JP2018081883A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system capable of calculating a component parameter.SOLUTION: A fuel cell system 1 according to the present invention includes a secondary cell 11, a booster converter 15 that boosts an output voltage of the secondary cell 11, a relay circuit 16 provided between the secondary cell 11 and the booster converter 15, a fuel cell 12, a boost converter 17 that boosts an output voltage of the fuel cell 12, a relay circuit 18 provided between the booster converter 17 and a smoothing capacitor C 12 provided in the booster converter 15, and a control circuit 19, the control circuit 19 measures a time constant τ1 in the case of being precharged by closing the relay circuit 16 with the relay circuit 18 closed, a time constant τ2 in the case of being precharged by closing the relay circuit 16 with the relay circuit 18 opened, and a time constant τ3 in the case of being precharged by closing the relay circuit 18 with the relay circuit 16 closed to calculate parameter of a component.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell system.

  Development of a fuel cell system that supplies electric power to a load such as a motor using a fuel cell and a secondary battery that assists the fuel cell is progressing. For example, a fuel cell system disclosed in Patent Document 1 includes a fuel cell, a power storage device such as a secondary battery, and a DC / DC converter that can connect the fuel cell and the power storage device on a power feeding circuit. After the precharge to the smoothing capacitor provided in the DC / DC converter is completed, the fuel cell is started.

JP 2009-224036 A

The inventors have found the following problems.
In the fuel cell system disclosed in Patent Document 1, parameters of components (for example, a capacitance value of a smoothing capacitor provided in a DC / DC converter, and a contactor provided between the DC / DC converter and a power storage device) The case where the resistance value of the resistor, etc.) fluctuates due to environmental dependence is not considered. For this reason, the fuel cell system disclosed in Patent Document 1 has a problem in that when the parameters of the components fluctuate due to environmental dependence, it is not possible to supply accurate power to the load.

  The present invention has been made in view of the above, and an object of the present invention is to provide a fuel cell system capable of calculating parameters of components.

  A fuel cell system according to an aspect of the present invention includes a secondary battery, a first boosting converter that includes a first smoothing capacitor provided in an output stage, and boosts the output voltage of the secondary battery; and the secondary battery A second booster that boosts the output voltage of the fuel cell, having a first relay circuit provided between the battery and the first boost converter, a fuel cell, and a second smoothing capacitor provided in the output stage A fuel cell system comprising a converter, a second boost converter, a second relay circuit provided between the first boost converter and the first smoothing capacitor provided in the first boost converter, and a control circuit. The control circuit has a first time constant when the first smoothing capacitor is precharged by closing the first relay circuit with the second relay circuit closed, and the second relay A second time constant when the first smoothing capacitor is precharged by closing the first relay circuit with the path open, and the second relay with the first relay circuit closed. A measuring instrument for measuring a third time constant when the second smoothing capacitor is precharged by closing the circuit, and the first and second relays based on a measurement result by the measuring instrument. And an arithmetic unit for calculating each limiting resistance value of the circuit and a capacitance value of the second smoothing capacitor. By switching the open / closed state of the first and second relay circuits before precharging, the target of the capacitor to be precharged changes. Therefore, from the measurement result of the time (time constant) required for each precharge, Parameters can be calculated. As a result, accurate power can be supplied to the load.

  According to the present invention, it is possible to provide a fuel cell system capable of calculating parameters of components.

It is a figure which shows the structural example of the fuel cell system which concerns on this invention. 2 is a flowchart showing a method for calculating parameters of component parts by the fuel cell system shown in FIG. 1. It is a timing chart which shows the measuring method of the 1st time constant by the fuel cell system shown in FIG. 3 is a timing chart showing a method for measuring a second time constant and a third time constant by the fuel cell system shown in FIG.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiment. In addition, for clarity of explanation, the following description and drawings are simplified as appropriate.

First, a fuel cell system 1 according to the present invention will be described with reference to FIG.
FIG. 1 is a diagram showing a configuration example of a fuel cell system 1 according to the present invention. The fuel cell system 1 according to the present invention is a system that supplies power to a load such as a motor using a fuel cell and a secondary battery.

  Specifically, the fuel cell system 1 includes a secondary battery 11, a fuel cell 12, an inverter 13, a motor 14, a boost converter (first boost converter) 15, a relay circuit (SMR) 16, a booster A converter (second boost converter) 17, a relay circuit (FCR) 18, and a control circuit 19 are provided.

(Boost converter 15)
The boost converter 15 is a chopper type DCDC converter, and boosts the output voltage of the secondary battery 11. Specifically, the boost converter 15 includes a smoothing capacitor C11, a smoothing capacitor (first smoothing capacitor) C12, transistors Tr11 and Tr12, diodes D11 and D12, and an inductor L1.

  The smoothing capacitor C11 is provided at the input stage of the boost converter 15. The smoothing capacitor C12 is provided at the output stage of the boost converter 15.

  The transistor Tr11 is an NPN bipolar transistor, the collector is connected to the high potential side output terminal of the boost converter 15, the emitter is connected to the node N1 on the high potential side power supply line 51, and the base is connected to the control circuit 19 from the control circuit 19. A control signal is supplied. A diode D11 is provided between the collector and emitter of the transistor Tr11. That is, the transistor Tr11 is used as an upper arm element.

  The transistor Tr12 is an NPN bipolar transistor, and has a collector connected to the node N1, an emitter connected to the low potential side input terminal of the boost converter 15, and a control signal from the control circuit 19 supplied to the base. A diode D12 is provided between the collector and emitter of the transistor Tr12. That is, the transistor Tr12 is used as a lower arm element.

  The inductor L1 is provided between the high potential side input terminal of the boost converter 15 and the node N1. For example, the inductor L1 stores energy supplied from the secondary battery 11 when the transistor Tr11 is turned off and the transistor Tr12 is turned on, and is stored when the transistor Tr11 is turned on and the transistor Tr12 is turned off. Release energy.

(Relay circuit 16)
The relay circuit 16 is provided between the secondary battery 11 and the boost converter 15. By closing the relay circuit 16, the secondary battery 11 and the boost converter 15 are electrically connected, and by opening the relay circuit 16, the connection between the secondary battery 11 and the boost converter 15 is disconnected.

  Specifically, the relay circuit 16 includes switch elements SW11 to SW13 and a resistance element R1. The switch element SW11 is provided on the high potential side power line 51 of the secondary battery 11. The switch elements SW12 and SW13 are provided in parallel on the low potential side power supply line 52 of the secondary battery 11. The resistor element R1 is a limiting resistor for preventing overcurrent, and is provided in series with the switch element SW12. When closing the relay circuit 16, first, the switch elements SW11 and SW12 are closed, and after the fear of overcurrent is eliminated, the switch element SW13 is closed. Thereafter, the switch element SW12 is opened.

(Boost converter 17)
The boost converter 17 is a chopper type DCDC converter, and boosts the output voltage of the fuel cell 12. Specifically, the boost converter 17 includes a smoothing capacitor C21, a smoothing capacitor (second smoothing capacitor) C22, a transistor Tr21, diodes D21 and D2, and an inductor L2.

  The smoothing capacitor C21 is provided at the input stage of the boost converter 17. The smoothing capacitor C22 is provided in the output stage of the boost converter 17.

  The diode D2 is an element for preventing a backflow. Specifically, the anode of the diode D2 is connected to the node N2 on the high potential side power supply line 53, and the cathode of the diode D2 is connected to the high potential side output terminal of the boost converter 17.

  The transistor Tr21 is an NPN bipolar transistor having a collector connected to the node N2, an emitter connected to the low potential side input terminal of the boost converter 17, and a control signal from the control circuit 19 supplied to the base. A diode D21 is provided between the collector and emitter of the transistor Tr21.

  The inductor L2 is provided between the high potential side input terminal of the boost converter 17 and the node N2. For example, the inductor L2 stores energy supplied from the fuel cell 12 when the transistor Tr21 is turned on, and releases the stored energy when the transistor Tr21 is turned off.

(Relay circuit 18)
The relay circuit 18 is provided between the boost converter 17 and the smoothing capacitor C12 of the boost converter 15. By closing relay circuit 18, boost converter 17 and smoothing capacitor C12 are electrically connected, and by opening relay circuit 18, connection between boost converter 17 and smoothing capacitor C12 is disconnected.

  Specifically, the relay circuit 18 includes switch elements SW21 to SW23 and a resistance element R2. The switch element SW21 is provided on the high potential side power supply line 53 of the fuel cell 12. The switch elements SW22 and SW23 are provided in parallel on the low potential side power line 54 of the fuel cell 12. The resistor element R2 is a limiting resistor for preventing overcurrent, and is provided in series with the switch element SW22. When closing the relay circuit 18, first, the switch elements SW21 and SW22 are closed, and after the fear of overcurrent is eliminated, the switch element SW23 is closed. Thereafter, the switch element SW22 is opened.

(Inverter 13 and motor 14)
The voltages of the power supply lines 53 and 54 (the voltage obtained by boosting the output voltage of the fuel cell 12 and the voltage obtained by boosting the output voltage of the secondary battery 11) are supplied to the inverter 13. The inverter 13 drives the motor 14 by converting the current (electric power) from direct current to alternating current and supplying it to the motor 14.

(Control circuit 19)
The control circuit 19 controls the opening and closing of the relay circuits 16 and 18 and controls the switching operation of the boost converters 15 and 17. Further, the control circuit 19 has a measurement function (measuring instrument) for measuring a time constant and an arithmetic function (calculator) for calculating parameters of the component parts based on the measurement result.

(Part parameter calculation method)
Next, a method for calculating component parameters by the fuel cell system 1 will be described. FIG. 2 is a flowchart showing a method for calculating the component parameters by the fuel cell system 1. FIG. 3 is a timing chart showing a method for measuring the first time constant by the fuel cell system 1. FIG. 4 is a timing chart showing a method for measuring the second time constant and the third time constant by the fuel cell system 1.

  As shown in FIG. 2, first, the boost circuit 17 and the smoothing capacitor C12 are electrically connected by closing the relay circuit (FCR) 18 (step S101). Specifically, as shown in FIG. 3, first, the switch element SW21 is closed (time t11), and then the switch element SW22 is closed (time t12). After the fear of overcurrent is eliminated, the switch element SW23 is closed. (Time t13).

  Here, when the switch elements SW21 and SW22 are closed, the smoothing capacitors C22 and C12 become conductive, so that part of the electric charge accumulated in the smoothing capacitor C22 by the output voltage of the fuel cell 12 moves to the smoothing capacitor C12, The voltage FVH of the smoothing capacitor C22 and the voltage VH of the smoothing capacitor C12 are balanced.

  Thereafter, the secondary battery 11 and the boost converter 15 are electrically connected by closing the relay circuit (SMR) 16 (step S102). Specifically, as shown in FIG. 3, first, the switch element SW11 is closed (time t14), then the switch element SW12 is closed (time t15), and after the fear of overcurrent is eliminated, the switch element SW13 is closed. (Time t16). Here, when the switch elements SW11 and SW12 are closed, the secondary battery 11 and the boost converter 15 become conductive, so that charges are accumulated in the smoothing capacitors C11, C12, and C22 by the output voltage VB (VB1) of the secondary battery 11. Is done. That is, the smoothing capacitors C11, C12, and C22 are precharged by the output voltage VB (VB1) of the secondary battery 11.

  At this time, the control circuit 19 measures the time constant τ1 when the smoothing capacitor C12 is precharged by closing the relay circuit 16 with the relay circuit 18 closed (step S103).

  Here, the voltage VH of the smoothing capacitor C12 is expressed as VH = VB1 × (1−exp (−t / C · R)), where t is the elapsed precharge time, C is the total capacitance value, and R is the total resistance value. Can be represented. In this equation, VH≈0.63 × VB1 holds when t = R · C. Therefore, by measuring the time from the start of precharge until the voltage VH reaches about 63% of the voltage VB1, The time constant τ1 can be obtained.

  Since VH≈0.86 × VB1 holds when t = 2 (R · C), by measuring the time from the start of precharge until the voltage VH reaches approximately 86% of the voltage VB1 The time constant τ1 × 2 can be obtained. Similarly, since VH≈0.95 × VB1 holds when t = 3 (R · C), the time until the voltage VH reaches about 95% of the voltage VB1 after the precharge is started is measured. Thus, the time constant τ1 × 3 can be obtained. An average value of a plurality of time constants τ1 obtained by these may be adopted as the formal time constant τ1.

  This time constant τ1 is determined by the resistance value of the resistance element R1 and the capacitance values of the smoothing capacitors C11, C12, C22. Specifically, the time constant τ1 is expressed as the following formula (1).

  τ1 = R1 × (C11 + C12 + C22) (1)

  After completing the measurement of the time constant τ1, both relay circuits 16 and 18 are opened. Thereby, the smoothing capacitors C11, C12, C22 are discharged (step S104).

  Thereafter, the secondary battery 11 and the boost converter 15 are electrically connected by closing the relay circuit (SMR) 16 (step S105). Specifically, as shown in FIG. 4, first, the switch element SW11 is closed (time t21), then the switch element SW12 is closed (time t22), and after the fear of overcurrent is eliminated, the switch element SW13 is closed. (Time t23).

  Here, when the switch elements SW11 and SW12 are closed, the secondary battery 11 and the boost converter 15 are brought into conduction, so that charges are accumulated in the smoothing capacitors C11 and C12 by the output voltage VB (VB2) of the secondary battery 11. . That is, the smoothing capacitors C11 and C12 are precharged by the output voltage VB (VB2) of the secondary battery 11.

  At this time, the control circuit 19 measures the time constant τ2 when the smoothing capacitor C12 is precharged by closing the relay circuit 16 with the relay circuit 18 open (step S106).

  Here, the voltage VH of the smoothing capacitor C12 is expressed as VH = VB2 × (1−exp (−t / C · R)), where t is a precharge elapsed time, C is a total capacitance value, and R is a total resistance value. Can be represented. In this equation, VH≈0.63 × VB2 holds when t = R · C. Therefore, by measuring the time from the start of precharging until the voltage VH reaches about 63% of the voltage VB2, The time constant τ2 can be obtained.

  Since VH≈0.86 × VB2 holds when t = 2 (R · C), by measuring the time from the start of precharge until the voltage VH reaches approximately 86% of the voltage VB2. The time constant τ2 × 2 can be obtained. Similarly, since VH≈0.95 × VB2 holds when t = 3 (R · C), the time from when the precharge is started until the voltage VH reaches about 95% of the voltage VB2 is measured. Thus, the time constant τ2 × 3 can be obtained. An average value of the plurality of time constants τ2 obtained by these may be adopted as the formal time constant τ2.

  This time constant τ2 is determined by the resistance value of the resistance element R1 and the capacitance values of the smoothing capacitors C11 and C12. Specifically, the time constant τ2 is expressed as the following formula (2).

  τ2 = R1 × (C11 + C12) (2)

  After the measurement of the time constant τ2, the voltage VH of the smoothing capacitor C12 increases due to the boosting operation of the boosting converter 15.

  Thereafter, the secondary battery 11 and the boost converter 15 are electrically connected by closing the relay circuit (FCR) 18 (step S107). Specifically, as shown in FIG. 4, first, the switch element SW21 is closed (time t24), and then the switch element SW22 is closed (time t25). After the fear of overcurrent is eliminated, the switch element SW23 is closed. (Time t26). Here, when the switch elements SW21 and SW22 are closed, the smoothing capacitors C22 and C12 are turned on, so that the smoothing capacitor C22 is precharged by the voltage of the smoothing capacitor C12 boosted by the boost converter 15. That is, the voltage FVH of the smoothing capacitor C22 increases.

  At this time, the control circuit 19 measures the time constant τ3 when the smoothing capacitor C22 is precharged by closing the relay circuit 18 with the relay circuit 16 closed (step S108). The method for measuring the time constant τ3 is basically the same as the method for measuring the time constants τ1 and τ2.

  The time constant τ3 is determined by the resistance value of the resistance element R2 and the capacitance value of the smoothing capacitor C22. Specifically, the time constant τ3 is expressed as the following formula (3).

  τ3 = R2 × C22 (3)

  After completing the measurement of the time constant τ3, the control circuit 19 determines the parameters of the components (in this example, the resistance values of the resistance elements R1 and R2 and the capacitance of the smoothing capacitor C22 based on the measurement results of the time constants τ1 to τ3. Value). Specifically, it is calculated as follows using equations (1) to (3). Note that set values are used for the capacitance values C11 and C12.

Resistance value R1 = τ2 / (C11 + C12)
Capacitance value C22 = {(τ1 / τ2) −1)} × (C11 + C12)
Resistance value R2 = τ3 / [{(τ1 / τ2) −1)} × (C11 + C12)]

  As described above, in the fuel cell system 1 according to the present embodiment, the target of the capacitor to be precharged is changed by switching the open / close state of the relay circuits 16 and 18 before the precharge. The parameter of the component can be calculated from the measurement result of the time (time constant) required. As a result, accurate power can be supplied to the load.

DESCRIPTION OF SYMBOLS 1 Fuel cell system 11 Secondary battery 12 Fuel cell 13 Inverter 14 Motor 15 Boost converter 16 Relay circuit (SMR)
17 Boost converter 18 Relay circuit (FCR)
19 control circuit 51 high potential side power supply line 52 low potential side power supply line 53 high potential side power supply line 54 low potential side power supply line C11 smoothing capacitor C12 smoothing capacitor C21 smoothing capacitor C22 smoothing capacitor D11 diode D12 diode D2 diode D21 diode L1 inductor L2 Inductor R1 Resistance element R2 Resistance element SW11 to SW13 Switch element SW21 to SW23 Switch element Tr11, Tr12 transistor Tr21 transistor

Claims (1)

A secondary battery,
A first boost converter having a first smoothing capacitor provided in an output stage and boosting the output voltage of the secondary battery;
A first relay circuit provided between the secondary battery and the first boost converter;
A fuel cell;
A second boost converter having a second smoothing capacitor provided in an output stage and boosting the output voltage of the fuel cell;
A second relay circuit provided between the second boost converter and the first smoothing capacitor provided in the first boost converter;
A fuel cell system comprising a control circuit,
The control circuit includes:
A first time constant when the first smoothing capacitor is precharged by closing the first relay circuit with the second relay circuit closed, and the first time constant with the second relay circuit open. A second time constant when the first smoothing capacitor is precharged by closing one relay circuit, and the second time constant by closing the second relay circuit with the first relay circuit closed. A measuring instrument for measuring the third time constant when the smoothing capacitor is precharged, and
A fuel cell system comprising: an arithmetic unit that calculates a limiting resistance value of each of the first and second relay circuits and a capacitance value of the second smoothing capacitor based on a measurement result by the measuring device.

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