JP2016122624A - Control device for fuel battery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for a fuel battery system that can suppress occurrence of fuel shortage during stop period and high voltage degradation of a unit cell.SOLUTION: A control device 200 of a fuel battery system 100 executes voltage reducing control of supplying fuel gas so that anode pressure is equal to predetermined pressure when the stack voltage during a stop period is not less than a predetermined voltage, calculates a fuel gas residual amount based on at least the pressure of a fuel gas source 22, estimates a fuel gas supply amount required to increase the anode pressure till the predetermined pressure, calculates an executable frequency of the voltage reducing control based on the fuel gas residual amount and the fuel gas supply amount, and notifies the supplement timing of the fuel gas based on the executable frequency and a time when the stack voltage can be kept to be less than the predetermined voltage after the voltage reducing control is executed. The control device 200 estimates the fuel gas supply amount based on the atmosphere pressure, or corrects a reference fuel gas supply amount required to increase the anode pressure from a reference pressure to a predetermined pressure based on the atmospheric pressure and estimates the fuel gas supply amount.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a control device for a fuel cell system.

  As a control device of a conventional fuel cell system, when air flows into the fuel cell stack during the stop period of the fuel cell system, the voltage of the fuel cell stack increases even during the stop period, and as a result, the fuel Since the power generation performance deteriorates due to high voltage deterioration that causes deterioration of the catalyst in the electrode of the single battery cell, the voltage of the fuel cell stack during the stop period is monitored, and fuel gas is appropriately supplied according to the magnitude. In some cases, the voltage is reduced (see Patent Document 1).

JP 2007-265786 A

  When supplying fuel gas in order to suppress high voltage deterioration of a single cell of the fuel cell during the stop period of the fuel cell system, the fuel gas is maintained until the pressure of the fuel gas passage in the fuel cell stack reaches a predetermined pressure. Can be considered. Since the pressure of the fuel gas passage during the stop period decreases during the stop period and is usually close to atmospheric pressure, this will change the pressure of the fuel gas passage from the pressure near atmospheric pressure to a predetermined pressure. Fuel gas will be supplied until it becomes.

  In addition, in order to suppress high voltage degradation of a single fuel cell, even if the fuel gas is supplied and the voltage is once reduced, the inflow of air into the fuel cell stack during the stop period cannot be stopped. The voltage rises. Therefore, the fuel gas is repeatedly supplied during the stop period. Therefore, when supplying fuel gas in order to suppress high-voltage degradation of a single fuel cell during the stop period of the fuel cell system, in order to prevent the fuel gas from running out, preferably when the fuel cell system is stopped, for example, It is conceivable to notify the replenishment timing of the fuel gas according to the fuel gas remaining amount at the time of stoppage.

  However, since the atmospheric pressure changes depending on where the fuel cell system is stopped or installed, when the fuel cell system is stopped at a high altitude, etc., the reference altitude at which the fuel cell system is normally used is assumed. The atmospheric pressure is lower than the reference atmospheric pressure (standard atmospheric pressure) on the flat ground. Therefore, when the fuel cell system is stopped at a high altitude or the like, the amount of fuel gas supplied during the stop period of the fuel cell system becomes larger than expected. As a result, the remaining amount of fuel gas is reduced earlier than expected during the stop period of the fuel cell system, causing the fuel gas to run out earlier than the notified fuel gas replenishment time, and high voltage degradation of the fuel cell single cell is caused. May occur.

  The present invention has been made paying attention to such problems, and notifies the appropriate fuel gas replenishment timing by accurately estimating the amount of fuel gas supplied during the stop period of the fuel cell system. An object of the present invention is to suppress the occurrence of fuel shortage during a stop period and the high voltage deterioration of a single fuel cell.

  In order to solve the above problems, according to one aspect of the present invention, a fuel cell stack that generates power by an electrochemical reaction between a fuel gas and an oxidant gas, and a fuel gas source for storing the fuel gas are included. A fuel gas supply / discharge device for supplying and discharging fuel gas to / from the fuel cell stack, a stack voltage sensor for detecting a stack voltage that is a voltage of the fuel cell stack, and a pressure of the fuel gas passage in the fuel cell stack A control device for controlling a fuel cell system, comprising: an anode pressure sensor that detects an anode pressure, a fuel gas source pressure sensor that detects a pressure of a fuel gas source, and an atmospheric pressure sensor that detects an atmospheric pressure; If the stack voltage detected during the battery system outage is equal to or higher than the predetermined voltage, the fuel cell stack is burned during the outage so that the anode pressure becomes the predetermined pressure. A voltage reduction control execution unit that performs voltage reduction control for reducing gas stack by supplying gas, a fuel gas remaining amount calculation unit that calculates a remaining amount of fuel gas based on at least the pressure of the fuel gas source, and during a stop period When the voltage drop control is performed, the fuel gas supply amount estimation unit for estimating the fuel gas supply amount necessary for increasing the anode pressure to a predetermined pressure, and the voltage based on the remaining fuel gas amount and the fuel gas supply amount The fuel gas source is replenished with the fuel gas based on the feasible frequency calculation unit that calculates the feasible frequency of the decrease control, and the time that the stack voltage can be maintained below the predetermined voltage after the voltage lowering control is performed. A notification unit for notifying when it is necessary. The fuel gas supply amount estimation unit estimates the fuel gas supply amount based on the atmospheric pressure detected by the atmospheric pressure sensor, or the anode pressure is preset when the voltage drop control is performed during the stop period. The fuel gas supply amount is estimated by correcting the reference fuel gas supply amount necessary for increasing the pressure from the reference pressure to a predetermined pressure based on the atmospheric pressure detected by the atmospheric pressure sensor.

  According to the present invention, it is possible to accurately estimate the fuel gas supply amount supplied to the fuel cell stack during the voltage drop control during the system stop period according to the atmospheric pressure at the place where the fuel cell system is stopped. As a result, it is possible to notify the user of the fuel cell system of an appropriate fuel gas replenishment time and prompt the fuel gas to be replenished. Can be suppressed.

FIG. 1 is a schematic configuration diagram of a fuel cell system and an electronic control unit that controls the fuel cell system according to an embodiment of the present invention. FIG. 2 is a time chart for explaining the voltage drop control performed during the system stop period. FIG. 3 is a flowchart illustrating system stop control according to an embodiment of the present invention. FIG. 4 is a table for calculating the expected hydrogen supply amount based on the atmospheric pressure.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals are assigned to similar components.

  FIG. 1 is a schematic configuration diagram of a fuel cell system 100 and an electronic control unit 200 that controls the fuel cell system 100 according to an embodiment of the present invention.

  The fuel cell system 100 includes a fuel cell stack 10, a fuel gas supply / discharge device 20 for supplying / discharging fuel gas to / from the fuel cell stack 10, and supplying / discharging oxidant gas to / from the fuel cell stack 10. An oxidant gas supply / discharge device 30 for carrying out, a cooling water circulation device 40 for circulating cooling water for cooling the fuel cell stack 10, and an electric load unit 50 electrically connected to an output terminal of the fuel cell stack 10 And comprising.

  The fuel cell stack 10 is formed by stacking a plurality of fuel cell single cells (hereinafter referred to as “single cells”) 1 along the stacking direction and electrically connecting the single cells 1 in series. Each single cell 1 includes a membrane electrode assembly 1a. The membrane electrode assembly 1a includes a membrane electrolyte (hereinafter referred to as “electrolyte membrane”), an anode electrode formed on one side of the electrolyte membrane, and a cathode electrode formed on the other side of the electrolyte membrane. .

When power generation is performed in the fuel cell stack 10, the following electrochemical reactions occur at the anode and cathode electrodes.
Anode electrode: 2H ₂ → 4H ⁺ + 4e ⁻
Cathode electrode: 4H ⁺ + 4e ⁻ + O ₂ → 2H ₂ O

  In each single cell 1, a hydrogen flow passage 2a for supplying hydrogen as fuel gas to the anode electrode and an air flow passage 3a for supplying air as oxidant gas to the cathode electrode are formed. The Further, a cooling water flow passage 4a for supplying cooling water is formed between two adjacent single cells 1.

  The hydrogen flow passage 2a, the air flow passage 3a, and the cooling water flow passage 4a of each unit cell 1 are connected in parallel in the fuel cell stack 10, respectively, so that the hydrogen passage 2 and the air passage are provided in the fuel cell stack 10. 3 and the cooling water passage 4 are formed. The inlets and outlets of the hydrogen passage 2, the air passage 3, and the cooling water passage 4 are respectively provided on one end side in the stacking direction of the fuel cell stack 10. In the present embodiment, hydrogen and air are respectively supplied to the hydrogen passage 2 and the air passage 3 so that the flow directions of hydrogen and air in the fuel cell stack 10 are opposite to each other. Hydrogen and air may be supplied. In this embodiment, the direction in which the cooling water flows is the same as the direction in which hydrogen flows, but it may be reversed.

  The fuel gas supply / discharge device 20 includes a hydrogen supply pipe 21, a high-pressure hydrogen tank 22 as a hydrogen source, a hydrogen supply control valve 23, a buffer unit 24, a purge pipe 25, and a purge control valve 26.

  The hydrogen supply pipe 21 is a pipe through which hydrogen supplied to the hydrogen passage 2 flows. One end of the hydrogen supply pipe 21 is connected to the high-pressure hydrogen tank 22 and the other end is connected to the inlet of the hydrogen passage 2.

  The high-pressure hydrogen tank 22 stores hydrogen to be supplied to the hydrogen passage 2 through the hydrogen supply pipe 21. The high pressure hydrogen tank 22 is provided with a tank pressure sensor 218 for detecting the pressure in the high pressure hydrogen tank 22.

  The hydrogen supply control valve 23 includes a shutoff valve 231, a regulator 232, and an injector 233.

  The shut-off valve 231 is an electromagnetic valve that is opened and closed by the electronic control unit 200 and is provided in the hydrogen supply pipe 21. When the shut-off valve 231 is opened, hydrogen flows out from the high-pressure hydrogen tank 22 to the hydrogen supply pipe 21. When the shut-off valve 231 is closed, hydrogen does not flow out from the high-pressure hydrogen tank 22 to the hydrogen supply pipe 21.

  The regulator 232 is provided in the hydrogen supply pipe 21 downstream from the shutoff valve 231. The regulator 232 is a pressure control valve capable of adjusting the opening degree continuously or stepwise, and the opening degree is controlled by the electronic control unit 200. By controlling the opening degree of the regulator 232, the pressure of hydrogen downstream of the regulator 232, that is, the pressure of hydrogen injected from the injector 233 is controlled.

  The injector 233 is provided in the hydrogen supply pipe 21 downstream from the regulator 232. The injector 233 is a needle valve that can adjust the opening degree continuously or stepwise, and the opening degree is controlled by the electronic control unit 200. By controlling the opening degree of the injector 233, the flow rate of hydrogen injected from the injector 233 is controlled.

  Thus, the hydrogen supply control valve 23 controls the supply of hydrogen from the high-pressure hydrogen tank 22 to the hydrogen passage 2. That is, hydrogen controlled to a desired pressure and flow rate by the hydrogen supply control valve 23 is intermittently supplied to the hydrogen passage 2.

  An anode pressure sensor 211 is provided in the hydrogen supply pipe 21 downstream of the injector 233. The anode pressure sensor 211 detects the pressure of hydrogen in the hydrogen supply pipe 21 downstream of the injector 233 as a value representative of the pressure of hydrogen in the hydrogen passage 2 (hereinafter referred to as “anode pressure”).

  The buffer unit 24 is, for example, a tank that communicates with the outlet of the hydrogen passage 2, and temporarily stores the anode off gas that has flowed out of the hydrogen passage 2. The anode off-gas is composed of surplus hydrogen that has not been used for the electrochemical reaction in each single cell 1 and inert gas such as nitrogen or water vapor leaking from the air passage 3 to the hydrogen passage 2 through the membrane electrode assembly 1a. And mixed gas. The buffer unit 24 only needs to have a function of temporarily storing the anode off gas. For example, a space is formed on the downstream side (near the outlet) of the hydrogen passage 2 to the extent that the anode off gas can be temporarily stored. The space may be used as the buffer unit 24. That is, the hydrogen passage 2 may be formed so that the downstream side of the hydrogen passage 2 functions as the buffer portion 24.

  The purge pipe 25 has one end connected to the buffer unit 24 and the other end connected to a diluter 39 provided in a cathode offgas pipe 37 described later.

  The purge control valve 26 is an electromagnetic valve that is opened and closed by the electronic control unit 200 and is provided in the purge pipe 25. The purge control valve 26 is normally closed and is periodically opened over a short time. When the purge control valve 26 is opened, the anode off gas in the buffer unit 24 flows into the diluter 39 through the purge pipe 25.

  The oxidant gas supply / discharge device 30 includes an air supply pipe 31, an air cleaner 32, a compressor 33, an intercooler 34, a bypass control valve 35, a bypass pipe 36, a cathode offgas pipe 37, and a cathode pressure control valve 38. And a diluter 39.

  The air supply pipe 31 is a pipe through which air supplied to the air passage 3 flows. One end of the air supply pipe 31 is connected to the air cleaner 32 and the other end is connected to the inlet of the air passage 3.

  The air cleaner 32 removes foreign matter in the air sucked into the air supply pipe 31. The air cleaner 32 is disposed in the atmosphere serving as the oxygen source 32a. That is, the oxygen source 32a communicates with the air supply pipe 31 via the air cleaner.

  The compressor 33 is, for example, a centrifugal or axial flow turbo compressor, and is provided in the air supply pipe 31. The compressor 33 compresses and discharges the air sucked into the air supply pipe 31 via the air cleaner 32.

  The intercooler 34 is provided in the air supply pipe 31 downstream of the compressor 33, and cools the air discharged from the compressor 33 with, for example, traveling wind or cooling water.

  A first flow rate sensor 212 is provided in the air supply pipe 31 between the compressor 33 and the intercooler 34. The first flow rate sensor 212 detects the flow rate of the air discharged from the compressor 33. Note that the first flow rate sensor 212 may be provided in the air supply pipe 31 upstream of the compressor 33, and the first flow rate sensor 212 may detect the flow rate of the air sucked by the compressor 33.

  The bypass pipe 36 is a pipe for allowing a part or all of the air discharged from the compressor 33 to flow directly into the cathode offgas pipe 37 without passing through the fuel cell stack 10 as necessary. One end of the bypass pipe 36 is connected to the second outlet port 35 c of the bypass control valve 35, and is connected to a cathode offgas pipe 37 between the cathode pressure control valve 38 and the diluter 39.

  The bypass pipe 36 is provided with a second flow rate sensor 213. The second flow rate sensor 213 detects the flow rate of air (hereinafter referred to as “bypass air”) that has flowed into the bypass pipe 36 via the bypass control valve 35.

  The bypass control valve 35 is an electric three-way valve whose opening degree can be adjusted continuously or stepwise, and includes an inlet port 35a, a first outlet port 35b, and a second outlet port 35c. The opening degree of the bypass control valve 35 is controlled by the electronic control unit 200. The inlet port 35a is connected to the air supply pipe 31 on the intercooler 34 side. The first outlet port 35b is connected to the air supply pipe 31 on the fuel cell stack 10 side. The second outlet port 35 c is connected to the bypass pipe 36. By adjusting the opening degree of the bypass control valve 35, the communication state between the inlet port 35a, the first outlet port 35b, and the second outlet port 35c is adjusted.

  Specifically, when the bypass control valve 35 is fully closed, the inlet port 35a and the first outlet port 35b are in communication with each other, and the inlet port 35a and the second outlet port 35c are in communication with each other. As a result, the air discharged from the compressor 33 does not flow into the bypass pipe 36 but flows entirely into the air passage 3 from the air supply pipe 31 via the bypass control valve 35.

  On the other hand, when the bypass control valve 35 is fully opened, the inlet port 35a and the first outlet port 35b are not communicated, and the inlet port 35a and the second outlet port 35c are communicated. As a result, all the air discharged from the compressor 33 flows into the bypass pipe 36 via the bypass control valve 35 and does not flow into the air passage 3.

  When the bypass valve control valve is opened to any opening other than fully closed and fully open (arbitrary intermediate opening), the inlet port 35a communicates with the first outlet port 35b and the second outlet port 35c, respectively. Become. As a result, a part of the air discharged from the compressor 33 according to the opening degree of the bypass control valve 35 flows into the bypass pipe 36 via the bypass control valve 35, and the rest flows through the bypass control valve 35. 31 flows into the air passage 3. The larger the opening degree of the bypass control valve 35, the higher the ratio of the air flowing into the bypass pipe 36 out of the air discharged from the compressor 33.

  Thus, the bypass control valve 35 controls the amount of air supplied to the air passage 3 and the amount of air flowing into the bypass pipe 36 out of the air discharged from the compressor 33.

  The cathode offgas pipe 37 is a pipe through which the cathode offgas flowing out from the outlet of the air passage 3 flows. One end of the cathode offgas pipe 37 is connected to the outlet of the air passage 3 and the other end opens to the atmosphere. The cathode off gas is a mixed gas of excess oxygen that has not been used for the electrochemical reaction in each single cell 1, an inert gas such as nitrogen, and water vapor generated by the electrochemical reaction.

  The cathode pressure control valve 38 is provided in the cathode offgas pipe 37. The cathode pressure control valve 38 is an electromagnetic valve whose opening degree can be adjusted continuously or stepwise, and the opening degree is controlled by the electronic control unit 200. By controlling the opening of the cathode pressure control valve 38, the cathode pressure, which is the pressure in the air passage 3, is controlled.

  A cathode pressure sensor 214 is provided in the cathode offgas pipe 37 upstream of the cathode pressure control valve 38. The cathode pressure sensor 214 detects the pressure in the cathode offgas pipe 37 upstream of the cathode pressure control valve 38 as a value representing the cathode pressure (pressure in the air passage 3).

  The diluter 39 is provided in the cathode offgas pipe 37 downstream of the cathode pressure control valve 38. As described above, the purge pipe 25 is connected to the diluter 39, and cathode off gas and bypass air flow in through the cathode off gas pipe 37, and anode off gas flows in through the purge pipe 25. As a result, the cathode off gas, the bypass air, and the anode off gas are mixed inside the diluter 39, and these mixed gases are discharged as exhaust gas from the cathode off gas pipe 37 downstream of the diluter 39 to the atmosphere. In this way, by mixing the cathode offgas, the bypass air, and the anode offgas inside the diluter 39, the hydrogen in the anode offgas is diluted with the cathode offgas and the bypass air, and the hydrogen concentration of the exhaust gas discharged to the atmosphere is reduced. The concentration is less than the reference concentration (for example, 4%).

  As described above, in this embodiment, the anode off-gas flowing out from the hydrogen passage 2 to the purge pipe 25 is discharged to the atmosphere from the cathode off-gas pipe 37 without returning to the hydrogen supply pipe 21. That is, the fuel cell system 100 according to the present embodiment is a hydrogen non-circulation type.

  In the case of the hydrogen non-circulation type fuel cell system 100, a circulation pump or the like for returning the anode off gas to the hydrogen supply pipe 21 and circulating it is compared with a hydrogen circulation type system for returning the anode off gas to the hydrogen supply pipe 21 and circulating it. It becomes unnecessary. Therefore, the hydrogen non-circulation type fuel cell system 100 does not require electric power for driving the circulation pump as compared with the hydrogen circulation type system, and can improve fuel efficiency and simplify the configuration. Cost can be reduced.

  The cooling water circulation device 40 includes a cooling water circulation pipe 41, a cooling water pump 42, a radiator 43, a radiator bypass pipe 44, and a radiator bypass control valve 45.

  The cooling water circulation pipe 41 is a pipe that circulates cooling water for cooling the fuel cell stack 10, and has one end connected to the inlet of the cooling water passage 4 and the other end connected to the outlet of the cooling water passage 4. . Hereinafter, the outlet side of the cooling water passage 4 is defined as upstream of the cooling water circulation pipe 41, and the inlet side of the cooling water passage 4 is defined as downstream of the cooling water circulation pipe 41.

  The cooling water pump 42 is provided on the downstream side of the cooling water circulation pipe 41 and circulates the cooling water.

  The radiator 43 is provided in the cooling water circulation pipe 41 upstream of the cooling water pump 42, and cools the cooling water flowing out from the outlet of the cooling water passage 4 by, for example, running air or air sucked by the radiator fan 46.

  The radiator bypass pipe 44 is a pipe provided so that cooling water can be circulated without passing through the radiator 43, and one end is connected to the radiator bypass control valve 45 and the other end is connected to the radiator 43 and the cooling water. It is connected to a cooling water circulation pipe 41 between the pump 42.

  The radiator bypass control valve 45 is, for example, a thermostat, and is provided in the cooling water circulation pipe 41 upstream of the radiator 43. The radiator bypass control valve 45 switches the cooling water circulation path according to the temperature of the cooling water. Specifically, when the temperature of the cooling water is higher than a preset reference temperature, the cooling water that has flowed out of the cooling water passage 4 into the cooling water circulation pipe 41 flows again into the cooling water passage 4 via the radiator 43. Switch the cooling water circulation path so that it flows. On the contrary, when the temperature of the cooling water is lower than the reference temperature, the cooling water flowing out from the cooling water passage 4 to the cooling water circulation pipe 41 flows through the radiator bypass pipe 44 without passing through the radiator 43 and directly enters the cooling water passage 4. The cooling water circulation path is switched so as to flow into the.

  A coolant temperature sensor 215 is provided in the coolant circulation pipe 41 upstream of the radiator bypass control valve 45. The water temperature sensor 215 detects the temperature of the cooling water flowing out from the cooling water passage 4 to the cooling water circulation pipe 41.

  The electrical load unit 50 includes a first converter 51, a circuit breaker 52, a battery 53, a second converter 54, a motor generator 55, and an inverter 56. A connection line 57 between the electric load unit 50 and the output terminal of the fuel cell stack 10 includes a current sensor 216 for detecting a current (hereinafter referred to as “output current”) extracted from the fuel cell stack 10, and a fuel cell stack. And a voltage sensor 217 for detecting an inter-terminal voltage (hereinafter referred to as “stack voltage”) of the ten output terminals.

  The first converter 51 is a bidirectional DC / DC converter provided with an electric circuit capable of increasing / decreasing the voltage between terminals of the primary side terminal, and the primary side terminal is a fuel cell via the circuit breaker 52. Connected to the output terminal of the stack 10, the secondary side terminal is connected to the DC side terminal of the inverter 56. The first converter 51 raises or lowers the stack voltage, which is the primary terminal voltage, based on a control signal from the electronic control unit 200, and sets the stack voltage according to the operating state of the fuel cell system 100. Control to voltage.

  The circuit breaker 52 is opened and closed by the electronic control unit 200 and electrically connects or disconnects the fuel cell stack 10 and the electric load unit 50. The circuit breaker 52 is not necessarily provided.

  The battery 53 is a rechargeable secondary battery such as a nickel / cadmium storage battery, a nickel / hydrogen storage battery, or a lithium ion battery. The battery 53 is charged with surplus power from the fuel cell stack 10 and regenerative power from the motor generator 55. The electric power charged in the battery 53 is used to drive each control component provided in the fuel cell system 100 such as the motor generator 55 and the compressor 33 as necessary.

  The second converter 54 is a bidirectional DC / DC converter provided with an electric circuit capable of increasing / decreasing the voltage between terminals of the secondary side terminal, for example, and the primary side terminal is connected to the output terminal of the battery 53. The secondary side terminal is connected to the DC side terminal of the inverter 56. The second converter 54 raises or lowers the input voltage of the inverter 56 that is the secondary terminal voltage based on the control signal from the electronic control unit 200, and sets the input voltage according to the operating state of the fuel cell system 100. The target input voltage is controlled.

  The motor generator 55 is, for example, a three-phase permanent magnet type synchronous motor, and has a function as a motor that generates power of a vehicle on which the fuel cell system 100 is mounted, and a function as a generator that generates power when the vehicle is decelerated. Prepare. Motor generator 55 is connected to the AC side terminal of inverter 56, and is driven by the generated power of fuel cell stack 10 and the power of battery 53.

  The inverter 56 converts a DC current input from the DC side terminal into an AC current based on a control signal from the electronic control unit 200 and outputs the AC current from the AC side terminal, and conversely based on a control signal from the electronic control unit 200. And an electric circuit capable of converting an alternating current input from the alternating current side terminal into a direct current and outputting the direct current from the direct current side terminal. The DC side terminal of inverter 56 is connected to the secondary side terminals of first converter 51 and second converter 54, and the AC side terminal of inverter 56 is connected to the input / output terminal of motor generator 55. When the motor generator 55 functions as a motor, the inverter 56 converts the combined direct current of the output current of the fuel cell stack 10 and the output current of the battery 53 into an alternating current (three-phase alternating current in the present embodiment) and converts the motor into a motor. This is supplied to the generator 55. On the other hand, when the motor generator 55 functions as a generator, the inverter 56 converts the alternating current from the motor generator 55 into a direct current and supplies it to the battery 53 and the like.

  The electronic control unit 200 is composed of a digital computer and is connected to each other by a bi-directional bus 201. A ROM (read only memory) 202, a RAM (random access memory) 203, a CPU (microprocessor) 204, an input port 205, and an output port 206.

  The input port 205 includes an anode pressure sensor 211, a first flow sensor 212, a second flow sensor 213, a cathode pressure sensor 214, a water temperature sensor 215, a current sensor 216, a voltage sensor 217, a tank pressure sensor 218, and a large pressure sensor. An output signal from the atmospheric pressure sensor 219 or the like for detecting the atmospheric pressure is input via each corresponding AD converter 207. In addition, an output signal from the start switch 220 for determining whether the fuel cell system 100 is started or stopped is input to the input port 205. As described above, output signals of various sensors necessary for controlling the fuel cell system 100 are input to the input port 205.

  The output port 206 is connected to the hydrogen supply control valve 23 (shutoff valve 231, regulator 232 and injector 233), purge control valve 26, compressor 33, bypass control valve 35, cathode pressure control valve 38, via a corresponding drive circuit 208. Control components such as the cooling water pump 42, the first converter 51, the circuit breaker 52, the second converter 54, the motor generator 55, and the inverter 56 are electrically connected.

  The electronic control unit 200 outputs a control signal for controlling each control component from the output port 206 based on output signals of various sensors input to the input port 205.

  If the electronic control unit 200 determines that there is a system stop request based on the output signal of the start switch 220, the electronic control unit 200 completely stops the fuel cell system 100 after performing a predetermined stop process. Deterioration of the catalyst in the electrode of the single cell 1 due to the stack voltage (open circuit voltage) being maintained at a high voltage during the system stop period from when the fuel cell system 100 is completely stopped to when it is next started ( In order to suppress a high voltage deterioration), the oxygen remaining in the air passage 3 is consumed by power generation at the time of the system stop request, and the air passage 3 is almost filled with nitrogen. The hydrogen passage 2 is sealed with the passage filled with hydrogen. That is, the fuel cell system 100 is completely stopped with the shut-off valve 231, the purge control valve 26 and the cathode pressure control valve 38 being fully closed, and the bypass control valve 35 being fully open.

  As described above, the air passage 3 is hermetically sealed in a state where the inside of the air passage 3 is almost filled with nitrogen by the stop processing performed when the system is stopped. However, the air passage 3 entered the cathode offgas pipe 37 during the system stop period. Air gradually diffuses upstream and flows from the inlet and outlet of the air passage 3 through the cathode pressure control valve 38 and the bypass control valve 35. When air flows into the air passage 3 during the system stop period, the stack voltage gradually rises, and if left as it is, the high voltage deterioration of the single cell 1 occurs.

  In order to prevent the inflow of air into the air passage 3 during the system stop period, it is effective to provide the cathode pressure control valve 38 and the bypass control valve 35 with a high sealing function (seal function). However, if the cathode pressure control valve 38 and the bypass control valve 35 have a high sealing function, the cost increases correspondingly, which is not practical.

  Therefore, in the present embodiment, the stack voltage is detected periodically or continuously during the system stop period, and if the stack voltage is equal to or higher than the predetermined voltage, the fuel cell is set during the system stop period so that the anode pressure becomes the predetermined pressure. Hydrogen reduction is supplied to the stack 10 to perform voltage reduction control for reducing the stack voltage. FIG. 2 is a time chart for explaining the voltage drop control performed during the system stop period.

  The predetermined voltage is a voltage value appropriately selected from voltages that cause high voltage degradation of the single cell 1, that is, a voltage value lower than a voltage at which the catalyst in the electrode of the single cell 1 begins to deteriorate. (0.5 V (single cell voltage) × number of single cells).

  The predetermined pressure is the anode pressure when hydrogen necessary for reducing the stack voltage, which has been raised to a predetermined voltage, to a desired voltage (for example, 0 V) is supplied to the hydrogen passage 2, that is, flows into the air passage 3 during the system stop period. The pressure value is appropriately selected from pressure values equal to or higher than the anode pressure when hydrogen necessary for consuming oxygen in the air is supplied to the hydrogen passage 2. Since the anode pressure during the system stop period is almost atmospheric pressure, in this embodiment, the atmospheric pressure on the flat ground (standard atmospheric pressure; about 100 kPa) is set as the reference atmospheric pressure, and the anode pressure is stacked from the reference atmospheric pressure. The anode pressure (for example, 120 kPa) when hydrogen necessary for reducing the voltage to a desired voltage is supplied to the fuel cell stack 10 is set to a predetermined pressure.

  As shown in FIG. 2, when the voltage drop control is performed during the system stop period at time t1 and hydrogen is supplied to the fuel cell stack 10 until the anode pressure reaches a predetermined pressure, the cathode pressure during the system stop period is also increased. Since the atmospheric pressure is almost the atmospheric pressure, the hydrogen in the hydrogen passage 2 passes through the membrane electrode assembly 1a due to the pressure difference between the pressure in the hydrogen passage 2 (anode pressure) and the pressure in the air passage 3 (cathode pressure). And penetrates into the air passage 3. As a result, hydrogen that has permeated into the air passage 3 reacts with oxygen at the cathode electrode, and hydrogen and oxygen are consumed in the air passage 3 to decrease the anode pressure and the stack voltage (time t1 to t2).

  On the other hand, when the voltage drop control is performed during the system stop period, the hydrogen supplied from the high-pressure hydrogen tank 22 to the fuel cell stack 10 reacts with oxygen and is consumed. The remaining amount of hydrogen will decrease.

  Even if the voltage drop control is performed during the system stop period and the stack voltage is once lowered (time t2), air again flows into the air passage 3 after that, so that the stack voltage rises again (time). t2-t3). Therefore, if the system shutdown period becomes longer, the voltage drop control is performed a plurality of times during the system shutdown period. Therefore, as shown in FIG. 2 (C), the hydrogen remaining in the high-pressure hydrogen tank 22 is suspended during the system shutdown period. The amount gradually decreases. As a result, fuel may run out. In order to prevent such a fuel shortage, for example, when the remaining amount of hydrogen falls below a predetermined amount, the voltage drop control can be prohibited. However, after the voltage drop control is prohibited, the high voltage deterioration of the single cell 1 is prevented. It cannot be prevented.

  Therefore, when the voltage drop control is performed during the system stop period, the fuel cell system 100 is preferably stopped when the system is stopped, for example, according to the remaining amount of fuel gas when the system is stopped. It is desirable to notify the user of the time when the high pressure hydrogen tank 22 needs to be refilled with hydrogen. By notifying the user of the fuel cell system 100 when it is necessary to supply hydrogen and urging the user to supply hydrogen, it is possible to suppress the occurrence of fuel shortage and high voltage deterioration of the single cell 1 during the system stop period. it can.

  However, in the present embodiment, when the voltage drop control is performed, hydrogen is supplied to the fuel cell stack 10 until the anode pressure reaches a predetermined pressure, and it has been found that the following problems occur.

  That is, as shown in FIG. 2 (B), the atmospheric pressure changes depending on where the fuel cell system 100 is stopped or installed. Therefore, for example, when the fuel cell system 100 is stopped at a high altitude, the atmospheric pressure is lower than the standard atmospheric pressure on a flat ground (reference altitude) where the fuel cell system 100 is assumed to be normally used. Therefore, when the fuel cell system 100 is stopped at a place where the atmospheric pressure, such as a high altitude, is lower than the standard atmospheric pressure, the amount of hydrogen supply necessary to increase the anode pressure to a predetermined pressure is less than the level of the fuel cell system 100 It will be more than if it was stopped at.

  As a result, the remaining amount of hydrogen decreases earlier than expected during the system shutdown period, and there is a risk of running out of fuel earlier than the notified hydrogen replenishment time. In addition, when the fuel runs out, the voltage drop control cannot be performed, so that the high voltage deterioration of the single cell 1 may occur.

  Therefore, in the present embodiment, the hydrogen supply amount supplied to the fuel cell stack 10 during the voltage drop control during the system stop period can be accurately estimated according to the atmospheric pressure so that an appropriate hydrogen replenishment timing can be notified when the system is stopped. did. Hereinafter, the system stop control according to this embodiment will be described.

  FIG. 3 is a flowchart for explaining the system stop control according to this embodiment performed by the electronic control unit 200.

  In step S1, the electronic control unit 200 determines whether there is a system stop request based on the output signal of the start switch 220. If there is no system stop request, the electronic control unit 200 ends the system stop control, and if there is a system stop request, the electronic control unit 200 proceeds to the process of step S2.

  In step S2, the electronic control unit 200 performs a stop process. Specifically, the electronic control unit 200 fully closes the cathode pressure control valve 38, fully opens the bypass control valve 35, seals the air passage 3, and fully closes the purge control valve 26. While supplying hydrogen to the passage 2, power generation is continued for a predetermined time to consume oxygen in the air passage 3. When the electronic control unit 200 continues the power generation for a predetermined time, the electronic control unit 200 closes the shut-off valve 231 and proceeds to step S3.

  In step S3, the electronic control unit 200 calculates the remaining amount of hydrogen that can be supplied to the fuel cell stack 10 during the system stop period. In the present embodiment, the hydrogen amount in the high-pressure hydrogen tank 22 calculated based on the tank pressure detected by the tank pressure sensor 218 is used as the remaining amount of hydrogen. For example, the anode pressure sensor 211 is added to the hydrogen amount in the high-pressure hydrogen tank 22. A value obtained by adding the amount of hydrogen in the hydrogen supply pipe 21 calculated based on the anode pressure detected in step 1 may be used as the remaining amount of hydrogen.

  In step S4, the electronic control unit 200 reads the atmospheric pressure detected by the atmospheric pressure sensor 219.

  In step S5, when the voltage drop control is performed during the system stop period, the electronic control unit 200 uses the amount of hydrogen supplied to the fuel cell stack 10 by the one voltage drop control as an expected hydrogen supply amount. calculate. In the present embodiment, the electronic control unit 200 refers to the table of FIG. 4, and based on the atmospheric pressure read in step S4, the fuel cell stack 10 increases the anode pressure from the read atmospheric pressure to a predetermined pressure. The amount of hydrogen that needs to be supplied to is calculated as the expected hydrogen supply.

  Note that the method for calculating the expected hydrogen supply amount is not limited to this. For example, the amount of hydrogen that needs to be supplied to the fuel cell stack 10 in order to increase the anode pressure from the reference atmospheric pressure to a predetermined pressure is determined as the reference hydrogen. The expected hydrogen supply amount may be calculated by obtaining the supply amount in advance by experiments or the like and correcting the reference hydrogen supply amount based on the atmospheric pressure read in step S4. In this case, the correction amount added to the reference hydrogen supply amount becomes larger as the atmospheric pressure becomes lower than the reference atmospheric pressure, and the correction amount subtracted from the reference hydrogen supply amount as the atmospheric pressure becomes higher than the reference atmospheric pressure. Just make it bigger.

  In step S6, the electronic control unit 200 calculates the number of times that the voltage reduction control can be performed during the system stop period, that is, the number of times that the voltage reduction control can be performed, based on the remaining amount of hydrogen and the expected hydrogen supply amount. In this embodiment, the number of times that the voltage drop control can be performed is calculated by dividing the remaining hydrogen amount by the expected hydrogen supply amount, but the voltage drop is calculated from the remaining hydrogen amount and the expected hydrogen supply amount with reference to a map or the like. The number of times control can be performed may be calculated.

  In step S7, the electronic control unit 200 stops the system that can prevent the high voltage deterioration of the single cell 1 based on the number of times the voltage drop control can be performed and the high voltage deterioration prevention time per one voltage drop control. Calculate the upper limit of time. In this embodiment, the upper limit value of the system stop time is calculated by multiplying the number of times that the voltage drop control can be performed by the time that can prevent high voltage deterioration. The upper limit value of the system stop time may be calculated from the high voltage deterioration prevention possible time.

  The high voltage deterioration prevention possible time is the time during which the stack voltage can be maintained below the predetermined voltage after the voltage drop control is performed, and the time required for the stack voltage to rise again to the predetermined voltage after the voltage drop control is performed. The maximum is a time appropriately selected from that time. The high voltage degradation preventable time can be obtained in advance by experiments or the like. In this embodiment, the high voltage deterioration prevention time is a fixed value. For example, as the atmospheric pressure decreases, the amount of hydrogen supplied to the fuel cell stack 10 during the voltage drop control increases, and the high voltage deterioration prevention time also increases. Since it is thought that it becomes long, it is good also as a variable value which becomes long, so that atmospheric pressure becomes low.

  In step S8, the electronic control unit 200 determines the time when the high-pressure hydrogen tank 22 needs to be replenished based on the upper limit value of the system stop time by using a message such as “requires hydrogen filling within 3 days”. The user of the battery system 100 is notified and the fuel cell system 100 is stopped. As a notification method of the hydrogen replenishment time, a message may be displayed on a display, or data may be transmitted and displayed on a user's portable terminal or the like.

  In addition, when the fuel cell system 100 is mounted on a moving body such as a vehicle, it is necessary to leave the hydrogen necessary for the movement of the vehicle. It is desirable to notify when it is necessary to replenish. On the other hand, if the fuel cell system 100 is, for example, a stationary system and it is not necessary to move the fuel cell system 100 when hydrogen is replenished, the upper limit of the system stop time is set to the time when hydrogen replenishment is required. You may notify as.

  After notifying the high-pressure hydrogen tank 22 when hydrogen needs to be replenished in step S8 and stopping the fuel cell system 100, the electronic control unit 200 detects the stack voltage periodically or continuously to detect the stack voltage. If the voltage is equal to or higher than a predetermined voltage, voltage reduction control is performed to supply hydrogen to the fuel cell stack 10 during the system stop period so as to lower the stack voltage so that the anode pressure becomes a predetermined pressure.

  According to the present embodiment described above, the fuel cell stack 10 that generates electric power by an electrochemical reaction between hydrogen as fuel gas and air as oxidant gas, and a high-pressure hydrogen tank (fuel gas) for storing hydrogen A fuel gas supply / discharge device 20 for supplying and discharging hydrogen to and from the fuel cell stack 10, a voltage sensor 217 for detecting a stack voltage that is a voltage of the fuel cell stack 10, and a fuel cell stack 10, an anode pressure sensor 211 that detects the anode pressure that is the pressure of the hydrogen passage (fuel gas passage) 2, a tank pressure sensor (fuel gas source pressure sensor) 218 that detects the pressure of the high-pressure hydrogen tank 22, and atmospheric pressure An electronic control unit (control device) 200 for controlling the fuel cell system 100 including an atmospheric pressure sensor 219 for detecting the If the stack voltage detected during the stop period of the system 100 is equal to or higher than the predetermined voltage, the voltage reduction control for supplying hydrogen to the fuel cell stack 10 during the stop period so as to reduce the stack voltage so that the anode pressure becomes the predetermined pressure. A voltage reduction control execution unit that performs the following, a fuel gas remaining amount calculation unit that calculates the remaining amount of hydrogen based on at least the pressure of the high-pressure hydrogen tank 22, and an anode pressure that is predetermined when the voltage reduction control is performed during the stop period A fuel gas supply amount estimation unit that estimates an expected hydrogen supply amount required to increase the pressure to a pressure, and an executable number calculation unit that calculates the number of times the voltage drop control can be performed based on the remaining amount of hydrogen and the expected hydrogen supply amount And the high-pressure hydrogen tank 22 needs to be replenished with hydrogen based on the possible number of times and the time during which the stack voltage can be maintained below the predetermined voltage after the voltage drop control is performed. The fuel gas supply amount estimation unit estimates the expected hydrogen supply amount based on the atmospheric pressure detected by the atmospheric pressure sensor 219, or the stop period. When the voltage drop control is performed, the reference hydrogen supply amount necessary for increasing the anode pressure from the preset reference atmospheric pressure (reference pressure) to the predetermined pressure is set to the atmospheric pressure detected by the atmospheric pressure sensor 219. The predicted hydrogen supply amount is estimated based on the correction.

  Therefore, the amount of hydrogen supplied to the fuel cell stack 10 during the voltage drop control during the system stop period can be accurately estimated according to the atmospheric pressure at the place where the fuel cell system 100 is stopped. As a result, it is possible to notify the user of the fuel cell system 100 of an appropriate hydrogen replenishment time and promote hydrogen replenishment, thereby suppressing the occurrence of fuel shortage and high voltage deterioration of the single cell 1 during the system stop period. can do.

  Further, high voltage deterioration of the single cell 1 during the system stop period can be suppressed without giving the cathode pressure control valve 38 and the bypass control valve 35 a high sealing function, and an increase in cost can be suppressed.

  The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

  For example, in the above embodiment, the hydrogen replenishment time is notified when the system is stopped. However, the hydrogen replenishment time may be notified by transmitting data to, for example, a portable terminal during the system stop period.

  In the above embodiment, various operations for notifying the hydrogen replenishment timing are performed after the stop process is performed. However, if the amount of hydrogen consumed by the stop process can be predicted, the system is stopped. Various calculations for notifying the hydrogen replenishment timing are performed in parallel with the stop process, using the hydrogen amount in the high-pressure hydrogen tank 22 at the time of request minus the expected hydrogen consumption by the stop process as the remaining amount of hydrogen. Also good.

  In the above embodiment, the hydrogen non-circulation type fuel cell system 100 has been described as an example. However, a hydrogen circulation type fuel cell system may be used.

10 Fuel Cell Stack 20 Fuel Gas Supply / Exhaust Device 22 High Pressure Hydrogen Tank (Fuel Gas Source)
100 Fuel Cell System 200 Electronic Control Unit (Control Device)
211 Anode pressure sensor 217 Voltage sensor 218 Tank pressure sensor (fuel gas source pressure sensor)
219 Atmospheric pressure sensor

Claims (1)

A fuel cell stack that generates electric power by an electrochemical reaction between a fuel gas and an oxidant gas;
A fuel gas supply / discharge device for supplying and discharging fuel gas to and from the fuel cell stack, including a fuel gas source for storing fuel gas;
A voltage sensor for detecting a stack voltage which is a voltage of the fuel cell stack;
An anode pressure sensor that detects an anode pressure that is a pressure of a fuel gas passage in the fuel cell stack;
A fuel gas source pressure sensor for detecting the pressure of the fuel gas source;
An atmospheric pressure sensor for detecting atmospheric pressure;
A control device for a fuel cell system comprising:
If the stack voltage detected during the stop period of the fuel cell system is equal to or higher than a predetermined voltage, the stack voltage is lowered by supplying fuel gas to the fuel cell stack during the stop period so that the anode pressure becomes a predetermined pressure. A voltage drop control execution unit for performing voltage drop control to be performed;
A fuel gas remaining amount calculating section for calculating a fuel gas remaining amount based on at least the pressure of the fuel gas source;
A fuel gas supply amount estimation unit configured to estimate a fuel gas supply amount necessary to increase the anode pressure to the predetermined pressure when the voltage drop control is performed during the stop period;
Based on the fuel gas remaining amount and the fuel gas supply amount, a feasible number calculating unit that calculates the feasible number of times of the voltage drop control;
A notification unit for notifying the fuel gas source of the time when the fuel gas needs to be replenished based on the possible number of times and the time during which the stack voltage can be maintained below the predetermined voltage after the voltage drop control is performed; ,
With
The fuel gas supply amount estimation unit includes:
The fuel gas supply amount is estimated based on the atmospheric pressure detected by the atmospheric pressure sensor, or when the voltage drop control is performed during a stop period, the anode pressure is set to the predetermined pressure from a preset reference pressure. Correcting the reference fuel gas supply amount necessary for increasing the pressure up to the atmospheric pressure detected by the atmospheric pressure sensor to estimate the fuel gas supply amount,
A control apparatus for a fuel cell system.

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