JP2007026891A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of suppressing deterioration of a fuel cell by suppressing differential pressure between membranes of the fuel cell at starting and suppressing over-voltage of the fuel cell at the starting. <P>SOLUTION: The fuel cell system comprises a fuel cell 1, a hydrogen supply system to supply hydrogen, an air supply system to supply air, a gas supply control part which establishes the supply pressure of hydrogen and air at the starting time at a pressure higher than at a normal power generation time, a voltage sensor 21 which detects voltage parameter of the fuel cell (voltage parameter detecting means), and an output control means (output extraction device 20, and output control part of a controller 30) which starts extraction of output of the fuel cell 1 and controls so that the voltage parameter may not exceed the prescribed upper limit voltage during a period from starting till the normal power generation start, when the voltage parameter of the fuel cell 1 detected by the voltage sensor 21 reaches a prescribed threshold voltage lower than a prescribed upper limit voltage. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly, to a fuel cell system capable of suppressing a transmembrane differential pressure of a fuel cell at the time of startup, and suppressing deterioration of the fuel cell by suppressing an overvoltage of the fuel cell at the time of startup.

  The fuel cell system supplies hydrogen as a fuel gas to the fuel electrode of the fuel cell, supplies air as the oxidant gas to the oxidant electrode of the fuel cell, and causes the hydrogen and oxygen in the air to react electrochemically. To obtain generated power. Such a fuel cell system is highly expected to be put into practical use, for example, as a power source for automobiles, and research and development for practical use are being actively carried out.

  As a fuel cell used in a fuel cell system. For example, a solid polymer type fuel cell is known as being suitable for mounting in an automobile. A solid polymer type fuel cell is provided with a solid polymer membrane as an electrolyte membrane between a fuel electrode and an oxidant electrode. In this solid polymer type fuel cell, the solid polymer membrane functions as an ion conductor, a reaction occurs in which hydrogen is separated into hydrogen ions and electrons at the fuel electrode, and oxygen and hydrogen in the air at the oxidant electrode. A reaction for generating water from ions and electrons is performed.

  In such a fuel cell system, when the fuel gas is supplied at the same gas pressure as that of the fuel gas supplied during normal operation of the fuel cell at startup, the fuel gas is instantaneously generated in the fuel chamber. There is a problem that uneven distribution of the gas and the replacement gas occurs, and an electrochemical reaction occurs due to the uneven distribution and the electrode deteriorates.

In order to cope with such a problem, in the “fuel cell system” disclosed in Japanese Patent Application Laid-Open No. 2004-139984, the hydrogen pressure to be supplied is set higher than the supply pressure at the time of normal power generation at the time of startup, and the hydrogen pump is driven. At the same time, the hydrogen supply valve is opened, and oxygen remaining in the anode is discharged in a short time and replaced with hydrogen gas, thereby suppressing deterioration of the fuel cell.
JP 2004-139984 A

  However, in the technique disclosed in Patent Document 1 described above, air must be supplied at the same time in order to suppress the transmembrane differential pressure of the fuel cell. Since there is a problem that the voltage of the battery rises and this voltage rise works in the direction of promoting the deterioration of the fuel cell, it is necessary to take measures to prevent overvoltage.

  Here, when the high voltage start is performed, the voltage rise rate is higher than that of the low voltage start, the delay of the electrochemical reaction of the fuel cell and the delay of the response of the output extraction device (or relay for resistance connection) Because the voltage overshoot associated with increases, a control that takes out a predetermined output when a predetermined voltage near the upper limit voltage is reached, regardless of differences in gas composition, as in conventional low-voltage startup, is There was a situation that it was not possible to suppress the overvoltage.

  The present invention has been made in view of the above-described conventional circumstances, and suppresses the transmembrane pressure difference of the fuel cell at the time of startup, and suppresses the deterioration of the fuel cell by suppressing the overvoltage of the fuel cell at the time of startup. The object is to provide a fuel cell system.

  In order to solve the above-mentioned object, the present invention provides a fuel cell that generates power by supplying fuel gas and oxidant gas, fuel gas supply means for supplying fuel gas to the fuel cell, and oxidant gas for the fuel cell. Supplying oxidant gas supply means, gas supply control means for setting the supply pressure of the fuel gas and the oxidant gas to a pressure higher than that during normal power generation at startup, and voltage for detecting a voltage parameter of the fuel cell When the fuel cell voltage parameter detected by the parameter detection means and the voltage parameter detection means reaches a predetermined threshold voltage lower than a predetermined upper limit voltage, the output of the fuel cell is started. Output control means for controlling the voltage parameter so as not to exceed a predetermined upper limit voltage during a period from start to normal power generation. .

  In the fuel cell system according to the present invention, at startup, the supply pressure of the fuel gas and the oxidant gas is set to a pressure higher than that during normal power generation, and the detected voltage parameter is a predetermined threshold value lower than the upper limit voltage. By starting the control to extract the output when it reaches the voltage, the voltage parameter is controlled so that it does not exceed a predetermined upper limit voltage from the start to the start of normal power generation. Even if the influence of the chemical reaction delay or the response delay of the output take-out device on the voltage overshoot cannot be ignored, the total voltage of the fuel cell can be prevented from being excessively deteriorated. It is possible to prevent the input voltage of the output extraction device from becoming excessive.

  Hereinafter, embodiments of the fuel cell system of the present invention will be described in detail in the order of [Embodiment 1] and [Embodiment 2] with reference to the drawings.

  FIG. 1 is a configuration diagram of a fuel cell system according to Embodiment 1 of the present invention, and FIG. 2 is a configuration diagram of a controller 30. The fuel cell system of this embodiment is used as a driving power source of a fuel cell vehicle, for example, and includes a fuel cell 1 that generates power by supplying hydrogen and air as shown in FIG.

  As a hydrogen supply system (fuel gas supply means), a hydrogen tank 2, a hydrogen tank main valve 3, a pressure reducing valve 4, a hydrogen supply valve 5, a pressure sensor 6a, a hydrogen circulation device 7, a purge valve 8, and a waste hydrogen treatment device 9 are used. As an air supply system (oxidant gas supply means), a compressor 10, a humidifier 11, a pressure sensor 6b, and an air pressure regulating valve 12. The cooling mechanism includes a cooling water pump 13, a three-way valve 16, a radiator 17, and a radiator. A fan 18 and temperature sensors 14 and 15 are provided.

  Further, the load system includes an output take-out device (output control means) 20 and a voltage sensor (voltage parameter detection means) 21, and the control system includes a hydrogen supply system, an air supply system, a cooling mechanism, various sensors for the load system, This configuration includes a controller 30 that controls each component of the hydrogen supply system, the air supply system, the cooling mechanism, and the load system based on detection signals from other various instruments.

  The fuel cell 1 includes a fuel electrode (anode) supplied with hydrogen as a fuel gas and an oxidant electrode (cathode) supplied with air as an oxidant gas with an electrolyte interposed therebetween to form a power generation cell. In addition, it has a stack structure in which a plurality of power generation cells are stacked in multiple stages, and converts chemical energy into electrical energy by an electrochemical reaction based on hydrogen and oxygen in the air. Hydrogen gas is supplied to the anode and air is supplied to the cathode, and the electrode reaction shown below proceeds to generate electric power.

(Equation 1)
Anode: H ₂ → 2H ⁺ + 2e ⁻ (1)
(Equation 2)
Cathode: 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O (2)
That is, in each power generation cell of the fuel cell 1, a reaction occurs in which hydrogen supplied to the anode is separated into hydrogen ions and electrons, the hydrogen ions pass through the electrolyte, and the electrons pass through an external circuit to generate power, Each moves to the cathode. At the cathode, oxygen in the supplied air reacts with hydrogen ions and electrons that have moved through the electrolyte to produce water, which is discharged to the outside.

  As the electrolyte of the fuel cell 1, for example, a solid polymer electrolyte membrane is used in consideration of high energy density, low cost, light weight, and the like. The solid polymer electrolyte membrane is made of an ion (proton) conductive polymer membrane such as a fluororesin ion exchange membrane, and functions as an ion conductive electrolyte when saturated with water.

  In order to generate power in the fuel cell stack 3, it is necessary to supply hydrogen as fuel gas or air as oxidant gas to the fuel electrode (anode) or oxidant electrode (cathode) of each power generation cell. Then, a hydrogen supply system and an air supply system are provided as a mechanism for that purpose.

  In the hydrogen supply system, hydrogen is supplied to the anode from the hydrogen tank 2 through the hydrogen tank main valve 3, the pressure reducing valve 4, and the hydrogen supply valve 5. The high-pressure hydrogen supplied from the hydrogen tank 2 is mechanically reduced to a predetermined pressure by the pressure reducing valve 4, and the hydrogen pressure in the fuel cell 1 is controlled to a desired hydrogen pressure by the hydrogen supply valve 5.

  A hydrogen circulation device (pump or the like) 7 is installed to recycle hydrogen that has not been consumed at the anode. The hydrogen pressure of the anode is controlled by driving the hydrogen supply valve 5 by feeding back the hydrogen pressure detected by the controller 30 with the pressure sensor 6a. By controlling the hydrogen pressure to a desired target pressure, the hydrogen consumed by the fuel cell is automatically compensated.

  The purge valve 8 plays the following role. First, in order to ensure the hydrogen circulation function, nitrogen accumulated in the hydrogen supply system is discharged. When hydrogen is circulated and used, impurities such as nitrogen and CO may accumulate in the system as the hydrogen circulates. If the impurities accumulate excessively, the hydrogen partial pressure will drop and the fuel will decrease. In addition to reducing the efficiency of the battery stack 3, the average mass of the circulating gas is increased, so that the hydrogen circulation flow rate in the ejector 1 is decreased. Is purged out of the system from the hydrogen exhaust passage together with hydrogen. Second, in order to recover the cell voltage of the fuel cell 1, water clogging in the gas flow path is blown away. Thirdly, in order to replace the hydrogen system with hydrogen at the time of start-up, the gas in the hydrogen system is discharged.

  Further, the exhaust hydrogen treatment device 9 dilutes the hydrogen discharged from the purge valve 8 with air so that the hydrogen concentration is lower than the flammable concentration, and discharges it outside the vehicle, or causes hydrogen and air to react to burn. This reduces the exhaust hydrogen concentration.

  On the other hand, in the air supply system, air to the cathode is supplied by the compressor 10. The humidifier 11 humidifies the supplied air. The air pressure of the cathode is controlled by driving the air pressure regulating valve 12 by feeding back the air pressure detected by the controller 30 with the pressure sensor 6b.

  In the fuel cell system of this embodiment, a cooling mechanism for cooling the fuel cell 1 is provided. The cooling mechanism has a cooling water circulation channel and a cooling water pump 13 for circulating the refrigerant, and cools the fuel cell 1 by circulating cooling water in which, for example, an anti-freezing agent such as ethylene glycol is mixed in the water. Maintain a suitable temperature.

  In the cooling water circulation flow path of the cooling mechanism, there are provided a radiator 17 and a radiator fan 18 that cools the cooling water by passing air through the radiator 17. The temperature of the cooling water in the cooling water circulation channel is detected by the temperature sensor 14 and the temperature of the fuel cell 1 outlet is detected by the temperature sensor 15. The temperature of the fuel cell 1 outlet is detected by the controller 13 based on the detection results. By the drive control of the radiator fan 18, the temperature is adjusted so that the coolant temperature becomes a desired temperature. In addition, a radiator bypass flow path is provided in parallel with the radiator 17, and a three-way valve 16 is provided at a branching portion. The three-way valve 16 operates in accordance with the temperature of the cooling water, so that the flow path of the coolant is changed. Can be switched.

  In the load system, the output take-out device 20 takes the output (current or power) from the fuel cell 1 and supplies it to a motor (not shown) that drives the vehicle. Here, the output extraction device 20 may be configured to be able to extract a variable output, or may be configured to control the output to be extracted by connecting / disconnecting a fixed resistor.

  Further, the controller 30 is configured as a microcomputer having, for example, a CPU, a ROM, a RAM, a peripheral interface, and the like, and is detected from various sensors of a hydrogen supply system, an air supply system, a cooling mechanism, a load system, and other various instruments. Based on the signal, each component of the hydrogen supply system, air supply system, cooling mechanism, and load system is controlled (by driving various actuators) to control power generation of the fuel cell system.

  In FIG. 2, the controller 30 includes a start start trigger calculation unit 101, a gas supply control unit (gas supply control unit) 102, and an output control unit (output control unit) 104 as characteristic components of the present invention. However, these represent a functional group of programs executed on the CPU, and the activation start trigger calculation unit 101 generates an activation start trigger of the fuel cell system based on the operation of the ignition key (IGN key). Based on the output of the start start trigger calculation unit 101, the gas supply control unit 102 sets the supply pressures of the fuel gas (hydrogen) and the oxidant gas (air) to a pressure higher than that during normal power generation based on the output. Then, the gas supply control is performed, and the output control unit 104 detects the output of the start start trigger calculation unit 101 and the voltage parameter of the fuel cell 1. That on the basis of the output of the voltage parameter detector 103 (voltage sensor 21 in FIG. 1), to control the output extracted from the fuel cell 1.

  Here, the voltage parameter detection means 103 (voltage sensor 21) can read the voltage values of a plurality of cell groups constituting the fuel cell 1, and the total voltage of the fuel cell 1 and the fuel cell 1 are used as voltage parameters. The maximum value of the plurality of stack voltages to be configured or the maximum cell voltage of the fuel cell 1 is used.

  The output control means in the claims is realized by the output take-out device 20 and the output control unit 104 of the controller 30, and the voltage parameter of the fuel cell 1 detected by the voltage parameter detection means 103 is a predetermined upper limit voltage. When a predetermined threshold voltage lower than that is reached, the output extraction device 20 starts to extract the output of the fuel cell 1, and the voltage parameter exceeds the predetermined upper limit voltage during the period from the start to the normal power generation Control to not.

  Next, the operation control at the time of starting of the fuel cell system of the present embodiment configured as described above will be described with reference to the flowcharts of FIGS. 3 to 5 and the explanatory diagrams of FIGS. Here, FIG. 3 is a flowchart for explaining operation control until normal power generation is started when the fuel cell system is started, FIG. 4 is a flowchart for explaining a subroutine for voltage parameter determination, and FIG. 5 is a flowchart for output control. It is a flowchart explaining a subroutine.

  First, the control of the hydrogen (fuel gas) supply system is started (step S101 in FIG. 3), the gas composition is estimated (step S102), and the gas pressure / flow rate control of hydrogen and air is started (step S103).

  That is, the gas supply control unit 102 sets the supply pressure of the fuel gas (hydrogen) and the oxidant gas (air) to a pressure higher than that during normal power generation at the time of startup based on the output of the startup start trigger calculation unit 101. Here, the gas composition estimation (step S102) is performed in the “relation between the hydrogen concentration of the fuel electrode at the time of start-up and the stop time” shown in FIG. “Relationship between hydrogen concentration in fuel electrode and temperature of fuel cell 1 at stop” or “Relationship between component concentration other than fuel electrode hydrogen concentration at startup and torque or current of hydrogen supply system” shown in FIG. The gas composition can be estimated by estimating the hydrogen concentration at startup based on the temperature of the fuel cell 1 at startup.

  Next, the voltage parameter is determined (step S104). The voltage parameter determination of this embodiment is processed according to the subroutine shown in FIG. That is, it is determined whether or not the detected voltage parameter V1 of the fuel cell 1 has reached a predetermined threshold voltage V0max lower than a predetermined upper limit voltage. First, the voltage parameter detecting means 103 detects the voltage parameter V1 of the fuel cell 1 (step S201 in FIG. 4). Next, it is determined whether or not the voltage parameter V1 exceeds the threshold voltage V0max (step S202). If it is determined in step S202 that the voltage parameter V1 exceeds the threshold voltage V0max, the determination flag is set to 1 (step S203). If the voltage parameter V1 is equal to or lower than the threshold voltage V0max, the determination flag is set to 0 ( Step S204) The process ends.

  Here, the voltage parameter V1 may be the total voltage of the entire fuel cell 1, or may be the maximum value of each sub-stack voltage when the fuel cell 1 is composed of a plurality of sub-stacks. Further, it may be the maximum value of all cell voltages or cell group voltages.

  Further, the threshold voltage V0max is referred to the relationship between the threshold voltage V0max and the hydrogen concentration as shown in FIG. 9 based on the hydrogen concentration at the time of startup estimated in the gas composition estimation (step S102) in FIG. It is calculated by calculating. That is, the threshold voltage V0max is set low when the hydrogen concentration at the fuel electrode 1 of the fuel cell 1 at the time of startup is high, and is set high when the hydrogen concentration is low. As a result, it is possible to set the optimum threshold voltage V0max with respect to the hydrogen concentration at the start-up, and it is possible to prevent the voltage parameter V1 from exceeding the predetermined upper limit voltage. The relationship between the threshold voltage V0max and the hydrogen concentration in FIG. 9 can be set by conducting an experiment or the like in advance.

  Next, returning to FIG. 3 again, it is determined whether or not the determination flag as a result of the voltage parameter determination (step S104) is 1 (step S105). When the determination flag is 1, the voltage parameter V1 has reached the threshold voltage V0max, and the process proceeds to output control (step S106) in order to start the output extraction of the output of the fuel cell 1 by the output extraction device 20. If the determination flag is 0, the process returns to step S104, and the voltage parameter determination is repeated until the voltage parameter V1 reaches the threshold voltage V0max.

  Next, output extraction control is performed (step S106). The output control is processed according to a subroutine shown in FIG. First, the voltage parameter detection means 103 detects the voltage parameter V1 of the fuel cell 1 (step S301 in FIG. 5), then calculates the target voltage Vtarg (step S302), and further calculates the output command value TPower (step S302). In step S303, an output signal command is output (step S304).

  Here, the calculation of the output command value TPower (step S303) may be performed by calculating the output command value TPower from the target voltage Vtarg and the voltage parameter V1 using feedback control such as PI control, or the voltage parameter V1. The output command value TPower may be calculated in a feed forward manner based on the above.

  The initial value of the output command value TPower is based on the hydrogen concentration at the time of startup estimated in the gas composition estimation (step S102) in FIG. 3, and refers to the relationship between the output initial value Pc and the hydrogen concentration shown in FIG. It is obtained by calculating. That is, the initial value of the output command value TPower is set large when the hydrogen concentration in the fuel electrode 1 of the fuel cell 1 at the time of startup is high, and is set small when the hydrogen concentration is low. As a result, it is possible to set an optimum output command value TPower for the hydrogen concentration at the time of start-up, and it is possible to prevent the voltage parameter V1 from exceeding a predetermined upper limit voltage. The output command value TPower may be electric power or current.

  The output signal command (step S304) is normally output to the output take-out device 20 and controlled to take out an output corresponding to the command. However, when a fixed resistor is connected as the output take-out device 20, the output signal command (step S304) is output. It may be configured to output a signal for turning on / off the fixed resistor as a signal.

  Next, it is determined whether or not normal power generation is possible (step S305). If normal power generation is possible, the normal power generation condition flag is set to 1 (step S306). If normal power generation is not possible, the normal power generation condition flag is set to 0 (step S307), and the process ends.

  Here, whether or not normal power generation is possible (step S305) is determined by the characteristics of the hydrogen concentration and the stop time of the fuel electrode at the time of startup shown in FIG. 6, or the characteristics of the fuel electrode at the time of startup shown in FIG. The determination is based on the characteristics of the hydrogen concentration and the temperature of the fuel cell 1 at the time of stoppage, and the time from the start of gas supply. Further, referring to the characteristics of the component concentration other than the hydrogen concentration of the fuel electrode at the time of start-up shown in FIG. 8 and the torque or current of the hydrogen supply system, the gas composition of the fuel electrode is estimated momentarily and judged from the result. You may make it do.

  Next, returning to FIG. 3 again, it is determined whether or not the normal power generation condition flag set in the output control (step S106) is 1 (step S107). If the normal power generation condition flag is 1, it is determined that normal power generation is possible, and the process proceeds to normal power generation (step S108). If the normal power generation condition flag is 0, the process returns to step S106, Output control is repeated until it is determined that power generation is possible.

  Finally, normal power generation control is started (step S108), and the activation is completed.

  FIG. 11 shows (a) the air pressure and hydrogen pressure of the gas control system and the rotation speed of the hydrogen circulation pump, and (b) the anode system when the operation control at the start-up in the fuel cell system of the present embodiment described above is used. (Fuel electrode) Hydrogen concentration, (c) Fuel cell 1 voltage, (d) Fuel cell 1 current change over time. For comparison with the present embodiment, a similar explanatory diagram according to the prior art is shown in FIG.

  In the prior art (FIG. 12), the hydrogen pressure is increased after turning the hydrogen circulation device at start-up, the hydrogen concentration in the anode system (fuel electrode) is increased at once, and at the same time, the air pressure is increased to increase the transmembrane pressure difference. Driving to protect. However, since hydrogen and air are supplied at the same time, an open-ended voltage is generated in the fuel cell even in a state before normal power generation, and an overshoot of the voltage due to pressurization occurs. As in T12, the fuel cell voltage may exceed the upper limit value, which may promote deterioration of the fuel cell.

  On the other hand, in this embodiment (FIG. 11), after hydrogen and air are supplied and the pressure is increased, when the voltage of the fuel cell 1 reaches a predetermined threshold value, the fuel cell 1 receives a predetermined value. By taking out this current, the voltage of the fuel cell 1 is prevented from rising and exceeding the upper limit voltage. Thereby, when the hydrogen front is passing through the fuel cell, it is possible to prevent the fuel cell 1 from being deteriorated due to an excessive voltage at the same time.

  As described above, in the fuel cell system of this embodiment, the fuel cell 1 that generates power by supplying fuel gas (hydrogen) and oxidant gas (air), and the hydrogen supply system that supplies hydrogen to the fuel cell 1 An air supply system for supplying air to the fuel cell 1, a gas supply control unit 102 for setting the supply pressure of hydrogen and air to a pressure higher than that during normal power generation at startup, and a voltage parameter of the fuel cell 1 are detected When the voltage parameter detection means 103 (voltage sensor 21) and the voltage parameter V1 of the fuel cell 1 detected by the voltage parameter detection means 103 reach a predetermined threshold voltage V0max lower than a predetermined upper limit voltage, the fuel cell Output control means for controlling the voltage parameter V1 so as not to exceed a predetermined upper limit voltage during the period from the start of the output of 1 to the start of normal power generation And out the output control unit 104 of the device 20 and controller 30) are configured with a.

  As described above, when the gas supply is controlled based on the start trigger, the start is performed by controlling the gas pressure to a high pressure, and the detected voltage parameter V1 is set to a predetermined threshold voltage V0max lower than the upper limit voltage. Since the control is performed so that the voltage parameter V1 does not exceed a predetermined upper limit voltage during the period from the start to the start of normal power generation by starting the control for taking out the output when it reaches the fuel cell. 1. Even if the influence of the electrochemical reaction delay of 1 or the response delay of the output take-out device 20 on the voltage overshoot cannot be ignored, it is prevented that the total voltage of the fuel cell 1 is excessively deteriorated. In addition, the input voltage of the output extraction device 20 can be prevented from becoming excessive. As a result, it is possible to realize a fuel cell system that can suppress the transmembrane pressure difference of the fuel cell at the start-up and suppress the overvoltage of the fuel cell at the start-up to suppress the deterioration of the fuel cell.

  In the fuel cell system of this embodiment, the output control means controls the output taken out from the fuel cell 1 by feedback control so that the voltage parameter V1 of the fuel cell 1 becomes a predetermined target voltage equal to or lower than the upper limit voltage. Thus, it is possible to control so as not to exceed the upper limit voltage.

  In the fuel cell system of the present embodiment, the output control means controls the output taken out from the fuel cell 1 by feedforward control, and determines the output in a feedforward manner until normal power generation is started. It is possible to control so as not to exceed the upper limit voltage with a simple configuration.

  In the fuel cell system of the present embodiment, the output extracted from the fuel cell 1 by the output control means is large when the fuel gas (hydrogen) concentration at the fuel electrode of the fuel cell 1 at the time of startup is high, and the fuel gas ( When the concentration of hydrogen is low, it is set to a small value, so that the rate of voltage increase differs depending on the gas composition of the fuel electrode at the time of startup. Therefore, the electrochemical reaction delay of the fuel cell 1 and the response delay of the output extraction device 20 Even if the influence on the overshoot cannot be ignored, it is possible to control so as not to exceed the upper limit voltage.

  Further, in the fuel cell system of the present embodiment, the output control means includes the output take-out device 20 that can take out the variable output, so that take-out control by feedback, a constant output is changed according to the fuel gas concentration, etc. Free setting is possible. Moreover, since the extracted output can be stored in the battery of the power generation system, energy can be used efficiently. Further, in the case of the output extraction device 20 that controls the output extracted by connecting / disconnecting the fixed resistor, it can be realized with a simpler configuration.

  Further, in the fuel cell system of the present embodiment, in the output control means, the threshold voltage V0max is low when the fuel gas (hydrogen) concentration in the fuel electrode of the fuel cell 1 at the time of startup is high, and the fuel gas (hydrogen) ) Since the voltage rise speed differs depending on the gas composition of the fuel electrode at the start-up because the concentration is low, the voltage rise rate varies depending on the electrochemical reaction delay of the fuel cell 1 and the response delay of the output extraction device. Even if the influence on the chute cannot be ignored, it is possible to control so as not to exceed the upper limit voltage.

  In the fuel cell system of the present embodiment, the fuel gas (hydrogen) concentration at the fuel electrode of the fuel cell 1 is set to at least the time during which the fuel cell system is stopped, the temperature of the fuel cell 1 at the previous stop, The fuel gas (hydrogen) concentration can be accurately calculated by simple calculation because it is estimated from the drive torque of the fuel gas circulation device (hydrogen circulation system) or the current consumption of the fuel gas circulation device (hydrogen circulation system) at startup. Can be estimated.

  Further, in the fuel cell system of the present embodiment, when the total voltage of the fuel cell 1 is used as the voltage parameter V1, the deterioration of the fuel cell due to excessive voltage can be surely suppressed with an easy calculation. In addition, even when the maximum value of a plurality of stack voltages constituting the fuel cell 1 or the maximum cell voltage of the fuel cell 1 is used as the voltage parameter V1, the deterioration of the fuel cell due to the excessive voltage is surely suppressed by simple calculation. can do.

  Next, a fuel cell system according to Example 2 of the present invention will be described. The configuration of the fuel cell system of Example 2 is the same as that of Example 1 (FIGS. 1 and 2), and a specific description of each component is omitted.

  However, in the first embodiment, the control for extracting the output is started when the voltage parameter V1 reaches the threshold voltage V0max during the startup sequence, whereas in the present embodiment, the first voltage parameter is set to a predetermined value during the startup sequence. When the value is reached and the second voltage parameter satisfies a predetermined minimum value, control for extracting the output is started.

  That is, the first voltage parameter detected by the voltage parameter detecting means 103 (voltage sensor 21) is the total voltage of the fuel cell 1, the maximum value of a plurality of stack voltages constituting the fuel cell 1, or the maximum value of the fuel cell 1. The cell voltage is set, and the second voltage parameter is set to the minimum value of a plurality of stack voltages constituting the fuel cell 1 or the minimum cell voltage of the fuel cell 1, and output control means (outputs of the output extraction device 20 and the controller 30). In the control unit 104), the output of the fuel cell 1 when the first voltage parameter reaches the first threshold voltage and the second voltage parameter exceeds a predetermined lower limit voltage (second threshold voltage). This is different from the first embodiment in that the take-out operation is started.

  Next, the operation control at the time of starting the fuel cell system of the present embodiment will be described with reference to the flowcharts of FIGS. 3, 13, and 5. FIG. 13 is a flowchart for explaining a voltage parameter determination subroutine according to the second embodiment.

  In this embodiment, the voltage parameter determination in step S104 in the flowchart of FIG. 3 is processed according to the subroutine shown in FIG.

  As in the first embodiment, first, the control of the hydrogen (fuel gas) supply system is started (step S101 in FIG. 3), the gas composition is estimated (step S102), and the gas pressure / flow rate control of hydrogen and air is started. (Step S103).

  Next, the voltage parameter is determined (step S104). In FIG. 13, first, the voltage parameter detection means 103 detects the first and second voltage parameters V1 and V2 of the fuel cell 1 (step S401). Next, it is determined whether or not the first voltage parameter V1 exceeds the first threshold voltage V0max (step S402). If it is determined in step S402 that the first voltage parameter V1 exceeds the first threshold voltage V0max, the process proceeds to step S403, and whether or not the second voltage parameter V2 exceeds the second threshold voltage V0min. Is determined (step S403).

  If it is determined in step S403 that the second voltage parameter V2 exceeds the second threshold voltage V0min, that is, the first voltage parameter V1 exceeds the first threshold voltage V0max, and the second voltage parameter If V2 exceeds the second threshold voltage V0min, the determination flag is set to 1 (step S404). If the voltage parameter V1 is equal to or lower than the threshold voltage V0max in the determination in step S402, or the second voltage If the parameter V2 is less than or equal to the second threshold voltage V0min, the determination flag = 0 is set (step S405) and the process ends.

  Here, the first voltage parameter V1 may be the total voltage of the entire fuel cell 1, or may be the maximum value of each substack voltage when the fuel cell 1 is composed of a plurality of substacks. Further, it may be the maximum value of all cell voltages or cell group voltages. The second voltage parameter V2 may be the minimum value of each substack voltage when the fuel cell 1 is composed of a plurality of substacks, or the minimum value of all cell voltages or cell group voltages. Also good.

  Further, the first threshold voltage V0max is similar to the threshold voltage V0max of the first embodiment, based on the hydrogen concentration at startup estimated in the gas composition estimation (step S102) in FIG. It is obtained by calculating with reference to the relationship between the threshold voltage V0max and the hydrogen concentration as shown. As a result, it is possible to set the optimum threshold voltage V0max with respect to the hydrogen concentration at the start-up, and it is possible to prevent the voltage parameter V1 from exceeding the predetermined upper limit voltage. The relationship between the threshold voltage V0max and the hydrogen concentration in FIG. 9 can be set by conducting an experiment or the like in advance.

  The second threshold voltage V0min is determined based on a voltage value that the fuel cell deteriorates when the output is taken out while the minimum voltage of the sub stack or the minimum voltage of the cell or the cell group is lower than this value. That's fine. This value can also be set by conducting an experiment or the like in advance.

  Next, returning to FIG. 3 again, it is determined whether or not the determination flag as a result of the voltage parameter determination (step S104) is 1 (step S105). When the determination flag is 1, the output extraction device 20 proceeds to output control (step S106) to start extraction of the output of the fuel cell 1, but when the determination flag is 0, the process returns to step S104 to The voltage parameter determination is repeated until the parameter V1 reaches the threshold voltage V0max.

  Next, output extraction control is performed (step S106). The output control is processed according to the subroutine shown in FIG.

  Next, it is determined whether or not the normal power generation condition flag set in the output control (step S106) is 1 (step S107). If the normal power generation condition flag is 1, it is determined that normal power generation is possible, and the process proceeds to normal power generation (step S108). If the normal power generation condition flag is 0, the process returns to step S106, Output control is repeated until it is determined that power generation is possible.

  Finally, normal power generation control is started (step S108), and the activation is completed.

  As described above, in the fuel cell system of the present embodiment, the maximum value and the minimum value of the plurality of stack voltages constituting the fuel cell 1 are used as the voltage parameters, and the maximum value is set to the first threshold value in the output control means. Since the output of the fuel cell 1 is started when the value voltage V0max is reached and the minimum value exceeds a predetermined lower limit voltage (second threshold voltage V0min), the deterioration of the fuel cell 1 due to excessive voltage, Both deterioration of the fuel cell 1 accompanying cell reversal can be suppressed simultaneously.

  Further, in the fuel cell system of the present embodiment, the maximum cell voltage and the minimum cell voltage of the fuel cell 1 are used as voltage parameters, and the maximum cell voltage reaches the first threshold voltage V0max and is minimum in the output control means. Since the output of the fuel cell 1 is started when the cell voltage exceeds a predetermined lower limit voltage (second threshold voltage V0min), the fuel cell is deteriorated due to excessive voltage, and the fuel cell accompanying cell reversal. It is possible to simultaneously suppress both of the deteriorations.

1 is a configuration diagram of a fuel cell system according to Embodiment 1 of the present invention. FIG. 2 is a configuration diagram of a controller 30. FIG. It is a flowchart explaining the operation control until normal power generation is started at the time of starting of the fuel cell system. 6 is a flowchart for explaining a voltage parameter determination subroutine (Example 1); It is a flowchart explaining the subroutine of output control. It is explanatory drawing explaining the relationship between the hydrogen concentration of the fuel electrode at the time of starting, and stop time. It is explanatory drawing explaining the relationship between the hydrogen concentration of the fuel electrode at the time of starting, and the temperature of the fuel cell 1 at the time of a stop. It is explanatory drawing explaining the relationship between component concentration other than the hydrogen concentration of a fuel electrode at the time of starting, and the torque or electric current of a hydrogen supply system. It is explanatory drawing explaining the relationship between threshold voltage V0max and hydrogen concentration. It is explanatory drawing explaining the relationship between the output initial value Pc and hydrogen concentration. (A) The air pressure and hydrogen pressure of the gas control system and the rotation speed of the hydrogen circulation pump, (b) the anode system (fuel electrode) hydrogen concentration, (c) It is explanatory drawing explaining the time change of the voltage of the fuel cell 1, and (d) each current of the fuel cell 1. FIG. It is explanatory drawing at the time of using the operation control at the time of starting by the prior art. 10 is a flowchart for explaining a subroutine for voltage parameter determination (second embodiment).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Hydrogen tank 3 Hydrogen tank main valve 4 Pressure reducing valve 5 Hydrogen supply valve 6a, 6b Pressure sensor 7 Hydrogen circulation device 8 Purge valve 9 Exhaust hydrogen treatment device 10 Compressor 11 Humidifier 12 Air pressure adjustment valve 13 Cooling water pump 14 15 Temperature sensor 16 Three-way valve 17 Radiator 18 Radiator fan 20 Output extraction device (output control means)
21 Voltage sensor (voltage parameter detection means)
30 controller 101 start start trigger calculation unit 102 gas supply control unit (gas supply control means)
103 Voltage parameter detection means 104 Output control unit (output control means)

Claims (13)

A fuel cell that generates power by supplying fuel gas and oxidant gas;
Fuel gas supply means for supplying fuel gas to the fuel cell;
An oxidant gas supply means for supplying an oxidant gas to the fuel cell;
Gas supply control means for setting the supply pressure of the fuel gas and the oxidant gas to a pressure higher than that during normal power generation at startup;
Voltage parameter detecting means for detecting a voltage parameter of the fuel cell;
When the voltage parameter of the fuel cell detected by the voltage parameter detection means reaches a predetermined threshold voltage lower than a predetermined upper limit voltage, the output of the fuel cell is started and normal power generation is started from the start. Output control means for controlling the voltage parameter so as not to exceed a predetermined upper limit voltage during a period until the start;
A fuel cell system comprising:   2. The output control unit controls output output from the fuel cell by feedback control so that a voltage parameter of the fuel cell becomes a predetermined target voltage equal to or lower than the upper limit voltage. 3. Fuel cell system.   2. The fuel cell system according to claim 1, wherein the output control unit controls an output to be extracted from the fuel cell by feedforward control.   The output control means sets the output taken out from the fuel cell to be large when the fuel gas concentration at the fuel electrode of the fuel cell at the time of start-up is high, and to be small when the fuel gas concentration is low. Item 4. The fuel cell system according to Item 3.   The fuel cell system according to any one of claims 1 to 4, wherein the output control means includes an output extraction device capable of extracting a variable output.   5. The fuel cell according to claim 1, wherein the output control means includes an output extraction device that controls an output to be extracted by connecting / disconnecting a fixed resistor. system.   The output control means sets the threshold voltage to be low when the fuel gas concentration at the fuel electrode of the fuel cell at startup is high, and to be high when the fuel gas concentration is low. The fuel cell system according to any one of claims 1 to 6.   The fuel gas concentration at the fuel electrode of the fuel cell is at least the time during which the fuel cell system has been stopped, the temperature of the fuel cell at the previous stop, the drive torque of the fuel gas circulation device at the start, or the start The fuel cell system according to any one of claims 1 to 7, wherein the fuel cell system is obtained by estimating the current consumption of the fuel gas circulation device.   The fuel cell system according to any one of claims 1 to 8, wherein the voltage parameter is a total voltage of the fuel cell.   The fuel cell system according to any one of claims 1 to 8, wherein the voltage parameter is a maximum value of a plurality of stack voltages constituting the fuel cell.   The fuel cell system according to any one of claims 1 to 8, wherein the voltage parameter is a maximum cell voltage of the fuel cell. The voltage parameter is a maximum value and a minimum value of a plurality of stack voltages constituting the fuel cell,
The output control means starts taking out an output of the fuel cell when the maximum value reaches the threshold voltage and the minimum value exceeds a predetermined lower limit voltage. The fuel cell system according to any one of claims 8 to 9. The voltage parameter is a maximum cell voltage and a minimum cell voltage of the fuel cell;
The output control means starts taking out the output of the fuel cell when the maximum cell voltage reaches the threshold voltage and the minimum cell voltage exceeds a predetermined lower limit voltage. The fuel cell system according to any one of claims 1 to 8.

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