JP2007220625A - Fuel cell system - Google Patents

Abstract

An object of the present invention is to perform an abnormality diagnosis of an air supply system more reliably.
A target air flow rate calculation unit 31 of a system control device 30 calculates a target air flow rate, and an operation amount calculation unit 32 calculates an air flow rate of an air supply system based on a detected value of the flow meter 10 and a target air flow rate. The feedback control is performed, and the predetermined range setting unit 33 sets the normal range of the feedback amount in the feedback control, and includes the normal range of the feedback amount, and the air flow rate is allowed to operate the fuel cell system normally. An allowable range of the feedback amount that is a range is set, an area outside the normal range of the feedback amount and within the allowable range of the feedback amount is set as a predetermined range, and the abnormality determination unit 34 determines the feedback amount in the feedback control within the predetermined range. When it is outside, it is determined that the air supply is abnormal.
[Selection] Figure 1

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system capable of more reliably diagnosing an abnormality in an air supply system using control parameters for air flow rate control and maintaining high reliability.

  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, if a failure occurs in the air supply system that supplies air to the fuel cell, it becomes difficult to supply air to the fuel cell at a flow rate and pressure suitable for power generation. Proper implementation is important in maintaining the reliability of the fuel cell system. As a conventional air supply system failure determination method, for example, there is a “fuel cell device air supply system failure determination method” disclosed in Japanese Patent Application Laid-Open No. 2004-179072.

This conventional example is applied to a fuel cell device including a fuel cell that is supplied with fuel and an oxidant to generate power, and an air supply system that has a compressor that supplies air as an oxidant to the fuel cell. If the absolute value of the difference between the command value and the command value is greater than or equal to a predetermined value and a predetermined time has elapsed, it is determined that the air supply system has failed. Specifically, the rotation speed of the compressor is calculated based on the flow rate detected by the air flow meter or directly detected.
JP 2004-179072 A

  However, in the technique disclosed in Patent Document 1 described above, the rotational speed of the compressor used for failure determination is based on the detection result of an instrument such as an air flow meter, and the instrument such as an air flow meter operates normally. Based on the assumption that the compressor is rotating, the abnormality diagnosis of the air supply system (compressor, flow path resistance) is performed based on the feedback amount (difference between the rotation speed and the command value) with respect to the command value of the compressor rotation speed.

  Therefore, in a system that cannot accurately determine whether the instrument such as an air flow meter is normal or abnormal, there is a possibility that an abnormality diagnosis of the air supply system cannot be performed. In order to accurately determine whether the operation is normal or abnormal, there is a situation in which it is necessary to add a part for performing abnormality / normality diagnosis.

  The present invention has been made in view of the above-described conventional circumstances, and even when the operation determination of whether the instrument is normal or abnormal cannot be accurately performed, the control parameter of the air flow rate control is used more reliably. It is another object of the present invention to provide a fuel cell system capable of diagnosing air supply system abnormality and maintaining high reliability.

  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. Oxidant gas supply means to supply; flow rate detection means for detecting a flow rate of oxidant gas supplied by the oxidant gas supply means; oxidant gas target flow rate calculation means for calculating a target flow rate of the oxidant gas; Based on the detection value of the flow rate detection means and the target flow rate of the oxidant gas, a flow rate control means for feedback control of the oxidant gas flow rate of the oxidant gas supply means, and a normal range of the feedback amount in the feedback control, The normal amount range of the feedback amount is included, and the oxidant gas flow rate is allowed to operate the fuel cell system normally. A predetermined range setting means for setting an allowable range of the feedback amount as a range, and setting a region outside the normal range of the feedback amount and within the allowable range of the feedback amount as a predetermined range; and the feedback amount in the feedback control is the And an abnormality determining means for determining that the oxidant gas supply is abnormal when it is outside the predetermined range.

  In the fuel cell system according to the present invention, when the allowable range of the feedback amount is set by the predetermined range setting unit, the predetermined amount is determined according to the guaranteed accuracy of the component performance that affects the feedback amount of the operation amount in the oxidant gas supply unit. Since the margin from the range to the allowable range of the feedback amount can be variably set, it is possible to suppress erroneous determination by the abnormality determination means, and as a result, it is not possible to accurately determine whether the instrument is normal or abnormal However, it is possible to more reliably diagnose the abnormality of the air supply system using the control parameters of the air flow rate control and maintain high reliability.

  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 an embodiment of the present invention. The fuel cell system of the present embodiment is used as a driving power source of a fuel cell vehicle, for example. As shown in FIG. 1, a fuel gas containing hydrogen (for example, hydrogen gas) and an oxidizer containing oxygen A fuel cell stack 3 is provided that is supplied with gas (for example, air) and generates electricity by electrochemically reacting hydrogen and oxygen.

  Further, as a hydrogen supply system, a hydrogen gas supply device 1, a pressure regulating valve 6, a hydrogen gas supply channel 7, a gas circulation device 8, a hydrogen gas circulation channel 9, a pressure sensor 23, a temperature sensor 24, a flow rate control valve (purge) Valve) 11 and a hydrogen gas discharge channel 12, and as an air supply system, an air compressor 2, an aftercooler 13, a humidifier 14, an air supply channel 40, 41, 42, 15, a filter 14, an air exhaust channel 16 , 18, a pressure adjustment valve 17, a flow meter (flow rate detection means) 10, a pressure sensor 26, and a temperature sensor 27.

  Furthermore, the fuel cell system of this embodiment includes various sensors such as a hydrogen supply system and an air supply system, or a cooling mechanism (not shown), and other various sensors (atmospheric pressure sensor 28, outside air temperature sensor 29, and voltage sensor (voltage Based on the detection signal from the detection means) 20), the system control device 30 is provided for controlling each component such as a hydrogen supply system and an air supply system or a cooling mechanism.

  In the fuel cell stack 3, an anode (fuel electrode) 4 supplied with hydrogen gas as a fuel gas and a cathode (oxidant electrode) 5 supplied with air as an oxidant gas are overlapped with an electrolyte membrane interposed therebetween. A power generation cell is configured, and 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. is there. In each power generation cell of the fuel cell stack 3, a reaction occurs in which the hydrogen gas supplied to the anode 4 is separated into hydrogen ions and electrons. The hydrogen ions pass through the electrolyte membrane, and the electrons pass through an external circuit to generate power. And move to the cathode 5 respectively. At the cathode 5, oxygen in the supplied air reacts with hydrogen ions and electrons that have moved through the electrolyte membrane to generate water, which is discharged to the outside.

  As the electrolyte membrane 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 addition, the electrolyte membrane is kept in a wet state by supplying supply air humidified by the humidifier 14, and efficient power generation can be performed.

  In order to generate power in the fuel cell stack 3, it is necessary to supply hydrogen gas as a fuel gas and air as an oxidant gas to the anode 4 and the cathode 5 of each power generation cell, respectively. A hydrogen supply system and an air supply system are provided.

  First, the hydrogen supply system includes a hydrogen gas supply device 1 that holds the hydrogen gas supplied to the fuel cell stack 3 in a high pressure state, and a pressure adjustment valve 6 that adjusts the pressure of the hydrogen gas supplied from the hydrogen gas supply device 1. , A gas circulation device 8 for circulating the hydrogen gas discharged from the fuel cell stack 3 to the hydrogen gas circulation passage 9, and a hydrogen gas for supplying the hydrogen gas discharged from the fuel cell stack 3 to the fuel cell stack 3 again A circulation passage (fuel gas circulation passage) 9, a flow rate control valve (purge valve) 11 for discharging the hydrogen gas in the hydrogen gas circulation passage 9 to the outside, and a hydrogen gas discharge connected downstream of the flow rate control valve 11 A flow path (fuel gas discharge flow path) 12.

  The hydrogen gas flowing out from the hydrogen gas supply device 1 flows through the hydrogen gas supply channel 7 and is supplied to the anode 4 of the fuel cell stack 3. The pressure regulating valve 6 is disposed on the hydrogen gas supply channel 7 and regulates the high-pressure hydrogen gas flowing out from the hydrogen gas supply device 1 to an appropriate pressure (anode operating pressure) and flow rate in the anode 4. . A pressure sensor 23 for detecting the pressure of the hydrogen gas (anode operating pressure) is disposed on the hydrogen gas supply flow path 7 downstream of the pressure regulating valve 6, and the system controller 30 is connected to the pressure sensor 23. The anode operating pressure of the fuel cell stack 3 is adjusted by feeding back the detected value and controlling the operation of the pressure regulating valve 6.

  The hydrogen gas circulation channel 9 connects between the hydrogen gas outlet of the anode 4 and the hydrogen gas supply channel 7, and the gas circulation device 8 converts the unreacted hydrogen gas into the hydrogen gas circulation channel. It is circulated again to the anode 4 through 9. Further, the hydrogen gas discharge channel 12 is branched from the hydrogen gas circulation channel 9, the flow control valve 11 is disposed on the hydrogen gas discharge channel 12, and the opening degree of the flow control valve 11 is controlled by the system controller 30. By adjusting, the discharge flow rate of the hydrogen gas (anode off gas) discharged from the hydrogen gas discharge channel 12 is adjusted. The hydrogen gas (anode off gas) discharged from the hydrogen gas discharge channel 12 is sufficiently diluted with the cathode off gas in the air discharge channel 18 and discharged to the outside.

  During normal power generation, a gas (for example, nitrogen) that does not contribute to power generation of the fuel cell stack 3 present in the cathode 5 is electrolyte from the cathode 5 to the anode 4 according to the nitrogen partial pressure difference between the cathode 5 and the anode 4. Permeates through the membrane. The circulation flow rate of the gas circulation device 8 has a limit value based on the gas circulation performance of the gas circulation device 8 and the pressure loss of the anode 4 and the pressure loss of the hydrogen gas circulation passage 9. Therefore, there is a limit value (upper limit allowable nitrogen concentration) of the nitrogen concentration that can be allowed in the hydrogen gas circulation passage 9 based on the hydrogen flow rate required according to the power generation of the fuel cell stack 3. That is, in order to adjust the nitrogen concentration in the hydrogen gas circulation passage 9 to be equal to or lower than the upper limit allowable nitrogen concentration, it is necessary to discharge the permeated nitrogen from the cathode 5 to the outside. Since the gas can be discharged from the gas discharge channel 12 to the outside, the nitrogen concentration in the hydrogen gas circulation channel 9 can be adjusted by adjusting the opening of the purge valve 11.

  Next, the air supply system includes an air compressor 2 that compresses and supplies air to the fuel cell stack 3, a flow meter 10 that detects the flow rate of the air sucked by the air compressor 2, and the air that is pumped by the compressor 2. An aftercooler 13 that cools the fuel, a humidifier 14 that moves moisture from the air discharged from the fuel cell stack 3 (exhaust air) to the air supplied to the fuel cell stack 3 (supply air), and the fuel cell stack 3 And a pressure adjusting valve 17 for adjusting the pressure of the discharged air.

  The air discharged from the air compressor 2 flows through the air supply flow path 15 and is supplied to the cathode 5 of the fuel cell stack 3, and the air discharged from the cathode 5 flows through the air discharge flow path 18 and is discharged outside the apparatus. Is done. The air flowing out from the air compressor 2 is cooled to a temperature suitable for the electrochemical reaction in the fuel cell stack 3 by the aftercooler 13. The air discharged from the cathode 5 becomes a cathode off-gas containing a portion of oxygen consumed and water generated by power generation. The humidifier 14 humidifies the air supplied to the fuel cell stack 3 using moisture contained in the cathode off gas. A pressure sensor 26 that detects the pressure of the air (cathode operating pressure) is disposed on the air supply flow path 15 downstream of the humidifier 14, and the system controller 30 detects the detected values of the pressure sensors 23 and 26. The cathode operation pressure of the fuel cell stack 3 is adjusted by feeding back and controlling the operation of the pressure adjusting valve 17 according to the anode operation pressure.

  The system control device 30 is configured as a microcomputer having, for example, a CPU, ROM, RAM, peripheral interface, and the like. The system controller 30 includes various sensors such as a hydrogen supply system and an air supply system, other various sensors (for example, an atmospheric pressure sensor 28 that detects atmospheric pressure, an outside air temperature sensor 29 that detects outside air temperature, and a fuel cell. The detection value is input from each fuel cell in the stack 3 or a sensor for detecting the current value of the entire fuel cell stack 3 or the voltage sensor 20 for detecting the voltage value. A signal is output to control the operation of each part of the fuel cell system.

  In FIG. 1, the system control device 30 includes a target air flow rate calculation unit 31, an operation amount calculation unit 32, a predetermined range setting unit 33, and an abnormality detection unit 34, which are functions of a program executed on the CPU. It represents a unity.

  The target air flow rate calculation unit 31 corresponds to the oxidant gas target flow rate calculation means in the claims, and calculates the target air flow rate of air (oxidant gas) in accordance with the required load (generated current).

  The manipulated variable calculation unit 32 corresponds to a flow rate control unit, and based on the flow rate detection value of the flow meter (flow rate detection unit) 10 and the target air flow rate calculated by the target air flow rate calculation unit 31, a target is supplied to the fuel cell stack 3 by feedback control. In order to supply the air flow rate, the operation amount (feedback amount) of the compressor 2 is calculated.

  The manipulated variable calculation unit 32 includes a volume flow rate calculation unit, a compressor pressure ratio calculation unit, and a map (not shown). Here, the volume flow rate calculation unit calculates the volume flow rate based on the target air flow rate, the detection value of the atmospheric pressure sensor 28, and the detection value of the outside air temperature sensor 29. The compressor pressure ratio calculation unit is based on the target air flow rate, the detection value of the atmospheric pressure sensor 28, the detection value of the outside air temperature sensor 29, the detection value of the pressure sensor 26 of the air supply system, and the detection value of the temperature sensor 27. The upstream pressure and downstream pressure of the compressor 2 are estimated, and the compressor pressure ratio is calculated.

  That is, the operation amount calculation unit 32 refers to a preset map from the volume flow rate calculated by the volume flow rate calculation unit and the pressure ratio calculated by the compressor pressure ratio calculation unit, from the compressor 2 to the fuel cell stack 3. The compressor command rotational speed for supplying the target air flow rate to is calculated. Note that the system control device 30 performs feedback control based on the target air flow rate and the detected value of the flow meter 10 with the rotational speed of the compressor 2 as an operation amount (feedback amount).

  The predetermined range setting unit 33 sets a normal range of the feedback amount in the feedback control, includes the normal range of the feedback amount, and the air flow rate is a system limit allowable range of the air flow rate at which the fuel cell system can be normally operated. An allowable range of the feedback amount is set, and an area outside the normal range of the feedback amount and within the allowable range of the feedback amount is set as a predetermined range.

  The predetermined range setting unit 33 sets the upper limit value of the predetermined range from a value between the upper limit value of the normal range of the feedback amount and the upper limit value of the allowable range of the feedback amount to the upper limit value of the allowable range of the feedback amount. The lower limit value of the predetermined range is a value between the lower limit value of the normal range of the feedback amount and the lower limit value of the allowable range of the feedback amount to the lower limit value of the allowable range of the feedback amount. Set as.

  In addition, the predetermined range setting unit 33 sets the system limit allowable range of the air flow rate to be equal to or less than the air flow rate that can prevent the power generation performance from being lowered due to the decrease in the moisture content of the fuel cell stack 3, thereby preventing excessive supply of air. As a first predetermined range, a range from a value between the upper limit value of the normal range of the feedback amount and the upper limit value of the allowable range of the feedback amount to the upper limit value of the allowable range of the feedback amount is set.

  Further, the predetermined range setting unit 33 sets the system limit allowable range of the air flow rate to be equal to or higher than the air flow rate that can prevent a decrease in power generation performance caused by insufficient supply of the oxidant gas necessary for power generation of the fuel cell stack 3. As a second predetermined range that can prevent air supply shortage, a range from a value between the lower limit value of the normal range of the feedback amount and the lower limit value of the allowable range of the feedback amount to the lower limit value of the allowable range of the feedback amount Set. A more detailed description of the predetermined range setting unit 33 will be described later based on the principle description.

  Furthermore, the abnormality detection unit 34 determines that the air supply is abnormal when the feedback amount in the feedback control is outside the predetermined range. Moreover, the abnormality detection part 34 determines with air supply abnormality, when the feedback amount in feedback control exceeds the flow excess diagnostic threshold set in the 1st predetermined range. Moreover, the abnormality detection part 34 determines with air supply abnormality, when the feedback amount in feedback control is less than the flow shortage diagnosis threshold set in the 2nd predetermined range. Furthermore, when it is determined that the air supply is abnormal, or when abnormality is determined by determining whether each component is abnormal / normal, an alarm is generated via the alarm generator 35.

  Next, referring to FIGS. 2 to 5, the predetermined range set by the predetermined range setting unit 33, the first predetermined range that can prevent excessive air supply, and the second predetermined range that can prevent insufficient air supply. This will be described in detail. 2 is an explanatory diagram for explaining the transition of the air flow rate with respect to the generated current, and FIG. 3 is an explanatory diagram for explaining the establishment range of the target air flow rate based on the system allowable upper limit air flow rate and the system lower limit air flow rate. 4 is an explanatory diagram for explaining the normal range of the feedback amount of the compressor 2 and the allowable range of the feedback amount, and FIG. 5 is an explanatory diagram for explaining the establishment range of the diagnostic threshold in the excessive air flow diagnosis and the insufficient air flow diagnosis.

  First, with reference to FIG. 2 and FIG. 3, selection of the target air flow rate at which the fuel cell system can be operated safely and stably will be described.

  In FIG. 2, Qa is a transition of the air flow rate necessary for power generation of the fuel cell stack 3 with respect to a required load (generated current). Therefore, if the air flow rate is equal to or higher than the air flow rate Qa, a decrease in output due to an insufficient air flow rate to the fuel cell stack 3 can be prevented.

  Moreover, Qb is a transition with respect to the required load (generated current) of the air flow rate capable of keeping the moisture content of the electrolyte membrane of the fuel cell stack 3 at a predetermined required value. Therefore, if the air flow rate is less than or equal to the air flow rate Qb, the moisture content of the electrolyte can be secured above the required value, and dry-out of the electrolyte membrane can be prevented.

  Here, when moisture contained in the electrolyte membrane of the cells constituting the fuel cell stack 3 is taken away by the continuously supplied reaction gas, the cause of reducing the output of the fuel cell stack 3 (dryout of the electrolyte membrane) It becomes. That is, in order to stably obtain a high output in the fuel cell system, it is necessary to keep the water content of the electrolyte at or above the required value. If the operating temperature and operating pressure are known according to the required load of the fuel cell system, the moisture content of the electrolyte is kept at the required value from the amount of water produced according to the required load and the amount of water taken out by the reaction gas. The air flow rate can be calculated. In this example, the required value of the moisture content of the electrolyte is calculated based on experimental values.

  Further, Qc is a change with respect to a required load (generated current) of an air flow rate at which hydrogen contained in the purge gas discharged from the flow control valve (purge valve) 11 can be sufficiently diluted with the cathode off gas and discharged to the outside. It is. Therefore, if the air flow rate is equal to or higher than the air flow rate Qc, the hydrogen contained in the purge gas discharged from the flow control valve 11 can be sufficiently diluted with the cathode off gas and discharged to the outside.

  Here, the flow rate of the purge gas discharged from the flow control valve 11 can be calculated from the vertical pressure difference of the flow control valve 11 and the gas temperature when the opening area of the flow control valve 11 is determined. That is, when the operating temperature and the operating pressure are known according to the required load of the fuel cell system, the purge gas flow rate can be calculated. In this embodiment, the purge gas contains nitrogen. However, in consideration of safety, the purge gas is assumed to have a hydrogen concentration of 100%, and the purge gas having a hydrogen concentration of 100% can be sufficiently diluted and discharged to the outside. Calculate as flow rate.

  Therefore, an air flow rate establishment range in which the fuel cell system can be safely operated and a high output can be stably obtained is an air flow rate equal to or lower than the air flow rate Qb that can prevent the electrolyte membrane from being dried out. Thus, the condition is that the air flow rate Qa required for power generation of the fuel cell stack 3 and the air flow rate Qc that can dilute the hydrogen discharged from the flow rate control valve 11 are equal to or larger than the air flow rate that is larger.

  That is, as shown in FIG. 3, in the air flow rate characteristics with respect to the required load (generated current), the air flow rate Qb that can prevent the electrolyte membrane dryout is set as the system allowable upper limit air flow rate QU, and the electrolyte membrane dryout can be prevented. The air flow rate that is equal to or lower than the air flow rate Qb and that is larger than the air flow rate Qa necessary for power generation of the fuel cell stack 3 and the air flow rate Qc that can dilute the hydrogen discharged from the flow control valve 11 is It is necessary to select the target air flow rate within the range (the hatched portion Qarea in the figure) that is the system allowable lower limit air flow rate QL. In the example shown in FIG. 3, the target air flow rate Qt is selected as an air flow rate that gives a margin to the system allowable lower limit air flow rate QL according to the generated current.

  Further, in this way, the system limit allowable range of the air flow used for setting the predetermined range, the first predetermined range, and the second predetermined range in the predetermined range setting unit 33 is the system allowable upper limit air flow rate QU and the system allowable range. It is set by the lower limit air flow rate QL.

  Next, with reference to FIG. 4, the operation amount (rotation speed) of the compressor 2, that is, the normal range and the allowable range of the feedback amount will be described.

  FIG. 4A shows the normal range of the feedback amount corresponding to the air flow rate. Here, the normal range of the feedback amount is a range of the feedback amount when each component of the air supply system is normal.

  The air supply system of the present embodiment includes a compressor 2, a flow meter 10, an after cooler 13, a humidifier 14, and air supply channels 15, 40, 41, and 42. The normal range of the feedback amount includes the detection accuracy of the flow meter 10, the performance guarantee range of the discharge flow rate of the compressor 2, the pressure loss guarantee range of the aftercooler 13, the pressure loss guarantee range of the humidifier 14, and the air supply flow path. It is calculated based on the pressure loss guarantee range of 15, 40, 41, and 42 and the calculation accuracy of the operation amount calculation unit 32. The calculation accuracy of the operation amount calculation unit 32 includes the detection accuracy of the atmospheric pressure sensor 28, the detection accuracy of the outside air temperature sensor 29, the detection accuracy of the pressure sensor 26, and the detection accuracy of the temperature sensor 27.

  Therefore, as shown in FIG. 4A, the normal range of the feedback amount corresponds to the air flow rate Q2 drifted downward due to the component variation from the feedback amount corresponding to the air flow rate Q1 drifted upward due to the component variation. The range is up to the feedback amount.

  On the other hand, FIG. 4B shows the allowable range of the feedback amount corresponding to the air flow rate. If the feedback amount is within this allowable range, even if the detection accuracy of the flow meter 10 decreases, the air flow supplied from the compressor 2 is equal to or lower than the system allowable lower limit air flow QL or equal to or higher than the system allowable upper limit air flow QU. The allowable range of the feedback amount is set so that it does not occur.

  In other words, the allowable range of the feedback amount is that the flow rate of air supplied from the compressor 2 is acceptable for the system even though the detection value of the flow meter 10 matches the target air flow rate as a result of the decrease in detection accuracy of the flow meter 10. When the upper limit air flow rate QU or the system allowable lower limit air flow rate QL is equal, the detection accuracy of the flow meter 10, the performance guarantee range of the discharge flow rate of the compressor 2, the pressure loss guarantee range of the after cooler 13, and the humidifier 14 It is calculated based on the pressure loss guarantee range, the pressure loss guarantee range of the air supply passages 15, 40, 41, and 42, and the calculation accuracy of the operation amount calculation unit 32.

  That is, as shown in FIG. 4B, the allowable range of the feedback amount is determined based on the feedback amount corresponding to the air flow rate Q3 drifting downward from the system allowable upper limit air flow rate QU due to these component variations. This is a range up to the feedback amount corresponding to the air flow rate Q4 drifted upward due to more component variations.

  Thus, the allowable range of the feedback amount is set corresponding to the system limit allowable range of the air flow rate at which the fuel cell system can be normally operated, and the abnormality detection unit 34 determines that the feedback amount of the compressor rotation speed is within the allowable range. An abnormality is detected by monitoring whether or not there is.

  Specifically, as the predetermined range of the feedback amount that the abnormality detection unit 34 determines as an air supply abnormality, the upper limit value of the predetermined range is set as the upper limit value (Q1) of the normal range of the feedback amount and the upper limit value of the allowable range of the feedback amount. (Q3) and the upper limit value (Q3) of the allowable range of the feedback amount, and the lower limit value of the predetermined range is set as the lower limit value (Q2) of the normal range of the feedback amount and the feedback It is set as a value between a value between the lower limit value (Q4) of the allowable range of the amount and a lower limit value (Q4) of the allowable range of the feedback amount.

  Further, in this embodiment, in order to perform an excessive air flow diagnosis and an insufficient air flow diagnosis, an excessive flow diagnosis threshold and an insufficient flow diagnosis threshold are set, respectively, exceeding the excessive flow diagnosis threshold or falling below the insufficient flow diagnosis threshold. When the oxidant gas supply abnormality is determined, the first predetermined range and the second predetermined range are set as ranges for selecting the excessive flow rate diagnosis threshold value and the insufficient flow rate diagnosis threshold value, respectively. .

  Next, referring to FIG. 5, the first predetermined range and the second predetermined range, the excessive flow diagnosis threshold in the excessive air flow diagnosis. In addition, selection of an insufficient flow rate diagnosis threshold in the insufficient air flow rate diagnosis will be described.

  A region A in FIG. 5 is a first predetermined range, and is a region in which an overflow diagnosis threshold for overflow diagnosis can be set. That is, the first predetermined range (region A) is an upper limit value of the allowable range of feedback amount from a value between the upper limit value (Q1) of the normal range of feedback amount and the upper limit value (Q3) of the allowable range of feedback amount. This is set as a range up to (Q3). Here, it is set as a range from the upper limit value (Q1) of the normal range of feedback amount to the upper limit value (Q3) of the allowable range of feedback amount.

  Area B is the second predetermined range, and is an area in which an insufficient air flow diagnosis threshold for air flow insufficient diagnosis can be set. That is, the second predetermined range (region B) is a value between the lower limit value (Q2) of the normal range of feedback amount and the lower limit value (Q4) of the allowable range of feedback amount to the lower limit value of the allowable range of feedback amount. It is set as a range up to (Q4). Here, it is set as a range from the lower limit value (Q2) of the normal range of the feedback amount to the lower limit value (Q4) of the allowable range of the feedback amount.

  In the first predetermined range (region A) and the second predetermined range (region B), when the excessive flow rate diagnosis threshold and the insufficient flow rate diagnosis threshold are selected closer to the normal range of the feedback amount, While it is possible to operate the fuel cell system on the safer side with respect to the insufficient flow rate, erroneous determination by the abnormality detection unit 34 is likely to occur. Therefore, in order to suppress erroneous determination by the abnormality detection unit 34 while operating the fuel cell system on the safer side with respect to excessive air flow or insufficient air flow, the first predetermined range (region A) and the second It is desirable to select a diagnostic threshold value as the median value of the predetermined range (region B).

  In addition, when calculating the allowable range of the feedback amount of the compressor speed, if the performance guarantee accuracy of each part that affects the feedback amount can be accurately estimated, the margin from the diagnostic threshold to the allowable range of the feedback amount is increased. Can be expected small. Therefore, in order to suppress erroneous determination by the abnormality detection unit 34, the upper limit and lower limit sides of the allowable range of the feedback amount are further determined from the median values of the first predetermined range (region A) and the second predetermined range (region B). Therefore, it is desirable to set a diagnostic threshold. In this embodiment, for each required load, the overflow diagnosis threshold is set to the median value of the first predetermined range (area A) in the overflow diagnosis, and the underflow diagnosis threshold is set to the second predetermined range (in the airflow shortage diagnosis). The median of region B) is selected.

  Next, based on the above-described configuration and the principle description, refer to FIG. 6 to FIG. 8 for the procedure of the excess air flow diagnosis and the insufficient air flow diagnosis performed by the abnormality determination unit 34 of the fuel cell system of the present embodiment. To explain. Here, FIG. 6 is a flowchart for explaining the procedure of the air flow excess diagnosis and the air flow shortage diagnosis according to the present embodiment. FIG. 7 shows a table TA of the flow shortage diagnosis threshold value corresponding to the generated current used in the air flow shortage diagnosis. FIG. 8 is an explanatory diagram for explaining a table TB of excessive flow rate diagnosis threshold values corresponding to the generated current used in the excessive air flow rate diagnosis.

  First, the feedback amount of the compressor speed is read from the operation amount calculation unit 32 (step S101), the generated current of the fuel cell stack 3 is read (step S102), and the table TA is referred to based on the read current value. Then, an insufficient flow rate diagnosis threshold used for air flow shortage diagnosis is read (step S103). Here, the table TA is a numerical table of flow rate shortage diagnosis threshold values for each required load (generated current), and is set as the median value of the first predetermined range (region A) as described above, as shown in FIG. It has special characteristics.

  Next, referring to the table TB from the power generation current read in step S102, the flow excess diagnosis threshold used for the air flow excess diagnosis is read (step S104). Here, the table TB is a numerical table of flow excess diagnosis threshold values for each required load (generated current), and is set as the median value of the second predetermined range (region B) as described above, as shown in FIG. It has special characteristics.

  Next, the feedback amount of the compressor rotation speed read in step S101 is compared with the insufficient flow rate diagnosis threshold value read in step S103, and the state where the feedback amount is below the insufficient flow rate diagnosis threshold value (insufficient air supply) continues for a predetermined time. Whether the air supply is abnormal (insufficient air flow rate) or not is determined based on whether or not it has been performed (step S105). If it is determined that the air supply is abnormal (insufficient air flow rate), the process proceeds to step S107, and if the feedback amount is greater than or equal to the insufficient flow rate diagnosis threshold or if the insufficient air supply state has not continued for a predetermined time, the process proceeds to step S106.

  That is, the processing of steps S101 to S105 is performed every sampling time of a predetermined cycle, and the feedback amount is diagnosed as insufficient for a predetermined amount of time measured by the hardware timer or software timer after the feedback amount falls below the insufficient flow rate diagnosis threshold. Judgment is made based on whether or not the state below the threshold value (air supply shortage) continues, and when the air supply shortage state continues for a predetermined time, it is determined that there is an air supply abnormality (air flow shortage).

  Next, the feedback amount of the compressor rotation speed read in step S101 is compared with the excessive flow rate diagnosis threshold value read in step S104, and the state where the feedback amount exceeds the excessive flow rate diagnosis threshold value (excessive air supply) continues for a predetermined time. Whether or not the air supply is abnormal (the air flow rate is excessive) is determined based on whether or not it has been performed (step S106). When it is determined that the air supply is abnormal (excessive air flow rate), the process proceeds to step S107, and when the feedback amount is equal to or less than the insufficient flow rate diagnosis threshold or when the excessive air supply state has not continued for a predetermined time, the process returns to step S101.

  In other words, the processing of steps S101 to S106 is performed every sampling time of a predetermined period, and the feedback amount is overflow diagnosis for a predetermined time measured by the hardware timer or software timer after the feedback amount exceeds the overflow diagnosis threshold. Judgment is made based on whether or not the state exceeding the threshold (excessive air supply) continues, and when the excessive air supply state continues for a predetermined time, it is determined that the air supply is abnormal (excessive air flow).

  If it is determined in step S105 that the air supply is abnormal (insufficient air flow), or if it is determined in step S106 that the air supply is abnormal (excessive air flow), alarm information is notified via the alarm generator 35 ( Step S107), the system is stopped (Step S108). Here, various types of alarm information can be reported, such as generation of an alarm sound, sound output of an alarm message, display of an alarm message on a display panel, or blinking display of a predetermined location on the display panel.

  As described above, in the fuel cell system of this embodiment, the fuel cell stack 3 that generates power by supplying hydrogen gas (fuel gas) and air (oxidant gas), and the hydrogen supply system (fuel) that supplies hydrogen gas. In a fuel cell system comprising a gas supply means), an air supply system for supplying air (oxidant gas supply means), and a flow meter (flow rate detection means) 10 for detecting an air flow rate supplied by the air supply system, The target air flow rate calculation unit 31 of the system controller 30 calculates the target air flow rate, and the operation amount calculation unit (flow rate control means) 32 calculates the air flow rate of the air supply system based on the detected value of the flow meter 10 and the target air flow rate. The predetermined range setting unit 33 sets a normal range of the feedback amount in the feedback control, and normalizes the feedback amount. A feedback amount tolerance range that is within the system limit tolerance range of the air flow rate that allows the fuel cell system to operate normally, and is outside the normal feedback amount range and within the feedback amount tolerance range. Is set as a predetermined range, and the abnormality determination unit 34 determines that the air supply is abnormal when the feedback amount in the feedback control is outside the predetermined range.

  Specifically, in the predetermined range setting 33, the normal range and allowable range of the feedback amount are set as follows: normal detection accuracy of the flow meter 10, flow rate accuracy guaranteed range of the air supply system (performance guaranteed range of discharge flow rate of the compressor 2, after sales The pressure loss guarantee range of the cooler 13 and the pressure loss guarantee range of the humidifier 14), the flow resistance guarantee range of the flow path for supplying air (the pressure loss guarantee range of the air supply flow paths 15, 40, 41, 42), and It is desirable to set the upper limit value of the predetermined range based on the value between the upper limit value of the normal range of the feedback amount and the upper limit value of the allowable range of the feedback amount. The lower limit value of the predetermined range is set to the lower limit value of the normal range of the feedback amount and the allowable range of the feedback amount. Set of values between a lower limit value as a value between to the lower limit value of the allowable range of the amount of feedback.

  As described above, when setting the allowable range of the feedback amount by the predetermined range setting 33, the feedback from the predetermined range is performed according to the guaranteed accuracy of the component performance that affects the feedback amount of the operation amount in the air supply system (compressor 2). If the margin up to the allowable range (from the diagnosis threshold of the air flow shortage diagnosis and the excessive air flow rate diagnosis to the allowable range of the feedback amount) is variably set, erroneous determination by the abnormality determination unit 34 can be suppressed, and as a result Even when the operation of the instrument is normal or abnormal, it is possible to accurately diagnose the abnormality of the air supply system using the air flow control parameters and maintain high reliability. A battery system can be realized.

  Further, in the fuel cell system of the present embodiment, in the predetermined range setting 33, the system limit allowable range of the air flow rate is set so as to be equal to or less than the air flow rate that can prevent a decrease in power generation performance caused by a decrease in the moisture content of the fuel cell stack 3. As a first predetermined range in which excessive air supply can be prevented, a range from a value between the upper limit value of the normal range of the feedback amount and the upper limit value of the allowable range of the feedback amount to the upper limit value of the allowable range of the feedback amount is set. The abnormality determining unit 34 determines that the air supply abnormality (excessive air flow rate) is detected when the feedback amount in the feedback control exceeds the excessive flow rate diagnosis threshold set within the first predetermined range. As a result, an excessive air supply can be detected before the power generation performance decreases due to a decrease in the water content of the fuel cell stack 3, and an abnormality diagnosis of the air supply system can be performed more reliably, maintaining high reliability. A fuel cell system can be realized.

  Further, in the fuel cell system of the present embodiment, in the predetermined range setting 33, the system limit allowable range of the air flow rate is set to an air flow rate that can prevent a decrease in power generation performance caused by insufficient supply of air necessary for power generation of the fuel cell stack 3. As a second predetermined range that can be set to be above and prevent air supply shortage, the lower limit of the allowable range of the feedback amount from the value between the lower limit value of the normal range of the feedback amount and the lower limit value of the allowable range of the feedback amount A range up to the value is set, and when the feedback amount in the feedback control falls below the flow shortage diagnosis threshold set within the second predetermined range, the abnormality determination unit 34 determines that the air supply is abnormal (air flow shortage). Thus, before the power generation performance of the fuel cell stack 3 is deteriorated due to insufficient supply of air necessary for the power generation of the fuel cell stack 3, the shortage of air supply can be detected, and the abnormality diagnosis of the air supply system can be performed more reliably. It is possible to realize a fuel cell system that can be performed and maintains high reliability.

  Further, in the fuel cell system of the present embodiment, in the predetermined range setting 33, the hydrogen gas discharged from the hydrogen gas discharge passage 12 can be discharged to the outside within the air exhaust passage 18 within the system limit allowable range of the air flow rate. Set the air flow rate so that it can be reduced to the hydrogen gas concentration. Thereby, before the hydrogen gas discharged from the hydrogen gas discharge channel 12 cannot be reduced to a hydrogen gas concentration that can be discharged to the outside in the air exhaust channel 18, it is possible to detect an air supply shortage and more reliably the air supply system. Thus, a fuel cell system maintaining high reliability can be realized.

  Further, in the fuel cell system of the present embodiment, in the predetermined range setting 33, the system limit allowable range of the air flow rate is set to an air flow rate that can prevent a decrease in power generation performance caused by insufficient supply of air necessary for power generation of the fuel cell stack 3. And the air flow rate that can reduce the hydrogen gas discharged from the hydrogen gas discharge flow channel 12 to the hydrogen gas concentration that can be discharged to the outside in the air exhaust flow channel 18 is set to be higher than the larger air flow rate. . As a result, the hydrogen gas discharged from the hydrogen gas discharge passage 12 is exhausted before the deterioration of the power generation performance of the fuel cell stack 3 due to insufficient supply of air necessary for the power generation of the fuel cell stack 3. Before it becomes impossible to reduce the hydrogen gas concentration that can be discharged to the outside in the flow path 18, it is possible to detect air supply shortage, more reliably perform abnormality diagnosis of the air supply system, and maintain high reliability. Can be realized.

  Furthermore, in the fuel cell system of the present embodiment, when the abnormality determination unit 34 determines that the air supply is abnormal, the operation of the fuel cell system is stopped. Thus, when it is determined that the air supply is abnormal, the fuel cell system can be safely stopped, so that the power generation performance of the fuel cell stack 3 can be prevented from being lowered.

  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 (FIG. 1), and a specific description of each component is omitted.

  However, the voltage sensor 20 is indispensable as voltage detection means for detecting at least one of the voltage or total voltage of each cell constituting the fuel cell stack 3, and the voltage sensor is used when the abnormality detection unit 34 determines that the air supply is abnormal. The difference from the first embodiment is that the operation of the fuel cell system is stopped when the detected value of 20 falls below a predetermined voltage that can prevent the deterioration of the components of the fuel cell stack 3.

  In this embodiment, the system allowable lower limit air flow rate QL (see FIG. 3) is set based only on the air flow rate Qa (see FIG. 2) necessary for power generation of the fuel cell stack 3. This is because when the amount of nitrogen passing through the electrolyte membrane from the cathode 5 to the anode 4 is small, the flow rate of the purge gas discharged from the flow rate control valve (purge valve) 11 is small, which is necessary for power generation of the fuel cell stack 3. This is because the air flow rate Qa is always sufficiently larger than the air flow rate Qc that can dilute the hydrogen discharged from the flow control valve 11.

  Next, the procedure of the excess air flow diagnosis and the insufficient air flow diagnosis performed by the abnormality determination unit 34 of the fuel cell system of the present embodiment will be described with reference to FIGS. 9 and 10. Here, FIG. 9 is a flowchart for explaining the procedure of the air flow excess diagnosis and the air flow shortage diagnosis of the present embodiment, and FIG. 10 is an explanation for explaining a table TC of the reference cell voltage corresponding to the current of the fuel cell stack 3. FIG.

  First, the feedback amount of the compressor rotation speed is read from the operation amount calculation unit 32 (step S201), the generated current of the fuel cell stack 3 is read (step S202), and the air is referred to the table TA based on the read current value. An insufficient flow rate diagnosis threshold value used for the insufficient flow rate diagnosis is read (step S203), and further, an excessive flow rate diagnosis threshold value used for the excessive air flow rate diagnosis is read based on the read current value (step S204).

  Next, the feedback amount of the compressor rotation speed read in step S201 is compared with the insufficient flow rate diagnosis threshold value read in step S203, and the feedback amount is below the insufficient flow rate diagnosis threshold value (insufficient air supply) for a predetermined time. Whether or not the air supply is abnormal (insufficient air flow rate) is determined based on whether or not it has been performed (step S205). When it is determined that the air supply is abnormal (air flow shortage), the process proceeds to step S207, and when the feedback amount is equal to or greater than the flow shortage diagnosis threshold or when the air supply shortage state does not continue for a predetermined time, the process proceeds to step S206.

  Next, the feedback amount of the compressor rotation speed read in step S201 is compared with the excessive flow rate diagnosis threshold value read in step S204, and the state where the feedback amount exceeds the excessive flow rate diagnosis threshold value (excessive air supply) continues for a predetermined time. It is determined whether or not the air supply is abnormal (excessive air flow rate) depending on whether or not it has been performed (step S206). When it is determined that the air supply abnormality (excessive air flow rate) is determined, the process proceeds to step S207, and when the feedback amount is equal to or less than the insufficient flow rate diagnosis threshold or when the excessive air supply state has not continued for a predetermined time, the process returns to step S201.

  If it is determined in step S205 that the air supply is abnormal (air flow is insufficient), or if it is determined in step S206 that the air supply is abnormal (excessive air flow), alarm information is notified via the alarm generator 35 ( Step S207).

  Next, the generated current of the fuel cell stack 3 is read (step S208), the reference cell voltage of the fuel cell stack 3 corresponding to the current value read in step S207 is read with reference to the table TC (step S209), and further Then, the minimum value of the cell voltage of the fuel cell stack 3 is read (step S210). Here, the table TC is a numerical table of reference cell voltages for each generated current, calculated based on the current-voltage characteristics of the fuel cell stack 3, and has characteristics as shown in FIG.

  Next, the minimum value of the cell voltage read in step 210 and the reference cell voltage read in step 209 are compared, and power can be stably obtained from the fuel cell stack 3 according to the required load (generated current). It is determined whether it is possible (step S211).

  Specifically, when the state where the minimum value of the cell voltage is lower than the reference cell voltage continues for a predetermined time, it is possible to stably obtain power from the fuel cell stack 3 according to the required load (generated current). Determination is made and the system proceeds to step S212 to stop the system. On the other hand, when the minimum value of the cell voltage is equal to or higher than the reference cell voltage or the state where the minimum value of the cell voltage is lower than the reference cell voltage does not continue for a predetermined time, the fuel cell stack 3 is stabilized according to the required load. Then, it is determined that power can be obtained, and the process returns to step S201.

  As described above, in the fuel cell system of this embodiment, when the abnormality detection unit 34 determines that the air supply is abnormal, the detection value of the voltage sensor 20 (the minimum value of the cell voltage) is the component of the fuel cell stack 3. When the voltage falls below a predetermined voltage (reference cell voltage) that can prevent deterioration, the operation of the fuel cell system is stopped.

  Thereby, when the detected value (minimum value of the cell voltage) of the voltage sensor 20 is lower than the predetermined voltage (reference cell voltage), the operation of the fuel cell system can be stopped, so the air supplied from the air supply system (compressor 2) Even if a supply abnormality (excessive air flow rate or insufficient air flow rate) occurs, the detected value (minimum value of the cell voltage) of the voltage sensor 20 is monitored by monitoring the minimum cell voltage according to the generated current of the fuel cell stack 3. The fuel cell system can continue to operate until the voltage falls below a predetermined voltage (reference cell voltage).

  Next, a fuel cell system according to Example 3 of the present invention will be described. The configuration of the fuel cell system of Example 3 is the same as that of Example 1 (FIG. 1), and a specific description of each component is omitted.

  However, the voltage sensor 20 is indispensable as voltage detection means for detecting at least one of the voltage or total voltage of each cell constituting the fuel cell stack 3, and the abnormality detection unit 34 determines that the air supply is abnormal (excessive air flow). When the detected value of the voltage sensor 20 falls below a predetermined voltage that can prevent the deterioration of the components of the fuel cell stack 3, the operation of the fuel cell system is stopped, or the abnormality detection unit 34 detects an air supply abnormality ( The difference from Embodiment 1 is that the operation of the fuel cell system is stopped when it is determined that the air flow rate is insufficient.

  Next, the procedure of the excess air flow diagnosis and the insufficient air flow diagnosis performed by the abnormality determination unit 34 of the fuel cell system of the present embodiment will be described. The procedure of the air flow excess diagnosis and the air flow shortage diagnosis in the present embodiment is as follows. When the air supply abnormality (air flow shortage) is determined in step S205 in the flowchart of FIG. Is different from the second embodiment in that the operation of the fuel cell system is stopped. Therefore, illustration is omitted.

  Thereby, when the detected value (minimum value of the cell voltage) of the voltage sensor 20 is lower than the predetermined voltage (reference cell voltage), the operation of the fuel cell system can be stopped, so the air supplied from the air supply system (compressor 2) Even if a supply abnormality (excessive air flow rate) occurs, the detection value of the voltage sensor 20 (minimum value of the cell voltage) is set to a predetermined voltage (by monitoring the minimum cell voltage corresponding to the generated current of the fuel cell stack 3). The fuel cell system can continue to operate until it falls below the reference cell voltage. Furthermore, before the hydrogen gas discharged from the hydrogen gas discharge passage 12 can be reduced to a hydrogen gas concentration that can be discharged to the outside in the air exhaust passage 18, it is possible to detect a shortage of air supply and more reliably Abnormality diagnosis can be performed, and a fuel cell system maintaining high reliability can be realized.

  Next, a fuel cell system according to Example 4 of the present invention will be described. The configuration of the fuel cell system of Example 4 is the same as that of Example 1 (FIG. 1), and a specific description of each component is omitted.

  However, when the abnormality detection unit 34 determines that an air supply abnormality (excessive air flow rate) is detected when the feedback amount in the feedback control exceeds the excessive flow rate diagnosis threshold set within the first predetermined range, the target air flow rate calculation unit 31 decreases the target air flow rate, and the abnormality detection unit 34 determines that the air supply abnormality (insufficient air flow rate) occurs when the feedback amount in the feedback control falls below the flow rate shortage diagnosis threshold set within the second predetermined range. When this is done, the target air flow rate calculation unit 31 is different from that of the first embodiment in that the target air flow rate is increased until an air supply abnormality (insufficient air flow rate) can be avoided.

  Next, refer to the flowchart shown in FIG. 11 for the processing of the air flow excess diagnosis and air flow shortage diagnosis performed by the abnormality determination unit 34 of the fuel cell system of this embodiment and the target air flow rate calculation unit 31 after diagnosis. I will explain.

  First, the feedback amount of the compressor rotation speed is read from the operation amount calculation unit 32 (step S301), the generated current of the fuel cell stack 3 is read (step S302), and the air is referred to based on the read current value by referring to the table TA. An insufficient flow rate diagnosis threshold value used for the insufficient flow rate diagnosis is read (step S303), and further, an excessive flow rate diagnosis threshold value used for air flow excess diagnosis is read based on the read current value (step S304).

  Next, the feedback amount of the compressor rotation speed read in step S301 is compared with the insufficient flow rate diagnosis threshold value read in step S303, and the state where the feedback amount falls below the insufficient flow rate diagnosis threshold value (insufficient air supply) continues for a predetermined time. It is determined whether or not the air supply is abnormal (insufficient air flow rate) based on whether or not it has been performed (step S305). When it is determined that the air supply is abnormal (air flow shortage), the process proceeds to step S307. When the feedback amount is equal to or greater than the flow shortage diagnosis threshold or when the air supply shortage state has not continued for a predetermined time, the process proceeds to step S306.

  Next, the feedback amount of the compressor rotation speed read in step S301 is compared with the excessive flow rate diagnosis threshold value read in step S304, and the state where the feedback amount exceeds the excessive flow rate diagnosis threshold value (excessive air supply) continues for a predetermined time. Whether or not the air supply is abnormal (excessive air flow rate) is determined based on whether or not it has been performed (step S306). When it is determined that the air supply abnormality (excessive air flow rate) is determined, the process proceeds to step S309, and when the feedback amount is equal to or less than the insufficient flow rate diagnosis threshold or when the excessive air supply state has not continued for a predetermined time, the process returns to step S301.

  If it is determined in step S305 that the air supply is abnormal (air flow shortage), alarm information is notified via the alarm generator 35 (step S307), and the target air flow calculation unit 31 sets the target air flow to the previous target. The air flow rate is increased (step S308). Thus, when it is determined that the air supply is insufficient, the flow rate of air supplied from the compressor 2 can be increased by increasing the target air flow rate by a predetermined ratio. Then, after increasing the target air flow rate until the air supply abnormality (insufficient air flow rate) can be avoided, the process returns to step S301.

  On the other hand, when it is determined in step S306 that the air supply is abnormal (excessive air flow), alarm information is notified via the alarm generator 35 (step S309), and the target air flow rate calculation unit 31 sets the target air flow rate last time. Less than the target air flow rate (step S310). Thus, when it is determined that the air supply is excessive, the flow rate of air supplied from the compressor 2 can be reduced by reducing the target air flow rate by a predetermined ratio. Then, after the target air flow rate is decreased until the air supply abnormality (excessive air flow rate) can be avoided, the process returns to step S301.

  As described above, in the fuel cell system according to the present embodiment, the abnormality detection unit 34 causes the feedback amount in the feedback control to exceed the excessive flow rate diagnosis threshold set within the first predetermined range and the air supply abnormality (air flow rate) When it is determined that the air flow rate is excessive, the target air flow rate calculation unit 31 decreases the target air flow rate, and the abnormality detection unit 34 sets the feedback amount in the feedback control to be within the second predetermined range. When the air supply abnormality (air flow rate shortage) is determined to be below the target airflow, the target air flow rate calculation unit 31 increases the target air flow rate until the air supply abnormality (airflow shortage) can be avoided.

  As described above, when it is determined that the air supply abnormality (excessive air flow rate or air flow rate is excessive), the air supply abnormality can be avoided by changing the target air flow rate, so that the fuel cell system can be operated without stopping. Can continue.

1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention. It is explanatory drawing explaining transition of the air flow rate with respect to a generated electric current. It is explanatory drawing explaining the establishment range of the target air flow rate by a system permissible upper limit air flow rate and a system lower limit air flow rate. It is explanatory drawing explaining the normal range of the feedback amount of the compressor 2, and the allowable range of a feedback amount. It is explanatory drawing explaining the establishment range of the diagnostic threshold value in an air flow excess diagnosis and an air flow shortage diagnosis. It is a flowchart explaining the procedure of the air flow excess diagnosis and the air flow shortage diagnosis of Example 1. It is explanatory drawing explaining table TA of the flow shortage diagnosis threshold value according to the generated electric current used by air flow shortage diagnosis. It is explanatory drawing explaining table TB of the excessive flow rate diagnostic threshold value according to the electric power generation current used by excessive air flow rate diagnosis. It is a flowchart explaining the procedure of the air flow excess diagnosis and the air flow shortage diagnosis of Example 2. FIG. 5 is an explanatory diagram for explaining a table TC of reference cell voltages according to the current of the fuel cell stack 3; FIG. 10 is a flowchart for explaining the air flow excess diagnosis and the air flow shortage diagnosis performed by the abnormality determination unit 34 of the fuel cell system of Example 4 and the processing of the target air flow calculation unit 31 after diagnosis.

Explanation of symbols

1 Hydrogen gas supply device 2 Air compressor 3 Fuel cell stack 4 Anode (fuel electrode)
5 Cathode (oxidizer electrode)
6 Pressure regulating valve 7 Hydrogen gas supply flow path 8 Gas circulation device 9 Hydrogen gas circulation flow path 10 Flow meter (flow rate detection means)
11 Flow control valve (purge valve)
DESCRIPTION OF SYMBOLS 12 Hydrogen gas discharge flow path 13 After cooler 14 Humidifier 15, 40, 41, 42 Air supply flow path 16, 18 Air exhaust flow path 17 Pressure adjustment valve 20 Voltage sensor (voltage detection means)
23, 26 Pressure sensor 24, 27 Temperature sensor 30 System controller 31 Target air flow rate calculation unit (oxidant gas target flow rate calculation means)
32 Manipulation amount calculator (flow rate control means)
33 Predetermined range setting unit 34 Abnormality detection unit 35 Alarm generator

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;
A flow rate detection means for detecting a flow rate of the oxidant gas supplied by the oxidant gas supply means;
Oxidant gas target flow rate calculation means for calculating a target flow rate of the oxidant gas;
A flow rate control unit that feedback-controls an oxidant gas flow rate of the oxidant gas supply unit based on a detection value of the flow rate detection unit and a target flow rate of the oxidant gas;
A feedback amount that sets a normal range of the feedback amount in the feedback control, includes the normal range of the feedback amount, and the oxidant gas flow rate becomes a system limit allowable range of the oxidant gas flow rate that allows the fuel cell system to normally operate. A predetermined range setting means for setting a region outside the normal range of the feedback amount and within the allowable range of the feedback amount as a predetermined range;
An abnormality determining means for determining an oxidant gas supply abnormality when a feedback amount in the feedback control is outside the predetermined range;
A fuel cell system comprising:   The predetermined range setting unit includes a normal range of the feedback amount, a detection accuracy when the flow rate detection unit is normal, a flow rate accuracy guaranteed range of the oxidant gas supply unit, and a flow path of a flow path for supplying the oxidant gas. 2. The fuel cell system according to claim 1, wherein the fuel cell system is set based on a resistance guarantee range and calculation accuracy of the flow rate control means.   The predetermined range setting means includes an allowable range of the feedback amount, a detection accuracy of the flow rate detection means, a flow rate accuracy guarantee range of the oxidant gas supply means, and a flow path resistance guarantee range of the flow path for supplying the oxidant gas. The fuel cell system according to any one of claims 1 and 2, wherein the fuel cell system is set based on calculation accuracy of the flow rate control means.   The predetermined range setting means sets the upper limit value of the predetermined range from a value between the upper limit value of the normal range of the feedback amount and the upper limit value of the allowable range of the feedback amount to the upper limit value of the allowable range of the feedback amount. And setting the lower limit value of the predetermined range from a value between the lower limit value of the normal range of the feedback amount and the lower limit value of the allowable range of the feedback amount to the lower limit of the allowable range of the feedback amount The fuel cell system according to any one of claims 1 to 3, wherein the fuel cell system is set as a value up to a value. The predetermined range setting means sets the system limit allowable range of the oxidant gas flow rate to be equal to or less than an oxidant gas flow rate that can prevent a decrease in power generation performance caused by a decrease in the moisture content of the fuel cell, and the oxidant gas flow As a first predetermined range that can prevent an excessive supply, a range from a value between the upper limit value of the normal range of the feedback amount and the upper limit value of the allowable range of the feedback amount to the upper limit value of the allowable range of the feedback amount Set
The abnormality determination unit determines that an oxidant gas supply abnormality occurs when a feedback amount in the feedback control exceeds a flow excess diagnostic threshold set in the first predetermined range. Item 5. The fuel cell system according to any one of Item 4. The predetermined range setting means sets the system limit allowable range of the oxidant gas flow rate to be equal to or higher than the oxidant gas flow rate that can prevent a decrease in power generation performance caused by insufficient supply of the oxidant gas necessary for power generation of the fuel cell. As a second predetermined range that can be set and prevent insufficient supply of the oxidant gas, the feedback amount is allowed from a value between the lower limit value of the normal range of the feedback amount and the lower limit value of the allowable range of the feedback amount. Set the range up to the lower limit of the range,
The abnormality determination unit determines that an oxidant gas supply abnormality occurs when a feedback amount in the feedback control falls below a flow rate shortage diagnosis threshold set in the second predetermined range. 6. The fuel cell system according to any one of items 5. A fuel gas discharge passage through which the fuel gas flows;
An oxidant gas discharge passage through which an oxidant gas discharged from the fuel cell flows;
A connecting flow path connecting the fuel gas discharge flow path and the oxidant gas discharge flow path;
A mechanism for opening the outlet of the oxidant gas discharge channel to the outside,
The predetermined range setting means can reduce the system limit allowable range of the oxidant gas flow rate to a fuel gas concentration that allows the fuel gas discharged from the fuel gas discharge channel to be discharged to the outside in the oxidant gas channel. The fuel cell system according to claim 6, wherein the fuel cell system is set to be equal to or higher than an oxidant gas flow rate.   The predetermined range setting means includes a system limit allowable range of the oxidant gas flow rate, an oxidant gas flow rate capable of preventing a decrease in power generation performance caused by insufficient supply of oxidant gas necessary for power generation of the fuel cell, and the fuel The fuel gas discharged from the gas discharge channel is set to be higher than the oxidant gas flow rate that is larger than the oxidant gas flow rate that can be reduced to the fuel gas concentration that can be discharged outside in the oxidant gas flow channel. The fuel cell system according to claim 7, wherein:   9. The fuel cell system according to claim 1, wherein the abnormality determination unit stops the operation of the fuel cell system when determining that the supply of the oxidant gas is abnormal. . Voltage detection means for detecting at least one of the voltage or total voltage of each cell constituting the fuel cell;
When the abnormality determination unit determines that the supply of the oxidant gas is abnormal, the operation of the fuel cell system is performed when the detection value of the voltage detection unit falls below a predetermined voltage that can prevent deterioration of the components of the fuel cell. The fuel cell system according to any one of claims 1 to 6, wherein the fuel cell system is stopped. Voltage detection means for detecting at least one of the voltage or total voltage of each cell constituting the fuel cell;
When the abnormality determination means determines that an oxidant gas supply abnormality has occurred when the feedback amount in the feedback control exceeds the excessive flow rate diagnosis threshold set within the first predetermined range, the detection value of the voltage detection means is Insufficient flow rate diagnosis in which the operation of the fuel cell system is stopped or the feedback amount in the feedback control is set within the second predetermined range when the voltage falls below a predetermined voltage that can prevent deterioration of the components of the fuel cell. The fuel cell system according to any one of claims 7 to 8, wherein the operation of the fuel cell system is stopped when it is determined that the oxidant gas supply abnormality is below a threshold value.   When the abnormality determination means determines that an oxidant gas supply abnormality occurs when a feedback amount in the feedback control exceeds a flow excess diagnostic threshold set within the first predetermined range, the oxidant gas target flow rate calculation means The fuel cell system according to any one of claims 5 to 8, wherein the target flow rate of the oxidant gas is decreased.   When the abnormality determining means determines that an oxidant gas supply abnormality occurs when the feedback amount in the feedback control falls below a flow rate shortage diagnosis threshold set within the second predetermined range, the oxidant gas target flow rate calculating means 13. The fuel cell system according to claim 6, wherein the target flow rate of the oxidant gas is increased until an abnormal supply of the oxidant gas can be avoided.

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