JP2005056760A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system capable of preventing performance deterioration and occurrence of water clogging even if an air supply system is hindered.
When a fuel cell voltage detected by a voltage sensor 9 is lower than a predetermined value under a predetermined operating condition of the fuel cell, a controller 15 connects the compressor 2 to the fuel cell 1 until the reference voltage is recovered. Make corrections to increase air flow. If there is no voltage recovery even if the predetermined amount of air is increased, the controller 15 does not correct the increase of the air amount.
[Selection] Figure 1

Description

  The present invention relates to a fuel cell system, and more particularly, to a fuel cell system capable of continuing operation without degradation in performance even when a leak or the like occurs in an air supply system.

  In a fuel cell, a fuel gas such as hydrogen gas and an oxidizing gas containing oxygen are electrochemically reacted through an electrolyte, and electric energy is directly taken out between electrodes provided on both surfaces of the electrolyte. In particular, solid polymer fuel cells using solid polymer electrolytes are attracting attention as power sources for electric vehicles because of their low operating temperature and easy handling.

Fuel cells deteriorate in power generation performance due to secular change, so even if performance changes occur, the fuel cell sets the output according to the amount of reactant gas supplied in order to continue operation at an appropriate reaction gas utilization rate. A system operation control device is known (for example, Patent Document 1).
Japanese Patent Laid-Open No. 9-27335 (page 4, FIG. 1)

  However, in the conventional fuel cell system, when the required air flow rate of the fuel cell stack is increased due to, for example, air system leakage, this cannot be corrected. There is a problem that the air supply flow rate in the fuel cell stack is insufficient, water clogging occurs in the fuel cell stack, and there is a concern that a rapid performance deterioration may occur.

  In order to solve the above problems, the present invention provides an oxidant gas supply means for supplying an oxidant gas at a flow rate determined according to the power generation state of the fuel cell to the fuel cell, and a flow rate determined according to the power generation state of the fuel cell. A fuel gas supply means for supplying fuel gas to the fuel cell; a voltage detection means for detecting the fuel cell voltage; and a fuel cell voltage detected by the voltage detection means under a predetermined operating condition as a reference When the voltage is lower than the voltage, the gist is provided with a control means for correcting the increase in the oxidant gas flow rate until the fuel cell voltage becomes equal to or higher than the reference voltage.

  According to the present invention, it is detected whether the fuel cell voltage has reached the reference voltage under a predetermined operating condition. When the fuel cell voltage is lower than the reference voltage, the oxidant gas flow rate is set so that the fuel cell voltage becomes equal to or higher than the reference voltage. Since the correction control is performed, the excess air ratio is insufficient, so that the power generation efficiency in the fuel cell is reduced, and water clogging in the fuel cell can be prevented. Can provide.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. Each embodiment described below is a preferred embodiment for a fuel cell vehicle.

  FIG. 1 is a system configuration diagram illustrating the configuration of a first embodiment of a fuel cell system according to the present invention. In FIG. 1, a fuel cell system includes a fuel cell 1 that is a fuel cell body, a compressor 2 that supplies air as an oxidant gas to the fuel cell 1, and a pressure sensor 3 that detects the pressure of air supplied by the compressor 2. The pressure adjusting valve 4 for adjusting the pressure of the air discharged from the fuel cell 1, the hydrogen supply device 5 for supplying hydrogen as fuel gas to the fuel cell 1, and the pressure of the hydrogen gas supplied from the hydrogen supply device 5 are adjusted. The pressure control valve 6, an ejector (fluid pump) 7 that mixes hydrogen discharged from the fuel cell 1 and newly supplied hydrogen and supplies the fuel cell 1, and detects the pressure of hydrogen supplied to the fuel cell 1 Pressure sensor 8, voltage sensor 9 for detecting the power generation voltage of the fuel cell 1, current sensor 10 for detecting the output current of the fuel cell 1, and battery 12 and load When the output of the fuel cell 1 is insufficient, the power manager 11 controls the power supply from the battery 12 to the load device 13, the battery 12 which is a chargeable / dischargeable secondary battery, and the fuel cell 1 and a load device 13 supplied with power from at least one of the battery 12, a warning lamp 14 for notifying abnormality of the fuel cell system, and a controller 15 for controlling the entire fuel cell system.

  The fuel cell 1 is connected to fuel system and air system pipes. The air system is provided with a compressor 2 that pumps air from the upstream side, a pressure sensor 3 that detects air pressure at the fuel cell inlet, and a pressure adjustment valve 4 at the fuel cell outlet.

  From the upstream, the fuel system is provided with a hydrogen supply device 5, a pressure regulating valve 6, an ejector 7 for circulating hydrogen, and a pressure sensor 8 for detecting the hydrogen pressure at the fuel cell inlet. However, as the fuel circulation mechanism, a pump driven by power such as a motor may be provided in the fuel circulation path without using an ejector.

  The controller 15 is connected with pressure sensors 3 and 8, a voltage sensor 9, and a current sensor 11 as input devices, and is connected with a compressor 2, pressure regulating valves 4 and 6, and a warning lamp 14 as output devices.

  The controller 15 inputs the detected values of the pressure sensors 3 and 8, the voltage sensor 9 and the current sensor 11, determines the operating state based on these input values, the compressor 2, the pressure regulating valves 4 and 6, warnings A control signal is output to the lamp 14.

  The power manager 11 distributes the generated power of the fuel cell 1 to the battery 12 and the load device 13 and controls the power supply from the battery 12 to the load device 13 when the output of the fuel cell 1 is insufficient. It is. Further, the power manager 11 monitors the voltage and charge / discharge current of the battery 12, calculates the state of charge (SOC) of the battery 12, and outputs it to the controller 15. When the power manager 11 does not calculate the SOC, a voltage sensor and a current sensor may be provided in the battery 12 so that the controller 15 directly monitors the battery 12 and calculates the SOC.

  The battery 12 is a power storage unit that compensates for insufficient output of the fuel cell. In this embodiment, a rechargeable secondary battery such as a lithium ion battery or a nickel metal hydride battery is used. Instead of the secondary battery, an electric double layer capacitor or the like may be used as the power storage means.

The load device 13 is a vehicle drive motor when the present invention is applied to a fuel cell vehicle.
The warning lamp 14 is a warning lamp that is turned on by the controller 15 to warn that the fuel cell output voltage under a predetermined operating condition has decreased by a predetermined value or more from the reference voltage. The number of warning lamps 14 may be one, but a plurality of warning lights 14 may be provided for each cause of failure, and each may be turned on depending on the cause. In the embodiment, the air supply system and other failure causes are discriminated, and individual warning lights are turned on.

Next, the control content of the controller 15 in Example 1 is demonstrated with reference to the control flowchart of FIG.
First, in step (hereinafter, step is abbreviated as S) 1, the controller 15 determines whether or not an elapsed time: T from the previous control for air correction is equal to or longer than a predetermined time: St. . If the predetermined time has not been reached, the flow ends. If the predetermined time has elapsed, the process proceeds to S2.

  In S2, the controller 15 calculates the output P of the fuel cell based on the voltage value and the current value read from the voltage sensor 9 and the current sensor 10, and whether or not the output P of the fuel cell is equal to or higher than the predetermined output Sp. Determine whether. The predetermined output Sp is set to an operating condition in which the fluctuation rate of the fuel cell output becomes a certain value or less even when the air amount correction control is performed. This is because the output of the fuel cell changes during the air amount correction control, so that the ratio of the output change with respect to the fuel cell output is reduced to reduce deterioration in drivability.

  In addition, the operating conditions are set within a certain range where the fuel cell output is large to some extent, as shown in the fuel cell current-voltage characteristic diagram of FIG. 5, the difference in excess air ratio (or insufficient supply air amount) when the output current density is large. This is because the fluctuation (or decrease) in the fuel cell voltage due to the fuel cell is large, and it is easy to detect the recovery of the fuel cell output voltage due to the air increase.

In S3, air amount correction control is performed. Details of the air amount correction control will be described later with reference to detailed flowcharts of FIGS. 3 and 4.
In S4, based on the air amount data corrected in S3, the air amount map stored in the rewritable memory built in the controller 15 is corrected, and the process ends. The air amount map is a map of the supply air amount with respect to the required output of the fuel cell.

Next, the air amount correction control in S3 of FIG. 2 will be described using the detailed flowchart of FIG.
First, in S11, the state of charge (charge amount) of the battery 12: SOC is detected and compared with a predetermined charge amount: Ss when the air amount correction control can be started. This is the power that was not used by the fuel cell to generate more power than is necessary for driving in order to prevent deterioration of drivability in the operating conditions for detecting the presence or absence of voltage recovery due to an increase in the air supply amount of the fuel cell. This is because a predetermined free capacity is secured in the battery 12 for the battery 12 to absorb.

When the SOC of the battery 12 is equal to or lower than Ss, the process proceeds to S12, and when the SOC is equal to or higher than Ss, discharge for reducing the SOC is performed in S16.
In S12, the fuel cell operating condition is set as the fuel cell state detection condition. The operating condition set here is that the operating time of the fuel cell system has exceeded a predetermined time, or that the output of the fuel cell has exceeded a predetermined output (for example, 90% of the rated output), or an instruction from the driver. For example, there was an input, or high load operation (for example, 80% or more of the rated output) continued for a predetermined time or more.

  When the operation condition set in S12 is detected, in S13, the fuel cell voltage: CSAv, which is the voltage detection value of the voltage sensor 9, is compared with the reference voltage Sv, and the fuel cell voltage CSAv is reduced below the reference voltage Sv. It is determined whether or not. Here, the reference voltage Sv is stored as a map in the controller 15 as a reference voltage corresponding to the output current.

  If it is determined in S13 that CSAv is greater than or equal to Sv, the flow is terminated as it is not necessary to correct the air amount. If CSAv is smaller than Sv, air amount correction is necessary, and the process proceeds to S14.

  In S14, an increase: Δq is performed to a predetermined air amount with respect to the supply air amount: Q. In S15, the CSAv after the air increase is compared with Sv, and if it is still lower than Sv, the process returns to S14 to further increase the air, and if it exceeds Sv, the flow is terminated.

  As described above, in this embodiment, it is detected whether the fuel cell voltage has reached the reference voltage under a predetermined operating condition. When the fuel cell voltage is lower than the reference voltage, the total fuel cell voltage is set so that the fuel cell voltage becomes equal to or higher than the reference voltage. By increasing the air flow rate to the excess air rate where the voltage is equal to or higher than the reference voltage, and performing the operation to find the required excess air rate, correction control of the air flow rate is performed, so depending on the amount of leakage from the air system, etc. It is possible to cope with an increase in the required air flow rate to the CSA due to a decrease in the supply gas flow rate.

Therefore, since the excess air ratio is insufficient, it is possible to prevent the power generation efficiency in the fuel cell from being lowered or the occurrence of water clogging in the fuel cell.
In addition, since the air amount correction control is performed when the system operation time exceeds a predetermined time, it is possible to reliably detect an air system failure.

Furthermore, since the air amount correction control is performed when the fuel cell output becomes equal to or higher than the test condition, it is possible to reliably detect a failure in the air system without deteriorating the drivability.
In addition, since the control to lower the battery SOC to a predetermined value or less is performed before the air amount correction control is performed, the power is generated more than the power necessary for traveling, and the surplus power is absorbed by the battery. It has become possible to provide a fuel cell system that can reliably detect air system failures without deteriorating performance.

  Next, a second embodiment of the fuel cell system according to the present invention will be described. The system configuration of the second embodiment is the same as the system configuration shown in FIG. The schematic flowchart of the second embodiment is also the same as that of the first embodiment shown in FIG.

The air amount correction control (S3 in FIG. 1) in the second embodiment will be described with reference to the detailed control flowchart in FIG.
First, in S21, the charge amount (SOC) of the battery 12 is detected and compared with a predetermined charge amount during correction control: Ss.

  This is because, under the conditions for detecting the state of the fuel cell, in order not to deteriorate the drivability, the fuel cell generates power more than the power necessary for traveling, and a predetermined amount is used to absorb unused power by the battery. This is to ensure the capacity of the battery. If the battery SOC is less than or equal to Ss, the process proceeds to S22. If the battery SOC is greater than or equal to Ss, discharge is performed to reduce the SOC in S31.

  In S22, the operation condition of the fuel cell is set as the condition detection condition of the fuel cell. The operating condition set here is that the operating time of the fuel cell system has exceeded a predetermined time, or that the output of the fuel cell has exceeded a predetermined output (for example, 95% of the rated output), or an instruction from the driver. That is, there is an input, or a high load operation close to the rated output (for example, 90% or more of the rated output) has continued for a predetermined time or more.

  When the operating condition set in S22 is detected, in S23, the fuel cell voltage: CSAv, which is the voltage detection value of the voltage sensor 9, is compared with the reference voltage Sv, and the fuel cell voltage CSAv falls below the reference voltage Sv. It is determined whether or not. Here, the reference voltage Sv is stored as a map in the controller 15 as a reference voltage corresponding to the output current.

  If CSAv is greater than Sv, the flow is terminated as it is not necessary to correct the air amount. If CSAv is smaller than Sv, air amount correction is necessary and the process proceeds to S24.

  In S24, the reference voltage Sv-fuel cell voltage CSAv is compared with a predetermined value: Dv. This comparison is performed because there is a possibility of component failure when the CSAv descent is large. When Sv-CSAv is larger than Dv, the process proceeds to S25, and when Sv-CSAv is equal to or less than Dv, the process proceeds to S32.

In S25, control is performed to increase the predetermined air amount: Δq with respect to the supplied air amount: Q.
In S26, the CSAv and Sv after increasing the air amount are compared. If the CSAv is still lower than Sv, the process proceeds to S27. If Sv is exceeded, the warning lamp 14 is turned on to display the air system component failure in S37. This is because the output voltage of the fuel cell has dropped from the reference voltage by more than a predetermined value, but the output voltage has been restored to the reference voltage by increasing the amount of air. It is because it is thought that it is.

In S27, the air increase amount is integrated.
In S28, the increased air amount: Gq and the maximum increase amount: Dq are compared. If the excess air ratio is reduced due to a failure in the air system parts, etc., the output voltage of the fuel cell can be recovered by increasing the air volume. It is not necessarily a shortage. Therefore, if the output voltage does not recover even if the air amount is increased to the maximum increase amount Dq, it is determined that the cause is not the air system, and in S29, the air amount is not corrected, that is, before the air amount is corrected. Control to return to the amount of air.

In S30, it is determined that there is a failure other than the air system parts, and the warning lamp 14 indicating the failure other than the air system is turned on.
Since the control from S32 to S36 is the same as that from S25 to S29, the description is omitted.
The difference is that in S24, the reference voltage Sv-fuel cell voltage: CSAv is compared with the predetermined value: Dv to determine whether there is a possibility of component failure.

  As described above, according to the present embodiment, if the fuel cell voltage does not improve even if the air amount is increased by a predetermined value or more, the air flow correction control is not performed because it is not due to a failure due to an air system component. Therefore, the air consumption is not increased and the fuel consumption is not deteriorated.

  In addition, if the difference between the fuel cell voltage and the reference voltage is greater than or equal to the specified value, a warning is given that there is a failure in the component. Can do.

  In this embodiment, the air amount correction control is started based on the elapsed time and the driving output. However, the control may be performed based on an instruction from the driver. By doing so, the fuel cell operating state does not go against the driver's intention. In addition, since the driver gives an instruction, it is possible to perform control while the vehicle is stopped, and it is possible to eliminate deterioration in drivability.

  Further, the air amount correction control may be performed when the high load operation continues for a predetermined time or more. By doing so, it becomes possible to respond quickly when an abnormality occurs in an air system component under a high load condition.

1 is a system configuration diagram illustrating the configuration of a first embodiment of a fuel cell system according to the present invention. FIG. 3 is a schematic flowchart illustrating a control operation according to the first embodiment. 3 is a detailed flowchart illustrating air amount correction control according to the first embodiment. 10 is a detailed flowchart illustrating air amount correction control according to the second embodiment. It is a figure explaining the influence which the change of an excess air ratio has on the current-voltage characteristic of a fuel cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell 2 ... Compressor 3 ... Pressure sensor 4 ... Pressure adjustment valve 5 ... Hydrogen supply device 6 ... Pressure adjustment valve 7 ... Ejector 8 ... Pressure sensor 9 ... Voltage sensor 10 ... Current sensor 11 ... Power manager 12 ... Battery 13 ... Load device 14 ... warning light 15 ... controller

Claims (8)

Oxidant gas supply means for supplying the fuel cell with an oxidant gas having a flow rate determined according to the power generation state of the fuel cell;
A fuel cell system having fuel gas supply means for supplying a fuel gas at a flow rate determined according to a power generation state of the fuel cell to the fuel cell;
Voltage detection means for detecting the fuel cell voltage;
In a predetermined operating condition, when the fuel cell voltage detected by the voltage detection means is lower than a reference voltage, a control means for performing an increase correction of the oxidant gas flow rate until the fuel cell voltage becomes equal to or higher than the reference voltage;
A fuel cell system comprising:   2. The fuel cell system according to claim 1, wherein the control means does not perform correction control of the oxidant gas flow rate when the fuel cell voltage does not improve even if the air amount is increased by a predetermined flow rate or more.   3. The fuel cell system according to claim 1, further comprising warning means for warning an abnormality of the fuel cell system when the difference between the fuel cell voltage and the reference voltage is a predetermined value or more. Power storage means to compensate for the shortage of fuel cell output,
4. The control device according to claim 1, wherein the control unit performs control to lower a charging state of the power storage unit to a predetermined value or less before performing correction control of the oxidant gas flow rate. 5. The fuel cell system described in 1.   The fuel cell system according to any one of claims 1 to 4, wherein the predetermined operating condition is that an operating time of the system exceeds a predetermined time.   The fuel cell system according to any one of claims 1 to 4, wherein the predetermined operating condition is that the output of the fuel cell is equal to or higher than a predetermined output.   The fuel cell system according to any one of claims 1 to 4, wherein the predetermined operating condition is an instruction from a driver.   The fuel cell system according to any one of claims 1 to 4, wherein the predetermined operation condition is that high load operation has continued for a predetermined time or more.

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