JP2018037272A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system in which welding of a fuel cell is detected, regardless of the voltage of the fuel cell.SOLUTION: A fuel cell system 100 includes an output control section 105 having a first booster circuit 105b and a first capacitor, a fuel cell 102, and a FC step-up section 103 having a second booster circuit and a second capacitor 105c. Furthermore, a FC relay section 104 for connecting or disconnecting the output control section 105 and FC step-up section 103, and a controller 101 are included. When the fuel cell 102 is not generating power, the controller 101 increases the voltages of the first capacitor 103a and second capacitor 105c, respectively, to a check voltage Vch higher than the maximum voltage VFCmax of the fuel cell, connects any one of the relays in the FC relay section 104, and disconnects other relays, and furthermore, discharges the second capacitor 105c, to detect welding of the relay terminal.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fuel cell system.

  In recent years, systems using fuel cells that generate electricity by mixing fuel gas and oxidizing gas have been developed. Patent Document 1 discloses a fuel cell system in which a relay is provided between a fuel cell stack and a boost converter. In such a system, when the relay is turned on from off, the relay terminal may be welded by arc discharge. Therefore, the fuel cell system includes means for detecting welding of the relay terminal.

JP 2013-247084 A

  As a means for detecting the welding of the relay terminal, a method of detecting a change in voltage generated between the terminals of the relay by discharging a capacitor connected to the boost converter can be considered. However, when the fuel gas and the oxidizing gas remain in the fuel cell, the voltage of the fuel cell does not decrease, and there is a risk of erroneous detection when detecting welding.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a fuel cell system that detects welding of a relay terminal regardless of the voltage of the fuel cell.

  The fuel cell system according to the present invention includes a secondary battery, a first booster circuit that boosts the voltage of the secondary battery, and a first battery that accumulates charges according to the voltage boosted by the first booster circuit. An output control unit having a capacitor, a fuel cell, a second booster circuit that boosts the voltage of the fuel cell, and a voltage boosted by the first booster circuit or the second booster circuit A FC (Fuel Cell) booster having a second capacitor for accumulating the charge, a relay for connecting or disconnecting the high potential part of the output controller and the high potential part of the FC booster, and By measuring the voltage of the second capacitor and the FC relay unit including a plurality of relays that connect or cut off the low potential unit of the output control unit and the low potential unit of the FC boost unit, the FC relay unit Detect welding And the control device increases the voltages of the first capacitor and the second capacitor to a check voltage higher than the maximum voltage of the fuel cell, respectively, when the fuel cell is not generating power. When one of the relays included in the FC relay unit is connected, the other relays are shut off, and the first capacitor is discharged, the voltage of the second capacitor is When the voltage drops to the battery voltage, it is determined that one of the interrupted relays is welded, and when the voltage of the second capacitor is maintained at the check voltage, the disconnection is performed. It is determined that none of the relays are welded.

  In this way, by increasing the voltages of the first capacitor and the second capacitor to voltages higher than the maximum voltage of the fuel cell, the voltage of the first capacitor is not affected by the voltage of the fuel cell. Changes can be detected.

  According to the present invention, it is possible to provide a fuel cell system that detects welding of a relay terminal regardless of the voltage of the fuel cell.

1 is a circuit diagram of a fuel cell system 100 according to an embodiment. It is a flowchart of the welding detection in the fuel cell system 100 which concerns on embodiment. It is a time chart of welding detection in fuel cell system 100 concerning an embodiment. It is a time chart of welding detection in fuel cell system 100 concerning an embodiment.

<Embodiment>
First, an embodiment according to the present invention will be described. FIG. 1 is a circuit diagram of a fuel cell system according to an embodiment. The fuel cell system 100 includes a control unit 101, an FC stack 102, an FC boost converter 103, an FC relay 104, an output control unit 105, a drive motor 106, a compressor motor 107, a system main relay 108, and a secondary battery 109. The voltage generated by the FC stack 102 is boosted by the FC boost converter 103 and transmitted to the output control unit 105 via the FC relay 104. The voltage of the secondary battery 109 is transmitted to the output control unit 105 via the system main relay 108. The output control unit 105 drives the drive motor 106 and the compressor motor 107.

  Next, the detail of each part is demonstrated. The control unit 101 is connected to each unit and performs operation control. The control unit 101 is connected to voltmeters 200 to 204 and monitors the voltages V0 to V4. Similarly, the control unit 101 is connected to the ammeters 301 and 302 and monitors the currents A1 and A2. Further, the control unit 101 detects welding of the relay terminal.

  The FC stack 102 is a fuel cell that generates electric power by mixing fuel gas and oxidizing gas. The fuel gas is, for example, hydrogen. The oxidizing gas is, for example, air. The FC stack 102 generates power when supplied with fuel gas and oxidizing gas, and stops generating power when the supply of fuel gas and oxidizing gas is stopped. A voltmeter 200 is connected to both terminals of the FC stack, and the voltage V0 of the FC stack 102 is monitored.

  The FC boost converter 103 boosts the voltage of the power generated by the FC stack 102. The FC boost converter 103 includes a booster circuit including a capacitor 103a. The capacitor 103a accumulates electric charge according to the voltage boosted by the booster circuit. The FC boost converter 103 includes an ammeter 301 and a voltmeter 201. The ammeter 301 monitors the current A1 flowing through the switching transistor of the booster circuit. The voltmeter 201 is connected between both terminals of the capacitor 103a and monitors the voltage V1 of the capacitor 103a.

  The FC relay 104 includes a relay circuit that connects or disconnects the FC boost converter 103 and the output control unit 105. The FC relay 104 includes a relay FCRB on the plus side wiring. Further, the FC relay 104 includes a relay FCRP on the minus side wiring and a relay FCRG connected in parallel to the relay FCRP. The relay FCRP is a precharge relay, and a limiting resistor 104a is connected in series.

  The output control unit 105 converts the direct current of the FC relay 104 or the system main relay 108 into alternating current and drives the drive motor 106 and the compressor motor 107. The output control unit 105 includes a capacitor 105a, a booster circuit 105b, a capacitor 105c, an inverter 105d, a voltmeter 202, and a voltmeter 203. Capacitor 105 a stores a voltage supplied from secondary battery 109 via system main relay 108. The voltmeter 203 monitors the voltage V3 of the capacitor 105a. The booster circuit 105b boosts the voltage of the capacitor 105c. The capacitor 105c accumulates the voltage supplied via the FC relay 104 or the booster circuit 105b, and supplies the voltage to the inverter 105d. The voltmeter 202 monitors the voltage V2 of the capacitor 105c. The inverter 105d converts the direct current supplied from the capacitor 105c into alternating current. The inverter 105d is connected to the drive motor 106 and the compressor motor 107.

  The drive motor 106 and the compressor motor 107 are AC three-phase motors. The drive motor 106 is a motor for driving the fuel cell system 100. The compressor motor 107 is a motor for an air compressor for supplying gas to the fuel cell. By driving the drive motor 106 and the compressor motor 107, the voltage accumulated in the capacitor 105c is discharged. In the present embodiment, the control unit 101 can control the discharge speed of the capacitor 105 c by controlling the drive motor 106. At this time, the voltage value V <b> 2 of the capacitor 105 c is sequentially monitored by the voltmeter 202.

  The system main relay 108 includes a relay circuit that connects or disconnects the secondary battery 109 and the output control unit 105. The system main relay 108 includes a relay SMRB and an ammeter 302 on the plus side wiring. The system main relay 108 includes a relay SMRP on the minus side wiring and a relay SMRG connected in parallel to the relay SMRP. The relay SMRP is a battery precharge relay for precharging, and a limiting resistor 108a is connected in series. The ammeter 302 monitors the current A2.

  The secondary battery 109 is a chargeable / dischargeable secondary battery. The secondary battery is, for example, a nickel metal hydride battery or a lithium ion battery. The secondary battery 109 is connected to the system main relay 108. A voltmeter 204 is connected between both terminals of the secondary battery 109. The voltmeter 204 monitors the voltage V4 of the secondary battery.

  The circuit diagram of the fuel cell system 100 according to the present embodiment has been described so far. In the fuel cell system 100, the FC relay 104 and the system main relay 108 connect or cut off a high voltage of, for example, about 600 volts. Therefore, for example, when a circuit interrupted by each relay included in the FC relay 104 is connected, arc discharge occurs between the terminals of the relay, which may cause the terminals to become hot and the relay terminals to be welded. If the relay terminal is welded, the welded relay terminal cannot be cut off, causing a problem in the system. Therefore, the fuel cell system 100 performs a process of detecting that the relay terminal is not welded. Alternatively, when the relay terminal is welded, the fuel cell system 100 performs processing for detecting which terminal is welded.

  Next, welding detection processing in the fuel cell system 100 according to the present embodiment will be described. The following description is welding detection performed for each relay terminal included in the FC relay 104. Although welding detection is also performed for each relay terminal included in the system main relay 108, it is omitted here.

  FIG. 2 is a flowchart of welding detection in fuel cell system 100 according to the present embodiment. In fuel cell system 100 according to the present embodiment, welding detection is performed when the system is stopped.

  First, the control unit 101 receives a system stop command (step S10). When receiving a system stop command, the control unit 101 starts welding detection. In addition, before stopping the fuel cell system 100 at this time, among the relays provided in the FC relay 104, the relays FCRB and FCRG are connected. In addition, among the relays included in the system main relay, relay SMRB and relay SMRG are connected.

  The control unit 101 sets the V2 voltage command to the check voltage Vch (step S11). That is, the voltage V2 of the capacitor 105c is set to the check voltage Vch necessary for detecting welding. Here, the voltage of the FC stack 102 is assumed to be the voltage VFC. The maximum voltage that can be output by the FC stack 102 is defined as a voltage VFCmax. At this time, the check voltage Vch necessary for detecting welding is set to be higher than the voltage VFCmax.

  Next, the booster circuit 105b included in the output control unit 105 boosts the voltage V2 of the capacitor 105c. Then, the control unit 101 determines whether or not the voltage V2 of the voltmeter 202 is substantially equal to the check voltage Vch (step S12). When the voltage V2 of the voltmeter 202 is not equal to Vch (step S12: No), the control unit 101 maintains the operation of the booster circuit 105b. When the voltage V2 of the voltmeter 202 becomes substantially equal to the check voltage Vch (step S12: Yes), the control unit 101 stops the operation of the booster circuit 105b (step S13).

  Here, the voltage of the capacitor 105c is substantially equal to the check voltage Vch. At this time, the capacitor 103a is also connected to the output control unit 105 by an FC relay. Therefore, the voltage V1 of the capacitor 103a is boosted to the check voltage Vch, which is the same voltage as the capacitor 105c, by the booster circuit 105b. The FC boost converter 103 includes a diode, and the voltage of the capacitor 103a does not flow to the FC stack 102 side.

  Next, the control part 101 interrupts | blocks relay FCRG (step S14). As a result, the negative relays of the capacitor 103a and the capacitor 105c are cut off.

  Next, the control unit 101 performs discharge for detection of welding (step S15). Specifically, the control unit 101 drives the drive motor 106 and consumes the electric power stored in the capacitor 105c. When power is consumed by the drive motor 106, the voltage of the capacitor 105c decreases. It should be noted that the discharge for welding detection performed here satisfies the following two conditions in order to obtain a voltage of an amount necessary for performing welding detection described later.

  That is, as the condition 1, the voltage V2 of the capacitor 105c is set to be lower than the voltage VFC of the FC stack 102.

  Furthermore, as a condition 2, when the FC relay 104 is connected, the discharge amount is stopped so that the voltage of the capacitor 103a becomes the voltage VFC of the FC stack 102.

  By setting in this way, it is possible to measure whether the voltage V1 of the capacitor 103a is the check voltage Vch or the voltage VFC of the FC stack 102 and perform welding detection.

  Next, the control unit 101 determines whether or not the voltage V1 of the voltmeter 201 is substantially equal to the check voltage Vch (step S16). When the voltage V1 is substantially equal to the check voltage Vch (step S16: Yes), the voltage V1 of the capacitor 103a is not affected by other blocks. That is, among the relays included in the FC relay 104, it is determined that the interrupted relay FCRP and relay FCRG are not welded.

  On the other hand, when it is not determined that the voltage V1 is substantially equal to the check voltage Vch (step S16: No), the voltage V1 of the capacitor 103a is affected and changed by other blocks.

  Therefore, next, the control unit 101 determines whether or not the voltage V1 is substantially equal to the voltage VFC of the FC stack 102 (step S21).

  When the voltage V1 is substantially equal to the voltage VFC of the FC stack 102 (step S21: Yes), the control unit 101 determines that the relay FCRP or the relay FCRG is welded (step S22). That is, among the relays included in the FC relay 104, when the interrupted relay FCRP or relay FCRG is welded, the capacitor 103a and the capacitor 105c are connected. Further, the voltage of the capacitor 105c decreases due to the discharge. Along with this, the voltage of the capacitor 103a also decreases. When the voltage V1 of the capacitor 103a becomes lower than the voltage VFC of the FC stack 102, the voltage VFC of the FC stack 102 flows to the capacitor 103a. As a result, the voltage V1 becomes substantially equal to the voltage VFC.

  On the other hand, when the voltage V1 is not equal to the FC stack voltage VFC in step S21 (step S21: No), the control unit 101 determines that an error other than welding has occurred (step S25).

  In step S16, when it is determined that the relay FCRP and the relay FCRG being disconnected are not welded (step S16: Yes), the control unit 101 disconnects the relay FCRB (step S17). Subsequently, the control unit 101 connects the relay FCRP (step S18). Then, the control unit 101 detects welding of the plus side relay FCRB.

  The control unit 101 determines whether or not the voltage V1 is substantially equal to the check voltage Vch (step S19). When the voltage V1 is substantially equal to the check voltage Vch (step S19: Yes), the voltage V1 of the capacitor 103a is not affected by other blocks. That is, it is determined that the relay FCRB is not welded. Although it can be determined that the relay FCRP is not welded here, it has already been confirmed in step S16.

  In step S19, as a result of determining that the relay FCRB is not welded, all the relays included in the FC relay 104 are not welded. In this case (step S19: Yes), the welding detection process is terminated, and the capacitor 105c is finally discharged (step S20). The final discharge is performed until the voltage of the capacitor 105c approaches zero. Then, the fuel cell system 100 stops the system.

  On the other hand, when it is not determined that the voltage V1 is substantially equal to the check voltage Vch (step S19: No), the voltage V1 of the capacitor 103a is affected and changed by another block.

  Therefore, next, the control unit 101 determines whether or not the voltage V1 is substantially equal to the voltage VFC of the FC stack (step S23).

  When the voltage V1 is substantially equal to the FC stack voltage VFC (step S23: Yes), the control unit 101 determines that the relay FCRB is welded (step S24). That is, when relay FCRB is welded, capacitor 103a and capacitor 105c are connected. Further, the voltage of the capacitor 105c decreases due to the discharge. Along with this, the voltage of the capacitor 103a also decreases. When the voltage V1 of the capacitor 103a becomes lower than the voltage VFC of the FC stack 102, the voltage VFC of the FC stack 102 flows to the capacitor 103a. As a result, the voltage V1 becomes substantially equal to the voltage VFC.

  On the other hand, if the voltage V1 is not equal to the FC stack voltage VFC in step S23 (step S23: No), the control unit 101 determines that an error other than welding has occurred (step S25).

  In the foregoing, the flowchart of the welding detection in the fuel cell system according to the present embodiment has been described. Here, the minus side welding is detected and then the plus side welding is detected. However, the plus side welding may be detected first.

  Next, changes in main signals at the time of detection of welding will be described with reference to FIGS. FIG. 3 is a time chart for detection of welding in the fuel cell system according to the present embodiment. FIG. 3 is a specific example in the case where welding detection is performed on the negative relay in the FC relay 104. FIG. 3 shows the state of disconnection or connection of the relay FCRB, the relay FCRP, and the relay FCRG. Here, On shown in FIG. 3 is a connected state, and Off is a cut-off state. FIG. 3 shows the state of the discharge command DC. Here, On is a state in which the discharge command DC is on, and Off is a state in which the discharge command DC is off.

  Further, FIG. 3 shows the change of the voltage V1 of the capacitor 103a in accordance with the state of each relay and the signal of the discharge command. Here, the broken line Vok1 is a change in the voltage V1 when it is determined that the welding is not performed as a result of performing the welding detection on the minus side. A two-dot chain line Vng1 is a change in the voltage V1 when it is determined that welding is performed as a result of performing welding detection on the minus side.

  Below, each signal for every time is demonstrated. As shown in FIG. 2, upon receiving the system stop command (FIG. 2: step S10), the control device 101 activates the boost converter 105b, and sets the voltage V1 of the capacitor 103a and the voltage V2 of the capacitor 105c to the check voltage Vch. Set. In FIG. 3, the boost converter 105b is started from time t0, and the voltage V1 is boosted to the check voltage Vch before time t1.

  Next, at time t1, relay FCRG is cut off (FIG. 2: step S14), and subsequently, discharge command DC is turned on at time t2 (FIG. 2: step S15).

  Here, when the voltage V1 is in the state of the broken line Vok1, neither the negative relay FCRP nor the relay FCRG included in the FC relay 104 is welded (FIG. 2: Step S16: Yes). On the other hand, as indicated by a two-dot chain line Vng1, when either the negative relay FCRP or the relay FCRG included in the FC relay 104 is welded (FIG. 2: Step S16: No), the voltage V1 is the FC stack. The voltage drops to a voltage VFC of 102.

  Next, a specific example in the case where welding detection is performed for the positive relay FCRB in the FC relay 104 will be described with reference to FIG. FIG. 4 is a time chart for detection of welding in the fuel cell system according to the present embodiment.

  When welding is not detected in the negative relay of the FC relay 104 (FIG. 2: step S16: Yes), as shown in FIG. 4, the relay FCRB is shut off at time t3 (FIG. 2: step S17). Subsequently, at time t4, the relay FCRG is connected (FIG. 2: step S18).

  Here, when the voltage V1 is in the state of the broken line Vok2, the relay FCRB is not welded (FIG. 2: Step S19: Yes). On the other hand, as indicated by a two-dot chain line Vng2, when the relay FCRB is welded (FIG. 2: Step S19: No), the voltage V1 drops to the voltage VFC of the FC stack 102.

  When the welding detection for each relay included in the FC relay 104 is completed, the control unit 101 turns on the discharge command DC and performs the final discharge (FIG. 2: step S20). Specifically, the relay FCRP is cut off at time t5, and then discharge is performed between time t6 and time t7.

  As described above, the fuel cell system 100 according to the present embodiment increases the voltage V1 of the capacitor 103a and the voltage V2 of the capacitor 105c to voltages higher than the maximum voltage VFCmax of the fuel cell, respectively. The voltage change of the capacitor 103a can be detected without being affected by the voltage VFC. Therefore, it is possible to provide a fuel cell system that detects welding of each relay terminal included in the FC relay 104 regardless of the voltage of the FC stack 102.

  Note that the present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the present invention in addition to the contents described here.

DESCRIPTION OF SYMBOLS 100 Fuel cell system 101 Control part 102 FC stack 103 FC boost converter 104 FC relay 105 Output control part 106 Drive motor 107 Compressor motor 108 System main relay 109 Secondary battery 200, 201, 202, 203, 204 Voltmeter 301, 302 Current Total 103a, 105a, 105c Capacitor 104a, 108a Limiting resistor 105d Inverter FCRB, FCRG, FCRP relay SMRB, SMRG, SMRP relay Vch check voltage

Claims (1)

A secondary battery,
An output control unit comprising: a first booster circuit that boosts the voltage of the secondary battery; and a first capacitor that accumulates charges according to the voltage boosted by the first booster circuit;
A fuel cell;
FC booster comprising: a second booster circuit that boosts the voltage of the fuel cell; and a second capacitor that stores electric charge according to the voltage boosted by the first booster circuit or the second booster circuit. And
A relay that connects or disconnects the high potential terminal of the output control unit and the high potential terminal of the FC boosting unit, and a relay that connects or disconnects the low potential terminal of the output control unit and the low potential terminal of the FC boosting unit. An FC relay section comprising a plurality of relays;
A control device for detecting that the FC relay unit is welded by measuring the voltage of the second capacitor;
With
The controller is
When the fuel cell is not generating power, the voltages of the first capacitor and the second capacitor are increased to a check voltage higher than the maximum voltage of the fuel cell, respectively, and among the relays provided in the FC relay unit, When any one of the relays is connected, the other relays are shut off, and the first capacitor is discharged,
When the voltage of the second capacitor decreases to the voltage of the fuel cell, it is determined that any one of the interrupted relays is welded,
When the voltage of the second capacitor is maintained at the check voltage, it is determined that none of the relays that are cut off are welded.
Fuel cell system.

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