JP2015076246A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure the drainage of an anode gas passage in a fuel cell.SOLUTION: A fuel cell system for generating power by supplying anode gas and cathode gas to a fuel cell includes pulsation operation means for pulsating the pressure of anode gas supplied to a fuel cell, with a pulsation width and a step-up variation rate that are set upon drainage request of the fuel cell on the anode side, control means for limiting the pulsation width to small depending on the operation state of the fuel cell system, and correction means for correcting the step-up variation rate to increase when the pulsation width is limited to small by the limitation means.

Description

  The present invention relates to a fuel cell system.

  As a conventional fuel cell system, there is one that performs a pulsation operation that pulsates the pressure of an anode gas (see Patent Document 1).

JP 2005-243476 A

  In a fuel cell system that performs pulsation operation, in order to ensure drainability in the anode gas flow path in the fuel cell, the pulsation width during pulsation operation and the rate of change in pressure when increasing the pressure of the anode gas during pulsation operation Must be set appropriately.

  Thus, in the fuel cell system currently under development, the pulsation width is basically set according to the required power generation amount of the fuel cell. Also, the rate of change in pressure increase is set to the rate of change that can secure the gas flow rate required to discharge the generated water when the anode gas is boosted with the pulsation width set according to the required power generation amount of this fuel cell. Was.

  However, depending on the operating state of the fuel cell system, the pulsation width is limited, and it may be necessary to make the pulsation width smaller than the pulsation width set according to the required power generation amount of the fuel cell.

  Then, even though the pulsation width is limited, sufficient drainage is ensured if the anode gas is boosted at the rate of change in pressure according to the pulsation width set according to the required power generation amount of the fuel cell. There is a risk that it will not be possible.

  The present invention has been made paying attention to such problems, and even if the pulsation width is limited according to the operating state of the fuel cell system, the drainage on the anode side in the fuel cell is improved. An object of the present invention is to provide a fuel cell system that can be secured.

  According to an aspect of the present invention, pulsation operation means for pulsating the pressure of anode gas supplied to a fuel cell with a pulsation width and a rate of change in pressure set according to a drainage demand on the anode side of the fuel cell, and a fuel cell A fuel cell system is provided that includes a limiting unit that limits the pulsation width to a small value according to the operating state of the system, and a correction unit that increases and corrects the rate of change in pressure increase when the pulsation width is limited by the limiting unit. The

  According to this aspect, when the pulsation width set according to the drainage demand on the anode side of the fuel cell is limited to be small according to the operation state of the fuel cell system, the rate of change in pressure increase is corrected. It is possible to increase the pressure of the anode gas at an appropriate rate of change in pressure according to the limited pulsation width. Therefore, drainage on the anode side in the fuel cell can be ensured.

1 is a schematic perspective view of a fuel cell according to an embodiment of the present invention. It is II-II sectional drawing of the fuel cell of FIG. 1 is a schematic view of a fuel cell system according to an embodiment of the present invention. It is a block diagram which shows the detailed structure of the anode pressure control part by one Embodiment of this invention. It is a block diagram which shows the detailed structure of a hydrogen partial pressure lower limit calculating part. It is a block diagram which shows the detailed structure of a pressure | voltage rise change rate calculating part. It is a flowchart which shows the detailed structure of a pulsation control part. It is a time chart explaining operation | movement of the anode pressure control part by one Embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  In a fuel cell, an electrolyte membrane is sandwiched between an anode electrode (fuel electrode) and a cathode electrode (oxidant electrode), an anode gas containing hydrogen in the anode electrode (fuel gas), and a cathode gas containing oxygen in the cathode electrode (oxidant) Electricity is generated by supplying gas. The electrode reaction that proceeds in both the anode electrode and the cathode electrode is as follows.

Anode electrode: 2H ₂ → 4H ⁺ + 4e ⁻ (1)
Cathode electrode: 4H ⁺ + 4e ⁻ + O ₂ → 2H ₂ O (2)

  The fuel cell generates an electromotive force of about 1 volt by the electrode reactions (1) and (2).

  1 and 2 are diagrams illustrating the configuration of a fuel cell 10 according to an embodiment of the present invention. FIG. 1 is a schematic perspective view of the fuel cell 10. FIG. 2 is a II-II cross-sectional view of the fuel cell 10 of FIG.

  The fuel cell 10 is configured by arranging an anode separator 12 and a cathode separator 13 on both front and back surfaces of the MEA 11.

  The MEA 11 includes an electrolyte membrane 111, an anode electrode 112, and a cathode electrode 113. The MEA 11 has an anode electrode 112 on one surface of the electrolyte membrane 111 and a cathode electrode 113 on the other surface.

  The electrolyte membrane 111 is a proton-conductive ion exchange membrane formed of a fluorine-based resin. The electrolyte membrane 111 exhibits good electrical conductivity in a wet state.

  The anode electrode 112 includes a catalyst layer 112a and a gas diffusion layer 112b. The catalyst layer 112a is in contact with the electrolyte membrane 111. The catalyst layer 112a is formed of carbon black particles carrying platinum or platinum. The gas diffusion layer 112b is provided outside the catalyst layer 112a (on the opposite side of the electrolyte membrane 111) and is in contact with the anode separator 12. The gas diffusion layer 112b is formed of a member having sufficient gas diffusibility and conductivity, and is formed of, for example, a carbon cloth woven with yarns made of carbon fibers.

  Similarly to the anode electrode 112, the cathode electrode 113 includes a catalyst layer 113a and a gas diffusion layer 113b.

  The anode separator 12 is in contact with the gas diffusion layer 112b. The anode separator 12 has a plurality of groove-shaped anode gas flow passages 121 for supplying anode gas to the anode electrode 112.

  The cathode separator 13 is in contact with the gas diffusion layer 113b. The cathode separator 13 has a plurality of groove-like cathode gas flow paths 131 for supplying cathode gas to the cathode electrode 113.

  The anode gas flowing through the anode gas flow path 121 and the cathode gas flowing through the cathode gas flow path 131 flow in opposite directions in parallel to each other. You may make it flow in the same direction in parallel with each other.

  When such a fuel cell is used as a power source for automobiles, a large amount of electric power is required. Therefore, the fuel cell is used as a fuel cell stack 1 in which several hundred fuel cells are stacked. Then, the fuel cell system 100 that supplies the anode gas and the cathode gas to the fuel cell stack 1 is configured, and electric power for driving the vehicle is taken out.

  FIG. 3 is a schematic diagram of the fuel cell system 100 according to the first embodiment of the present invention.

  The fuel cell system 100 includes a fuel cell stack 1, a cathode gas supply / discharge device 2, an anode gas supply / discharge device 3, a stack cooling device 4, a power system 5, and a controller 6.

  The fuel cell stack 1 is formed by stacking a plurality of fuel cells 10 and receives power supplied from an anode gas and a cathode gas to generate electric power necessary for driving the vehicle. The fuel cell stack 1 includes an anode electrode side output terminal 1a and a cathode electrode side output terminal 1b as terminals for taking out electric power.

  The cathode gas supply / discharge device 2 includes a cathode gas supply passage 21, a cathode gas discharge passage 22, a filter 23, an airflow sensor 24, a cathode compressor 25, a cathode pressure sensor 26, and a water recovery device (Water Recovery Device; (Hereinafter referred to as “WRD”) 27 and a cathode pressure regulating valve 28. The cathode gas supply / discharge device 2 supplies the cathode gas to the fuel cell stack 1 and discharges the cathode off-gas discharged from the fuel cell stack 1 to the outside air.

  The cathode gas supply passage 21 is a passage through which the cathode gas supplied to the fuel cell stack 1 flows. The cathode gas supply passage 21 has one end connected to the filter 23 and the other end connected to the cathode gas inlet hole of the fuel cell stack 1.

  The cathode gas discharge passage 22 is a passage through which the cathode off gas discharged from the fuel cell stack 1 flows. One end of the cathode gas discharge passage 22 is connected to the cathode gas outlet hole of the fuel cell stack 1, and the other end is an open end. The cathode off gas is a mixed gas of the cathode gas and water vapor generated by the electrode reaction.

  The filter 23 removes foreign matters in the cathode gas taken into the cathode gas supply passage 21.

  The air flow sensor 24 is provided in the cathode gas supply passage 21 upstream of the cathode compressor 25. The air flow sensor 24 detects the flow rate of the cathode gas supplied to the cathode compressor 25 and finally supplied to the fuel cell stack 1.

  The cathode compressor 25 is provided in the cathode gas supply passage 21. The cathode compressor 25 takes air (outside air) as cathode gas through the filter 23 into the cathode gas supply passage 21 and supplies it to the fuel cell stack 1.

  The cathode pressure sensor 26 is provided in the cathode gas supply passage 21 between the cathode compressor 25 and the WRD 27. The cathode pressure sensor 26 detects the pressure of the cathode gas in the vicinity of the cathode gas inlet of the WRD 27. Hereinafter, the detection value of the cathode pressure sensor 26 is referred to as a detected cathode pressure.

  The WRD 27 is connected to each of the cathode gas supply passage 21 and the cathode gas discharge passage 22, collects moisture in the cathode off-gas flowing through the cathode gas discharge passage 22, and cathode that flows through the cathode gas supply passage 21 with the collected moisture. Humidify the gas.

  The cathode pressure regulating valve 28 is provided in the cathode gas discharge passage 22 downstream of the WRD 27. The cathode pressure regulating valve 28 is controlled to be opened and closed by the controller 6 and adjusts the pressure of the cathode gas supplied to the fuel cell stack 1 to a desired pressure. It should be noted that a restriction such as an orifice may be provided without providing the cathode pressure regulating valve 28.

  The anode gas supply / discharge device 3 supplies anode gas to the fuel cell stack 1 and discharges anode off-gas discharged from the fuel cell stack 1 to the cathode gas discharge passage 22. The anode gas supply / discharge device 3 includes a high pressure tank 31, an anode gas supply passage 32, an anode pressure regulating valve 33, an anode pressure sensor 34, an anode gas discharge passage 35, a buffer tank 36, a purge passage 37, and a purge. And a valve 38.

  The high pressure tank 31 stores the anode gas supplied to the fuel cell stack 1 in a high pressure state.

  The anode gas supply passage 32 is a passage for supplying the anode gas discharged from the high-pressure tank 31 to the fuel cell stack 1. The anode gas supply passage 32 has one end connected to the high pressure tank 31 and the other end connected to the anode gas inlet hole of the fuel cell stack 1.

  The anode pressure regulating valve 33 is provided in the anode gas supply passage 32. The anode pressure regulating valve 33 is controlled to be opened and closed by the controller 6 and adjusts the pressure of the anode gas supplied to the fuel cell stack 1 to a desired pressure.

  The anode pressure sensor 34 is provided in the anode gas supply passage 32 downstream from the anode pressure regulating valve 33 and detects the pressure of the anode gas supplied to the fuel cell stack 1 (hereinafter referred to as “anode pressure”). Hereinafter, the detected value of the anode pressure sensor 34 is referred to as “detected anode pressure”.

  The anode gas discharge passage 35 has one end connected to the anode gas outlet hole of the fuel cell stack 1 and the other end connected to the buffer tank 36. In the anode gas discharge passage 35, surplus anode gas that has not been used in the electrode reaction, inert gas containing nitrogen or moisture (product water or water vapor) that has permeated from the cathode electrode side to the anode electrode side, and The mixed gas (hereinafter referred to as “anode off gas”) is discharged.

  The buffer tank 36 temporarily stores the anode off gas that has flowed through the anode gas discharge passage 35. The anode off gas stored in the buffer tank 36 is discharged to the cathode gas discharge passage 22 through the purge passage 37 when the purge valve 38 is opened.

  The purge passage 37 has one end connected to the first anode gas discharge passage 35 and the other end connected to the cathode gas discharge passage 22.

  The purge valve 38 is provided in the purge passage 37. The purge valve 38 is controlled to be opened and closed by the controller 6 and controls the flow rate of the anode off gas discharged from the anode gas discharge passage 35 to the cathode gas discharge passage 22.

  The anode off gas discharged to the cathode gas discharge passage 22 via the anode gas discharge passage 35 is mixed with the cathode off gas in the cathode gas discharge passage 22 and discharged to the outside of the fuel cell system 100. Since the anode off gas contains surplus hydrogen that has not been used for the electrode reaction, the hydrogen concentration in the exhaust gas is determined in advance by mixing with the cathode off gas and discharging it to the outside of the fuel cell system 100. It is made to become below the predetermined concentration.

  The stack cooling device 4 is a device that cools the fuel cell stack 1 and maintains the fuel cell stack 1 at a temperature suitable for power generation. The stack cooling device 4 includes a cooling water circulation passage 41, a radiator 42, a bypass passage 43, a three-way valve 44, a circulation pump 45, a PTC heater 46, an inlet water temperature sensor 47, and an outlet water temperature sensor 48. .

  The cooling water circulation passage 41 is a passage through which cooling water for cooling the fuel cell stack 1 circulates, and one end is connected to the cooling water inlet hole of the fuel cell stack 1 and the other end is the cooling water of the fuel cell stack 1. Connected to the outlet hole.

  The radiator 42 is provided in the cooling water circulation passage 41. The radiator 42 cools the cooling water discharged from the fuel cell stack 1.

  The bypass passage 43 has one end connected to the coolant circulation passage 41 and the other end connected to the three-way valve 44 so that the coolant can be circulated by bypassing the radiator 42.

  The three-way valve 44 is provided in the cooling water circulation passage 41 on the downstream side of the radiator 42. The three-way valve 44 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 predetermined temperature, the cooling water is circulated so that the cooling water discharged from the fuel cell stack 1 is supplied again to the fuel cell stack 1 via the radiator 42. Switch routes. On the other hand, when the temperature of the cooling water is lower than the predetermined temperature, the cooling water discharged from the cooling water discharged from the fuel cell stack 1 flows through the bypass passage 43 without passing through the radiator 42 and is again fuel cell stack. The circulation path of the cooling water is switched so as to be supplied to 1.

  The circulation pump 45 is provided in the cooling water circulation passage 41 on the downstream side of the three-way valve 44 and circulates the cooling water.

  The PTC heater 46 is provided in the bypass passage 43. The PTC heater 46 is energized when the fuel cell stack 1 is warmed up to raise the temperature of the cooling water.

  The inlet water temperature sensor 47 is provided in the cooling water circulation passage near the cooling water inlet hole of the fuel cell stack 1. The inlet water temperature sensor 47 detects the temperature of cooling water flowing into the fuel cell stack 1 (hereinafter referred to as “inlet water temperature”).

  The outlet water temperature sensor 48 is provided in the cooling water circulation passage in the vicinity of the cooling water outlet hole of the fuel cell stack 1. The outlet water temperature sensor 48 detects the temperature of the cooling water discharged from the fuel cell stack 1 (hereinafter referred to as “outlet water temperature”).

  The power system 5 includes a current sensor 51, a voltage sensor 52, a traveling motor 53, an inverter 54, a battery 55, and a DC / DC converter 56.

  The current sensor 51 detects a current taken out from the fuel cell stack 1 (hereinafter referred to as “output current”).

  The voltage sensor 52 detects an inter-terminal voltage (hereinafter referred to as “output voltage”) between the anode electrode side output terminal 1a and the cathode electrode side output terminal 1b. Further, it is preferable that the voltage of each fuel cell 10 constituting the fuel cell stack 1 can be detected. Further, the voltage may be detected every two or more sheets.

  The travel motor 53 is a three-phase AC synchronous motor in which a permanent magnet is embedded in a rotor and a stator coil is wound around a stator. The travel motor 53 functions as an electric motor that is driven to rotate by receiving electric power supplied from the fuel cell stack 1 and the battery 55, and power generation that generates electromotive force at both ends of the stator coil during deceleration of the vehicle in which the rotor is rotated by external force. Function as a machine.

  The inverter 54 includes a plurality of semiconductor switches such as IGBTs (Insulated Gate Bipolar Transistors). The semiconductor switch of the inverter 54 is controlled to be opened / closed by the controller 6, whereby DC power is converted into AC power or AC power is converted into DC power. When the drive motor 53 functions as an electric motor, the inverter 54 converts the combined DC power of the power generated by the fuel cell stack 1 and the output power of the battery 55 into three-phase AC power and supplies the three-phase AC power to the drive motor 53. On the other hand, when the traveling motor 53 functions as a generator, the regenerative power (three-phase alternating current power) of the traveling motor 53 is converted into direct current power and supplied to the battery 55.

  The battery 55 charges the surplus power generated by the fuel cell stack 1 (output current × output voltage) and the regenerative power of the traveling motor 53. The electric power charged in the battery 55 is supplied to auxiliary equipment such as the cathode compressor 25 and the traveling motor 53 as necessary.

  The DC / DC converter 56 is a bidirectional voltage converter that raises and lowers the output voltage of the fuel cell stack 1. By controlling the output voltage of the fuel cell stack 1 by the DC / DC converter 56, the output current of the fuel cell stack 1, and thus the generated power, is controlled.

  The controller 6 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface).

  In addition to the airflow sensor 24 and the like described above, the controller 6 includes an accelerator stroke sensor 61 that detects the amount of depression of the accelerator pedal (hereinafter referred to as “accelerator operation amount”), an outside air temperature sensor 62 that detects the outside air temperature, and the like. Signals from various sensors for detecting the operating state of the fuel cell system 100 are input.

  The controller 6 calculates the target output current of the fuel cell stack 1 based on the operating state of the fuel cell system 100. Specifically, the target output current of the fuel cell stack 1 is calculated based on the required power of the traveling motor 53, the required power of auxiliary equipment such as the cathode compressor 25, and the charge / discharge request of the battery 55.

  Then, the controller 6 controls the output voltage of the fuel cell stack 1 by the DC / DC converter 56 so that the output current of the fuel cell stack 1 becomes the target output current, and supplies the electric power necessary for the traveling motor 53 and the auxiliary machinery. Supply. The controller 6 controls the flow rate and pressure of the cathode gas supplied to the fuel cell stack 1 according to the target output current. Specifically, as the target output current increases, the flow rate and pressure of the cathode gas supplied to the fuel cell stack 1 are increased.

  The controller 6 also determines the temperature in the buffer tank 36 (hereinafter referred to as “buffer”) based on the outside air temperature when the fuel cell system 100 is started and the operating state of the fuel cell system (for example, the outlet water temperature) after the start. It is detected by estimating the tank temperature. Note that a temperature sensor may be directly provided in the buffer tank 36 to detect the buffer tank temperature.

  Further, the controller 6 controls the cathode compressor 25, the circulation pump 45, and the like so that the wetness (water content) of the electrolyte membrane 111 becomes a wetness suitable for power generation. Specifically, the internal impedance (HFR; High Frequency Resistance) of the fuel cell stack 1 correlated with the wetness of the electrolyte membrane 111 is calculated by, for example, the alternating current impedance method, and the HFR becomes a target value. The cathode compressor 25 and the circulation pump 45 are controlled.

  Further, the controller 6 performs a pulsating operation that periodically increases or decreases the anode pressure based on the operating state of the fuel cell system 100. In the pulsation operation, the anode pressure is periodically raised and lowered within the range of the pulsation upper limit pressure and the pulsation lower limit pressure set according to the target output current of the fuel cell stack 1 to pulsate the anode pressure. By performing such pulsation operation, the liquid water in the anode gas passage 121 is discharged to the anode gas discharge passage 35 when the anode pressure is increased, and the drainage property in the anode gas passage 121 is secured.

  Here, in order to ensure drainage by pulsation operation, it is necessary to appropriately set the pulsation width and the anode pressure increase rate (pressure increase rate) during pulsation operation.

  The amount of liquid water in the anode gas passage 121 tends to increase as the target output current of the fuel cell stack 1 increases. For this reason, the pulsation width is basically set to increase as the target output current of the fuel cell stack 1 increases. When the anode pressure is increased by the pulsation width set in accordance with the target output current, the gas flow rate necessary for discharging the liquid water in the anode gas channel 121 can be secured. The rate of change was set.

  However, depending on the operating state of the fuel cell system 100, the anode pressure may not be increased or decreased to the pulsation upper limit pressure or the pulsation lower limit pressure set according to the target output current due to various limitations. That is, the actual pulsation width may be limited to be smaller than the pulsation width set according to the target output current.

  Even if the pulsation width is limited to a small value, if the rate of change in pressure increase of the anode pressure is set to the rate of change in pressure that can ensure drainage with the pulsation width set according to the target output current, May not be secured.

  Therefore, in the present embodiment, when the pulsation width is limited to be smaller than the pulsation width set according to the target output current, the pressure increase rate is increased by correcting the pressure increase rate to increase. did. Thereby, even if it was a case where the pulsation width | variety was restrict | limited small, the drainage of the anode gas flow path 121 was ensured.

  FIG. 4 is a block diagram showing a detailed configuration of the anode pressure control unit 7 according to the present embodiment.

  The anode pressure control unit 7 includes a pulsation lower limit pressure calculation unit 71, a pulsation upper limit pressure calculation unit 72, a pressure increase change rate calculation unit 73, and a pulsation control unit 74.

  The detected cathode pressure, atmospheric pressure, HFR, inlet water temperature, and outlet water temperature are input to the pulsation lower limit pressure calculation unit 71. Based on these input values, the pulsation lower limit pressure calculation unit 71 calculates a target value (hereinafter referred to as “pulsation lower limit pressure”) of the anode pressure on the lower limit side during the pulsation operation. Hereinafter, the pulsation lower limit pressure calculation unit 71 will be described in detail.

  The pulsation lower limit pressure calculation unit 71 includes a hydrogen partial pressure lower limit value calculation unit 711 and a pulsation lower limit pressure setting unit 712.

  The hydrogen partial pressure lower limit calculation unit 711 calculates a lower limit value of the anode pressure (hereinafter referred to as “hydrogen partial pressure lower limit value”) necessary to ensure the hydrogen partial pressure in the anode gas flow path 121.

  Impurities such as nitrogen and moisture (liquid water and water vapor) permeate into the anode gas channel 121 from the cathode gas channel 131 through the MEA 11. The amount of impurities permeated increases as the temperature of the fuel cell stack 1 increases. Further, the saturated water vapor amount increases as the temperature of the fuel cell stack 1 increases. Therefore, the higher the temperature of the fuel cell stack 1, the higher the partial pressure of the impurity gas in the anode gas channel 121 and the lower the hydrogen partial pressure. If the hydrogen partial pressure becomes too low, the hydrogen concentration in the power generation region of the anode electrode 112 will decrease. If power generation is continued in this state, the fuel cell 10 may be deteriorated.

  Therefore, in this embodiment, the hydrogen partial pressure lower limit value is calculated as the lower limit value of the anode pressure necessary to ensure the hydrogen partial pressure in the anode gas flow path 121, and the anode pressure is lower than the hydrogen partial pressure lower limit value. I try not to.

  FIG. 5 is a block diagram illustrating a detailed configuration of the hydrogen partial pressure lower limit value calculation unit 711.

  The hydrogen partial pressure lower limit value calculation unit 711 includes a basic lower limit value calculation unit 7111, a correction coefficient calculation unit 7112, and a hydrogen partial pressure lower limit value calculation unit 7113.

  The basic lower limit calculator 7111 receives the inlet water temperature and the outlet water temperature. The basic lower limit calculator 7111 calculates a basic lower limit based on the inlet water temperature and the outlet water temperature with reference to the map shown in FIG. As shown in the map of FIG. 5, the basic lower limit value increases as the inlet water temperature increases and the outlet water temperature increases. That is, the basic lower limit value increases as the temperature of the fuel cell stack 1 increases. This is because, as described above, the hydrogen partial pressure in the anode gas flow path 121 relatively decreases as the temperature of the fuel cell stack 1 increases.

  HFR is input to the correction coefficient calculation unit 7112. The correction coefficient calculator 7112 calculates a correction coefficient based on the HFR with reference to the table of FIG. As shown in the table of FIG. 5, the correction coefficient becomes larger when the HFR is small. This is because it is considered that the smaller the HFR, the higher the moisture content of the electrolyte membrane 111 and the greater the amount of water in the anode gas 121 flow path.

  The hydrogen partial pressure lower limit calculation unit 7113 calculates a hydrogen hydrogen partial pressure lower limit value obtained by adding the atmospheric pressure to the gauge hydrogen partial pressure lower limit value obtained by multiplying the basic lower limit value by a correction coefficient and converting it to an absolute pressure.

  Returning to FIG. 4 again, the pulsation lower limit pressure setting unit 712 of the pulsation lower limit pressure calculation unit 71 will be described.

  The detected cathode pressure and the hydrogen partial pressure lower limit value are input to the pulsation lower limit pressure setting unit 712. The pulsation lower limit pressure setting unit 712 sets the larger one of these two input values as the pulsation lower limit pressure. The pulsation lower limit pressure setting unit 712 normally sets the detected cathode pressure as the pulsation lower limit pressure. When the hydrogen partial pressure lower limit increases in accordance with the operating state of the fuel cell system 100 and becomes larger than the detected cathode pressure, the hydrogen partial pressure lower limit is set as the pulsation lower limit pressure to ensure the hydrogen partial pressure. To do.

  Atmospheric pressure, detected cathode pressure, target output current, and HFR are input to the pulsation upper limit pressure calculation unit 72. The pulsation upper limit pressure calculation unit 72 calculates a target value of the anode pressure on the upper limit side during pulsation operation (hereinafter referred to as “pulsation upper limit pressure”) based on these input values. Hereinafter, the pulsation upper limit pressure calculation unit 72 will be described in detail.

  The pulsation upper limit pressure calculation unit 72 includes a system upper limit value calculation unit 721, a membrane protection upper limit value calculation unit 722, a pulsation width calculation unit 723, a basic pulsation upper limit pressure calculation unit 724, and a pulsation upper limit pressure setting unit 725. Prepare.

  The atmospheric pressure is input to the system upper limit value calculation unit 721. The system upper limit value calculation unit 721 is obtained by adding a predetermined system pressure resistance to the atmospheric pressure, and an upper limit value of the anode pressure necessary for ensuring the durability of the fuel cell system 100 (hereinafter referred to as “system upper limit value”). Calculate as The system pressure resistance is a predetermined value determined according to the pressure resistance performance of the fuel cell stack 1, the anode gas supply passage 32, and the like. That is, the system upper limit value is a limit value on the upper limit side of the anode pressure for preventing the pressure exceeding the pressure resistance performance from being applied to the fuel cell stack 1, the anode gas supply passage 32, and the like.

  The detected cathode pressure is input to the membrane protection upper limit calculation unit 722. The membrane protection upper limit value calculation unit 722 is obtained by adding a predetermined allowable transmembrane pressure to the detected cathode pressure to obtain an upper limit value of the anode pressure necessary for ensuring the durability of the electrolyte membrane 111 (hereinafter referred to as “membrane protection upper limit value”). Calculated as “value”). The membrane protection upper limit value is a limit value on the upper limit side of the anode pressure so that the differential pressure between the anode side and the cathode side in the fuel cell stack 1 does not become an excessive value that degrades the electrolyte membrane 111. It is.

  The target output current and HFR are input to the pulsation width calculator 723. The pulsation width calculation unit 723 calculates the pulsation width based on the target output current and the HFR with reference to the map shown in FIG. As shown in the map of FIG. 4, the pulsation width increases as the target output current increases and as the HFR decreases. That is, the larger the amount of water in the fuel cell stack 1, the larger the amount.

  The basic pulsation upper limit pressure calculation unit 724 receives the pulsation width and the pulsation lower limit pressure. The basic pulsation upper limit pressure calculation unit 724 calculates a value obtained by adding the pulsation lower limit pressure to the pulsation width as the basic pulsation upper limit pressure.

  The pulsation upper limit pressure setting unit 725 receives the system upper limit value, the membrane protection upper limit value, and the basic pulsation upper limit pressure. The pulsation upper limit pressure setting unit 725 sets the smallest one of these three input values as the pulsation upper limit pressure. The pulsation upper limit pressure setting unit 725 normally sets the basic pulsation upper limit pressure as the pulsation upper limit pressure. When the basic pulsation upper limit pressure becomes larger than the system upper limit value or the membrane protection upper limit value, the system upper limit value or the membrane protection upper limit value is set as the pulsation upper limit pressure.

  As described above, when the system upper limit value or the membrane protection upper limit value is set as the pulsation upper limit pressure, the actual pulsation width is limited to be smaller than the pulsation width set according to the target output current.

  The pulsation upper limit pressure, the pulsation lower limit pressure, the buffer tank temperature, the inlet water temperature, and the outlet water temperature are input to the pressure increase change rate calculation unit 73. Based on these input values, the step-up change rate calculation unit 73 calculates a step-up change rate (step-up speed) when the anode pressure is increased during pulsation operation. Hereinafter, the step-up change rate calculation unit 73 will be described in detail with reference to FIG.

  FIG. 6 is a block diagram showing a detailed configuration of the step-up change rate calculation unit 73.

  The step-up change rate calculation unit 73 includes a reference step-up change rate calculation unit 731, a correction value calculation unit 732, a temperature correction coefficient calculation unit 733, and a step-up change rate calculation unit 734.

  The pulsation upper limit pressure is input to the reference boost change rate calculation unit 731. First, the reference pressure increase rate calculating unit 731 multiplies a predetermined drainage required volume flow rate by a predetermined conversion coefficient to calculate a pressure increase rate necessary for making the anode gas supply flow rate the drainage required volume flow rate under atmospheric pressure. To do.

  When the pulsation operation is performed with the pulsation width set according to the target output current, the required drainage volume flow rate is the lowest in the fuel cell stack 1 in order to obtain the gas flow rate necessary for ensuring drainage of the anode gas passage 121. This is the supply flow rate of the anode gas that must be supplied in a limited amount. In the present embodiment, the required drainage volume flow rate is set to a predetermined value determined in advance through experiments or the like, but may be increased as the target output current increases. The conversion coefficient is also set to a predetermined value determined in advance in an experiment or the like.

  The rate of change in pressure obtained by multiplying the required drainage volume flow rate by a conversion coefficient is a change rate for obtaining a gas flow rate at which the flow rate of the anode gas supplied to the fuel cell stack 1 becomes the required drainage volume flow rate at atmospheric pressure. is there. Since the gas flow rate decreases as the anode pressure increases, in order to obtain a gas flow rate corresponding to the required drainage volume flow rate, it is necessary to increase the pressure increase rate as the pressure increases. For this reason, in this embodiment, the pressure increase rate obtained by multiplying the required drainage volume flow rate by the conversion coefficient is multiplied by the pressure correction coefficient obtained by dividing the pulsation upper limit pressure by the reference pressure (atmospheric pressure). To do.

  The correction value calculation unit 732 receives the pulsation upper limit pressure, the pulsation lower limit pressure, and the pulsation width. The correction value calculation unit 732 is a correction value (hereinafter referred to as a correction value) for increasing the reference boosting change rate when the actual pulsation width is limited to be smaller than the pulsation width set according to the target output current. (Referred to as “step-up change rate correction value”).

  For this purpose, the correction value calculation unit 732 first calculates the actual pulsation width during pulsation operation by subtracting the pulsation lower limit pressure from the pulsation upper limit pressure. Then, the actual pulsation width is subtracted from the pulsation width (= the pulsation width calculated by the pulsation width calculation unit 723) set according to the target output current, thereby calculating the pulsation width shortage allowance. Then, with reference to the table of FIG. 6, a pressure increase rate correction value is calculated based on the pulsation width deficiency. As shown in the table of FIG. 6, as the pulsation width deficiency increases, drainage becomes more severe, and the pressure increase change rate correction value increases.

  The temperature correction coefficient calculator 733 receives the buffer tank temperature, the inlet water temperature, and the outlet water temperature. At the time of pressure increase during the pulsation operation, new anode gas is supplied to the anode gas passage 121 and the anode off gas remaining in the anode gas passage 121 is pushed into the buffer tank 36.

  At this time, the volume of the anode off gas in the buffer tank 36 increases as the buffer tank temperature increases. Therefore, when the buffer tank temperature is higher than the temperature of the fuel cell stack 1, it remains in the anode gas flow path 121. It becomes difficult to push the anode off gas into the buffer tank 36. Conversely, when the buffer tank temperature is lower than the temperature of the fuel cell stack 1, the anode off gas remaining in the anode gas flow path 121 is easily pushed into the buffer tank 36.

  Therefore, in this embodiment, the buffer tank temperature is a predetermined value determined in advance by experiments or the like to a value (hereinafter referred to as “temperature ratio”) obtained by dividing the buffer tank temperature by the average water temperature of the inlet water temperature and the outlet water temperature calculated by the average water temperature calculator 7331. Multiplying the constant is calculated as a temperature correction coefficient.

  The step-up change rate calculation unit 734 receives a reference step-up change rate, a step-up change rate correction value, and a temperature correction coefficient. The step-up change rate calculation unit 734 calculates the step-up change rate by multiplying the reference step-up change rate plus the step-up change rate correction value by the temperature correction coefficient.

  Returning to FIG. 4 again, the pulsation controller 74 will be described.

  The detected anode pressure, the pulsation upper limit pressure, the pulsation lower limit pressure, and the pressure increase rate are input to the pulsation control unit 74. Based on these input values, the pulsation control unit 74 controls the anode pressure regulating valve 33 according to the flowchart of FIG. 7 to pulsate the anode pressure.

  FIG. 7 is a flowchart showing a detailed configuration of the pulsation control unit 74.

  In step S1, the controller 6 determines whether or not the anode pressure is equal to or higher than the pulsation upper limit pressure. If the anode pressure is equal to or higher than the pulsation upper limit pressure, the controller 6 performs the process of step S2 to reduce the anode pressure. On the other hand, if the anode pressure is less than the pulsation upper limit pressure, the process of step S3 is performed.

  In step S2, the controller 6 sets the target anode pressure to the pulsation lower limit pressure.

  In step S3, the controller 6 determines whether or not the anode pressure is equal to or lower than the pulsation lower limit pressure. If the anode pressure is equal to or lower than the pulsation lower limit pressure, the controller 6 performs the process of step S4 to increase the anode pressure. On the other hand, if the anode pressure is higher than the pulsation lower limit pressure, the process of step S5 is performed.

  In step S4, the controller 6 sets the target anode pressure to the pulsation upper limit pressure.

  In step S5, the controller 6 sets the target anode pressure to the same target anode pressure as the previous time.

  In step S6, when the pulsation lower limit pressure is set as the target anode pressure, the controller 6 feedback-controls the anode pressure regulating valve 33 so that the anode pressure becomes the pulsation lower limit pressure. As a result of this feedback control, the opening of the anode pressure regulating valve 33 is normally fully closed, and the supply of anode gas from the high-pressure tank 31 to the fuel cell stack 1 is stopped. As a result, the anode pressure decreases due to the consumption of the anode gas in the fuel cell stack 1 by power generation.

  On the other hand, when the pulsation upper limit pressure is set as the target anode pressure, the controller 6 feedback-controls the anode pressure regulating valve 33 so that the anode pressure is increased to the pulsation upper limit pressure at the set pressure increase rate. As a result of this feedback control, the anode pressure regulating valve 33 is opened to a desired opening degree, the anode gas is supplied from the high-pressure tank 31 to the fuel cell stack 1, and the anode pressure rises at the set pressure increase rate.

  FIG. 8 is a time chart for explaining the operation of the anode pressure control unit 7 according to the present embodiment.

  When the fuel cell system 100 is started at time t1, the warm-up operation is performed until time t2 when the average water temperature of the inlet water temperature and the outlet water temperature reaches the warm-up completion temperature (for example, 60 ° C.).

  When the warm-up operation ends at time t2, for example, when the accelerator operation amount increases and the target output current increases, the pulsation width set according to the target output current also increases. Then, the pulsation operation is performed with the pulsation width set according to the target output current.

  At time t3, when the cooling performance of the radiator 42 is insufficient and the average water temperature increases with respect to the heat generation amount of the fuel cell stack 1 due to the increase in the target output current, the hydrogen partial pressure lower limit value increases. Thereby, the hydrogen partial pressure lower limit value becomes larger than the detected cathode pressure, and the pulsation lower limit pressure becomes higher than normal (when the detected cathode pressure is set as the pulsation lower limit pressure).

  As a result of the pulsation upper limit pressure becoming higher than normal, the basic pulsation upper limit pressure, which is obtained by adding the pulsation width to the pulsation lower limit pressure, is also higher, but is still smaller than the system upper limit value and the membrane protection upper limit value. The pulsation operation is performed with the pulsation width set accordingly.

  At time t4, when the basic pulsation upper limit pressure obtained by adding the pulsation width to the pulsation lower limit pressure reaches the membrane protection upper limit value, the membrane protection upper limit value is set as the pulsation upper limit pressure. As a result, the pulsation operation is performed in a state where the pulsation width is limited to be smaller than the pulsation width set according to the target output current.

  Therefore, after time t4, the step-up change rate is increased and corrected according to the pulsation width shortage allowance. Therefore, even when the pulsation width is limited to be small, the drainage performance of the anode gas passage 121 can be ensured.

  When the target output current decreases at time t5, the pulsation operation is performed with the pulsation width set according to the target output current again as usual.

  The fuel cell system 100 according to the present embodiment described above pulsates the pressure of the anode gas supplied to the fuel cell stack 1 with the pulsation width and the rate of change in pressure set according to the drainage demand of the anode gas flow path 121, The pulsation width is limited to be small according to the operating state of the fuel cell system 100. When the pulsation width is limited to a small value, the rate of change in pressure increase is corrected to increase.

  As described above, when the pulsation width set according to the drainage demand of the anode gas passage 121 is limited to be small according to the operating state of the fuel cell system 100, the pressure increase rate of change is increased and corrected. The pressure of the anode gas can be increased at an appropriate rate of increase in pressure corresponding to the pulsation width. Therefore, the drainage property in the anode gas channel 121 can be ensured.

  The fuel cell system 100 according to the present embodiment boosts the pressure based on the supply flow rate of the anode gas that must be supplied to the fuel cell stack 1 in order to obtain the gas flow rate necessary for ensuring the drainage of the anode gas flow path 121. Set the rate of change.

  In order to ensure the drainage of the anode gas passage 121, it is considered that the rate of change in pressure increase may be simply increased. However, if the step-up change rate is increased, the number of pulsations per unit time increases. As the number of pulsations per unit time increases, the number of times the anode pressure regulating valve 33 is opened and closed also increases, so that the anode pressure regulating valve 33 is quickly deteriorated. In addition, since the number of times the differential pressure is applied between the anode side and the cathode side increases, the deterioration of the electrolyte membrane 111 is accelerated.

  Therefore, as in the present embodiment, the rate of change in pressure increase is based on the supply flow rate of the anode gas that must be supplied to the fuel cell stack 1 at a minimum in order to obtain the gas flow rate necessary for ensuring drainage of the anode gas flow path 121. By setting this, the drainage property in the anode gas channel 121 can be ensured even when the pulsation width is limited to a small value while minimizing the rate of change in pressure increase. Therefore, deterioration of durability of the anode pressure regulating valve 33 and the electrolyte membrane 111 can be suppressed, and as a result, durability and reliability of the fuel cell system 100 can be ensured.

  Further, in the fuel cell system 100 according to the present embodiment, the difference between the pulsation upper limit pressure and the pulsation lower limit pressure, that is, the actual pulsation width becomes smaller than the pulsation width set according to the drainage request of the anode gas flow path 121. The increase rate of the pressure increase is corrected based on the difference (the pulsation width shortage allowance).

  In this way, the anode gas flow path is reliably corrected by correcting the pressure increase rate based on the short pulsation width (pulsation width shortage allowance) with respect to the pulsation width set according to the drainage demand of the anode gas flow path 121. The drainage at 121 can be secured.

  Further, the fuel cell system 100 according to the present embodiment further corrects the increase rate of pressure increase corrected based on the pulsation width shortage allowance (difference) according to the temperature ratio between the buffer tank temperature and the temperature of the fuel cell stack 1. . Specifically, correction is performed such that the higher the buffer tank temperature is, and the lower the temperature of the fuel cell stack 1 is, the higher the rate of change in pressure increase is.

  Since the volume of the anode off gas in the buffer tank 36 increases as the buffer tank temperature increases, when the buffer tank temperature is higher than the temperature of the fuel cell stack 1, the anode off gas remaining in the anode gas flow path 121 is reduced. It becomes difficult to push into the buffer tank 36. Conversely, when the buffer tank temperature is lower than the temperature of the fuel cell stack 1, the anode off gas remaining in the anode gas flow path 121 is easily pushed into the buffer tank 36.

  Therefore, as in this embodiment, by further correcting the rate of change in pressure increase according to the temperature ratio between the buffer tank temperature and the temperature of the fuel cell stack 1, the drainage performance in the anode gas flow path 121 can be more reliably ensured. be able to.

  In the fuel cell system 100 according to the present embodiment, the anode gas pressure is a membrane obtained by adding a predetermined allowable transmembrane pressure for protecting the electrolyte membrane 111 to the cathode gas pressure supplied to the fuel cell stack 1. The protection upper limit value and the system upper limit value for protecting the pressure resistance of the fuel cell system 100 are not exceeded.

  Therefore, the durability of the fuel cell system 100 can be ensured.

  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.

  In the above embodiment, the pulsation width is varied according to the target output current of the fuel cell stack 1, but may be constant.

  Further, in the above embodiment, the buffer tank 36 is provided as a space for storing the anode off gas. However, without providing such a buffer tank 36, for example, the internal manifold of the fuel cell stack 1 may be used as a space instead of the buffer tank 36. The internal manifold here is a space inside the fuel cell stack 1 where the anode off-gas that has finished flowing through the anode gas flow path 121 is collected, and the anode off-gas is discharged to the anode gas discharge passage 35 through the manifold. .

1 Fuel cell stack (fuel cell)
6 Controller (Pulsation operation means, correction means, means for estimating the temperature of the buffer unit)
36 Buffer tank (buffer part)
47 Inlet water temperature sensor (means for detecting fuel cell temperature)
48 outlet water temperature sensor (means for detecting the temperature of the fuel cell)
100 Fuel Cell System 111 Electrolyte Membrane

Claims (6)

A fuel cell system for generating power by supplying anode gas and cathode gas to a fuel cell,
Pulsation operation means for pulsating the pressure of the anode gas supplied to the fuel cell with a pulsation width and a rate of change in pressure set according to the drainage demand on the anode side of the fuel cell;
Limiting means for limiting the pulsation width small according to the operating state of the fuel cell system;
When the pulsation width is limited to be small by the limiting unit, a correcting unit that increases and corrects the step-up change rate;
A fuel cell system comprising: The pulsation driving means includes
Based on the load of the fuel cell, set the pulsation width,
Setting the rate of change in pressure increase based on the supply flow rate of the anode gas that must be supplied to the fuel cell stack in order to obtain the gas flow rate necessary for ensuring drainage on the anode side of the fuel cell;
The fuel cell system according to claim 1. The limiting means is
The larger one of the pressure lower limit value of the anode gas for securing the hydrogen partial pressure in the fuel cell and the pressure of the cathode gas supplied to the fuel cell is set as the pulsation lower limit pressure,
The smaller one of the basic pulsation upper limit pressure calculated based on the pulsation width and the pulsation lower limit pressure and the anode gas pressure upper limit value calculated according to the operating state of the fuel cell system is set as the pulsation upper limit pressure. Means,
The correction means includes
When the difference between the pulsation upper limit pressure and the pulsation lower limit pressure becomes smaller than the pulsation width, the pressure increase rate of change is increased and corrected based on the difference.
The fuel cell system according to claim 1 or 2, characterized by the above. A buffer unit for storing anode off-gas discharged from the fuel cell;
Buffer temperature detecting means for detecting the temperature of the buffer unit;
Fuel cell temperature detecting means for detecting the temperature of the fuel cell;
With
The correction means includes
The step-up change rate corrected to increase based on the difference is further corrected according to a temperature ratio between the temperature of the buffer unit and the temperature of the fuel cell.
The fuel cell system according to claim 3. The correction means includes
The step-up change rate is corrected so that the step-up change rate increases as the temperature of the buffer unit increases and the temperature of the fuel cell decreases.
The fuel cell system according to claim 4. The upper pressure limit of the anode gas is
A pressure obtained by adding a predetermined value for protecting the electrolyte membrane of the fuel cell to the pressure of the cathode gas supplied to the fuel cell and a predetermined pressure for protecting the pressure resistance of the fuel cell. ,
The fuel cell system according to any one of claims 3 to 5, wherein

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