JP2020205208A - Fuel cell system - Google Patents

Abstract

To provide a technique capable of suppressing the number of occurrences of abnormal voltage, without increasing hydrogen supply amount excessively.SOLUTION: A fuel cell system includes a fuel cell stack for generating electricity by receiving supply of anode gas and cathode gas, an anode gas supply part for supplying anode gas to the fuel cell stack, a voltage measurement unit for measuring the output voltage of the fuel cell stack, an abnormal voltage detector for detecting occurrence of abnormal voltage in the fuel cell stack during stoppage of the fuel cell system, and a control section for stopping the fuel cell system when an abnormal voltage is detected during previous stoppage of the fuel cell system, by controlling the anode gas supply part so that the supply amount of anode gas exceeds that during previous stoppage of the fuel cell system.SELECTED DRAWING: Figure 3

Description

The present invention relates to a fuel cell system.

In a fuel cell system, for example, as described in Patent Document 1, a predetermined amount of hydrogen is applied when the system is stopped in order to suppress the generation of an abnormal voltage when the system is stopped. The technology to supply is known.

JP-A-2019-29350

In the above technology, if the hydrogen partial pressure at the time of power generation stoppage is assumed to be the lowest expected hydrogen partial pressure and the amount of hydrogen to be supplied is determined, there is a risk of supplying more hydrogen than necessary, resulting in fuel efficiency. The inventors of the present application have found a problem that it may lead to a decrease in hydrogen. Further, although the inventors of the present application have considered supplying a fixed amount of hydrogen each time the fuel cell system is stopped in order not to reduce fuel consumption, the frequency of occurrence of abnormal voltage may increase depending on the usage mode of the fuel cell system. I found the problem of having sex.

The present invention has been made to solve the above-mentioned problems, and can be realized as the following forms.

According to one embodiment of the present invention, a fuel cell system is provided. This fuel cell system supplies a fuel cell stack that generates power by receiving supply of an anode gas and a cathode gas, an anode gas supply unit that supplies the anode gas to the fuel cell stack, and an output voltage of the fuel cell stack. An abnormal voltage measuring unit for measuring, an abnormal voltage detecting unit for detecting the presence or absence of an abnormal voltage in the fuel cell stack while the fuel cell system is stopped, and an abnormal voltage during the previous stopping of the fuel cell system. When is detected, the fuel cell system is controlled by controlling the anode gas supply unit so that the supply amount of the anode gas is larger than the supply amount of the anode gas at the time when the fuel cell system was stopped last time. It is provided with a control unit for stopping. According to this form of fuel cell system, when an abnormal voltage is detected during the previous shutdown of the fuel cell system, the amount of anode gas supplied when the fuel cell system is stopped this time is set to the amount of anode gas supplied when the system was stopped last time. Since it is set to be larger than the supply amount of the anode gas, the number of occurrences of abnormal voltage can be suppressed without excessively increasing the hydrogen supply amount.

The present invention can be realized in various forms, for example, a power generation device including a fuel cell system, a vehicle equipped with a fuel cell system, a control method of the fuel cell system, and the like. Is.

It is a figure which shows the schematic structure of the fuel cell system. It is a flowchart which shows an example of the procedure of abnormal voltage detection processing. It is a flowchart which shows an example of the procedure of stop processing.

A. First Embodiment:
FIG. 1 is a diagram showing a schematic configuration of a fuel cell system 100 according to an embodiment of the present invention. The fuel cell system 100 includes a fuel cell stack 10, a control unit 20, a cathode gas supply unit 30, and an anode gas supply unit 50. Further, the fuel cell system 100 includes a DC / DC converter 80, a power control unit (hereinafter referred to as “PCU81”) 81, a load 82, a voltage measuring unit 83, and an ammeter 84. The fuel cell system 100 of the present embodiment is mounted on, for example, a fuel cell vehicle.

The fuel cell stack 10 is a polymer electrolyte fuel cell that generates electricity by being supplied with an anode gas (for example, hydrogen gas) and a cathode gas (for example, air) as reaction gases. The fuel cell stack 10 is configured by stacking a plurality of single cells 11. Each single cell 11 sandwiches a membrane electrode assembly (not shown) in which an anode (not shown) and a cathode (not shown) are arranged on both sides of an electrolyte membrane (not shown) and a membrane electrode assembly. It has a set of separators (not shown).

The control unit 20 is configured as a computer including a CPU, a memory, and an interface circuit to which each component described later is connected. By executing the control program stored in the memory, the CPU controls the power generation by the fuel cell system 100 so that the anode gas partial pressure, which will be described later, becomes the target partial pressure. The control unit 20 outputs a signal for controlling the start and stop of each device in the fuel cell stack 10 in response to an instruction from the ECU (Electronic Control Unit) 21. The control unit 20 includes an abnormal voltage detection unit 22. The abnormal voltage detection unit 22 detects whether or not an abnormal voltage is generated in the fuel cell stack 10 while the fuel cell system 100 is stopped. More specifically, when the output voltage of the fuel cell stack 10 detected by the voltage measuring unit 83, which will be described later, rises above a predetermined threshold value, it is determined that an abnormal voltage has occurred. The threshold is, for example, 1.5V. The control unit 20 may realize a part or all of these controls by a hardware circuit.

The ECU 21 is a control unit that controls the entire device (for example, a vehicle) including the fuel cell system 100. For example, in a fuel cell vehicle, the ECU 21 controls the vehicle according to a plurality of input values such as the amount of depression of the accelerator pedal, the amount of depression of the brake pedal, and the vehicle speed. The ECU 21 may be included as a part of the function of the control unit 20.

The cathode gas supply unit 30 includes a cathode gas pipe 31, an air flow meter 32, a compressor 33, a first on-off valve 34, a cathode off gas pipe 41, and a first regulator 42. The cathode gas pipe 31 is connected to the fuel cell stack 10 and supplies air taken in from the outside to the fuel cell stack 10.

The air flow meter 32 is provided in the cathode gas pipe 31 and measures the flow rate of the taken-in air. The compressor 33 compresses the air taken in from the outside in response to the control signal from the control unit 20, and supplies the air as the cathode gas to the fuel cell stack 10. The first on-off valve 34 is provided between the compressor 33 and the fuel cell stack 10. The cathode pressure gauge 35 measures the pressure at the cathode gas inlet of the fuel cell stack 10 (hereinafter referred to as “cathode gas pressure”) and transmits it to the control unit 20.

The cathode off gas pipe 41 discharges the cathode off gas discharged from the fuel cell stack 10 to the outside of the fuel cell system 100. The first regulator 42 adjusts the pressure at the cathode gas outlet of the fuel cell stack 10 in response to the control signal from the control unit 20.

The anode gas supply unit 50 includes an anode gas pipe 51, an anode gas tank 52, a second on-off valve 53, a second regulator 54, an injector 55, an anode pressure gauge 56, an anode off-gas pipe 61, and gas-liquid separation. The vessel 62, the exhaust / drain valve 63, the circulation pipe 64, and the anode gas pump 65 are provided. Below, the side downstream of the injector 55 of the anode gas pipe 51, the flow path of the anode gas in the fuel cell stack 10, the anode off-gas pipe 61, the gas-liquid separator 62, the circulation pipe 64, and the anode gas pump 65. The flow path composed of the above is also referred to as a circulation flow path 66. The circulation flow path 66 is a flow path for circulating the anode off gas of the fuel cell stack 10 to the fuel cell stack 10.

The anode gas tank 52 is connected to the anode gas inlet of the fuel cell stack 10 via the anode gas pipe 51, and supplies the anode gas to the fuel cell stack 10. The second on-off valve 53, the second regulator 54, the injector 55, and the anode pressure gauge 56 are provided in the anode gas pipe 51 in this order from the upstream side, that is, the side closer to the anode gas tank 52.

The second on-off valve 53 opens and closes in response to a control signal from the control unit 20. When the fuel cell system 100 is stopped, the second on-off valve 53 is closed. The second regulator 54 adjusts the anode gas pressure on the upstream side of the injector 55 in response to the control signal from the control unit 20. The injector 55 is an electromagnetically driven on-off valve in which the valve body is electromagnetically driven according to the drive cycle and valve opening time set by the control unit 20. The control unit 20 controls the flow rate of the anode gas supplied to the fuel cell stack 10 by controlling the drive cycle and valve opening time of the injector 55. The anode pressure gauge 56 measures the pressure at the anode gas inlet of the fuel cell stack 10 and transmits it to the control unit 20. The anode pressure gauge 56 may be provided on the anode gas outlet side of the fuel cell stack 10. In that case, it is preferable that the cathode pressure gauge 35 described above is also provided on the cathode gas outlet side of the fuel cell stack 10. In any of these cases, the pressure measured by the anode pressure gauge 56 can be referred to as "anode gas pressure".

The anode off-gas pipe 61 is a pipe that connects the anode gas outlet of the fuel cell stack 10 and the gas-liquid separator 62. The anode off-gas pipe 61 guides the anode-off gas containing hydrogen gas, nitrogen gas, etc., which has not been used in the power generation reaction, to the gas-liquid separator 62.

The gas-liquid separator 62 is connected between the anode off-gas pipe 61 of the circulation flow path 66 and the circulation pipe 64. The gas-liquid separator 62 separates water as an impurity from the anode-off gas in the circulation flow path 66 and stores it.

The exhaust drain valve 63 is provided in the lower part of the gas-liquid separator 62. The exhaust / drain valve 63 drains the water stored in the gas-liquid separator 62 and exhausts unnecessary gas (mainly nitrogen gas) in the gas-liquid separator 62. During the operation of the fuel cell system 100, the exhaust / drain valve 63 is normally closed and opens / closes in response to a control signal from the control unit 20. In the present embodiment, the exhaust drain valve 63 is connected to the cathode off gas pipe 41, and the water discharged by the exhaust drain valve 63 and unnecessary gas are discharged to the outside through the cathode off gas pipe 41.

The circulation pipe 64 is connected to a portion of the anode gas pipe 51 downstream of the injector 55. The circulation pipe 64 is provided with an anode gas pump 65 that is driven in response to a control signal from the control unit 20. The anode off gas from which water has been separated by the gas-liquid separator 62 is sent out to the anode gas pipe 51 by the anode gas pump 65. In the fuel cell system 100, the anode off gas containing hydrogen is circulated and supplied to the fuel cell stack 10 again to improve the utilization efficiency of the anode gas.

The DC / DC converter 80 boosts the output voltage of the fuel cell stack 10 and supplies it to the PCU 81. The PCU 81 has a built-in inverter, and supplies electric power to the load 82 via the inverter according to the control of the control unit 20. Further, the PCU 81 limits the current of the fuel cell stack 10 under the control of the control unit 20.

The voltage measuring unit 83 measures the output voltage of the fuel cell stack 10. The voltage measuring unit 83 transmits the measured output voltage to the abnormal voltage detecting unit 22. In the present embodiment, the voltage measuring unit 83 transmits the total of the output voltages of the single cells 11 to the abnormal voltage detecting unit 22 as the output voltage of the fuel cell stack 10. The ammeter 84 measures the output current value of the fuel cell stack 10.

The electric power of the fuel cell stack 10 is supplied to a load 82 such as a traction motor (not shown) for driving wheels (not shown) via a power supply circuit including a PCU 81, a compressor 33 described above, an anode gas pump 65, and the like. It is supplied to various valves.

FIG. 2 is a flowchart showing an example of the procedure of the abnormal voltage detection process in the present embodiment. The abnormal voltage detection unit 22 repeatedly executes this process while the fuel cell system 100 is stopped. First, the abnormal voltage detection unit 22 determines in step S100 whether or not an abnormal voltage has been detected. More specifically, the abnormal voltage detection unit 22 determines whether or not the output voltage of the fuel cell stack 10 acquired from the voltage measurement unit 83 has risen above a predetermined threshold value. When the abnormal voltage is detected, the abnormal voltage detection unit 22 proceeds to step S110, turns on the abnormal voltage flag, non-volatilely records the value of the flag in the memory, and ends the abnormal voltage detection process. On the other hand, when the abnormal voltage is not detected, the abnormal voltage detection unit 22 ends the abnormal voltage detection process. The abnormal voltage flag is reset to OFF every time the fuel cell system 100 is stopped.

The "abnormal voltage" refers to an electrode voltage in which the cathode potential rises from under normal power generation conditions and the cathode voltage rises to a level at which deterioration of the cathode (that is, corrosion of carbon) progresses. It is considered that one of the causes of the abnormal voltage is a local hydrogen deficiency caused by oxygen permeating from the cathode to the anode when the fuel cell system 100 is left for a long time at the anode of the fuel cell. ..

FIG. 3 is a flowchart showing an example of the stop processing procedure in the present embodiment. The control unit 20 starts this process when the fuel cell system 100 is stopped.

First, the control unit 20 estimates the anode gas partial pressure in step S200. In the present embodiment, the control unit 20 estimates the anode gas partial pressure based on a map or function in which the relationship between the anode gas pressure and the partial pressure of a gas other than the anode gas is defined in advance. The "gas other than the anode gas" is, for example, nitrogen, oxygen, water vapor, etc. that have permeated through the cathode. The anode partial pressure is a value obtained by subtracting the partial pressure of a gas other than the anode gas obtained by using a map or a function from the current anode gas pressure measured by using the anode pressure gauge 56. If the anode gas partial pressure cannot be estimated, a predetermined constant may be used as the anode gas partial pressure. The estimation of the partial pressure of the anode gas is described in, for example, Patent Document 1.

Next, in step S210, the control unit 20 determines whether or not the abnormal voltage flag is ON. That is, it is determined whether or not an abnormal voltage is detected during the previous stop of the fuel cell system 100. The "previous stop" means that the fuel cell system 100 has been stopped immediately before the start of the current stop process. When the abnormal voltage flag is ON, that is, when an abnormal voltage is detected during the previous stop, the control unit 20 increases the target value of the anode gas partial pressure in step S220. More specifically, the control unit 20 sets the target value of the anode gas partial pressure to a value of the anode gas partial pressure larger than the target value in the previous stop control. In the present embodiment, the control unit 20 sets the target value to a value obtained by increasing the target value in the previous stop control by a predetermined value (for example, 10 kPa). When increasing the target value for the first time, set the standard target value to a predetermined value or an increased value. The "standard target value" is a value of the anode gas partial pressure at which an abnormal voltage is not generated while the fuel cell system 100 is stopped for a predetermined period, and can be determined by performing a simulation or an experiment in advance. On the other hand, when the abnormal voltage flag is OFF, that is, when the abnormal voltage is not detected during the previous stop, the control unit 20 proceeds to the process of step S230.

Subsequently, in step S230, the control unit 20 determines whether or not the anode gas partial pressure estimated in step S200 is larger than a predetermined target value. The predetermined target value is the target value or the standard target value increased in step S220. When the anode gas partial pressure is equal to or less than the target value, the control unit 20 controls the anode gas supply unit 50 so that the anode gas partial pressure becomes the target value in step S240 to supply the anode gas, and performs the process of step S250. move on. The control unit 20 controls the anode gas supply unit 50 so that the larger the target value, the more anode gas is supplied. On the other hand, when the partial pressure of the anode gas is larger than the target value, hydrogen is not supplied and the process proceeds to step S250.

Finally, the control unit 20 controls the stop of the fuel cell system 100 in step S250. The control unit 20 controls, for example, stopping the supply of the cathode gas, sealing the cathode gas pipe 31, sealing the anode gas pipe 51, and the like.

According to the fuel cell system 100 of the present embodiment described above, the control unit 20 determines the supply amount of the anode gas when an abnormal voltage is detected while the fuel cell system 100 is stopped last time. Set more than the amount of anode gas supplied when stopped. Therefore, the supply amount of the anode gas can be set according to the usage mode of the fuel cell system 100, specifically, the length of the leaving period of the fuel cell system 100. As a result, the number of occurrences of abnormal voltage can be suppressed. Further, when the abnormal voltage is not detected during the previous shutdown of the fuel cell system 100, the control unit 20 sets the anodic gas supply amount to a fixed amount, so that it is possible to suppress the supply of hydrogen more than necessary. .. Therefore, according to the present embodiment, the number of occurrences of abnormal voltage can be suppressed without excessively increasing the hydrogen supply amount.

B. Other embodiments:
In the above-described embodiment, the control unit 20 supplies the anode gas according to the partial pressure of the anode gas in the stop processing. Instead, the control unit 20 may supply the anode gas according to the remaining amount of the anode gas in the fuel cell stack 10. In this case, the target value is the remaining amount of anode gas. In step S240, the control unit 20 can supply the anode gas so that the remaining amount of the anode gas becomes the target value. The remaining amount of the anode gas can be estimated from the partial pressure of the anode gas. Further, it can be obtained by subtracting the amount of the consumed anode gas estimated by using the amount of power generated by the fuel cell stack 10 from the amount of the anode gas supplied from the anode gas tank 52.

The present invention is not limited to the above-described embodiment, and can be realized with various configurations without departing from the spirit of the present invention. For example, the technical features in the embodiments corresponding to the technical features in each form described in the column of the outline of the invention are for solving the above-mentioned problems or for achieving a part or all of the above-mentioned effects. In addition, it is possible to replace or combine them as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be appropriately deleted.

10 ... Fuel cell stack, 11 ... Single cell, 20 ... Control unit, 21 ... ECU, 22 ... Abnormal voltage detection unit, 30 ... Cathode gas supply unit, 31 ... Cathode gas piping, 32 ... Air flow meter, 33 ... Compressor, 34 ... 1st on-off valve, 35 ... Cathode pressure gauge, 41 ... Cathode off gas piping, 42 ... 1st regulator, 50 ... Anode gas supply unit, 51 ... Anode gas piping, 52 ... Anode gas tank, 53 ... 2nd on-off valve, 54 ... 2nd regulator, 55 ... Injector, 56 ... Anode pressure gauge, 61 ... Anode off gas pipe, 62 ... Gas-liquid separator, 63 ... Exhaust drain valve, 64 ... Circulation pipe, 65 ... Anode gas pump, 66 ... Circulation flow path, 80 ... DC / DC converter, 81 ... PCU, 82 ... load, 83 ... voltage measuring unit, 84 ... anode, 100 ... fuel cell system

Claims (1)

It ’s a fuel cell system,
A fuel cell stack that generates electricity by receiving the supply of anode gas and cathode gas,
An anode gas supply unit that supplies the anode gas to the fuel cell stack,
A voltage measuring unit that measures the output voltage of the fuel cell stack,
An abnormal voltage detection unit that detects the presence or absence of an abnormal voltage in the fuel cell stack while the fuel cell system is stopped.
When an abnormal voltage is detected during the previous shutdown of the fuel cell system, the anode gas is supplied so as to be larger than the supply amount of the anode gas at the time of the previous shutdown of the fuel cell system. A fuel cell system including a control unit that controls a supply unit and stops the fuel cell system.

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