JP5135665B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system, and in particular, in a fuel cell system that learns the characteristics of the output current and output voltage of a fuel cell, the relationship between the power generation amount of the fuel cell and the pressure of the fuel gas or oxidant gas is temporarily. The present invention relates to a fuel cell system capable of performing appropriate various determinations and various controls based on the learned current-voltage characteristics of a fuel cell without changing the learning result even if a phenomenon different from a set value occurs.

  As a conventional system for learning the characteristics of the current and voltage of a fuel cell, there is a “fuel cell power generation apparatus and its cell stack deterioration diagnosis method” disclosed in Japanese Patent Application Laid-Open No. 2000-357526. In this conventional example, the maximum cell stack current calculation means obtains the maximum cell stack current which is a cell stack current at a predetermined lower limit cell stack voltage from an approximate expression of the relationship between the cell stack current and the cell stack voltage. In the current margin value calculation means, a cell stack current margin value that is the difference between the maximum stack current and a predetermined cell stack current at the time of output is obtained, and the cell stack current margin diagnosis means determines the cell stack current margin value in advance. Cell stack deterioration diagnosis is performed by comparing with the determined judgment value, and the cell stack current lifetime diagnosis means reduces the cell stack current margin value from the relationship between the maximum cell stack current, cell stack current margin value, and power generation time. Obtain the speed and set the cell stack current margin to zero or a predetermined value. By calculating the period until the, is to determine when replacement of the cell stack.

  In other words, in this conventional example, an approximate expression of the relationship between the current and voltage of the cell stack is derived, the coefficient of each term of the approximate expression is used as a learning parameter, and the learning parameter is calculated using a predetermined learning algorithm to calculate the current. The voltage characteristic is learned, the deterioration state of the cell stack is diagnosed based on the current voltage characteristic, and the replacement time of the cell stack is determined.

Also, in addition to those that perform fuel cell deterioration diagnosis and replacement timing determination based on the learned current-voltage characteristics as in this conventional example, those that are applied to various controls such as gas supply amount control and power generation amount control are also proposed. Has been.
JP-A-2000-357526

  By the way, in the conventional fuel cell system, the fuel gas supplied to the fuel cell generally constitutes a circulation system. In such a configuration, when the power generation amount of the fuel cell is reduced in a short time In addition, since the consumption of the fuel gas is reduced, the decrease in the pressure of the fuel gas is delayed. In this case, the relationship between the amount of power generated by the fuel cell and the pressure of the fuel gas is different from the temporarily set relationship, and the amount of power generated by the fuel cell is also the same for the oxidant gas due to a delay in the supply device. And the pressure of the oxidant gas may be different from the temporarily set relationship. On the other hand, since the relationship between the output current and the output voltage of the fuel cell changes depending on the pressure change of the supply gas, when the gas pressure is different from the desired pressure, the relationship between the output current and the output voltage is temporary. Will change. Therefore, in such a case, if learning of the characteristics of the current and voltage of the fuel cell is performed, the learning result temporarily fluctuates, and as a result, proper deterioration diagnosis of the fuel cell and determination of the replacement time are performed. There is a problem that it cannot be performed, or various controls such as gas supply amount control and power generation amount control cannot be performed properly.

  The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide a fuel cell system that learns characteristics of output current and output voltage of a fuel cell, and a power generation amount of the fuel cell. Even if the relationship with the pressure of the fuel gas or oxidant gas temporarily differs from the set value, it is possible to make various appropriate judgments based on the current voltage characteristics of the learned fuel cell without changing the learning result. It aims at providing the fuel cell system which can perform various control.

In order to solve the above-described object, the present invention provides a fuel cell that generates power by supplying fuel gas and oxidant gas, output current detecting means for detecting an output current of the fuel cell, and detecting an output voltage in the fuel cell. Output voltage detection means, current voltage characteristic learning means for learning the relationship between the output current and the output voltage of the fuel cell, and the pressure of at least one of the oxidant gas and the fuel gas is an operation of the fuel cell. A learning control means for prohibiting learning of the relationship between the output current and the output voltage by the current-voltage characteristic learning means when the pressure is different from a reference pressure corresponding to a condition; and a threshold setting means for setting a first threshold ; The learning control means is configured such that a difference between a pressure of at least one of the oxidant gas and the fuel gas and a reference pressure corresponding to an operation condition of the fuel cell is the first pressure. When the value is equal to or greater than the value, learning of the relationship between the output current and the output voltage by the current-voltage characteristic learning unit is prohibited, and the threshold setting unit changes the pressure of at least one of the oxidant gas and the fuel gas. as operating conditions change is large in the output voltage with respect to, it characterized that you set smaller the first threshold.

  In the fuel cell system according to the present invention, the learning of the relationship between the output current and the output voltage of the fuel cell is prohibited when the pressure of the oxidant gas or the fuel gas is different from the reference value corresponding to the operating condition of the fuel cell. When the operating condition of the fuel cell is different from the set relationship between the pressure of the oxidant gas or the fuel gas, the learning result of the relationship between the output current and the output voltage can be prevented, and the learned fuel cell Various appropriate determinations and various controls can be performed based on the current-voltage characteristics.

  Hereinafter, embodiments of the fuel cell system of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration diagram of a fuel cell system according to Embodiment 1 of the present invention. In the figure, the fuel cell system of the present embodiment includes an ejector 1, a hydrogen circulation channel 2, a fuel cell stack 3, a hydrogen purge valve 4, a compressor 6, an air supply channel 7, a hydrogen inlet temperature sensor 8, and a hydrogen inlet pressure. Sensor 9, exhaust air flow path 11, air pressure control valve 12, controller 13, hydrogen pressure control valve 14, air inlet pressure sensor 15, air inlet temperature sensor 16, current sensor 17, voltage sensor 18, air outlet pressure sensor 19, The configuration includes a hydrogen concentration sensor 20, a tank temperature sensor 22, a tank pressure sensor 21, a hydrogen tank 23, a power control device 24, a coolant temperature sensor 28, a coolant circulation pump 29, and a heat exchanger 30.

    The fuel cell stack 3 includes a fuel cell supplied with hydrogen as a fuel gas and an oxidant electrode supplied with air as an oxidant gas with an electrolyte interposed therebetween to form a power generation cell. It has a stack structure in which 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. In each power generation cell of the fuel cell stack 3, a reaction occurs in which hydrogen supplied to the fuel electrode 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. , Move to the oxidizer electrode. At the oxidizer electrode, hydrogen 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 stack 3, 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, which is a fuel gas, or air, which is an oxidant gas, to the fuel electrode and oxidant electrode of each power generation cell. A hydrogen supply system and an air supply system are provided.

  The hydrogen supply system includes a hydrogen tank 23, a hydrogen pressure control valve 14, a hydrogen circulation channel 2, and an ejector 1. Hydrogen supplied from the hydrogen tank 23 is supplied to the ejector 1 via the hydrogen pressure control valve 14. The ejector 1 is mixed with hydrogen that has passed through the hydrogen circulation passage 2 and supplied to the fuel electrode of the fuel cell stack 3. The hydrogen temperature and pressure at the inlet of the fuel cell stack 3 are measured by a hydrogen inlet temperature sensor 8 and a hydrogen inlet pressure sensor 9, respectively. The control of the hydrogen pressure control valve 14 is performed based on the pressure measured by the hydrogen inlet pressure sensor 9, whereby the fuel electrode pressure of the fuel cell stack 3 is maintained at a desired pressure. The temperature and pressure in the hydrogen tank 23 are measured by the tank pressure sensor 21 and the tank temperature sensor 22, respectively, and the concentration of hydrogen supplied to the fuel cell stack 3 is measured by the hydrogen concentration sensor 20.

  In the fuel cell stack 3, not all of the supplied hydrogen is consumed, and the remaining hydrogen (hydrogen discharged from the fuel electrode of the fuel cell stack 3) is newly supplied from the hydrogen tank 23 and supplied to the hydrogen supply flow. The hydrogen flowing through the path is mixed with the ejector 1 and supplied again to the fuel electrode of the fuel cell stack 3. Therefore, the hydrogen circulation channel 2 is connected to the fuel electrode outlet side of the fuel cell stack 3, and hydrogen discharged from the fuel electrode of the fuel cell stack 3 flows back to the ejector 1 through the hydrogen circulation channel 2. It has come to be. The hydrogen flowing through the hydrogen circulation channel 2 is circulated using the fluid energy of the hydrogen flowing through the ejector 1 and the hydrogen supply channel.

  Further, a hydrogen exhaust passage for introducing hydrogen from the fuel electrode of the fuel cell stack 3 downstream is connected to the fuel electrode outlet side of the fuel cell stack 3 so as to branch from the hydrogen circulation passage 2. A hydrogen purge valve 4 is provided downstream of the branch position of the hydrogen exhaust passage with the hydrogen circulation passage 2. The hydrogen purge valve 4 has a function of switching the flow path of hydrogen discharged from the fuel electrode of the fuel cell stack 3, and is opened when hydrogen purge is performed and discharged from the fuel electrode of the fuel cell stack 3. Hydrogen to be introduced is introduced downstream. The hydrogen purged from the hydrogen system is diluted into the air system by a hydrogen diffuser (not shown) in this introduction portion and discharged to the outside.

  As described above, when hydrogen is circulated and used, impurities such as nitrogen and CO may accumulate in the system as the hydrogen circulates, and if the impurities accumulate excessively, the hydrogen partial pressure As a result, the average mass of the circulating gas increases and the hydrogen circulation flow rate in the ejector 1 decreases. In such a case, the hydrogen purge valve 4 Is purged by purging hydrogen to discharge the impurity together with hydrogen from the hydrogen exhaust passage.

  On the other hand, the air supply system includes a compressor 6 and an air supply channel 7 for sucking outside air and pumping the air to the oxidant electrode of the fuel cell stack 3. Air is supplied into the air supply channel 7 by the compressor 6. It is sent to the oxidant electrode of the fuel cell stack 3. The pressure of the air at the inlet of the fuel cell stack 3 is measured by the air inlet pressure sensor 15, and the temperature of the air is measured by the air inlet temperature sensor 16.

  Further, an exhaust air flow path 11 for discharging air from the fuel cell stack 3 is connected to the oxidant electrode outlet side of the fuel cell stack 3, so that oxygen and air not consumed by the fuel cell stack 3 are in the air. Other components are discharged out of the system through the exhaust air flow path 11. Further, an air pressure control valve 12 is provided in the exhaust air flow path 11, the air electrode pressure of the fuel cell stack 3 is detected by an air outlet pressure sensor 19, and the controller 13 detects values detected by the air pressure sensors 15 and 19. Is fed back to control the operation of the air pressure control valve 12, whereby the fuel electrode pressure of the fuel cell stack 3 is maintained at a desired pressure.

  A cooling fluid circulation pump 29 and a heat exchanger 30 are provided as a cooling mechanism. The coolant that cools the fuel cell stack 3 is circulated by the coolant circulation pump 29, supplied to the fuel cell stack 3, and warmed. The temperature of the coolant warmed from the fuel cell stack 3 is measured by the coolant temperature sensor 28 and cooled by the heat exchanger 30.

  Further, the output current of the fuel cell stack 3 is measured by the current sensor 17 corresponding to the output current detecting means, and the output voltage is measured by the voltage sensor 18 corresponding to the output voltage detecting means. Further, the electric power taken out from the fuel cell stack 3 is controlled by the electric power control device 24. The power control device 24 is a step-up / step-down DC / DC converter, which is disposed between the fuel cell stack 3 and an electric load, and controls the generated power of the fuel cell stack 3. In the DC / DC converter, the switching elements to be operated are different in step-up conversion and step-down conversion, and a desired voltage can be output according to the duty ratio of a control signal applied to the switching elements. At the time of step-up, the switching element is controlled so as to output a voltage equal to or higher than the input voltage, and at the time of step-down, the switching element is controlled so as to output a voltage equal to or lower than the input voltage.

  The operating pressure of the fuel cell stack 3 is a variable pressure. That is, when the output taken out from the fuel cell stack 3 is high, the operating pressure is increased, and when the output is low, the operating pressure is decreased. Outputs of various sensors and actuator drive signals such as the hydrogen purge valve 4 are connected to the controller 13.

  The controller 13 is configured, for example, as a microcomputer having a CPU, ROM, RAM, peripheral interface, etc., reads the detection values of various sensors, and outputs various control signals according to the judgments and the calculation results for the detection values. The operation of each part of the fuel cell system is controlled.

  In FIG. 1, the controller 13 includes a current voltage characteristic learning unit 51, a learning control unit 52, and a threshold setting unit 53 as components, which represent a functional group of programs executed on the CPU. The current / voltage characteristic learning means 51 learns the relationship between the output current and the output voltage of the fuel cell, and the learning control means 52 has a pressure of at least one of the oxidant gas (air) and the fuel gas (hydrogen). When the pressure is different from the reference pressure corresponding to the operating condition of the fuel cell, learning of the relationship between the output current and the output voltage by the current-voltage characteristic learning means 51 is prohibited. The threshold value setting means 53 is a means for setting various threshold values used by the learning control means 52 in the second and third embodiments to be described later, and is not used in this embodiment.

  Next, the operation at the time of learning the current-voltage characteristic in the fuel cell system of the present embodiment configured as described above will be described with reference to FIGS. Here, FIG. 2 is a flowchart for explaining the operation at the time of learning the current-voltage characteristic of the fuel cell stack 3, and FIG. 3 is an explanatory diagram for explaining the current-pressure table data referred to when calculating the target gas pressure.

  The procedure at the time of learning the current-voltage characteristics of the fuel cell stack 3 shown in FIG. 2 is executed every predetermined time period. First, a current value output from the fuel cell stack 3 is detected based on the output of the current sensor 17 (step S101).

  Next, the pressure value of hydrogen at the inlet of the fuel cell stack 3 is detected based on the output of the hydrogen inlet pressure sensor 9, and the pressure of air at the inlet of the fuel cell stack 3 is detected based on the output of the air inlet pressure sensor 15. A value is detected (step S102).

  Next, the target gas pressure supplied to the fuel cell stack 3 is calculated based on the current extracted from the fuel cell stack 3 (step S103). This is calculated using, for example, the table data shown in FIG. This gas pressure is set as a reference gas pressure when learning a current-voltage characteristic described later (step S106).

  Next, it is determined whether or not to learn the current-voltage characteristics (step S104). Here, the values of both the hydrogen pressure and the air pressure detected in step S102 are compared with the reference pressure calculated in step S103. If either pressure value is different, the current-voltage characteristics The learning process is prohibited, and this process ends. On the other hand, if the pressure values are the same, the process proceeds to step S105.

  Next, the power generation state is regularly determined (step S105). This steady state determination is performed in order to remove current voltage data that has not been stably measured when the load of the fuel cell system changes. Here, if the amount of change of the detected current or voltage from the previous value is equal to or less than the predetermined value, it is determined that the current is steady and the process proceeds to step S106. The characteristic learning process (step S106) is skipped, and this process ends. As another method for determining the steady state of the power generation state, a method of determining that the current or voltage distribution value measured for a predetermined time is equal to or less than a predetermined value may be applied.

Next, learning of current-voltage characteristics that change from moment to moment is performed (step S106). Here, the current current-voltage characteristic is expressed by a linear function that approximates an input as a current and an output as a voltage.
(Equation 1)
Y = A · X + B (1)
And formulated. Here, X is a current, and Y is a voltage. As learning parameters, the slope of the linear function in the current-voltage characteristic is A, and the intercept of the Y axis is B. The learning value update method is based on the error between the measured actual voltage and the learned value obtained by inputting the actual current in the above equation (1). This is achieved by updating with a parameter estimation algorithm.

  As another method for learning the current-voltage characteristics, it has table data that outputs current as a learning result for the current and updates the table data based on the relationship between the detected current and voltage. A method of performing learning may be used. Further, learning may be performed using map data that outputs voltage with current and operating temperature as inputs.

  As described above, in the fuel cell system of this embodiment, the output current of the fuel cell is detected by the current sensor (output current detection means) 17 and the output voltage is supplied to the fuel cell by the voltage sensor (output voltage detection means) 18. When the learning control means 52 detects that the pressure of at least one of air (oxidant gas) and hydrogen (fuel gas) is different from the reference pressure corresponding to the operating condition of the fuel cell, the current voltage characteristic learning means 51 Since learning of the relationship between the output current and output voltage of the fuel cell is prohibited, the relationship between the fuel cell operating conditions (power generation amount) and the pressure of air (oxidant gas) or hydrogen (fuel gas) is temporarily Even if a phenomenon that is different from the set value occurs, the learning result is not changed. It is possible.

  Next, a fuel cell system according to Example 2 of the present invention will be described.

  In this embodiment, the configuration of the fuel cell system shown in FIG. Note that the threshold setting unit 53, which is a component of the controller 13, is used, and the threshold setting unit 53 sets the first threshold, the second threshold, or the third threshold and uses the determination by the learning control unit 52. Further, the learning control means 52 has a difference between the pressure of at least one of the oxidant gas (air) and the fuel gas (hydrogen) and the reference pressure corresponding to the operating condition of the fuel cell equal to or greater than the first threshold value. In this case, the learning of the relationship between the output current and the output voltage by the current-voltage characteristic learning unit 51 is prohibited.

  Next, the operation at the time of learning the current-voltage characteristic in the fuel cell system of the present embodiment will be described. The processing procedure is the same as that of FIG. 2 referred to in the first embodiment, and only the processing content of the current voltage characteristic learning permission determination in step S104 is different. Therefore, the description of the processing content of other steps is omitted, and step S104 is performed. Only will be described.

  In step S104, it is determined whether or not to learn the current-voltage characteristics. Here, both the hydrogen pressure and the air pressure detected in step S102 and the reference pressure calculated in step S103 are used. If any one of the pressure differences is equal to or greater than a first threshold value set in advance, learning of the current-voltage characteristic is prohibited.

  Here, since the voltage change of the current-voltage characteristic becomes larger as the pressure detected in step S102 is higher, the first threshold value is higher in the operating condition where the change in the output voltage is larger with respect to the change in the pressure of at least one of air and hydrogen. If the first threshold value is decreased, or the first threshold value is set to be smaller as the pressure of at least one of air and hydrogen is larger, more accurate current-voltage characteristics can be learned.

  As described above, in the fuel cell system of the present embodiment, the first threshold value is set by the threshold value setting means 53, and at least one of air (oxidant gas) and hydrogen (fuel gas) is set in the learning control means 52. When the magnitude of the difference between the pressure and the reference pressure corresponding to the operating condition of the fuel cell is greater than or equal to the first threshold value, the learning of the relationship between the output current and the output voltage by the current-voltage characteristic learning means 51 is prohibited. Therefore, when the pressure of air (oxidant gas) or hydrogen (fuel gas) deviates by more than a predetermined amount from the reference value corresponding to the operating conditions of the fuel cell, the relationship between the output current and output voltage of the fuel cell When the phenomenon that the relationship between the fuel cell operating conditions and the pressure of air (oxidant gas) or hydrogen (fuel gas) temporarily differs from the set value by a predetermined amount or more occurs Learning Since the result is not changed, appropriate various determinations and various controls can be performed based on the learned current-voltage characteristics of the fuel cell.

  Further, in the threshold setting means 53, the first threshold is set to be smaller in the operating condition in which the change in the output voltage with respect to the change in the pressure of at least one of air (oxidant gas) and hydrogen (fuel gas) is large. Learning of the relationship between the output current and output voltage of the fuel cell can be prohibited within a range where the deviation of the pressure of air (oxidant gas) or hydrogen (fuel gas) from the reference value corresponding to the operating condition of the fuel cell is small. The variation of the learning result of the relationship between the output current and the output voltage can be more effectively prevented under the condition that the variation of the learning result of the relationship between the output current and the output voltage is large.

  Furthermore, the threshold value setting means 53 may set the first threshold value smaller as the pressure of at least one of air (oxidant gas) and hydrogen (fuel gas) is larger. As the pressure of air (oxidant gas) or hydrogen (fuel gas) increases, the voltage change in the current-voltage characteristics increases. Therefore, the greater the pressure of air (oxidant gas) or hydrogen (fuel gas), the more air (oxidation gas). In the range where the deviation of the pressure of the agent gas) or hydrogen (fuel gas) from the reference value corresponding to the operating conditions of the fuel cell is small, learning of the relationship between the output current and output voltage of the fuel cell can be prohibited, and the output Under the condition that the variation in the learning result of the relationship between the current and the output voltage is large, the variation in the learning result of the relationship between the output current and the output voltage can be more effectively prevented.

  In the above description, the difference between the hydrogen pressure and the air pressure and the reference pressure is compared with the common first threshold value. However, the air pressure and the hydrogen pressure may be compared separately with two threshold values. . That is, the threshold value setting unit 53 sets the second threshold value and the third threshold value, and the learning control unit 52 sets the air (oxidant gas) corresponding to the pressure of the air (oxidant gas) and the operating condition of the fuel cell. The magnitude of the difference from the reference pressure is greater than or equal to the second threshold, or the magnitude of the difference between the hydrogen (fuel gas) pressure and the hydrogen (fuel gas) reference pressure corresponding to the operating conditions of the fuel cell Is not greater than the third threshold value, the learning of the relationship between the output current and the output voltage by the current-voltage characteristic learning means 51 is prohibited.

  Thus, depending on the relationship between the change in the output voltage of the fuel cell with respect to the change in air (oxidant gas) and the change in the output voltage of the fuel cell with respect to change in hydrogen (fuel gas), air (oxidant gas) or hydrogen The deviation of the (fuel gas) from the reference value corresponding to the operating conditions of the fuel cell can be set to prohibit the learning of the relationship between the output current and the output voltage of the fuel cell. According to the magnitude of the fluctuation of the relationship learning result, the fluctuation of the learning result of the relation between the output current and the output voltage can be more effectively prevented.

  In this case, if the threshold value setting means 53 sets the second threshold value to be smaller for operating conditions in which the change in output voltage with respect to the change in pressure of air (oxidant gas) is larger, the fuel cell with respect to change in air (oxidant gas). The greater the change in the output voltage, the less the deviation of the air (oxidant gas) pressure from the reference value corresponding to the operating conditions of the fuel cell, the less the relationship between the output current and output voltage of the fuel cell is learned. The change in the learning result of the relationship between the output current and the output voltage can be more effectively changed under the condition that the fluctuation of the learning result of the relationship between the output current and the output voltage is large due to the pressure change of the air (oxidant gas). Can be prevented.

  Further, the threshold value setting means 53 may set the second threshold value smaller as the pressure of air (oxidant gas) is larger. Thereby, it is considered that the change in the output voltage of the fuel cell with respect to the change in the pressure of the air (oxidant gas) is large. As the pressure of the air (oxidant gas) is larger, the fuel cell of the air (oxidant gas) The learning of the relationship between the output current and output voltage of the fuel cell can be prohibited in a range where the deviation from the reference value corresponding to the operating conditions is small. Therefore, the output current and output can be controlled by changing the pressure of air (oxidant gas). It is possible to more effectively prevent the fluctuation of the learning result of the relationship between the output current and the output voltage under the condition that the fluctuation of the learning result of the voltage relation is large.

  Further, in the threshold setting means 53, if the third threshold value is set smaller for an operating condition in which the change in output voltage with respect to the change in hydrogen (fuel gas) pressure is larger, the output voltage of the fuel cell with respect to the change in hydrogen (fuel gas). The larger the change in the pressure, the more the learning of the relationship between the output current and the output voltage of the fuel cell is prohibited in a range where the deviation of the hydrogen (fuel gas) pressure from the reference value corresponding to the operating condition of the fuel cell is small. The variation in the learning result of the relationship between the output current and the output voltage can be more effectively prevented under the condition that the variation in the learning result of the relationship between the output current and the output voltage is large due to the change in the pressure of the fuel gas.

  Further, the threshold value setting means 53 may set the third threshold value smaller as the hydrogen (fuel gas) pressure increases. As a result, the change in the output voltage of the fuel cell with respect to the change in the pressure of hydrogen (fuel gas) is considered to be large. As the pressure of hydrogen (fuel gas) increases, the operating condition of the fuel cell of hydrogen (fuel gas) Learning of the relationship between the output current and output voltage of the fuel cell can be prohibited within a range where the deviation from the reference value corresponding to is small. Therefore, the relationship between the output current and output voltage can be learned by the pressure change of hydrogen (fuel gas). It is possible to more effectively prevent the learning result of the relationship between the output current and the output voltage from being changed under the condition that the fluctuation of the result is large.

Further, since the air pressure has a larger voltage change in the current-voltage characteristics than the hydrogen pressure, it is desirable that the threshold value setting means 53 set the second threshold value to be smaller than the third threshold value to reduce the air pressure threshold value. As a result, the change in the output voltage of the fuel cell with respect to the change in the pressure of the air (oxidant gas) with respect to the pressure of the hydrogen (fuel gas) is considered to be large. Learning of the relationship between the output current and the output voltage of the fuel cell can be prohibited within a range where the deviation from the reference value is small, and accordingly, depending on the respective effects of air (oxidant gas) and hydrogen (fuel gas) The learning result of the relationship between the output current and the output voltage can be more effectively prevented under the condition that the learning result of the relationship between the output current and the output voltage is large. can do.

  Furthermore, a fuel cell system according to Embodiment 3 of the present invention will be described.

  In this embodiment, the configuration of the fuel cell system shown in FIG. Note that the threshold setting unit 53, which is a component of the controller 13, is used, and the threshold setting unit 53 sets the fourth threshold and the fifth threshold larger than the fourth threshold, and the learning control unit 52 determines To serve. Further, the learning control means 52 determines that the ratio of the oxygen partial pressure of the oxidant gas (air) and the hydrogen partial pressure of the fuel gas (hydrogen) is smaller than the fourth threshold value or larger than the fifth threshold value. Furthermore, learning of the relationship between the output current and the output voltage by the current-voltage characteristic learning means 51 is prohibited.

  Next, the operation at the time of learning the current-voltage characteristic in the fuel cell system of the present embodiment will be described with reference to FIG. Here, FIG. 4 is a flowchart for explaining the operation at the time of learning the current-voltage characteristic of the fuel cell stack 3.

  The procedure for learning the current-voltage characteristics of the fuel cell stack 3 shown in FIG. 4 is executed every predetermined time period as in the first embodiment. First, the hydrogen pressure value at the inlet of the fuel cell stack 3 is detected based on the output of the hydrogen inlet pressure sensor 9, and the air pressure value at the inlet of the fuel cell stack 3 is detected based on the output of the air inlet pressure sensor 15. Further, the pressure value of the air at the outlet of the fuel cell stack 3 is detected based on the output of the air outlet pressure sensor 19 (step S201).

  Next, the temperature of the air at the inlet of the fuel cell stack 3 is detected based on the output of the air inlet temperature sensor 16 (step S202). Further, the hydrogen concentration at the inlet of the fuel cell stack 3 is detected based on the output of the hydrogen concentration sensor 20 (step S203).

  Next, the hydrogen partial pressure is calculated (step S204). Here, the hydrogen partial pressure is obtained by multiplying the hydrogen pressure at the inlet of the fuel cell stack 3 detected in step S201 by the hydrogen concentration at the inlet of the fuel cell stack 3 detected in step S203.

Next, the oxygen partial pressure is calculated (step S205). Here, the oxygen partial pressure is obtained using the following equation (Equation 2)
Oxygen partial pressure = (P1-P2) × R (2)
Here, P1 is the pressure of the air at the inlet of the fuel cell stack 3 detected in step S201, P2 is the saturated water vapor pressure at the inlet of the fuel cell stack 3, and R is the proportion of oxygen in the atmosphere (for example, 21 %).

  Assuming that the air at the inlet of the fuel cell stack 3 is saturated or near saturated, the saturated water vapor pressure increases as the temperature calculated in step S202 increases. Therefore, the saturated water vapor pressure based on the temperature can be estimated from a known saturated water vapor pressure curve.

  Next, it is determined whether or not to learn current-voltage characteristics (step S206). Here, the ratio of the hydrogen partial pressure and the oxygen partial pressure calculated in step S204 and step S205 is smaller than the preset fourth threshold or larger than the fifth threshold larger than the fourth threshold. In this case, learning of the current-voltage characteristic is prohibited, and this process is terminated. On the other hand, if the ratio of the hydrogen partial pressure to the oxygen partial pressure is larger than the fourth threshold value and smaller than the fifth threshold value, the process proceeds to step S207.

  Next, steady determination of the power generation state (step S207) and learning of current-voltage characteristics (step S208) are performed, but the processing contents of these steps are the same as steps S105 and S106 of the first embodiment, respectively. Description is omitted.

  As described above, in the fuel cell system of the present embodiment, the fourth threshold value and the fifth threshold value are set by the threshold value setting means 53, and the oxygen partial pressure of air (oxidant gas) is set in the learning control means 52. When the ratio of hydrogen (fuel gas) to the hydrogen partial pressure is smaller than the fourth threshold value or larger than the fifth threshold value larger than the fourth threshold value, the output current by the current-voltage characteristic learning means 51 And learning of the relationship between the output voltage is prohibited.

  As a result, the relationship between the output current and the output voltage of the fuel cell changes depending on the ratio of the oxygen partial pressure and the hydrogen partial pressure, and accordingly, the change in the output voltage of the fuel cell with respect to the change in pressure is considered to be large. In such a case, learning of the relationship between the output current and the output voltage of the fuel cell can be prohibited within a range where the deviation from the reference value corresponding to the operating condition of the fuel cell is small. Therefore, according to the relationship between the pressures of hydrogen gas and oxygen gas, the learning result of the relationship between the output current and the output voltage is more effectively varied under the condition that the learning result of the relationship between the output current and the output voltage is large. As a result, appropriate various determinations and various controls can be performed based on the learned current-voltage characteristics of the fuel cell.

  Finally, the effects of the present invention will be described more specifically with reference to FIGS. FIG. 5 is an explanatory diagram for explaining the temporal transition of the extraction current and the hydrogen pressure when the extraction current is dropped from the rated load to the no load, and FIG. 6 is a diagram for explaining the change in the current-voltage characteristics when the pressure changes. It is explanatory drawing.

  In the conventional method of learning current-voltage characteristics, for example, when hydrogen is in the circulation path, the current taken out from the fuel cell stack 3 is transiently dropped from the rated load to the no load as shown in FIG. In this case, since no gas is consumed in the fuel cell stack 3, the relationship between the current and the pressure is different from the temporarily set relationship. In other words, as shown in FIG. 6, when the pressure changes, the relationship between the current and the voltage changes. In such a case, when learning the relationship between the output current and the output voltage of the fuel cell, the learning value is temporarily changed. There is a problem that it fluctuates.

  On the other hand, when the present invention is applied, when the current taken out from the fuel cell stack 3 changes transiently, the pressure at the inlet of the fuel cell stack 3 is different from the reference pressure corresponding to the operating condition of the fuel cell. Alternatively, when the magnitude of the difference between the reference pressure value and the pressure value at the inlet of the fuel cell stack 3 exceeds a preset threshold value, learning of the current-voltage characteristics is prohibited. . Thereby, even when the current taken out from the fuel cell stack 3 is changed transiently, the current-voltage characteristic of the fuel cell stack 3 can be learned with high accuracy. As a result, the learned current of the fuel cell can be obtained. Various appropriate determinations and various controls can be performed based on the voltage characteristics.

1 is a configuration diagram of a fuel cell system according to Embodiment 1 of the present invention. FIG. 6 is a flowchart for explaining an operation at the time of learning a current-voltage characteristic of the fuel cell stack according to the first embodiment. It is explanatory drawing explaining the current-pressure table data referred at the time of target gas pressure calculation. 12 is a flowchart for explaining an operation at the time of learning a current-voltage characteristic of a fuel cell stack according to a third embodiment. It is explanatory drawing explaining the time transition of extraction current and hydrogen pressure at the time of dropping extraction current from a rated load to no load. It is explanatory drawing explaining the change of the current-voltage characteristic at the time of a pressure change.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ejector 2 Hydrogen circulation flow path 3 Fuel cell stack 4 Hydrogen purge valve 6 Compressor 7 Air supply flow path 8 Hydrogen inlet temperature sensor 9 Hydrogen inlet pressure sensor 11 Exhaust air flow path 12 Air pressure control valve 13 Controller 14 Hydrogen pressure control valve 15 Air inlet pressure sensor 16 Air inlet temperature sensor 17 Current sensor (output current detection means)
18 Voltage sensor (output voltage detection means)
DESCRIPTION OF SYMBOLS 19 Air outlet pressure sensor 20 Hydrogen concentration sensor 21 Tank pressure sensor 22 Tank temperature sensor 23 Hydrogen tank 24 Electric power control apparatus 28 Coolant temperature sensor 29 Coolant circulation pump 30 Heat exchanger 51 Current voltage characteristic learning means 52 Learning control means 53 Threshold value Setting means

Claims (8)

A fuel cell that generates power by supplying fuel gas and oxidant gas;
Output current detection means for detecting the output current of the fuel cell;
Output voltage detection means for detecting the output voltage of the fuel cell;
Current-voltage characteristic learning means for learning a relationship between the output current of the fuel cell and the output voltage;
When the pressure of at least one of the oxidant gas and the fuel gas is different from the reference pressure corresponding to the operating condition of the fuel cell, the current voltage characteristic learning means learns the relationship between the output current and the output voltage. Prohibited learning control means;
Have a threshold value setting means for setting a first threshold value,
The learning control means, when the magnitude of the difference between the pressure of at least one of the oxidant gas and the fuel gas and the reference pressure corresponding to the operating condition of the fuel cell is equal to or greater than the first threshold value, Prohibiting learning of the relationship between the output current and the output voltage by the current-voltage characteristic learning means;
The threshold value setting means sets the first threshold value to be smaller in an operating condition in which the change in the output voltage is larger with respect to the change in the pressure of at least one of the oxidant gas and the fuel gas. . A fuel cell that generates power by supplying fuel gas and oxidant gas;
Output current detection means for detecting the output current of the fuel cell;
Output voltage detection means for detecting the output voltage of the fuel cell;
Current-voltage characteristic learning means for learning a relationship between the output current of the fuel cell and the output voltage;
When the pressure of at least one of the oxidant gas and the fuel gas is different from the reference pressure corresponding to the operating condition of the fuel cell, the current voltage characteristic learning means learns the relationship between the output current and the output voltage. Prohibited learning control means;
Threshold setting means for setting the first threshold;
The learning control means, when the magnitude of the difference between the pressure of at least one of the oxidant gas and the fuel gas and the reference pressure corresponding to the operating condition of the fuel cell is equal to or greater than the first threshold value, Prohibiting learning of the relationship between the output current and the output voltage by the current-voltage characteristic learning means ;
Said threshold setting means, wherein by at least one of the pressure of the oxidant gas and the fuel gas is large, fuel cell systems that and sets small the first threshold. A fuel cell that generates power by supplying fuel gas and oxidant gas;
Output current detection means for detecting the output current of the fuel cell;
Output voltage detection means for detecting the output voltage of the fuel cell;
Current-voltage characteristic learning means for learning a relationship between the output current of the fuel cell and the output voltage;
When the pressure of at least one of the oxidant gas and the fuel gas is different from the reference pressure corresponding to the operating condition of the fuel cell, the current voltage characteristic learning means learns the relationship between the output current and the output voltage. Prohibited learning control means;
Threshold setting means for setting the second threshold and the third threshold;
The learning control means is configured such that the difference between the pressure of the oxidant gas and the reference pressure of the oxidant gas corresponding to the operating condition of the fuel cell is equal to or greater than the second threshold value, or the fuel When the magnitude of the difference between the gas pressure and the reference pressure of the fuel gas corresponding to the operating condition of the fuel cell is equal to or greater than the third threshold, the output current and the output by the current-voltage characteristic learning means Prohibit learning of voltage relationships,
It said threshold setting means, the more the operating condition changes is large in the output voltage with respect to a change in pressure of the oxidant gas, fuel cell systems that and sets small the second threshold value. A fuel cell that generates power by supplying fuel gas and oxidant gas;
Output current detection means for detecting the output current of the fuel cell;
Output voltage detection means for detecting the output voltage of the fuel cell;
Current-voltage characteristic learning means for learning a relationship between the output current of the fuel cell and the output voltage;
When the pressure of at least one of the oxidant gas and the fuel gas is different from the reference pressure corresponding to the operating condition of the fuel cell, the current voltage characteristic learning means learns the relationship between the output current and the output voltage. Prohibited learning control means;
Threshold setting means for setting the second threshold and the third threshold;
The learning control means is configured such that the difference between the pressure of the oxidant gas and the reference pressure of the oxidant gas corresponding to the operating condition of the fuel cell is equal to or greater than the second threshold value, or the fuel When the magnitude of the difference between the gas pressure and the reference pressure of the fuel gas corresponding to the operating condition of the fuel cell is equal to or greater than the third threshold, the output current and the output by the current-voltage characteristic learning means Prohibit learning of voltage relationships,
Said threshold setting means, fuel cell systems that wherein as the pressure of the oxidant gas is large, setting a small second threshold value. A fuel cell that generates power by supplying fuel gas and oxidant gas;
Output current detection means for detecting the output current of the fuel cell;
Output voltage detection means for detecting the output voltage of the fuel cell;
Current-voltage characteristic learning means for learning a relationship between the output current of the fuel cell and the output voltage;
When the pressure of at least one of the oxidant gas and the fuel gas is different from the reference pressure corresponding to the operating condition of the fuel cell, the current voltage characteristic learning means learns the relationship between the output current and the output voltage. Prohibited learning control means;
Threshold setting means for setting the second threshold and the third threshold;
The learning control means is configured such that the difference between the pressure of the oxidant gas and the reference pressure of the oxidant gas corresponding to the operating condition of the fuel cell is equal to or greater than the second threshold value, or the fuel When the magnitude of the difference between the gas pressure and the reference pressure of the fuel gas corresponding to the operating condition of the fuel cell is equal to or greater than the third threshold, the output current and the output by the current-voltage characteristic learning means Prohibit learning of voltage relationships ,
Said threshold setting means, fuel cell systems that wherein the higher the change is large operating condition of the output voltage with respect to a change in pressure of the fuel gas is set smaller the third threshold value. A fuel cell that generates power by supplying fuel gas and oxidant gas;
Output current detection means for detecting the output current of the fuel cell;
Output voltage detection means for detecting the output voltage of the fuel cell;
Current-voltage characteristic learning means for learning a relationship between the output current of the fuel cell and the output voltage;
When the pressure of at least one of the oxidant gas and the fuel gas is different from the reference pressure corresponding to the operating condition of the fuel cell, the current voltage characteristic learning means learns the relationship between the output current and the output voltage. Prohibited learning control means;
Threshold setting means for setting the second threshold and the third threshold;
The learning control means is configured such that the difference between the pressure of the oxidant gas and the reference pressure of the oxidant gas corresponding to the operating condition of the fuel cell is equal to or greater than the second threshold value, or the fuel When the magnitude of the difference between the gas pressure and the reference pressure of the fuel gas corresponding to the operating condition of the fuel cell is equal to or greater than the third threshold, the output current and the output by the current-voltage characteristic learning means Prohibit learning of voltage relationships,
It said threshold setting means, said etc. pressure of the fuel gas is large Iho, the third fuel cell system that is characterized in that setting a small threshold. A fuel cell that generates power by supplying fuel gas and oxidant gas;
Output current detection means for detecting the output current of the fuel cell;
Output voltage detection means for detecting the output voltage of the fuel cell;
Current-voltage characteristic learning means for learning a relationship between the output current of the fuel cell and the output voltage;
When the pressure of at least one of the oxidant gas and the fuel gas is different from the reference pressure corresponding to the operating condition of the fuel cell, the current voltage characteristic learning means learns the relationship between the output current and the output voltage. Prohibited learning control means;
Threshold setting means for setting the second threshold and the third threshold;
The learning control means is configured such that the difference between the pressure of the oxidant gas and the reference pressure of the oxidant gas corresponding to the operating condition of the fuel cell is equal to or greater than the second threshold value, or the fuel When the magnitude of the difference between the gas pressure and the reference pressure of the fuel gas corresponding to the operating condition of the fuel cell is equal to or greater than the third threshold, the output current and the output by the current-voltage characteristic learning means Prohibit learning of voltage relationships,
It said threshold setting means, the third fuel cell system that is characterized in that smaller the second threshold value than the threshold of. A fuel cell that generates power by supplying fuel gas and oxidant gas;
Output current detection means for detecting the output current of the fuel cell;
Output voltage detection means for detecting the output voltage of the fuel cell;
Current-voltage characteristic learning means for learning a relationship between the output current of the fuel cell and the output voltage;
When the pressure of at least one of the oxidant gas and the fuel gas is different from the reference pressure corresponding to the operating condition of the fuel cell, the current voltage characteristic learning means learns the relationship between the output current and the output voltage. Prohibited learning control means;
Threshold setting means for setting a fourth threshold and a fifth threshold greater than the fourth threshold;
The learning control means is configured to reduce the current when the ratio between the oxygen partial pressure of the oxidant gas and the hydrogen partial pressure of the fuel gas is smaller than the fourth threshold value or larger than the fifth threshold value. fuel cell system that and inhibits learning of the relationship between the output current and the output voltage by the voltage characteristics learning means.

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