JP2024033282A - fuel cell system - Google Patents

Abstract

To shorten a time required to reduce a voltage applied to a fuel cell or a DCDC converter to a desired voltage in the event of emergency stop or abnormal stop of a fuel cell system.SOLUTION: At the time of emergency stop or abnormal stop of a fuel cell FC, a low-side switch SW2 of a DCDC converter CNV and a relay Re connected between the DCDC converter CNV and a power storage device B are always turned off, auxiliary equipment such as a hydrogen circulation pump HP is driven to prevent the fuel cell FC from generating electricity, and a current is caused to flow from the fuel cell FC to the auxiliary equipment via the an inductor L, a diode D1, and a capacitor C of the DCDC converter CNV.SELECTED DRAWING: Figure 1

Description

The present invention relates to a fuel cell system.

The fuel cell system includes a high-side diode, a low-side switch, an inductor connected between the connection point of the diode and switch and the fuel cell, and a capacitor connected in parallel to the diode and switch. Some devices include a DC/DC converter that increases the voltage of the fuel cell by turning on and off, and decreases the voltage of the fuel cell by turning off the switch. As a related technique, for example, there is Patent Document 1.

By the way, in the event of an emergency stop due to the user pressing the emergency stop button, or an abnormal stop due to a failure of a component within the fuel cell system, power is supplied from the fuel cell to the external load via the DC/DC converter. When stopping the operation, the DC/DC converter switch is always turned off and the auxiliary equipment is stopped.

Therefore, in the above fuel cell system, when the DCDC converter switch is constantly turned off and the auxiliary equipment is stopped during an emergency stop or abnormal stop, a relatively small current (dark current) flows through the fuel cell and the DCDC converter. In other words, there is a concern that it will take a relatively long time to reduce the voltage applied to the fuel cell or DC/DC converter to the desired voltage because the charge remaining in the fuel cell or DC/DC converter will be difficult to consume. be.

JP2022-82092A

An object of one aspect of the present invention is to reduce the time required to reduce the voltage applied to a fuel cell or a DC/DC converter to a desired voltage during an emergency or abnormal stop of a fuel cell system. .

A fuel cell system according to one embodiment of the present invention includes a fuel cell, a high-side diode, a low-side switch, and an inductor connected between a connection point between the diode and the switch and the fuel cell. , comprising the diode and a capacitor connected in parallel to the switch, and when the switch is turned on and off, the voltage of the fuel cell is increased, and when the switch is always turned off, the voltage of the fuel cell is decreased. a DCDC converter, a power storage device to which power output from the DCDC converter is supplied, a relay connected between the DCDC converter and the power storage device, and a relay connected between the DCDC converter and the relay; An auxiliary device for causing the fuel cell to generate electricity, and a control unit that controls the operation of the switch, the relay, and the auxiliary device, and the control unit controls the operation of the switch and the The relay is always turned off and the auxiliary machine is driven so that the fuel cell does not generate electricity, so that current flows from the fuel cell to the auxiliary machine via the inductor, the diode, and the capacitor.

This allows the auxiliary equipment to consume the electric charge remaining in the fuel cell or DC/DC converter during an emergency or abnormal stop, so it takes less charge to reduce the voltage applied to the fuel cell or DC/DC converter to the desired voltage. Time can be shortened.

In addition, the control unit may operate a hydrogen circulation pump as the auxiliary device to supply hydrogen gas discharged from the fuel cell again to the fuel cell during an emergency stop or an abnormal stop. The fuel cell may be configured to be driven so as to be discharged outside the fuel cell.

This allows the water inside the fuel cell to be actively discharged to the outside of the fuel cell in the event of an emergency or abnormal stop, thereby suppressing fuel cell deterioration caused by water remaining inside the fuel cell. can do.

Further, the control unit may be configured to drive two or more of the auxiliary machines during an emergency stop or an abnormal stop.

This increases the amount of charge remaining in the fuel cell or DC/DC converter consumed per unit time, further reducing the time required to reduce the voltage applied to the fuel cell or DC/DC converter to the desired voltage. be able to.

According to the present invention, it is possible to reduce the time required to reduce the voltage applied to the fuel cell or the DC/DC converter to a desired voltage during an emergency or abnormal stop of the fuel cell system.

It is a figure showing an example of application of a fuel cell system of an embodiment. FIG. 6 is a diagram showing another application example of the fuel cell system of the embodiment. It is a figure showing an example of a DC-DC converter. FIG. 3 is a diagram showing an example of a power generation control flag, a fuel cell voltage, a DCDC converter control flag, a relay control flag, and an auxiliary machine control flag at the time of starting power generation control. FIG. 3 is a diagram showing an example of a power generation control flag, a fuel cell voltage, a DCDC converter control flag, a relay control flag, and an auxiliary equipment control flag during an emergency stop/abnormal stop. FIG. 3 is a diagram showing an example of a power generation control flag, a fuel cell voltage, a DCDC converter control flag, a relay control flag, and an auxiliary equipment control flag during an emergency stop/abnormal stop.

Embodiments will be described in detail below based on the drawings.

FIG. 1 is a diagram showing an example of application of the fuel cell system of the embodiment.

In the application example of the fuel cell system shown in FIG. 1, a fuel cell system 1 is installed in a vehicle Ve. For example, the vehicle Ve is an industrial vehicle such as a forklift. It is also assumed that the vehicle Ve is equipped with an external load Lo such as an inverter that drives a driving motor, and that the fuel cell system 1 supplies electric power to the external load Lo.

Moreover, FIG. 2 is a diagram showing another application example of the fuel cell system of the embodiment. Note that the fuel cell system 1 shown in FIG. 2 is similar to the fuel cell system 1 shown in FIG. 1.

In the application example of the fuel cell system 1 shown in FIG. 2, the fuel cell system 1 is provided in a stationary generator Sg. For example, the stationary generator Sg is a generator that supplies power to an external load Lo in cooperation with a commercial power source, a solar power generator, etc., and power is supplied from the fuel cell system 1 to the external load Lo. shall be taken as a thing.

The fuel cell system 1 shown in FIG. 1 or 2 also includes a fuel cell FC, a fuel tank Tk, a main stop valve SV, an injector INJ, a gas-liquid separator GLS, a hydrogen circulation pump HP, and an exhaust drainage It includes a valve EDV, a diluter DIL, an air compressor ACP, an air pressure regulating valve ARV, and an air shut valve ASV.

Further, the fuel cell system 1 shown in FIG. 1 or 2 includes a radiator R, a fan F, a water pump WP, an intercooler IC, a DC/DC converter CNV, a power storage device B, a relay Re, and a current sensor Sif. , a voltage sensor Svf, a current sensor Sib, a voltage sensor Svb, a storage section 2, and a control section 3.

A fuel cell FC is configured by stacking a plurality of fuel cells, and generates electricity through an electrochemical reaction between hydrogen contained in hydrogen gas and oxygen contained in oxidant gas.

The fuel tank Tk is a storage container for hydrogen gas. Hydrogen gas stored in the fuel tank Tk is supplied to the fuel cell FC via the main stop valve SV and the injector INJ.

The main stop valve SV is composed of a solenoid valve or the like, and supplies hydrogen gas to the injector INJ. Further, the main stop valve SV cuts off the supply of hydrogen gas to the injector INJ under the operation control of the control unit 3. Note that when the fuel cell system 1 is installed in the vehicle Ve, the fuel tank Tk and the main stop valve SV are installed inside the vehicle Ve. When the fuel cell system 1 is included in the stationary generator Sg, the fuel tank Tk and the main stop valve SV are provided outside the stationary generator Sg.

The injector INJ adjusts the flow rate of hydrogen gas so that the pressure of the hydrogen gas supplied to the fuel cell FC is constant.

The gas-liquid separator GLS separates hydrogen gas and liquid water discharged from the fuel cell FC.

The hydrogen circulation pump HP resupplies the hydrogen gas separated by the gas-liquid separator GLS to the fuel cell FC.

The exhaust drain valve EDV sends the liquid water separated by the gas-liquid separator GLS to the diluter DIL. The liquid water sent to the diluter DIL accumulates in a tank (not shown) within the diluter DIL. Further, the oxidizing gas discharged from the fuel cell FC via the air pressure regulating valve ARV joins the hydrogen gas discharged from the exhaust drain valve EDV at the diluter DIL, and is discharged from the diluter DIL.

Air compressor ACP compresses surrounding oxidant gas and supplies the compressed oxidant gas to fuel cell FC via intercooler IC and air shut valve ASV. Note that the compression ratio of the air compressor ACP is controlled by adjusting the opening degree of an air pressure regulating valve ARV provided downstream of the fuel cell FC.

The intercooler IC exchanges heat between the oxidant gas, which has become high in temperature due to compression, with a refrigerant such as cooling water flowing through the intercooler IC.

The air shut valve ASV shuts off the supply of oxidizing gas to the fuel cell FC under the operation control of the control unit 3.

The air pressure regulating valve ARV adjusts the pressure and flow rate of the oxidizing gas supplied to the fuel cell FC.

The radiator R causes the refrigerant warmed by the heat generated by the fuel cell FC to exchange heat with the atmosphere around the radiator R.

The fan F increases the amount of heat dissipated from the radiator R.

Water pump WP supplies refrigerant cooled by radiator R to fuel cell FC via intercooler IC.

The DC/DC converter CNV is connected to the latter stage of the fuel cell FC, and increases or decreases the voltage of the fuel cell FC. Further, the electric power output from the DCDC converter CNV is supplied to the external load Lo, auxiliary machines such as the air compressor ACP, the hydrogen circulation pump HP, and the water pump WP, and the power storage device B. Further, the voltage output from the DC/DC converter CNV is stepped down by another DC/DC converter (not shown), and is supplied to auxiliary devices such as the fan F, the air shut valve ASV, and the air pressure regulating valve ARV.

Here, FIG. 3 is a diagram showing an example of the DCDC converter CNV.

The DCDC converter CNV shown in FIG. 3 includes a high-side switch SW1, a high-side diode D1 (diode) connected in parallel to the switch SW1, a low-side switch SW2 (switch) connected in series with the switch SW1, and a switch It includes a low-side diode D2 connected in parallel to SW2, an inductor L connected between the connection point of switches SW1 and SW2 and the fuel cell FC, and a capacitor C connected in parallel to switches SW1 and SW2.

For example, when the switches SW1 and SW2 are respectively MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), the diodes D1 and D2 are parasitic diodes of the switches SW1 and SW2.

Further, when the switches SW1 and SW2 are each MOSFET, one terminal of the inductor L is connected to one terminal of the fuel cell FC, and the other terminal of the inductor L is the connection point between the source terminal of the switch SW1 and the drain terminal of the switch SW2. It is connected to the. Further, the drain terminal of the switch SW1 is connected to one terminal of the capacitor C, and the source terminal of the switch SW2 is connected to the other terminal of the fuel cell FC and the other terminal of the capacitor C.

Further, one terminal of the capacitor C is connected to one terminal of each of the external load Lo and the auxiliary machine, and is also connected to the positive terminal of the power storage device B via the relay Re. Further, the other terminal of the capacitor C is connected to the other terminals of the external load Lo and the auxiliary equipment, and is also connected to the negative terminal of the power storage device B.

Power storage device B is configured with a lithium ion capacitor or the like, and is supplied with power output from the DC/DC converter CNV. In other words, if the supplied power corresponding to the difference between the power output from the DCDC converter CNV and the total value of the power supplied to the auxiliary equipment is greater than the required power required from the external load Lo, then Power corresponding to the required power is supplied to external load Lo, and the remaining power is supplied to power storage device B. When power is supplied from the DC/DC converter CNV to the power storage device B, the power storage device B is charged and the charge amount Ch of the power storage device B increases. In addition, if the supplied power corresponding to the difference between the power output from the DCDC converter CNV and the total value of the power supplied to the auxiliary equipment is smaller than the required power required from the external load Lo, the supplied power is At the same time, the insufficient power is supplied from power storage device B to external load Lo. When power is supplied from power storage device B to external load Lo, power storage device B is discharged and the amount of charge Ch of power storage device B decreases. Note that the charge amount Ch is the charging rate [%] of power storage device B (the ratio of the remaining capacity to the fully charged capacity of power storage device B), or the open state of power storage device B when no current is flowing through power storage device B. It is assumed that the circuit voltage [V], the closed circuit voltage [V] of power storage device B when current is flowing through power storage device B, or the integrated value [Ah] of the current flowing through power storage device B, or the like.

The relay Re is constituted by an electromagnetic relay or the like. One terminal of the relay Re is connected to one output terminal (one terminal of the capacitor C) of the DCDC converter CNV via the voltage sensor Svb, the current sensor Sib, the auxiliary equipment, and the external load Lo, and the other terminal of the relay Re is , is connected to the positive terminal of power storage device B. That is, a relay Re is connected between the DCDC converter CNV and the power storage device B, and an external load Lo and auxiliary equipment (air compressor ACP, hydrogen circulation pump HP, water pump WP, etc.) are connected between the DCDC converter CNV and the relay Re. ) are connected. When relay Re is turned on (conducted) under the operation control of control unit 3, power storage device B is electrically connected to DCDC converter CNV, external load Lo, and auxiliary equipment. On the other hand, when relay Re is turned off (cut off) by the operation control of control unit 3, DCDC converter CNV, external load Lo, auxiliary equipment, and power storage device B are electrically cut off.

The current sensor Sif is composed of a shunt resistor, a Hall element, etc., detects the current If flowing from the fuel cell FC to the DCDC converter CNV, and sends the detected current If to the control unit 3.

The voltage sensor Svf is constituted by a voltage dividing resistor, etc., detects the voltage Vf of the fuel cell FC, and sends the detected voltage Vf to the control section 3.

Current sensor Sib is composed of a shunt resistor, a Hall element, etc., and when relay Re is on, current Ib flows from fuel cell FC to power storage device B via DC/DC converter CNV and relay Re, or from power storage device B to relay. The current Ib flowing to the external load Lo via Re is detected, and the detected current Ib is sent to the control section 3.

Voltage sensor Svb is configured with a voltage dividing resistor, etc., and when relay Re is on, detects voltage Vb of power storage device B in a state where relay Re and power storage device B are connected in series; The voltage Vb is sent to the control section 3.

The storage unit 2 is composed of RAM (Random Access Memory), ROM (Read Only Memory), and the like. Note that the storage unit 2 stores a threshold value Vth, etc., which will be described later. For example, the threshold value Vth is the minimum value of the voltage handled by the fuel cell system 1 or the stationary generator Sg.

The control unit 3 is composed of a microcomputer or the like, and controls power generation of the fuel cell FC.

<When power generation control starts>
The control unit 3 controls when the power of the vehicle Ve changes from an off state to an on state due to the user operating an ignition key provided on the vehicle Ve, or when the power button provided on the stationary generator Sg is operated by the user. When the power of the stationary generator Sg changes from the off state to the on state, for example, the power generation control of the fuel cell FC is started.

For example, when starting power generation control of the fuel cell FC, the control unit 3 switches the power generation control flag from off to on. When switching the power generation control flag from OFF to ON, the control unit 3 switches the auxiliary machine control flag, the DCDC converter control flag, and the relay control flag from OFF to ON. When the control unit 3 switches the auxiliary equipment control flag from OFF to ON, it starts driving the auxiliary equipment, and when the DCDC converter control flag is switched from OFF to ON, it starts driving the DCDC converter CNV, and sets the relay control flag. Switching from off to on switches relay Re from off (blocking) to on (conducting).

<Power generation control in progress>
During power generation control of the fuel cell FC, the control unit 3 changes the target generated power Pt in stages according to the charge amount Ch of the power storage device B.

Further, during the power generation control of the fuel cell FC, the control unit 3 controls the operation of the auxiliary equipment so that the power generated by the fuel cell FC (the product of the current If and the voltage Vf) follows the target power generation Pt. For example, during power generation control of the fuel cell FC, the control unit 3 controls the motor of the air compressor ACP by PI (Proportional-Integral) control so that the difference between the power generated by the fuel cell FC and the target power generation Pt becomes zero. and the rotation speed of the motor of the hydrogen circulation pump HP.

Further, during power generation control of the fuel cell FC, the control unit 3 controls the voltage Vf of the fuel cell FC to be boosted to the target voltage Vt when the voltage Vf of the fuel cell FC is lower than the target voltage Vt (for example, 48V). , switches SW1 and SW2 are turned on and off alternately. Note that during the power generation control of the fuel cell FC, the control unit 3 constantly sets the switch SW1 so that, when the voltage Vf of the fuel cell FC is lower than the target voltage Vt, the voltage Vf of the fuel cell FC is boosted to the target voltage Vt. The switch SW2 may be configured to be turned on and off while being turned off. In this state, if the target voltage Vt is higher than the voltage of the external load Lo, current flows from the fuel cell FC to the external load Lo via the DC/DC converter CNV. Further, when target voltage Vt is higher than voltage Vb of power storage device B and relay Re is on, current flows from fuel cell FC to power storage device B via DCDC converter CNV and relay Re.

Further, during power generation control of the fuel cell FC, the control unit 3 turns off the switches SW1 and SW2 at all times so that the voltage Vf of the fuel cell FC is stepped down when the voltage Vf of the fuel cell FC is equal to or higher than the target voltage Vt. let Note that the control unit 3 may be configured to always turn on the switch SW1 and always turn off the switch SW2 when the voltage Vf of the fuel cell FC is equal to or higher than the target voltage Vt during power generation control of the fuel cell FC. . In this state, if the target voltage Vt is higher than the voltage of the external load Lo, current flows from the fuel cell FC to the external load Lo via the DC/DC converter CNV. Further, when target voltage Vt is higher than voltage Vb of power storage device B and relay Re is on, current flows from fuel cell FC to power storage device B via DCDC converter CNV and relay Re.

<When power generation control ends>
When the power of the vehicle Ve changes from an on state to an off state due to the user operating an ignition key provided on the vehicle Ve, or when a power button provided on the stationary generator Sg is operated by the user, the control unit 3 When the power source of the stationary generator Sg changes from the on state to the off state due to the above reason, the power generation control of the fuel cell FC is terminated.

For example, the control unit 3 switches the power generation control flag from on to off when power generation control of the fuel cell FC ends. When the power generation control flag is switched from on to off, the control unit 3 switches the auxiliary equipment control flag from on to off to stop the auxiliary equipment.

Further, the control unit 3 drives the DCDC converter CNV and always turns on the relay Re during the period from when the power generation control flag is switched from on to off until the voltage Vf of the fuel cell FC becomes equal to or less than the threshold value Vth. As a result, at the end of the power generation control of the fuel cell FC, during the period from when the power generation control flag is switched from on to off until the voltage Vf of the fuel cell FC becomes equal to or less than the threshold value Vth, the fuel cell FC is connected to the DCDC converter CNV and the relay Re. In other words, the charge remaining in the fuel cell FC or the DC/DC converter CNV can be actively transferred to the power storage device B, so that the The voltage Vf and the voltage of the DCDC converter CNV can be lowered to desired voltages.

Further, when the voltage Vf of the fuel cell FC becomes equal to or lower than the threshold value Vth after switching the power generation control flag from on to off, the control unit 3 switches the DCDC converter control flag from on to off to stop the DCDC converter CNV, The relay control flag is switched from on to off to keep the relay Re off at all times.

<During emergency stop/abnormal stop>
When the user presses an emergency stop button (not shown) provided in the vehicle Ve or the stationary generator Sg, or when an abnormality occurs in a component in the fuel cell system 1 (hydrogen circulation pump HP, etc.), the control unit 3 If so, in order to immediately stop the supply of power to external load Lo and power storage device B, the emergency stop/abnormal stop flag is switched from off to on and emergency stop/abnormal stop processing is started. For example, during power generation control of the fuel cell FC, when the current detected by a current sensor (not shown) that detects the current applied to the hydrogen circulation pump HP exceeds a predetermined current value, the control unit 3 controls the hydrogen circulation pump HP. It is determined that an abnormality has occurred.

Furthermore, when the emergency stop/abnormal stop flag is switched from off to on, the control unit 3 switches the DCDC converter control flag from on to off to keep switches SW1 and SW2 off at all times, and also switches the relay control flag from on to off. Switch to keep relay Re off all the time. In this way, during an emergency stop/abnormal stop, supply of power from the fuel cell FC to the power storage device B can be stopped by always turning off the relay Re.

Furthermore, the control unit 3 maintains the auxiliary equipment control flag on for a period from when the emergency stop/abnormal stop flag is switched from off to on until the voltage Vf of the fuel cell FC becomes equal to or less than the threshold value Vth. drive the auxiliary equipment so that it does not generate electricity. For example, when driving the air compressor ACP during the period from switching the emergency stop/abnormal stop flag from off to on until the voltage Vf of the fuel cell FC becomes equal to or lower than the threshold value Vth, the control unit 3 controls the air compressor ACP to By controlling the operation of the provided motor so that it does not rotate, current flows from the fuel cell FC to the motor of the air compressor ACP via the DC/DC converter CNV. In this way, during an emergency stop/abnormal stop, the auxiliary equipment is driven to prevent the fuel cell FC from generating power, so power generation by the fuel cell FC immediately stops and power is supplied to the external load Lo. You can stop things immediately. In addition, during an emergency stop/abnormal stop, current can be actively passed from the fuel cell FC to the auxiliary equipment via the inductor L, diode D1, and capacitor C. Since the charge remaining in the fuel cell FC can be consumed by the auxiliary equipment, the voltage Vf of the fuel cell FC or the voltage of the DCDC converter CNV can be lowered to a desired voltage. In addition, when driving the hydrogen circulation pump HP during an emergency stop/abnormal stop, it is possible to actively discharge the water inside the fuel cell FC to the outside of the fuel cell FC (scavenging process). Deterioration of the fuel cell FC caused by water remaining in the fuel cell FC can be suppressed. Note that when the emergency stop/abnormal stop flag is switched from off to on, power is basically not supplied from the fuel cell FC to the external load.

Further, the control unit 3 is configured to drive two or more auxiliary machines during a period from when the emergency stop/abnormal stop flag is switched from off to on until the voltage Vf of the fuel cell FC becomes equal to or less than the threshold value Vth. It's okay. For example, the control unit 3 drives the hydrogen circulation pump HP and the water pump WP during the period from when the emergency stop/abnormal stop flag is switched from off to on until the voltage Vf of the fuel cell FC becomes equal to or less than the threshold value Vth. may be configured. As a result, even if the hydrogen circulation pump HP is unable to consume the charge remaining in the fuel cell FC or DCDC converter CNV due to a failure of the hydrogen circulation pump HP, the fuel cell FC or DCDC converter CNV Since the charge remaining in the fuel cell FC can be consumed by the water pump WP, the voltage Vf of the fuel cell FC or the voltage of the DCDC converter CNV can be lowered to a desired voltage.

In addition, the control unit 3 selectively drives auxiliary equipment with relatively large power consumption during the period from when the emergency stop/abnormal stop flag is switched from off to on until the voltage Vf of the fuel cell FC becomes equal to or less than the threshold value Vth. It may also be configured to do so. As a result, during an emergency stop/abnormal stop, the charge remaining in the fuel cell FC or the DC/DC converter CNV can be consumed in a shorter time, and the voltage Vf of the fuel cell FC or the voltage of the DC/DC converter CNV can be adjusted to the desired voltage. can be lowered more quickly.

Further, after switching the emergency stop/abnormal stop flag from OFF to ON, when the voltage Vf of the fuel cell FC becomes equal to or lower than the threshold value Vth, the control unit 3 switches the auxiliary equipment control flag from ON to OFF and stops the auxiliary equipment. let

Here, FIG. 4 is a diagram showing an example of the power generation control flag, the voltage Vf of the fuel cell FC, the DCDC converter control flag, the relay control flag, and the auxiliary machine control flag at the time of starting the power generation control. The horizontal axis of each two-dimensional coordinate shown in FIGS. 4(a) to 4(e) indicates time, the vertical axis indicates voltage, and the solid line shown in FIG. 4(a) indicates the power generation control flag. The solid line shown in FIG. 4(b) shows the voltage Vf of the fuel cell FC, the solid line shown in FIG. 4(c) shows the DCDC converter control flag, and the solid line shown in FIG. 4(d) shows the relay control flag. The solid line shown in (e) shows the auxiliary machine control flag.

In the example shown in FIGS. 4(a) to 4(e), at time t11, when the power generation control flag switches from on (voltage Vhigh) to off (voltage Vlow), the auxiliary equipment control flag changes from on (voltage Vhigh) to off (voltage Vlow). Switched off (voltage Vlow). Furthermore, even when the power generation control flag is switched from on to off, the DCDC converter control flag and relay control flag are maintained on (voltage Vhigh). As a result, the power generation of the fuel cell FC is stopped, and current flows from the fuel cell FC to the power storage device B via the DC/DC converter CNV, and the voltage Vf of the fuel cell FC gradually decreases.

Then, at time t12, when the voltage Vf of the fuel cell FC becomes equal to or lower than the threshold value Vth, that is, when the voltage Vf of the fuel cell FC decreases to the minimum value of the voltage handled by the fuel cell system 1 or the stationary generator Sg, DCDC The converter control flag is switched from on to off (voltage Vlow) and switches SW1 and SW2 are always off, and the relay control flag is switched from on to off (voltage Vlow) and relay Re is always off.

By the way, in the event of an emergency stop/abnormal stop, if you want to immediately stop power being supplied to the external load Lo or power storage device B, wait until the emergency stop/abnormal stop flag is switched from off to on. It is conceivable to immediately switch the DCDC converter control flag, relay control flag, and auxiliary machine control flag from on to off.

FIG. 5 shows the power generation control flag in the case where the DCDC converter control flag, relay control flag, and auxiliary equipment control flag are switched from on to off immediately after the emergency stop/abnormal stop flag is switched from off to on. FIG. 3 is a diagram showing an example of a voltage Vf of a fuel cell FC, a DCDC converter control flag, a relay control flag, and an auxiliary equipment control flag. The horizontal axis of each two-dimensional coordinate shown in FIGS. 5(a) to 5(e) indicates time, the vertical axis indicates voltage, and the solid line shown in FIG. 5(a) indicates the emergency stop/abnormal stop flag. The solid line shown in FIG. 5(b) shows the voltage Vf of the fuel cell FC, the solid line shown in FIG. 5(c) shows the DCDC converter control flag, and the solid line shown in FIG. 5(d) shows the relay control flag. , the solid line shown in FIG. 5(e) indicates the auxiliary machine control flag.

In the example shown in FIGS. 5(a) to 5(e), at time t21, when the emergency stop/abnormal stop flag switches from off (voltage Vlow) to on (voltage Vhigh), the DCDC converter control flag and the relay control flag , and the auxiliary equipment control flag are respectively switched from on (voltage Vhigh) to off (voltage Vlow). Thereby, at the time of emergency stop/abnormal stop, supply of power to external load Lo and power storage device B can be immediately stopped.

However, in the event of an emergency stop/abnormal stop, if you immediately stop the DCDC converter CNV and auxiliary equipment and cut off the relay Re, only a relatively small current (dark current) flows through the fuel cell FC and the DCDC converter CNV. , the electric charge remaining in the fuel cell FC and the DCDC converter CNV becomes difficult to move from the fuel cell FC and the DCDC converter CNV, so the emergency stop/abnormal stop flag is turned off at time t21, as shown in FIG. 4(b). The period from when the fuel cell FC is turned on until the voltage Vf of the fuel cell FC becomes equal to or lower than the threshold value Vth at time t23 is relatively long.

Therefore, in the fuel cell system 1 of the embodiment, the auxiliary equipment is configured so that the fuel cell FC does not generate electricity for a period from when the emergency stop/abnormal stop flag is switched from off to on until the voltage Vf of the fuel cell FC becomes equal to or less than the threshold value Vth. is being driven.

FIG. 6 is a diagram showing an example of the power generation control flag, fuel cell FC voltage Vf, DCDC converter control flag, relay control flag, and auxiliary equipment control flag at the time of emergency stop/abnormal stop in the fuel cell system 1 of the embodiment. be. The horizontal axis of each two-dimensional coordinate shown in FIGS. 6(a) to 6(e) indicates time, the vertical axis indicates voltage, and the solid line shown in FIG. 6(a) indicates the emergency stop/abnormal stop flag. The solid line shown in FIG. 6(b) shows the voltage Vf of the fuel cell FC, the solid line shown in FIG. 6(c) shows the DCDC converter control flag, and the solid line shown in FIG. 6(d) shows the relay control flag. , the solid line shown in FIG. 6(e) indicates the auxiliary equipment control flag.

First, at time t21, when the emergency stop/abnormal stop flag switches from off (voltage Vlow) to on (voltage Vhigh), the DCDC converter control flag and relay control flag each switch from on (voltage Vhigh) to off (voltage Vlow). By switching, switches SW1, SW2 and relay Re are always turned off. In this way, during an emergency stop/abnormal stop, the relay Re is always turned off, so that the power supply from the fuel cell FC to the power storage device B can be immediately stopped.

Further, at time t21, when the emergency stop/abnormal stop flag is switched from off to on, the auxiliary equipment is driven so that the fuel cell FC does not generate electricity while the auxiliary equipment control flag remains on. Thereby, during an emergency stop/abnormal stop, the charge remaining in the fuel cell FC and the DC/DC converter CNV can be consumed by the auxiliary equipment.

Then, at time t22, when the voltage Vf of the fuel cell FC becomes equal to or lower than the threshold value Vth, the auxiliary machine control flag is switched from on to off, and the auxiliary machine stops.

As described above, in the fuel cell system 1 of the embodiment, even in a situation where the electric charge remaining in the fuel cell FC or the DC/DC converter CNV cannot be consumed by the power storage device B during an emergency stop/abnormal stop, the auxiliary equipment Compared to the case where the charge remaining in the fuel cell FC or the DCDC converter CNV is consumed by an element with a relatively small resistance value included in the DCDC converter, the charge remaining in the fuel cell FC or the DCDC converter CNV is It is possible to increase the consumption amount per unit time, and it is possible to shorten the time required to make the voltage Vf of the fuel cell FC and the voltage of the DC-DC converter CNV below the threshold value Vth. Furthermore, since the fuel cell system 1 completes the control for consuming electric charge, there is no need to provide a function to consume the electric charge remaining in the fuel cell FC or the DC/DC converter CNV by an external load. Therefore, there is no need to make any design changes to the application itself to which the fuel cell system 1 is applied.

In addition, in the fuel cell system 1 of the embodiment, the voltage Vf of the fuel cell FC and the voltage of the DCDC converter CNV can be reduced in a relatively short time during an emergency stop/abnormal stop. Malfunctioning parts can be replaced immediately.

Note that the present invention is not limited to the above-described embodiments, and various improvements and changes can be made without departing from the gist of the present invention.

<Modification 1>
In the above embodiment, when the control unit 3 switches the emergency stop/abnormal stop flag from off to on, it switches the DCDC converter control flag from on to off and turns off the switches SW1 and SW2 at all times. /When the abnormal stop flag is switched from OFF to ON, the DCDC converter control flag may be switched from ON to OFF, so that the switch SW1 is always turned on and the switch SW2 is always turned off.

<Modification 2>
In the DCDC converter CNV, the switch SW1 may be omitted. That is, when the switch SW1 is omitted, the DCDC converter CNV includes a high-side diode D1, a low-side switch SW2, an inductor L connected between the connection point of the diode D1 and the switch SW2, and the fuel cell FC, It is equipped with a diode D1 and a capacitor C connected in parallel to the switch SW2, and by turning on and off the switch SW2, the voltage Vf of the fuel cell FC is boosted, and by always turning off the switch SW2, the voltage Vf of the fuel cell FC is increased. Lower blood pressure.

<Modification 3>
In the above embodiment, a one-phase DC/DC converter CNV consisting of an inductor L, high-side elements (switch SW1 and diode D1), and low-side elements (switch SW2 and diode D2) is adopted, but two-phase or more A DC/DC converter CNV may also be employed. In addition, when employing a DCDC converter CNV with two or more phases, the control unit 3 shifts the on/off phases of the high-side element and the low-side element of each phase from each other, thereby adjusting the voltage Vf of the fuel cell FC. is boosted to the target voltage Vt.

1 Fuel cell system 2 Storage unit 3 Control unit Ve Vehicle Lo External load Sg Stationary generator FC Fuel cell Tk Fuel tank SV Main stop valve INJ Injector GLS Gas-liquid separator HP Hydrogen circulation pump EDV Exhaust drain valve DIL Diluter ACP Air Compressor ARV Air pressure regulating valve ASV Air shutoff valve R Radiator F Fan WP Water pump IC Intercooler CNV DCDC converter B Power storage device Sif Current sensor Svf Voltage sensor Sib Current sensor Svb Voltage sensor

Claims (3)

fuel cell and
a high-side diode, a low-side switch, an inductor connected between a connection point between the diode and the switch and the fuel cell, and a capacitor connected in parallel to the diode and the switch, the switch a DC/DC converter that increases the voltage of the fuel cell by turning on and off, and decreases the voltage of the fuel cell by turning off the switch;
a power storage device to which power output from the DCDC converter is supplied;
a relay connected between the DCDC converter and the power storage device;
an auxiliary machine connected between the DC/DC converter and the relay for causing the fuel cell to generate electricity;
a control unit that controls operations of the switch, the relay, and the auxiliary equipment;
Equipped with
At the time of an emergency stop or an abnormal stop, the control unit always turns off the switch and the relay and drives the auxiliary equipment so that the fuel cell does not generate power, so that the inductor, the diode, and the inductor are removed from the fuel cell. A fuel cell system characterized in that current is caused to flow through the auxiliary equipment through the capacitor. The fuel cell system according to claim 1,
At the time of an emergency stop or an abnormal stop, the control unit controls a hydrogen circulation pump for re-supplying hydrogen gas discharged from the fuel cell to the fuel cell as the auxiliary equipment so that the water in the fuel cell can be used as the auxiliary equipment. A fuel cell system characterized by being driven so that fuel is discharged outside the battery. The fuel cell system according to claim 1,
The fuel cell system is characterized in that the control unit drives two or more of the auxiliary machines during an emergency stop or an abnormal stop.

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