets the output voltage of the FC converter 3 to the open voltage of the fuel cell 2 (step S104).

  Subsequently, the control unit 9 determines whether or not the output voltage difference between the FC converter 3 and the Bat converter 5 obtained by subtracting the output voltage of the Bat converter 5 from the output voltage of the FC converter 3 is a predetermined value or less. Is determined (step S105). When this determination is YES (step S105; YES), the control unit 9 connects the switch SW to the circuit without the limiting resistance (step S110) and turns on the FC relays R1 and R2 (step S111). Then, the FC relay control process ends.

  On the other hand, when it is determined in step S105 that the output voltage difference is larger than the predetermined value (step S105; NO), the control unit 9 connects the switch SW to the circuit with limiting resistance (step S106). ), FC relays R1 and R2 are turned ON (step S107).

  Subsequently, the control unit 9 determines whether or not the output voltage difference between the FC converter 3 and the Bat converter 5 obtained by subtracting the output voltage of the Bat converter 5 from the output voltage of the FC converter 3 is a predetermined value or less. Is determined (step S108). When this determination is NO (step S108; NO), the control unit 9 repeatedly executes the determination in step S108.

  On the other hand, when it is determined in step S108 that the output voltage difference is equal to or smaller than the predetermined value (step S108; YES), the control unit 9 connects the switch SW to the circuit without limiting resistor (step S109). ). Then, the FC relay control process ends.

  As described above, according to the fuel cell system 1 in the present embodiment, when the power supply path is connected at the time of system startup, an output voltage difference larger than a predetermined value is present between the FC converter 3 and the Bat converter 5. Even if it occurs, the current flowing into the FC relays R1 and R2 can be reduced by the current limiting resistor LR. Therefore, the FC relays R1, R2 can be turned on without welding.

  Even if an output voltage difference larger than a predetermined value is generated between the FC converter 3 and the Bat converter 5, the output power of the FC converter 3 can be consumed by the current limiting resistor LR. The output voltage difference with the Bat converter 5 can be reduced in a short time.

  In the above-described embodiment, the switch SW for switching between the two circuits is used as a switch for switching whether or not the first voltage conversion unit and the FC relay R1 are connected via the current limiting resistor LR. It is not limited to this. For example, as shown in FIG. 3, a first switch SW1 that connects or disconnects a circuit in which the current limiting resistor LR is not disposed between the first voltage converter and the FC relay R1, and the first voltage converter A second switch SW2 that connects or cuts off a circuit in which the current limiting resistor LR is disposed between the switch and the FC relay R1 may be used. The first switch SW1 and the second switch SW2 are connected in parallel between one end of the capacitor C3 and one end of the FC relay R1 constituting the first voltage converter shown in FIG. In the case of such a configuration, for example, the following control can be performed.

  The controller 9 sets the output voltage of the Bat converter 5 to the open voltage of the battery 4 and sets the output voltage of the FC converter 3 to the open voltage of the fuel cell 2 when the fuel cell system 1 is started. Subsequently, the control unit 9 subtracts the output voltage of the Bat converter 5 from the output voltage of the FC converter 3 to obtain an output voltage difference between the FC converter 3 and the Bat converter 5. The controller 9 determines whether or not the output voltage difference is equal to or less than a predetermined value.

  When the output voltage difference is equal to or smaller than the predetermined value, the control unit 9 turns on the FC relays R1 and R2 after turning on the first switch SW1. On the other hand, when the output voltage difference is larger than a predetermined value, the control unit 9 turns on the second switch SW2 and then turns on the FC relays R1 and R2. Thereby, even if an output voltage difference larger than a predetermined value is generated between the FC converter 3 and the Bat converter 5, the current flowing into the FC relay R1 can be reduced by the current limiting resistor LR. Further, since the output power of the FC converter 3 can be consumed by the current limiting resistor LR, the output voltage difference between the FC converter 3 and the Bat converter 5 can be reduced in a short time. The controller 9 turns on the first switch SW1 and turns off the second switch SW2 when the output voltage difference between the FC converter 3 and the Bat converter 5 decreases to a predetermined value or less.

  Here, when the output voltage difference is larger than a predetermined value, both the first switch SW2 and the second switch SW2 may be turned on. This is because if the second switch SW2 can be turned on, the current flowing into the FC relay R1 can be reduced by the current limiting resistor LR. In this case, after that, when the output voltage difference decreases below a predetermined value, the second switch SW2 may be turned off.

  Further, the FC converter 3 in the above-described embodiment incorporates the elements of the voltage sensor V2, the switch SW, the current limiting resistor LR, and the FC relays R1 and R2 as constituent elements of the FC converter 3, Each element may be configured separately from the FC converter 3.

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Fuel cell, 3 ... FC converter, 4 ... Battery, 5 ... Bat converter, 6 ... Traction inverter, 7 ... Traction motor, 8a, 8b ... Auxiliary machine inverter, 9 ... Control part, C3, C4: capacitor, R1, R2 ... FC relay, LR: current limiting resistor, SW ... switch, SW1 ... first switch, SW2 ... second switch, V1, V2, V3, V4 ... voltage sensor.

Claims (5)

A fuel cell that receives supply of the fuel gas and the oxidizing gas and generates power by an electrochemical reaction of the fuel gas and the oxidizing gas;
An animal power unit capable of charging the power generated by the fuel cell;
A power consuming device that consumes power from the fuel cell and the livestock power unit;
A first voltage converter disposed between the fuel cell and the power consuming device;
A second voltage conversion unit disposed between the livestock power unit and the power consuming device;
A path for supplying power from the first voltage conversion unit to the power consuming device, wherein the connection unit connects or blocks the path that couples the first voltage conversion unit and the second voltage conversion unit. When,
A current limiting resistor disposed in parallel with a portion of the path between the first voltage converter and the connection;
A connection switching unit for switching whether to connect the first voltage conversion unit and the connection unit via the current limiting resistor;
Control means for controlling connection or disconnection of the path by the connection unit, and controlling the switching by the connection switching unit,
The control means controls the connection switching unit when a value obtained by subtracting the output voltage of the second voltage conversion unit from the output voltage of the first voltage conversion unit is greater than a predetermined value at system startup. Then, the first voltage conversion unit and the connection unit are connected via the current limiting resistor, and then the connection unit is controlled to connect the path.   The control means controls the connection unit to connect the path, and then subtracts the output voltage of the second voltage conversion unit from the output voltage of the first voltage conversion unit to a predetermined value or less. 2. The fuel cell system according to claim 1, wherein when the number is decreased, the connection switching unit is controlled to connect the first voltage conversion unit and the connection unit without passing through the current limiting resistor.   The control means controls the connection switching unit when a value obtained by subtracting the output voltage of the second voltage conversion unit from the output voltage of the first voltage conversion unit is equal to or less than a predetermined value at the time of system startup. The first voltage conversion unit and the connection unit are connected without passing through the current limiting resistor, and then the connection unit is controlled to connect the path. The fuel cell system described.   The connection switching unit includes a circuit in which the current limiting resistor is disposed between the first voltage conversion unit and the connection unit, and the current between the first voltage conversion unit and the connection unit. The fuel cell system according to any one of claims 1 to 3, wherein the fuel cell system is a switch for switching between a circuit in which no limiting resistor is arranged.   The connection switching unit includes a first switch for connecting or disconnecting a circuit in which the current limiting resistor is disposed between the first voltage conversion unit and the connection unit, and the first voltage conversion unit. A second switch for connecting or disconnecting a circuit in which the current limiting resistor is not disposed between the first switch and the connection portion, wherein the first switch and the second switch are the first voltage. The fuel cell system according to claim 1, wherein the fuel cell system is connected in parallel between the conversion unit and the connection unit.

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