JP2023085096A - fuel cell system - Google Patents

Abstract

To suppress deterioration due to potential variation of a fuel cell while suppressing stay of water in the fuel cell in a fuel cell system.SOLUTION: A fuel cell system FCS includes: a fuel cell FC; an air compressor ACP; and a control section CNT which controls an operation of the air compressor ACP. The control section CNT controls the operation of the air compressor ACP so that power requested by a load is supplied from the fuel cell system FCS to the load under a normal condition and controls the operation of the air compressor ACP so that the power requested by the load is supplied from the fuel cell system FCS to the load and a flow rate of oxidant gas to be supplied to the fuel cell FC becomes a prescribed flow rate or more under a prescribed condition different from the normal condition.SELECTED DRAWING: Figure 1

Description

The present invention relates to fuel cell systems.

As a fuel cell system, the amount of water remaining in the fuel cell is calculated from the flow rate of the oxidant gas supplied to the fuel cell (the volume of the oxidant gas per unit time). There is also a method in which water remaining in the fuel cell is discharged to the outside of the fuel cell by performing an air blow using an oxidant gas. As a related technology, there is Patent Document 1.

By the way, in executing the air blow with the oxidant gas, improvement was required for the case where the flow velocity of the oxidant gas is less than the desired flow velocity. If the flow velocity of the oxidant gas falls short of the desired flow velocity, it may become difficult to normally function the process for discharging the water remaining in the fuel cell. In particular, when the number of fuel cells constituting the fuel cell is relatively small, the flow velocity of the oxidant gas tends to fall short of the desired flow velocity.

On the other hand, if the supply amount is simply increased so that the flow rate of the oxidant gas meets the desired flow rate, the voltage of the fuel cell will rise and the fuel cell will deteriorate.

JP 2019-145320 A

An object of one aspect of the present invention is to suppress deterioration due to potential fluctuation of the fuel cell while suppressing retention of water in the fuel cell in a fuel cell system.

A fuel cell system according to one aspect of the present invention includes a fuel cell, an air compressor that supplies an oxidant gas to the fuel cell, and a controller that controls the operation of the air compressor.

The control unit controls the operation of the air compressor so that the electric power required by the load is supplied from the fuel cell system to the load under normal conditions, and under predetermined conditions different from the normal conditions, The air compressor operates so that the electric power required by the load is supplied from the fuel cell system to the load and the flow rate of the oxidant gas supplied to the fuel cell is equal to or higher than a predetermined flow rate. to control.

As a result, for example, the case where water tends to stay in the fuel cell is set as a predetermined condition, and the flow rate of the oxidizing gas that can discharge the water staying in the fuel cell to the outside of the fuel cell is set to a predetermined flow rate. By setting to amount can be reduced. In addition, since the power required by the load is supplied from the fuel cell system to the load, the consumption destination of the power generated by the fuel cell is ensured. As a result, an increase in the potential of the fuel cell can be suppressed, and deterioration of the fuel cell can be suppressed.

Further, the control unit may be configured to control the operation of the air compressor so that the electric power generated by the fuel cell changes stepwise under the normal condition or the predetermined condition. .

As a result, the flow rate of the oxidant gas output from the air compressor can be changed stepwise, so that the sudden change in noise generated by the air compressor can be suppressed, and the user's sense of discomfort regarding the noise can be alleviated. can. Moreover, since the frequency of changes in the power generated by the fuel cell can be reduced, deterioration of the fuel cell can be suppressed.

Further, the fuel cell system includes a power storage device that is charged when power is supplied from the fuel cell and discharged when power is supplied to the load, and the control unit controls, under the normal conditions, a second Within the range from one charge amount to a second charge amount larger than the first charge amount, the target power generation of the fuel cell increases and the charge amount of the power storage apparatus increases as the charge amount of the power storage device decreases. The operation of the air compressor is controlled so that the target generated power decreases as much as possible, and under the predetermined conditions, the target generated power of the fuel cell is reduced until the charge amount of the power storage device decreases to the first charge amount. The operation of the air compressor is controlled so that the target power generation of the fuel cell is maintained at zero and then increased until the charge amount of the power storage device rises to the second charge amount. good too.

Advantageous Effects of Invention According to the present invention, in a fuel cell system, it is possible to suppress deterioration due to potential fluctuation of the fuel cell while suppressing retention of water in the fuel cell.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows an example of the fuel cell system of embodiment. 4 is a flow chart showing an example of the operation of a control unit; 8 is a flow chart showing another example of the operation of the control unit; FIG. 4 is a diagram for explaining power generation control of a fuel cell under normal conditions; FIG. 4 is a diagram for explaining power generation control of a fuel cell under low load operating conditions; FIG. 4 is a diagram for explaining power generation control of a fuel cell when the power supply destination of the fuel cell system is an on-vehicle load during normal power generation control; FIG. 4 is a diagram for explaining power generation control of a fuel cell when the power supply destination of the fuel cell system is an external load during normal power generation control; FIG. 4 is a diagram for explaining power generation control of a fuel cell when the power supply destination of the fuel cell system is an external load during power generation control for low-load operation; FIG. 10 is a diagram for explaining power generation control of the fuel cell in modification 1; FIG. 10 is a diagram for explaining power generation control of a fuel cell in modification 2; FIG. 11 is a diagram for explaining power generation control of a fuel cell in Modification 3;

Embodiments will be described in detail below with reference to the drawings.

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

The fuel cell system FCS shown in FIG. 1 is mounted on a vehicle Ve and supplies electric power to an onboard load Lin mounted on the vehicle Ve, an external load Lout provided outside the vehicle Ve, and the like. The vehicle Ve is an industrial vehicle such as a forklift or an automobile. In addition, the on-vehicle load Lin is an inverter that drives a traveling motor, an inverter that drives a cargo handling motor, or the like. Assume that a relatively large amount of electric power is supplied from the fuel cell system FCS to the onboard load Lin. It is also assumed that the external load Lout is a home appliance such as a television and an electric fan, and that a relatively small amount of power is supplied from the fuel cell system FCS to the external load Lout.

The fuel cell system FCS includes a fuel cell FC, a hydrogen tank HT, an injector INJ, an air compressor ACP, an air pressure regulating valve ARV, a DCDC converter CNV, a power storage device B, a current sensor Sif, and a voltage sensor. Svf, a current sensor Sib, a voltage sensor Svb, switches SW1 and SW2, an inverter INV, and a control unit CNT.

A fuel cell FC is a fuel cell stack composed of a plurality of fuel cells connected in series with each other. Electricity is generated by an electrochemical reaction.

The hydrogen tank HT is a fuel gas storage container. The fuel gas stored in the hydrogen tank HT is supplied to the fuel cell FC through the injector INJ.

The injector INJ maintains the pressure of the fuel gas inside the fuel cell FC at a predetermined pressure by adjusting the flow rate of the fuel gas supplied to the fuel cell FC.

The air compressor ACP compresses the oxidant gas existing around the fuel cell system FCS and supplies it to the fuel cell FC.

The air pressure regulating valve ARV maintains the pressure of the oxidant gas in the fuel cell FC at a predetermined pressure by adjusting the flow rate of the oxidant gas supplied to the fuel cell FC.

The DCDC converter CNV is connected after the fuel cell FC and converts the voltage Vf output from the fuel cell FC into a predetermined voltage. The electric power output from the DCDC converter CNV is supplied to loads such as an onboard load Lin and an external load Lout, auxiliary equipment such as an injector INJ, an air compressor ACP, and an air pressure regulating valve ARV, and a power storage device B. For example, the DCDC converter CNV converts the voltage of the fuel cell FC to 48[V]. A part of the electric power output from the DCDC converter CNV is supplied to an air compressor ACP, etc., which is a 48 [V] system accessory. Also, the voltage converted to 48 [V] by the DCDC converter CNV is converted to a voltage of 12 [V] by another DCDC converter (not shown). Electric power output from other DCDC converters is supplied to the injector INJ and the air pressure regulating valve ARV, which are 12 [V] system auxiliary machines.

The power storage device B is composed of a capacitor or the like, and is connected between the DCDC converter CNV and the changeover switches SW1 and SW2. 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 48 [V] system auxiliary machine and the 12 [V] system auxiliary machine is supplied to the on-vehicle load Lin or If the required power from the external load Lout is greater than the required power, the requested power is supplied to the vehicle-mounted load Lin or the external load Lout, and the remaining power is supplied to the power storage device B. When electric power is supplied from the DCDC converter CNV to the power storage device B, the power storage device B is charged and the charge amount of the power storage device B increases. In addition, 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 48 [V] system auxiliary machine and the 12 [V] system auxiliary machine is the on-vehicle load. If the required power from Lin or external load Lout is smaller than the required power, the supplied power is supplied to onboard load Lin or external load Lout, and the shortage of power is supplied from power storage device B to onboard load Lin or external load Lout. be done. When electric power is supplied from the power storage device B to the vehicle-mounted load Lin or the external load Lout, the power storage device B is discharged and the charge amount of the power storage device B decreases. Note that the amount of charge means the charging rate [%] of power storage device B (ratio of remaining capacity to full charge capacity of power storage device B), or an open circuit of power storage device B when no current is flowing through power storage device B. The voltage [V], the closed-circuit voltage [V] of the power storage device B when current is flowing through the power storage device B, or the integrated value [Ah] of the current flowing through the power storage device B, or the like.

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

The voltage sensor Svf is composed of voltage dividing resistors, etc., detects the voltage Vf output from the fuel cell FC, and sends the detected voltage Vf to the control unit CNT. The controller CNT obtains the result of multiplication of the current If and the voltage Vf as the generated power (output power) of the fuel cell FC.

The current sensor Sib, which is composed of a shunt resistor, a Hall element, or the like, detects a current Ib flowing from the DCDC converter CNV to the power storage device B or a current Ib flowing from the power storage device B to the vehicle-mounted load Lin or the external load Lout. Ib is sent to the control unit CNT.

Voltage sensor Svb is composed of a voltage dividing resistor or the like, detects voltage Vb of power storage device B, and sends the detected voltage Vb to control unit CNT.

The changeover switches SW1 and SW2 are configured by electromagnetic relays or the like, and switch the output destination of the fuel cell system FCS to one of the on-vehicle load Lin and the external load Lout under operation control by the control unit CNT. As a configuration other than the present embodiment, the operation control by the control unit CNT may switch between both the vehicle load Lin and the external load Lout or only the vehicle load Lin as the output destination of the fuel cell system FCS.

The inverter INV converts the DC power output from the DCDC converter CNV or the power storage device B into AC power and supplies the AC power to the external load Lout.

The control unit CNT is composed of a microcomputer or the like, and controls the power generated by the fuel cell FC by controlling the operations of auxiliary equipment such as the air compressor ACP, the air pressure regulating valve ARV, and the injector INJ.

Further, the control unit CNT changes the target power generation Pt step by step according to the charge amount of the power storage device B during normal power generation control or power generation control for low load operation.

In addition, the control unit CNT controls the 48 [V] system auxiliary equipment and the 12 [V] The generated power of the fuel cell FC is controlled by controlling the operation of the auxiliary equipment of the system. For example, the control unit CNT performs PI (Proportional-Integral) control so that the difference between the generated power of the fuel cell FC and the target generated power Pt becomes zero. Controls the operation of system accessories.

FIG. 2 is a flow chart showing an example of the operation of the control unit CNT.

First, in step S1, the control unit CNT determines whether or not the user has pressed an external power supply button (not shown) provided on the fuel cell system FCS side or the vehicle Ve side.

Next, when the control unit CNT determines that the external power feeding button is not pressed by the user (step S1: No), it determines that the condition is normal (step S2). The normal condition is a condition in which the fuel cell system FCS is operated under normal power generation control, which will be described later, and a relatively large amount of electric power is supplied from the fuel cell system FCS to the on-vehicle load Lin. Under normal conditions, the power required by the on-vehicle load Lin becomes greater than the target generated power of the fuel cell FC, so that the output power of the power storage device B becomes relatively large, and the charge amount of the power storage device B sufficiently decreases. Sometimes. Further, under normal conditions, the target power generation Pt of the fuel cell FC and the flow rate of the oxidant gas supplied to the fuel cell FC increase as the charge amount of the power storage device B decreases due to the normal power generation control described later. , it is assumed that there is no need to intentionally increase the flow rate of the oxidant gas.

Next, when the control unit CNT determines that the normal condition exists, it controls the operation of the switches SW1 and SW2 so that the power supply destination of the fuel cell system FCS is the vehicle load Lin (step S3), and normal power generation is performed. The power generated by the fuel cell FC is controlled by control (step S4).

On the other hand, when the control unit CNT determines that the external power feeding button has been pressed by the user (step S1: Yes), it determines that the low load operating condition (predetermined condition) is in effect (step S5). The low-load operating condition is a condition under which the fuel cell system FCS is operated under low-load operation power generation control, which will be described later. Compared to normal power generation control, relatively small power is supplied from the fuel cell system FCS to the external load Lout. be. Note that under low-load operating conditions, the power required by the external load Lout is relatively small, so the output power of the power storage device B is relatively small, and the amount of charge in the power storage device B is less likely to decrease. Therefore, if normal power generation control, which will be described later, is performed under low-load operating conditions, the output power of the fuel cell FC is less likely to increase, and the flow rate of the oxidant gas supplied to the fuel cell FC is less likely to increase. Water tends to stay in the battery FC. Therefore, under low-load operating conditions, the target power generation of the fuel cell FC is set to Pt is forcibly increased to intentionally increase the flow rate of the oxidant gas supplied to the fuel cell FC. Also, under low-load operating conditions, in order to prevent the storage device B from being overcharged, the amount of charge in the storage device B is reduced before the target power generation Pt of the fuel cell FC is increased.

Next, when the control unit CNT determines that the operating condition is the low load, it controls the operation of the changeover switches SW1 and SW2 so that the power supply destination of the fuel cell system FCS becomes the external load Lout (step S6), After controlling the generated power of the fuel cell FC by the power generation control for low-load operation (step S7), it is determined again whether or not the external power supply button has been pressed by the user (step S8).

When the control unit CNT determines that the external power supply button has not been pressed by the user (step S8: No), it continues the power generation control for low load operation in step S7, and determines that the external power supply button has been pressed by the user. Then (step S8: Yes), it is determined that the low-load operating condition has been switched to the normal condition (step S2), and the processing after step S3 is executed.

That is, while the external power feeding button is not pressed by the user, the normal condition is established, and the low load operating condition is established after the external power feeding button is pushed by the user until the user pushes it again. The control unit CNT controls the power generated by the fuel cell FC by normal power generation control under normal conditions, and controls the power generated by the fuel cell FC by power generation control corresponding to low load operation under low load operation conditions. In this manner, by determining whether or not the external power supply button has been pressed, it is possible to easily switch between the normal power generation control and the power generation control corresponding to low load operation.

FIG. 3 is a flow chart showing another example of the operation of the control unit CNT. In the flowchart shown in FIG. 3, the same steps as those shown in FIG. 2 are given the same reference numerals, and the description thereof is omitted.

The flowchart shown in FIG. 3 differs from the flowchart shown in FIG. 2 in that if the output power of the fuel cell system FCS is greater than the predetermined power (step S1': No), it is determined that the condition is normal in step S2, When the output power of the fuel cell system FCS is equal to or less than the predetermined power for a certain period of time or longer (step S1': Yes), it is determined that the operating condition is low load in step S5. When the output power of the fuel cell system FCS continues to be equal to or lower than the predetermined power (step S8': No), the power generation control for low-load operation is continued, and the output power of the fuel cell system FCS is reduced to the predetermined power. If it becomes larger (step S8': Yes), it is determined that the low-load operating condition has been switched to the normal condition (step S2), and the processing after step S3 is executed.

That is, when the output power of the fuel cell system FCS is greater than the predetermined power, or when the state in which the output power of the fuel cell system FCS is less than or equal to the predetermined power does not continue for a certain period of time or more, the normal condition is established, and the output of the fuel cell system FCS The low-load operating condition is established from the time when the electric power is equal to or lower than the predetermined electric power continues for a predetermined time or longer until the output electric power of the fuel cell system FCS becomes greater than the predetermined electric power. The control unit CNT controls the power generated by the fuel cell FC by normal power generation control under normal conditions, and controls the power generated by the fuel cell FC by power generation control corresponding to low load operation under low load operation conditions. In this way, by determining whether or not the state in which the output power of the fuel cell system FCS is equal to or lower than the predetermined power continues for a certain period of time or longer, switching between the normal power generation control and the power generation control corresponding to low-load operation can be easily performed. be able to.

Further, when the flow chart shown in FIG. 3 is adopted as the power generation control of the fuel cell FC, the power supply destination of the fuel cell system FCS may be set only to the vehicle load Lin. In such a configuration, the changeover switches SW1 and SW2 may be omitted, and the vehicle load Lin may be directly connected to the DCDC converter CNV.

FIG. 4 is a diagram for explaining normal power generation control. It is assumed that the charge amount of the power storage device B changes in a range from the charge amount V1 (first charge amount) to the charge amount V2 (second charge amount) larger than the charge amount V1. Threshold Vth11 (charge amount V1)<threshold Vth12<threshold Vth13<threshold Vth14<threshold Vth15<threshold Vth16 (charge amount V2). Also, the target generated power Pt0 is set to zero, and the target generated power Pt0<target generated power Pt1<target generated power Pt2<target generated power Pt3. It is also assumed that when the output power of the fuel cell FC follows the target power generation Pt3, the water remaining in the fuel cell FC is discharged outside the fuel cell FC by a predetermined flow of oxidant gas. . Further, the difference between the target power generation Pt3 and the target power generation Pt2, the difference between the target power generation Pt2 and the target power generation Pt1, and the difference between the target power generation Pt1 and the target power generation Pt0 may each be a constant value, Different values are allowed. It is also assumed that the larger the target generated power Pt, the larger the power output from the fuel cell FC, and the smaller the target generated power Pt, the smaller the power output from the fuel cell FC. It is also assumed that when the target generated power Pt reaches the target generated power Pt0, the power generation of the fuel cell FC stops and the power output from the fuel cell FC becomes zero.

Control unit CNT changes target generated power Pt from target generated power Pt0 to target generated power Pt1 when the amount of charge in power storage device B becomes equal to or less than threshold Vth15 in a state where target generated power Pt is target generated power Pt0.

Further, in a state where the target power generation Pt is the target power generation Pt1, the control unit CNT changes the target power generation Pt from the target power generation Pt1 to the target power generation Pt2 when the amount of charge in the power storage device B becomes equal to or less than the threshold value Vth13. Let

Further, in a state where the target power generation Pt is the target power generation Pt2, the control unit CNT changes the target power generation Pt from the target power generation Pt2 to the target power generation Pt3 when the amount of charge of the power storage device B becomes equal to or less than the threshold value Vth11. Let

Further, in a state where the target power generation Pt is the target power generation Pt3, the control unit CNT changes the target power generation Pt from the target power generation Pt3 to the target power generation Pt2 when the amount of charge in the power storage device B reaches or exceeds the threshold value Vth12. Let

Further, in a state where the target power generation Pt is the target power generation Pt2, the control unit CNT changes the target power generation Pt from the target power generation Pt2 to the target power generation Pt1 when the amount of charge in the power storage device B becomes equal to or greater than the threshold value Vth14. Let

Further, in a state where the target power generation Pt is the target power generation Pt1, the control unit CNT changes the target power generation Pt from the target power generation Pt1 to the target power generation Pt0 when the amount of charge in the power storage device B reaches or exceeds the threshold value Vth16. Let

That is, the control unit CNT performs normal power generation control such that the power output from the fuel cell FC increases stepwise as the charge level of the power storage device B decreases, or the fuel cell FC increases as the charge level of the power storage device B increases. The power generated by the fuel cell FC is controlled so that the power output from the battery FC decreases stepwise.

As a result, under normal conditions, when the required electric power from the vehicle-mounted load Lin becomes relatively large and the amount of charge in the power storage device B becomes relatively small, the electric power supplied to the fuel cell FC is increased to increase the output electric power of the fuel cell FC. Since the flow rate of the oxidizing agent gas increases, the amount of water remaining in the fuel cell FC can be reduced.

FIG. 5 is a diagram for explaining power generation control for low-load operation. It is assumed that the charge amount of the power storage device B changes in a range from the charge amount V1 (first charge amount) to the charge amount V2 (second charge amount) larger than the charge amount V1. Threshold Vth21 (charging amount V1)<threshold Vth22<threshold Vth23<threshold Vth24<threshold Vth25<threshold Vth26 (charging amount V2). Also, the threshold Vth21 may be the same value as or different from the threshold Vt11. Also, the threshold Vth22 may be the same value as or different from the threshold Vt12. Also, the threshold Vth23 may be the same value as or different from the threshold Vt13. Also, the threshold Vth24 may be the same value as or different from the threshold Vt14. Also, the threshold Vth25 may be the same value as or different from the threshold Vt15. Also, the threshold Vth26 may be the same value as or different from the threshold Vt16.

Control unit CNT changes target generated power Pt from target generated power Pt0 to target generated power Pt1 when the amount of charge in power storage device B becomes equal to or less than threshold Vth21 in a state where target generated power Pt is target generated power Pt0.

Further, in a state where the target power generation Pt is the target power generation Pt1, the control unit CNT changes the target power generation Pt from the target power generation Pt1 to the target power generation Pt2 when the amount of charge in the power storage device B reaches or exceeds the threshold value Vth22. Let

Further, in a state where the target power generation Pt is the target power generation Pt2, the control unit CNT changes the target power generation Pt from the target power generation Pt2 to the target power generation Pt3 when the amount of charge in the power storage device B reaches or exceeds the threshold value Vth23. Let

Further, in a state where the target power generation Pt is the target power generation Pt3, the control unit CNT changes the target power generation Pt from the target power generation Pt3 to the target power generation Pt2 when the amount of charge of the power storage device B becomes equal to or greater than the threshold value Vth24. Let

Further, in a state where the target power generation Pt is the target power generation Pt2, the control unit CNT changes the target power generation Pt from the target power generation Pt2 to the target power generation Pt1 when the amount of charge in the power storage device B reaches or exceeds the threshold value Vth25. Let

Further, in a state where the target power generation Pt is the target power generation Pt1, the control unit CNT changes the target power generation Pt from the target power generation Pt1 to the target power generation Pt0 when the amount of charge in the power storage device B reaches or exceeds the threshold value Vth26. Let

Further, when the target generated power Pt changes from the target generated power Pt1 to the target generated power Pt0, the control unit CNT maintains the target generated power Pt at the target generated power Pt0 until the charge amount of the power storage device B becomes equal to or less than the threshold value Vth21. do.

That is, the control unit CNT controls the target generated power Pt until the charge amount of the power storage device B becomes equal to or less than the threshold value Vth21, regardless of the magnitude of the required power from the onboard load Lin or the external load Lout, as power generation control for low-load operation. After maintaining the target power generation Pt0, the target power generation Pt is forcibly changed from the target power generation Pt0 to the target power generation Pt3, and the target power generation Pt is forcibly changed from the target power generation Pt3 to the target power generation Pt0. Repeat.

As a result, even in a state where a relatively small amount of electric power is continuously supplied from the fuel cell system FCS to the external load Lout, such as under low-load operation conditions, the output from the fuel cell FC is controlled by the power generation control corresponding to low-load operation. Since the supplied electric power can be forcibly increased to the target generated electric power Pt3, the flow rate of the oxidant gas supplied to the fuel cell FC can be increased, and the amount of water remaining in the fuel cell FC can be reduced. can be reduced.

In addition, during normal power generation control or power generation control for low-load operation, the flow rate of the oxidant gas output from the air compressor ACP can be changed stepwise, so that the noise generated by the air compressor ACP can be changed sharply. can be suppressed, and the user's sense of incongruity regarding noise can be alleviated.

In addition, in the normal power generation control or the power generation control for low load operation, the power output from the fuel cell FC can be changed in stages according to the amount of charge in the power storage device B, so the power generated by the fuel cell FC changes. It is possible to reduce the frequency with which the fuel cell is degraded, thereby suppressing the deterioration of the fuel cell.

Further, since the power required by the onboard load Lin and the external load Lout is supplied from the fuel cell system FCS to the onboard load Lin and the external load Lout, the power consumption destination of the power generated by the fuel cell FC is ensured. As a result, an increase in the potential of the fuel cell FC can be suppressed, and deterioration of the fuel cell FC can be suppressed.

When the flow chart shown in FIG. 3 is adopted as the power generation control of the fuel cell FC, and when the power supply destination of the fuel cell system FCS is set only to the vehicle load Lin, regenerative electric power is supplied from the vehicle load Lin to the fuel cell system FCS. is supplied, the target generated power Pt is changed from the target generated power Pt0 to the target generated power Pt when the amount of charge in the power storage device B becomes equal to or greater than the threshold value Vth21 in a state where the target generated power Pt is the target generated power Pt0. It may be configured to change to Pt1.

Here, a specific example of normal power generation control will be described.

FIG. 6 is a diagram for explaining the power generation control of the fuel cell FC when the power supply destination of the fuel cell system FCS is the vehicle load Lin during normal power generation control. The horizontal axis of the two-dimensional coordinates in FIG. 6(a) indicates time, the vertical axis indicates the output power [kW] of the fuel cell system FCS, and the solid line in FIG. 6(a) indicates the normal power generation control shown in FIG. shows an example of change in the output power of the fuel cell system FCS over time when performing . In addition, the horizontal axis of the two-dimensional coordinates in FIG. 6B indicates time, the vertical axis indicates the amount of charge in the power storage device B, and the solid line in FIG. 4 shows an example of change in the charge amount of the power storage device B over time. The horizontal axis of the two-dimensional coordinates in FIG. 6(c) indicates time, the vertical axis indicates the output power [kW] of the fuel cell FC, and the solid line in FIG. 6(c) indicates the normal power generation control shown in FIG. 3 shows an example of change in the output power of the fuel cell FC with the lapse of time. The horizontal axis of the two-dimensional coordinates in FIG. 6(d) indicates time, the vertical axis indicates the flow rate [NL/min] of the oxidant gas supplied to the fuel cell FC, and the solid line in FIG. FIG. 5 shows an example of change in the flow rate of the oxidizing gas over time when the normal power generation control shown in FIG. 4 is performed. Also, the horizontal axes (time axes) of FIGS. 6A to 6D are the same. Further, from time t11 to time t13, the output power of the fuel cell system FCS (the power required by the on-vehicle load Lin) is greater than the target power generation Pt1 to Pt3, and the shortage of power is supplied from the power storage device B to the on-vehicle load. It is assumed that the power storage device B is discharged by being supplied to Lin, and the charge amount of the power storage device B decreases. Further, power P1<power P2<power P3. Further, flow rate F1<flow rate F2<flow rate F3. The flow rate F3 (predetermined flow rate) is the flow rate of the oxidant gas supplied to the fuel cell FC when the water remaining in the fuel cell FC is being discharged to the outside of the fuel cell FC.

First, when the amount of charge in the power storage device B is gradually decreasing due to the supply of power from the power storage device B to the on-vehicle load Lin, when the amount of charge in the power storage device B becomes equal to or less than the threshold Vth15 at time t11, the target power generation is reached. Power Pt changes from target power generation Pt0 to target power generation Pt1. Then, in order to raise the output power of the fuel cell FC from zero to the power P1 corresponding to the target generated power Pt1, the flow rate of the oxidant gas supplied to the fuel cell FC increases from zero to the flow rate F1.

Next, when the amount of charge in power storage device B continues to decrease due to the supply of power from power storage device B to on-vehicle load Lin, when the amount of charge in power storage device B becomes equal to or less than threshold Vth13 at time t12, The target power generation Pt changes from the target power generation Pt1 to the target power generation Pt2. Then, in order to increase the output power of the fuel cell FC from the power P1 corresponding to the target power generation Pt1 to the power P2 corresponding to the target power generation Pt2, the flow rate of the oxidant gas supplied to the fuel cell FC is changed from the flow rate F1 to The flow rate increases to F2.

Then, when the amount of charge in power storage device B continues to decrease due to the supply of power from power storage device B to on-vehicle load Lin, when the amount of charge in power storage device B becomes less than or equal to threshold Vth11 at time t13, target The generated power Pt changes from the target generated power Pt2 to the target generated power Pt3. Then, in order to increase the output power of the fuel cell FC from the power P2 corresponding to the target power generation Pt2 to the power P3 corresponding to the target power generation Pt3, the flow rate of the oxidant gas supplied to the fuel cell FC is changed from the flow rate F2 to The flow rate increases to F3.

As described above, in the normal power generation control, the output power of the fuel cell FC may rise to the voltage V3 corresponding to the target power generation Pt3 due to the power request from the on-vehicle load Lin, and the flow rate of the oxidant gas is reduced to the flow rate F3. Therefore, water remaining in the fuel cell FC can be reduced.

Next, a case will be described where the power generated by the fuel cell FC is controlled by the normal power generation control even after the power supply destination of the fuel cell system FCS is switched from the vehicle load Lin to the external load Lout.

FIG. 7 is a diagram for explaining power generation control of the fuel cell FC when the power supply destination of the fuel cell system FCS is the external load Lout during normal power generation control. The horizontal axis of the two-dimensional coordinates in FIG. 7(a) indicates time, the vertical axis indicates the output power [kW] of the fuel cell system FCS, and the solid line in FIG. 7(a) indicates the normal power generation control shown in FIG. shows an example of change in the output power of the fuel cell system FCS over time when performing . In addition, the horizontal axis of the two-dimensional coordinates in FIG. 7B indicates time, the vertical axis indicates the amount of charge in the power storage device B, and the solid line in FIG. 4 shows an example of change in the charge amount of the power storage device B over time. The horizontal axis of the two-dimensional coordinates in FIG. 7(c) indicates time, the vertical axis indicates the output power [kW] of the fuel cell FC, and the solid line in FIG. 7(c) indicates the normal power generation control shown in FIG. 3 shows an example of change in the output power of the fuel cell FC with the lapse of time. The horizontal axis of the two-dimensional coordinates in FIG. 7(d) indicates time, the vertical axis indicates the flow rate [NL/min] of the oxidant gas supplied to the fuel cell FC, and the solid line in FIG. FIG. 5 shows an example of change in the flow rate of the oxidizing gas over time when the normal power generation control shown in FIG. 4 is performed. Also, the horizontal axes (time axes) of FIGS. 7A to 7D are the same. Also, between time t21 and time t23, the output power of the fuel cell system FCS (the power required by the external load Lout) is smaller than the target power generation Pt1, and when the target power generation Pt changes to the target power generation Pt1, Assume that power storage device B is charged and the amount of charge in power storage device B increases. Further, power P1<power P2<power P3. Further, flow rate F1<flow rate F2<flow rate F3. The flow rate F1 is the flow rate of the oxidant gas supplied to the fuel cell FC when water tends to stay in the fuel cell FC. In FIG. 6B, the amount of charge in the power storage device B fluctuates depending on the difference between the supplied power and the required power, so strictly speaking, the waveform is complicated. ing. The same applies to subsequent FIGS. 7B, 8B, 9B, 10B, and 11B.

First, when the amount of charge in power storage device B decreases due to power being supplied from power storage device B to external load Lout, when the amount of charge in power storage device B becomes equal to or less than threshold Vth15 at time t21, target generated power Pt changes from the target power generation Pt0 to the target power generation Pt1. Then, in order to raise the output power of the fuel cell FC from zero to the power P1 corresponding to the target generated power Pt1, the flow rate of the oxidant gas supplied to the fuel cell FC increases from zero to the flow rate F1. In addition, power storage device B is charged with part of the electric power output from fuel cell FC, and the amount of charge in power storage device B increases.

Next, when the amount of charge in power storage device B becomes equal to or greater than threshold Vth16 at time t22, target generated power Pt changes from target generated power Pt1 to target generated power Pt0. Then, the output power of the fuel cell FC decreases from the power P1 corresponding to the target generated power Pt1 to zero, so the flow rate of the oxidant gas supplied to the fuel cell FC decreases from the flow rate F1 to zero. Further, when the output power of fuel cell FC becomes zero, electric power is supplied from power storage device B to external load Lout, and the amount of charge in power storage device B decreases again.

Next, when the amount of charge in power storage device B becomes equal to or less than threshold Vth15 at time t23, target generated power Pt changes from target generated power Pt0 to target generated power Pt1. Then, in order to raise the output power of the fuel cell FC from zero to the power P1 corresponding to the target generated power Pt1, the flow rate of the oxidant gas supplied to the fuel cell FC increases from zero to the flow rate F1. Further, power storage device B is charged with part of the power output from fuel cell FC, and the amount of charge in power storage device B increases again.

Thereafter, the flow rate of the oxidant gas repeats increase and decrease between zero and the flow rate F1.

In this way, when the generated power of the fuel cell FC is controlled by the normal power generation control even after the power supply destination of the fuel cell system FCS is switched from the onboard load Lin to the external load Lout, the charge amount of the power storage device B is set to the threshold value Vth16. , and the threshold Vth15, the output power of the fuel cell FC can only be increased up to the power P1 corresponding to the target power generation Pt1. Therefore, the flow rate of the oxidant gas supplied to the fuel cell FC can only be increased up to the flow rate F1, and water tends to stay in the fuel cell FC.

Therefore, in the fuel cell system FCS of the embodiment, after switching the power supply destination of the fuel cell system FCS from the on-vehicle load Lin to the external load Lout, the generated power of the fuel cell FC is controlled by the power generation control for low load operation.

FIG. 8 is a diagram for explaining the power generation control of the fuel cell FC when the power supply destination of the fuel cell system FCS is set to the external load Lout during power generation control for low load operation. The horizontal axis of the two-dimensional coordinates in FIG. 8(a) indicates time, the vertical axis indicates the output power [kW] of the fuel cell system FCS, and the solid line in FIG. 8(a) indicates the low-load operation shown in FIG. It shows an example of change in the output power of the fuel cell system FCS over time when the adaptive power generation control is performed. In addition, the horizontal axis of the two-dimensional coordinates in FIG. 8B indicates time, the vertical axis indicates the amount of charge in the power storage device B, and the solid line in FIG. 10 shows an example of change in the charge amount of the power storage device B with the lapse of time when the power storage device B is operated. The horizontal axis of the two-dimensional coordinates in FIG. 8(c) indicates time, the vertical axis indicates the output power [kW] of the fuel cell FC, and the solid line in FIG. 8(c) corresponds to the low load operation shown in FIG. 3 shows an example of change in the output power of the fuel cell FC over time when power generation control is performed. The horizontal axis of the two-dimensional coordinates in FIG. 8(d) indicates time, the vertical axis indicates the flow rate [NL/min] of the oxidant gas supplied to the fuel cell FC, and the solid line in FIG. FIG. 6 shows an example of change in the flow rate of the oxidizing gas over time when the power generation control for low-load operation shown in FIG. 5 is performed. Also, the horizontal axes (time axes) of FIGS. 8A to 8D are the same. Between time t30 and time t36, the output power of the fuel cell system FCS is smaller than the target power generation Pt1, and when the target power generation Pt changes to any of the target power generation Pt1 to Pt3, the power storage device B is charged. It is assumed that the charge amount of the power storage device B is increased. Further, power P1<power P2<power P3. Further, flow rate F1<flow rate F2<flow rate F3. The flow rate F3 is the flow rate of the oxidant gas supplied to the fuel cell FC when the water remaining in the fuel cell FC is being discharged to the outside of the fuel cell FC.

First, from time t30 to time t31, when target power generation Pt is maintained at target power generation Pt0, the amount of charge in power storage device B gradually decreases.

Next, when the amount of charge in power storage device B becomes equal to or less than threshold V21 at time t31, target power generation Pt changes from target power generation Pt0 to target power generation Pt1. Then, in order to raise the output power of the fuel cell FC from zero to the power P1 corresponding to the target generated power Pt1, the flow rate of the oxidant gas supplied to the fuel cell FC is increased from zero to the flow rate F1. In addition, power storage device B is charged with part of the electric power output from fuel cell FC, and the amount of charge in power storage device B increases.

Next, when the amount of charge in power storage device B becomes equal to or greater than threshold V22 at time t32, target power generation Pt changes from target power generation Pt1 to target power generation Pt2. Then, in order to increase the output power of the fuel cell FC from the power P1 corresponding to the target power generation Pt1 to the power P2 corresponding to the target power generation Pt2, the flow rate of the oxidant gas supplied to the fuel cell FC is changed from the flow rate F1 to Increase the flow rate to F2. In addition, power storage device B is charged with part of the electric power output from fuel cell FC, and the amount of charge in power storage device B further increases.

Next, when the amount of charge in power storage device B becomes equal to or greater than threshold V23 at time t33, target power generation Pt changes from target power generation Pt2 to target power generation Pt3. Then, in order to increase the output power of the fuel cell FC from the power P2 corresponding to the target power generation Pt2 to the power P3 corresponding to the target power generation Pt3, the flow rate of the oxidant gas supplied to the fuel cell FC is changed from the flow rate F2 to Increase the flow rate to F3. In addition, power storage device B is charged with part of the electric power output from fuel cell FC, and the amount of charge in power storage device B further increases.

Next, when the amount of charge in power storage device B becomes equal to or greater than threshold V24 at time t34, target power generation Pt changes from target power generation Pt3 to target power generation Pt2. Then, in order to reduce the output power of the fuel cell FC from the power P3 corresponding to the target power generation Pt3 to the power P2 corresponding to the target power generation Pt2, the flow rate of the oxidant gas supplied to the fuel cell FC is changed from the flow rate F3 to Decrease the flow rate to F2. In addition, power storage device B is charged with part of the electric power output from fuel cell FC, and the amount of charge in power storage device B further increases.

Next, when the amount of charge in power storage device B becomes equal to or greater than threshold V25 at time t35, target power generation Pt changes from target power generation Pt2 to target power generation Pt1. Then, in order to reduce the output power of the fuel cell FC from the power P2 corresponding to the target power generation Pt2 to the power P1 corresponding to the target power generation Pt1, the flow rate of the oxidant gas supplied to the fuel cell FC is changed from the flow rate F2 to the power P1 corresponding to the target power generation Pt1. Decrease the flow rate to F1. In addition, power storage device B is charged with part of the electric power output from fuel cell FC, and the amount of charge in power storage device B further increases.

Then, when the amount of charge in power storage device B becomes equal to or greater than threshold V26 at time t36, target generated power Pt changes from target generated power Pt1 to target generated power Pt0. Then, in order to reduce the output power of the fuel cell FC from the power P1 corresponding to the target generated power Pt1 to zero, the flow rate of the oxidant gas supplied to the fuel cell FC is reduced from the flow rate F1 to zero. Further, since the power output from the fuel cell FC becomes zero, the charge amount of the power storage device B gradually decreases again.

After that, the flow rate of the oxidant gas repeats increase and decrease between zero and the flow rate F3.

In this way, after switching the power supply destination of the fuel cell system FCS from the vehicle-mounted load Lin to the external load Lout, when the generated power of the fuel cell FC is controlled by the low-load operation power generation control, the output power of the fuel cell FC can be forcibly increased to the voltage V3 corresponding to the target generated power Pt3, the flow rate of the oxidant gas can be increased to the flow rate F3, and the amount of water remaining in the fuel cell FC can be reduced. .

The present invention is not limited to the above embodiments, and various improvements and modifications are possible without departing from the gist of the present invention.

<Modification 1>
In the state where the target generated power Pt is the target generated power Pt3 during the power generation control for low-load operation shown in FIG. The generated power Pt3 may be changed to the target generated power Pt0. Even with this configuration, for example, as shown in FIG. 9, the output power of the fuel cell FC can be increased to the power P3 corresponding to the target generated power Pt3. The gas flow rate can be increased to flow rate F3. Note that, in the case of such a configuration, it is not necessary to obtain the threshold Vth25 and the threshold Vth26 in advance.

<Modification 2>
In the state where the target generated power Pt is the target generated power Pt0 during the power generation control for low-load operation shown in FIG. The generated power Pt0 may be changed to the target generated power Pt3. Even with this configuration, for example, as shown in FIG. 10, the output power of the fuel cell FC can be increased to the power P3 corresponding to the target generated power Pt3, so that the oxidant supplied to the fuel cell FC The gas flow rate can be increased to flow rate F3. It should be noted that, in the case of such a configuration, it is not necessary to obtain the threshold Vth22 and the threshold Vth23 in advance.

<Modification 3>
In the state where the target generated power Pt is the target generated power Pt0 during the power generation control for low-load operation shown in FIG. In a state in which the generated power Pt0 is changed to the target generated power Pt3 and the target generated power Pt is the target generated power Pt3, the target generated power Pt is changed from the target generated power Pt3 to the target when the charge amount of the power storage device B becomes equal to or greater than the threshold value Vth24. It may be configured to change to the generated power Pt0. Even with this configuration, for example, as shown in FIG. The gas flow rate can be increased to flow rate F3. In this configuration, it is not necessary to obtain the threshold Vth22, the threshold Vth23, the threshold Vth25, and the threshold Vth26 in advance.

<Modification 4>
In the fuel cell system FCS of the above-described embodiment, the target power generation Pt of the fuel cell FC is changed (increased or decreased) step by step according to the charge level of the power storage device B. The target power generation Pt of the fuel cell FC may be linearly changed (increased or decreased).

<Modification 5>
The fuel cell system FCS of the above embodiment is configured as a generator that supplies power to the onboard load Lin or the external load Lout. It may be configured as a stationary generator to supply or as an emergency power source. In this case, the control unit CNT monitors the power demand of the external load, and when the demand power becomes equal to or less than a predetermined power and this state continues for a predetermined time or longer, the external load is the object of the power generation control for low-load operation. It is preferable to determine that

FCS Fuel cell system CNT Control unit Ve Vehicle Lin Vehicle load Kout External load FC Fuel cell HT Hydrogen tank INJ Injector ACP Air compressor CNV DCDC converter ARV Air pressure regulator INV Inverter B Power storage devices SW1, SW2 Changeover switches Svf, Svb Voltage sensor Sif, Sib current sensor

Claims (3)

a fuel cell;
an air compressor that supplies oxidant gas to the fuel cell;
a control unit that controls the operation of the air compressor;
with
The control unit
controlling the operation of the air compressor so that the power required by the load is supplied from the fuel cell system to the load under normal conditions;
Under predetermined conditions different from the normal conditions, the power required by the load is supplied from the fuel cell system to the load, and the flow rate of the oxidant gas supplied to the fuel cell is equal to or greater than a predetermined flow rate. A fuel cell system characterized by controlling the operation of the air compressor so that The fuel cell system according to claim 1,
The fuel cell system, wherein the control unit controls the operation of the air compressor so that power generated by the fuel cell changes stepwise under the normal condition or the predetermined condition. The fuel cell system according to claim 1,
A power storage device that is charged by being supplied with power from the fuel cell and is discharged by supplying power to the load,
The control unit
Under the normal condition, the target power generation of the fuel cell increases as the charge amount of the power storage device decreases within the range from the first charge amount to the second charge amount larger than the first charge amount, and the power storage device increases. controlling the operation of the air compressor so that the target power generation of the fuel cell decreases as the charge level of the device increases;
Under the predetermined condition, the target power generation of the fuel cell is maintained at zero until the charge amount of the power storage device decreases to the first charge amount, and thereafter the charge amount of the power storage device reaches the second charge amount. A fuel cell system, wherein the operation of the air compressor is controlled so that the target generated power of the fuel cell is increased until it rises.

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