JP2011103233A - Voltage monitoring system and failure determination method of voltage monitoring system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology by which failure determination of a voltage monitoring system of a fuel cell is performed. <P>SOLUTION: The voltage monitoring system 20 obtains an operation condition of fuel cells FC1-FC4 and outputs the voltage of the fuel cells FC1-FC4 by a voltage transmission circuit 40, and detects at least one of its maximum value and minimum value by a minimum value detection circuit 50 and a maximum value detection circuit 60. Then, when the operation condition is in a shutdown state or in an open state and the maximum value is a threshold TH or more, it is determined that the voltage transmission circuit 40 is abnormal. Further, the voltage transmission circuit 40 is constructed to make the output 0 V when there is a connection failure between the fuel cells FC1-FC4 and the voltage transmission circuit 40, and when the operation condition is in a load operation and the minimum value is 0 V and the minimum value (0 V) and the total voltage are contradictory, it is determined that the voltage transmission circuit 40 is abnormal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a voltage monitoring system for a fuel cell stack in which a plurality of fuel cells are stacked.

  Since the actual output of a single cell is less than 1V, the fuel cell is generally configured as a fuel cell stack in which a plurality of single cells are connected in series. In such a fuel cell stack, if an abnormality occurs even in a single cell, it is necessary to limit the output of the entire stack or stop the operation. For this reason, a voltage monitoring system that monitors the voltage of a single cell constituting the fuel cell stack has been proposed in order to suitably control the fuel cell stack (for example, Patent Document 1 below).

  However, when an abnormality occurs in the voltage monitoring system itself, the operation of the fuel cell stack may be improperly controlled based on an erroneous monitoring result detected along with the abnormality.

JP 2008-103201 A JP 2008-151682 A

  In view of the above problems, the problem to be solved by the present invention is to provide a technique for determining an abnormality in a voltage monitoring system for a fuel cell.

  The present invention has been made to solve the above-described problems, and can be realized as the following forms or application examples.

Application Example 1 A voltage monitoring system for a fuel cell stack in which a plurality of fuel cells are stacked, the voltage monitoring system being provided for each of the plurality of fuel cells, and taking out the voltage of each of the fuel cells from the fuel cell And collecting the voltage of the plurality of fuel cells output from the voltage transmission means and the voltage transmission means, and detecting at least one of the minimum value and the maximum value of the output voltages. Based on the specific detection means, the acquisition means for acquiring the operating state of the fuel cell, the at least one of the detected minimum value and the maximum value, and the acquired operating state of the fuel cell. A voltage monitoring system comprising a determination means for determining abnormality.

  The voltage monitoring system having such a configuration detects at least one of the minimum value and the maximum value of each voltage of the fuel cell, and based on at least one of the detected minimum value and maximum value and the operating state of the fuel cell. The abnormality of the voltage transmission means is determined. Therefore, the abnormality of the voltage monitoring system can be determined. In addition, the detection of the minimum value or the maximum value is originally performed for controlling the operation of the fuel cell, and since it is easy to obtain the operating state, it can be realized as a simple method.

Application Example 2 In the voltage monitoring system according to Application Example 1, the specific detection unit detects at least the maximum value, and the determination unit is in a state where the acquired operation state is stopped, or A voltage monitoring system that determines that the voltage transmission means is abnormal when the voltage is in an open state and the detected maximum value is equal to or greater than a predetermined threshold.

  The voltage monitoring system having such a configuration determines that the voltage transmission unit is abnormal when the operation state is stopped or in an open state and the maximum value is equal to or greater than a threshold value. If the voltage transmission means is normal, the voltage of the fuel cell when the operation state is stopped or open is relatively smaller than that during load operation. This is because there is a high possibility that an abnormality has occurred in the means. With such a configuration, it is possible to easily determine abnormality of the voltage transmission means.

[Application Example 3] The voltage monitoring system according to Application Example 1 or Application Example 2, further comprising an overall detection means for detecting the overall voltage of the plurality of fuel cells, wherein the voltage transmission means When there is a poor connection between any one of the fuel cells and the voltage transmission means, it is configured to output 0 volts, and the specific detection means detects at least the minimum value, and the determination means Is the voltage transmission means when the acquired operating state is under load operation, the detected minimum value is 0 volts, and the detected minimum voltage contradicts the detected overall voltage. Voltage monitoring system that determines that is abnormal.

  The voltage monitoring system having such a configuration is configured to output 0 volts when there is a connection failure between any one of the plurality of fuel cells and the voltage transmission means, so that the operation state is a load operation. Nevertheless, if 0V is detected as the minimum value, there is a high possibility that a connection failure has occurred in the voltage transmission means. In addition, in addition to the minimum value being 0 V, the abnormality of the voltage transmission means is determined on the condition that the minimum value (0 V) and the overall voltage contradict each other. Connection failure can be determined.

[Application Example 4] The voltage monitoring system according to Application Example 1 or Application Example 2, wherein the voltage transmission means has a connection failure between any of the plurality of fuel cells and the voltage transmission means. It is configured to output 0 volt, the specific detection means detects at least the minimum value, and the determination means is that the acquired operation state is under load operation, and the detected minimum A voltage monitoring system that determines that the voltage transmission means is abnormal when the value is 0 volts.

  The voltage monitoring system having such a configuration is configured to output 0 volts when there is a connection failure between any one of the plurality of fuel cells and the voltage transmission means, so that the operation state is a load operation. Nevertheless, if 0V is detected as the minimum value, there is a high possibility that a connection failure has occurred in the voltage transmission means. Therefore, the connection failure of the voltage transmission means can be determined by a simple method.

Application Example 5 In the voltage monitoring system according to any one of Application Example 1 to Application Example 4, the voltage transmission means includes a differential amplifier connected to the anode side and the cathode side of the plurality of fuel cells. And the specific detection means includes a diode provided in the same direction for each output of the differential amplifier, and a capacitor interposed between the diode and the ground.

  In the voltage monitoring system having such a configuration, the specific detection means includes a differential amplifier, a diode, and a capacitor, so that the configuration of the voltage monitoring system can be simplified. Moreover, since it can comprise using a general purpose component, manufacture is easy and can reduce cost.

Application Example 6 In the voltage monitoring system according to Application Example 5, the specific detection unit detects the minimum value and the maximum value, and the first direction is determined for each output of the differential amplifier. For each output of the differential amplifier, a first circuit including a first diode provided in the first capacitor and a first capacitor interposed between the first diode and the ground is provided. A second circuit including a second diode provided in a second direction opposite to the first direction, and a second capacitor interposed between the second diode and the ground The voltage monitoring system is configured to determine the abnormality based on the detected minimum value or maximum value in accordance with the acquired operating state.

  The voltage monitoring system having such a configuration detects the maximum value and the minimum value by the first circuit and the second circuit, and determines an abnormality according to the operating state. Therefore, the determination can be performed from a plurality of viewpoints according to the driving state, and the determination accuracy is improved. Further, since the first circuit and the second circuit are provided in parallel, the maximum value and the minimum value can be detected at the same time, so that the operation control of the fuel cell is performed using both the maximum value and the minimum value. The present invention can also be suitably applied to cases.

Application Example 7 In the voltage monitoring system according to Application Example 5, the specific detection unit detects the minimum value and the maximum value, and the first direction for each output of the differential amplifier. A first diode provided in a second direction, a second diode provided in a second direction opposite to the first direction, for each output of the differential amplifier, the differential amplifier, Connection switching means for switching connection with any one of the first diode and the second diode by a switch circuit, and interposed between the first diode, the second diode and the ground. A voltage monitoring system that determines the abnormality based on the detected minimum value or maximum value in accordance with the acquired operating state.

  The voltage monitoring system having such a configuration selectively detects the maximum value or the minimum value by switching the connection between the differential amplifier and one of the first diode and the second diode by a switch circuit, Abnormality can be determined according to the driving state. Therefore, the determination can be performed from a plurality of viewpoints according to the driving state, and the determination accuracy is improved. In addition, since the maximum value or the minimum value can be selectively detected by a common capacitor, it is not necessary to individually provide a capacitor for each of the first diode and the second diode, and the circuit configuration can be simplified. Further, since the maximum value or the minimum value is selectively detected, the output destination of the maximum value or the minimum value does not need to be handled at the same time, and the device configuration of the output destination can be simplified.

Application Example 8 In the voltage monitoring system according to Application Example 5, the specific detection unit detects the minimum value and the maximum value, and is provided in the same direction for each output of the differential amplifier. A diode, a capacitor interposed between the diode and ground, a first switch circuit interposed between the differential amplifier and the diode, and between the diode and the capacitor And a direction switching means capable of switching the direction of the diode by a second switch circuit interposed between the detection circuit and the determination means according to the acquired operating state, the detected minimum value or maximum value. A voltage monitoring system for determining the abnormality based on the above.

  The voltage monitoring system having such a configuration switches the direction of the diode by the first switch circuit and the second switch circuit, selectively detects the maximum value or the minimum value, and determines abnormality according to the operating state. It can be carried out. Therefore, the determination can be performed from a plurality of viewpoints according to the driving state, and the determination accuracy is improved. In addition, since a common diode and capacitor can be used for both detection of the maximum value and detection of the minimum value, the circuit configuration can be simplified. Further, since the maximum value or the minimum value is selectively detected, the output destination of the maximum value or the minimum value does not need to be handled at the same time, and the device configuration of the output destination can be simplified.

The present invention can also be realized as an abnormality determination method for the voltage monitoring system according to Application Example 9.
Application Example 9 An abnormality determination method for determining an abnormality in a voltage monitoring system of a fuel cell stack in which a plurality of fuel cells are stacked, wherein the voltage monitoring system is provided for each of the plurality of fuel cells, The voltage of each fuel cell is extracted from the fuel cell and output in an insulated state, and the voltages of the plurality of fuel cells output from the voltage transmission unit are collected and output. Specific detection means for outputting at least one of a minimum value and a maximum value of the voltage, and the voltage transmission means based on at least one of the detected minimum value and maximum value and the operating state of the fuel cell. An abnormality determination method for a voltage monitoring system for determining an abnormality in a battery.

2 is an explanatory diagram showing a schematic configuration of a voltage monitoring system 20. FIG. 4 is a flowchart showing a flow of abnormality determination processing in the voltage monitoring system 20. It is explanatory drawing which shows schematic structure of the voltage monitoring system 120 as a 2nd Example. It is explanatory drawing which shows schematic structure of the voltage monitoring system 220 as 3rd Example. It is explanatory drawing which shows schematic structure of the voltage transmission circuit 340 as a 4th Example. It is explanatory drawing which shows schematic structure of the voltage monitoring system 420 as a 5th Example.

A. First embodiment:
A-1. General configuration of the voltage monitoring system 20:
A schematic configuration of a voltage monitoring system 20 as a first embodiment of the present invention is shown in FIG. The voltage monitoring system 20 is a system that monitors the voltage of the fuel cell stack FC in which the four fuel cells FC1 to FC4 are stacked. The fuel cells FC1 to FC4 are so-called single cells, which are the minimum units of power generation.

  Each of the fuel cells FC1 to FC4 is a solid polymer type fuel cell, and is an electrolyte having a cathode electrode and an anode electrode on the surface of an electrolyte membrane that is a thin film of a solid polymer material showing good proton conductivity in a wet state. A gas diffusion layer, a flow path member, and a separator are laminated on both surfaces of the membrane / electrode assembly (not shown). The fuel cells FC1 to FC4 are sandwiched between terminals, insulators, and end plates disposed at both ends in the stacking direction, and connected to a fuel gas, oxidizing gas, and cooling water supply / discharge system (not shown). . The number of fuel cells constituting the fuel cell stack FC is not limited to four and may be set arbitrarily.

  As shown in the figure, the voltage monitoring system 20 includes a voltage monitoring circuit 25, an operational amplifier 70, an MCU 80, and a CPU 90. The voltage monitoring circuit 25 includes a voltage transmission circuit 40, a minimum value detection circuit 50, and a maximum value detection circuit 60.

  The voltage transmission circuit 40 is composed of the same circuit connected to each of the fuel cells FC1 to FC4. When viewed from the fuel cells FC1 to FC4, the voltage transmission circuit 40 has resistors 31 to 34 interposed between the anode and the cathode, and is connected to both input terminals of the operational amplifiers 41 to 44. The operational amplifiers 41 to 44 are differential amplifiers, and are voltages obtained by amplifying the voltages of the fuel cells FC1 to FC4 connected to both input terminals with a predetermined gain (in this case, the gain is set to 1, so that the fuel cells FC1 to FC1). The voltage of FC4 itself is isolated from the actual potential and output.

  Since the fuel cells FC1 to FC4 are stacked and electrically connected in series, the cathode voltage of each fuel cell corresponds to the number of fuel cells stacked up to that fuel cell with respect to the ground level. It is raised to the specified potential. Since differential amplifiers are used as the operational amplifiers 41 to 44, the outputs of the operational amplifiers 41 to 44 are values representing the voltages of the fuel cells FC1 to FC4 with respect to the ground level. In the present embodiment, the power supply 46 provided independently of the fuel cell stack FC is used as the power supply for the operational amplifiers 41 to 44.

  The minimum value detection circuit 50 is a circuit that detects the minimum value of the outputs of the fuel cells FC1 to FC4, and includes diodes 51 to 54, a capacitor C55, a power source 57, and a resistor 58. All the outputs of the operational amplifiers 41 to 44 described above are connected to diodes 51 to 54 in the reverse direction. For this reason, the output of each operational amplifier 41-44 is what is called wired OR connection. That is, the outputs of the operational amplifiers 41 to 44 have no influence on the outputs of the other operational amplifiers 41 to 44. A capacitor C55 having one end connected to the ground is connected to the outputs of the wired OR connected operational amplifiers 41 to 44, and a predetermined positive power source 57 is further connected via a pull-up resistor 58. . This voltage is set to a sufficiently large value with respect to the assumed output of the operational amplifiers 41 to 44. The operation of the minimum value detection circuit 50 will be described later.

  The maximum value detection circuit 60 is a circuit that detects the maximum value among the outputs of the fuel cells FC1 to FC4, and includes diodes 61 to 64, a capacitor C65, and a resistor 68. All the outputs of the operational amplifiers 41 to 44 described above are connected to the forward diodes 61 to 64. A capacitor C65 having one end connected to the ground is connected to the outputs of the operational amplifiers 41 to 44. The resistor 68 is a so-called pull-down resistor, and discharges the electric charge accumulated in the capacitor C65. If there is no output from the operational amplifiers 41 to 44, the voltage at the terminal TE2 of the capacitor C65 is made zero. The operation of the maximum value detection circuit 60 will be described later.

  The operational amplifier 70 is a voltage follower. The operational amplifier 70 outputs the entire voltage of the fuel cell stack FC to the CPU 90 at a predetermined timing. Since the number of fuel cells constituting the fuel cell stack FC is known from the overall voltage output in this way, it can be detected as an average voltage.

  The outputs of the minimum value detection circuit 50 and the maximum value detection circuit 60 are input to the MCU 80. In this embodiment, the MCU 80 is a microcomputer specialized for AD conversion, and includes two input ports and output ports for minimum value and maximum value. The MCU 80 AD-converts the input maximum value and minimum value and outputs the converted values to the CPU 90. However, the MCU 80 may have other functions, or the outputs of the minimum value detection circuit 50 and the maximum value detection circuit 60 may be directly input to the CPU 90.

  The CPU 90 controls the overall operation of the fuel cell system including the fuel cells FC1 to FC4 by developing and executing a program stored in a ROM (not shown) on a RAM (not shown). In particular, the CPU 90 receives an input of the entire voltage via the operational amplifier 70, and receives an input of the minimum and maximum values of the fuel cells FC1 to FC4 via the MCU 80, and a fuel cell system according to the values. Control the operation. The CPU 90 also functions as an operating state acquisition unit 91 and an abnormality determination unit 92. Details of these functions will be described later.

  A load 95 is connected to the terminal of the fuel cell stack FC connected to the voltage monitoring system 20 having such a configuration. The load 95 can be, for example, a secondary battery or a power consuming device (such as a motor). Switches 96 and 97 are interposed between the fuel cell stack FC and the load 95, and the connection relationship between the fuel cell stack FC and the load 95 is controlled in response to a signal from the CPU 90. In FIG. 1, the fuel cells FC1 to FC4 connected to the voltage monitoring circuit 25 and the fuel cells FC1 to FC4 constituting the fuel cell stack FC connected to the load 95 are the same. These are displayed in two places for convenience of illustration.

A-2. Minimum value detection operation:
The minimum value detection operation of the voltage monitoring system 20 will be described. The minimum value detection operation is an operation for detecting the minimum value among the voltages of the fuel cells FC1 to FC4. In order to simplify the description, the following operation will be described assuming that the voltage drop of the diodes 51 to 54 is 0 volts.
(1) If the operational amplifiers 41 to 44 are not operating and the outputs of the operational amplifiers 41 to 44 are in a high impedance state, no current flows into the outputs of the operational amplifiers 41 to 44, and the capacitor C55 is charged. The voltage at the terminal TE1 becomes equal to the voltage of the positive power supply 57 connected via the pull-up resistor 58.

  (2) Next, when the operational amplifiers 41 to 44 are operated at a predetermined timing, and the output voltages of the fuel cells FC1 to FC4 are detected and output by the operational amplifiers 41 to 44 as differential amplifiers, the diodes 51 to 54 are output. As a result, a current flows through the terminal TE1, and the voltage at the terminal TE1 of the capacitor C55 decreases. This operation continues until the voltage at the terminal TE1 becomes the lowest voltage Vmin1 among the outputs of the connected operational amplifiers 41 to 44. When the voltage at the terminal TE1 coincides with the voltage Vmin1, the other operational amplifiers 41 to 44 (op-amps other than the operational amplifier that outputs the voltage Vmin1) are higher than the voltage at the terminal TE1, so that current flows through the diodes 51 to 54. There is nothing.

  (3) If the voltage of any one of the fuel cells further decreases and the lowest voltage among the outputs of the connected operational amplifiers 41 to 44 becomes Vmin2 (Vmin1> Vmin2), the voltage at the terminal TE1 of the capacitor C55 Current flows into the operational amplifiers 41 to 44 that output a lower voltage through the diodes 51 to 54, and the voltage at the terminal TE1 of the capacitor C55 decreases. This operation continues until the voltage at the terminal TE1 becomes the voltage Vmin2. When the voltage at the terminal TE1 coincides with the voltage Vmin2, since the other operational amplifiers 41 to 44 are higher than the voltage at the terminal TE1, no current flows through the diodes 51 to 54.

  (4) Conversely, when the voltage of the fuel cell, which has been the minimum voltage until then, becomes high and the lowest voltage among the outputs of the connected operational amplifiers 41 to 44 becomes Vmin3 (Vmin1 <Vmin3), the operational amplifiers 41 to 41 Since 44 is higher than the voltage at the terminal TE1, no current flows through the diodes 51-54. Therefore, the capacitor C55 is gradually charged by the power source 57. This charging is continued until the voltage at the terminal TE1 of the capacitor C55 becomes the voltage Vmin3. When the voltage at the terminal TE1 exceeds the voltage Vmin3, a current flows through the diodes 51 to 54, and the voltage at the terminal TE1 of the capacitor C55 decreases.

  Actually, in any of the cases (2) to (4) described above, since the diode has a forward voltage drop (usually about 0.7 volts in the case of a silicon diode), the voltage at the terminal TE1 is The forward drop voltage is higher than the minimum output value of the operational amplifiers 41 to 44. However, since the forward drop voltage of each diode is known, each fuel cell is detected by detecting the voltage at the terminal TE1. It is easy to detect the minimum voltages of FC1 to FC4. If a forward drop voltage is measured with a transistor smaller than the configuration using a diode, a value closer to the actual voltage of the fuel cell can be detected. In this way, the capacitor C55 holds the minimum output of the operational amplifiers 41 to 44, that is, the voltage corresponding to the minimum voltage of the fuel cells FC1 to FC4, and is output to the MCU 80.

A-3. Maximum value detection operation:
The maximum value detection operation of the voltage monitoring system 20 will be described. The maximum value detection operation is an operation for detecting the maximum value among the voltages of the fuel cells FC1 to FC4. In order to simplify the description, the following operation will be described assuming that the voltage drop of the diodes 61 to 64 is 0 volts.
(1) When the operational amplifiers 41 to 44 are operated at a predetermined timing, and the output voltages of the fuel cells FC1 to FC4 are detected and output by the operational amplifiers 41 to 44 that are differential amplifiers, the diodes 61 to 64 are connected. Current flows in and the voltage at the terminal TE2 of the capacitor C65 rises. This operation continues until the voltage at the terminal TE2 reaches the highest voltage Vmax1 among the outputs of the connected operational amplifiers 41 to 44. When the voltage at the terminal TE2 coincides with the voltage Vmax1, since the other operational amplifiers 41 to 44 (op-amps other than the operational amplifier that outputs the voltage Vmax1) are lower than the voltage at the terminal TE2, current flows through the diodes 61 to 64. There is nothing.

  (2) If the voltage of one of the fuel cells further rises and the highest voltage among the outputs of the connected operational amplifiers 41 to 44 becomes Vmax2 (Vmax1 <Vmax2), the voltage at the terminal TE2 of the capacitor C65 Current flows from the operational amplifiers 41 to 44 that output a higher voltage through the diodes 61 to 64, and the voltage at the terminal TE2 of the capacitor C65 increases. This operation continues until the voltage at the terminal TE2 becomes the voltage Vmax2.

  (3) On the contrary, when the voltage of the fuel cell that has been the maximum voltage until then becomes low and the highest voltage among the outputs of the connected operational amplifiers 41 to 44 becomes Vmax3 (Vmax1> Vmax3), the capacitor C65 Since the voltage at the terminal TE2 is lower than the outputs of the operational amplifiers 41 to 44, no current flows from the operational amplifiers 41 to 44 to the capacitor C65. As a result, the capacitor C65 is discharged through the resistor 68 until the voltage changes from Vmax1 to Vmax3. Actually, in any of the cases (1) to (3) described above, the voltage at the terminal TE2 is lower than the maximum value of the outputs of the operational amplifiers 41 to 44 by this forward drop voltage, but the minimum. Similar to the value detection operation, it is easy to detect the maximum voltages of the fuel cells FC1 to FC4.

A-4. Abnormality judgment processing:
The abnormality determination process in the voltage monitoring system 20 will be described with reference to FIG. The abnormality determination process is a process for determining an abnormality of the voltage transmission circuit 40 in the voltage monitoring system 20. The abnormality determination process in the present embodiment is repeatedly executed regardless of the operating state of the fuel cell system including the fuel cells FC1 to FC4 (for example, during the power generation operation or during the power generation operation stop). When this process is started, the CPU 90 first acquires and determines the state of the power generation operation of the fuel cell system as the process of the operation state acquisition unit 91 (step S111). The determination in this embodiment is (1) during load operation (in a state where power generation operation is performed by connecting to a load), (2) during stop (in a state where power generation operation is not performed), or in an open state (load) In a state where the power generation operation is performed without being connected to. In the present embodiment, the CPU 90 acquires the state of the power generation operation by detecting the ON / OFF state of the switches 96 and 97 that switch the connection between the fuel cell stack FC and the load 95. However, the configuration for acquiring the operation state is not limited to this configuration, and may be acquired from an operation control parameter of the fuel cell stack FC, for example, a hydrogen supply amount within a predetermined period.

  If the result of determination in step S <b> 111 is that load operation is in progress, the CPU 90 determines an abnormality of the voltage transmission circuit 40 as a process of the abnormality determination unit 92. Specifically, the CPU 90 determines whether or not the minimum value detected by the minimum value detection circuit 50 and input to the CPU 90 via the MCU 80 is 0 (step S112). As a result, if the minimum value is not 0 (step S112: NO), it is determined that the voltage transmission circuit 40 is normal (step S113).

On the other hand, if the minimum value is 0 (step S112: YES), the CPU 90 outputs the minimum value (value 0) and the output of the operational amplifier 70 input through the operational amplifier 70, that is, the entire fuel cells FC1 to FC4. The consistency with the voltage is determined (step S114). In this embodiment, this determination is based on the number of fuel cells constituting the fuel cell stack and the voltage range that can be taken by the entire voltage, which is assumed from the detected minimum voltage and maximum voltage, and the actually detected entire voltage. This is done from the perspective of whether there is a contradiction with voltage. Specifically, the detected total voltage Vtotal of the fuel cells FC1 to FC4, the detected maximum value Vmax of the fuel cells FC1 to FC4, and the number N of fuel cells constituting the fuel cell stack (N is 1 or more) An integer (here, N = 4) is determined by whether or not the relationship of the following expression (1) is satisfied. That the detected minimum value is 0V means that at least one of the voltages of the fuel cells FC1 to FC4 is 0V, so that the assumed voltage range of the entire voltage is not less than Vmax (N−1 pieces). When the voltage of the fuel cell is 0V and the voltage of one fuel cell is Vmax), Vmax × (N−1) or less (the voltage of one fuel cell is 0V and N−1 fuels) Battery voltage is Vmax). Therefore, if the relationship of Formula (1) is satisfied, the minimum value and the overall voltage are matched. On the other hand, if the relationship of formula (1) is not satisfied, the minimum value and the overall voltage do not match.
Vtotal ≦ Vmax × (N−1) (1)

  As a result, if the minimum value matches the overall voltage (step S114: YES), the CPU 90 determines that the voltage transmission circuit 40 is normal (step S113). On the other hand, if the minimum value and the overall voltage are not matched (step S114: NO), the CPU 90 determines that the voltage transmission circuit 40 is abnormal (step S115). In the voltage transmission circuit 40, resistors 31 to 34 are interposed in the outputs of the fuel cells FC1 to FC4, and the terminals for outputting the outputs of the fuel cells FC1 to FC4 to the operational amplifiers 41 to 44 are disconnected. The operational amplifiers 41 to 44 are configured to have an output of 0V. Therefore, the fact that the above equation (1) is not satisfied is due to a poor connection between any of the fuel cells FC1 to FC4 and the voltage transmission circuit 40 even though the actual output of the fuel cells FC1 to FC4 is greater than 0V. The minimum value is likely detected as 0V. Therefore, such a determination is performed.

  On the other hand, if the determination in step S111 is stopped or open, the CPU 90 determines the abnormality of the voltage transmission circuit 40 by another method as the process of the abnormality determination unit 92. Specifically, the CPU 90 determines whether or not the maximum value detected by the maximum value detection circuit 60 and input to the CPU 90 via the MCU 80 is equal to or greater than a predetermined threshold value TH (step S116). As a result, if the maximum value is equal to or greater than the threshold value TH (step S116: YES), the CPU 90 determines that the voltage transmission circuit 40 is abnormal (step S117). Even if the operational amplifiers 41 to 44 are normal, the output may fluctuate even when the operational amplifiers 41 to 44 are in a stopped state or an open state, but a voltage as large as that during load operation is not output. This is because, if a large voltage is output in spite of being stopped or in an open state, there is a high possibility that an abnormality has occurred in any of the operational amplifiers 41 to 44.

  On the other hand, if the maximum value is less than the threshold value TH (step S116: NO), the CPU 90 determines that the voltage transmission circuit 40 is normal (step S113). Thus, when the normality or abnormality is determined, the abnormality determination process ends.

A-5. effect:
The voltage monitoring system 20 having such a configuration detects the maximum value and the minimum value of the voltages of the fuel cells FC1 to FC4, and determines the abnormality of the voltage transmission circuit 40 based on these and the operating state of the fuel cells FC1 to FC4. be able to.

  Further, the voltage monitoring system 20 utilizes the fact that the voltage of the fuel cell when the operation state is stopped or open when the voltage transmission circuit 40 is normal is relatively smaller than that during load operation, When the operation state is stopped or open, and the maximum value is equal to or greater than the threshold value TH, it is determined that the voltage transmission circuit 40 is abnormal. Therefore, the abnormality determination of the voltage transmission means can be easily performed.

  Further, in the voltage monitoring system 20, since the resistors 31 to 34 are interposed between the anodes and cathodes of the fuel cells FC1 to FC4 and are connected to both input terminals of the operational amplifiers 41 to 44, the fuel cells FC1 to FC4. When there is a connection failure between any of the above and the voltage transmission circuit 40, the operational amplifiers 41 to 44 output 0V. Therefore, even if the operation state of the fuel cells FC1 to FC4 is under load operation, if 0V is detected as the minimum value, there is a high possibility that the connection failure has occurred. In addition, the voltage monitoring system 20 determines that the voltage transmission circuit 40 is abnormal only when the minimum value is 0 V and the minimum value (0 V) contradicts the overall voltage. Therefore, the connection failure can be determined with high accuracy. In addition, since the detected maximum value is used in determining whether or not the minimum value (0 V) and the overall voltage contradict each other, it is possible to improve the determination accuracy of the contradiction.

  Further, the voltage monitoring system 20 detects the maximum value and the minimum value by the minimum value detection circuit 50 and the maximum value detection circuit 60, and uses different methods both during the load operation and during the stop or open state. Since abnormality determination can be performed, determination accuracy is improved. Further, since the minimum value detection circuit 50 and the maximum value detection circuit 60 are provided in parallel, the maximum value and the minimum value can be detected at the same time, so that the operation control of the fuel cell is performed using both the maximum value and the minimum value. The present invention can also be suitably applied when performing the above.

  In addition, the voltage monitoring system 20 collects the voltages of the plurality of fuel cells FC1 to FC4 that are output in a state where the voltage transmission circuit 40 is insulated, and detects the minimum value and the maximum value. Compared to the case where the voltage is detected and the minimum value and the maximum value are obtained by calculation, the calculation load can be reduced. As a result, it is possible to contribute to simplification of the configuration, which is a problem common to the voltage monitoring system. Moreover, since the voltage monitoring system 20 includes an operational amplifier, a diode, and a capacitor, the configuration can be simplified. Moreover, since it can comprise using a general purpose component, manufacture is easy and can reduce cost. Further, there is no interference between the circuits that take out the outputs of the fuel cells FC1 to FC4. Moreover, it is excellent in the responsiveness with respect to the voltage fluctuation of fuel cell FC1-FC4. In addition, since the capacitors C55 and C65 are used, and so to speak, an integration circuit is provided, the minimum voltage and the maximum voltage can be output without the influence of noise or the like.

B. Second embodiment:
A second embodiment of the present invention will be described.
B-1. General configuration of the voltage monitoring system 120:
The voltage monitoring system 120 according to the second embodiment differs from the voltage monitoring system 20 according to the first embodiment described above only in the configuration of the voltage monitoring circuit and the MCU. A schematic configuration of the voltage monitoring system 120 is shown in FIG. In FIG. 3, the same components as those in the first embodiment are denoted by the same reference numerals as those in FIG. As shown in FIG. 3, the voltage monitoring system 120 includes a voltage monitoring circuit 125, an operational amplifier 70, an MCU 180, and a CPU 90. The voltage monitoring circuit 125 includes a maximum / minimum value detection circuit 150 instead of the minimum value detection circuit 50 and the maximum value detection circuit 60 of the first embodiment. The maximum / minimum value detection circuit 150 is a circuit that selectively detects the maximum value and the minimum value among the outputs of the fuel cells FC1 to FC4.

  In the maximum / minimum value detection circuit 150, the outputs of the operational amplifiers 41 to 44 are all connected to the diodes 51 to 54 in the reverse direction. The outputs of the operational amplifiers 41 to 44 are all connected to the forward diodes 61 to 64 in parallel with the diodes 51 to 54. Switches SW11 to SW14 are interposed between the operational amplifiers 41 to 44 and the diodes 51 to 54, and switches SW21 to SW24 are interposed between the operational amplifiers 41 to 44 and the diodes 61 to 64. Similarly to the first embodiment, a capacitor C155 having one end connected to the ground is connected to the outputs of the operational amplifiers 41 to 44. Further, the power source 57 and the switch SW26 are connected via the switch SW16 and the resistor 58, respectively. A resistor 68 is connected through the terminal.

  The MCU 180 has the same function as the first embodiment, but differs from the first embodiment in that it has one input port and one output port.

B-2. Minimum / maximum value detection operation:
The minimum value detection operation and maximum value detection operation of the voltage monitoring system 120 will be described. In the minimum value detection operation of the voltage monitoring system 120, in response to a signal from the CPU 90, the switches SW11 to SW14 and the switch SW16 are turned on, and the switches SW21 to SW24 and the switch SW26 are turned off. As a result, the connection relationship of the maximum / minimum value detection circuit 150 is the same as that of the minimum value detection circuit 50 of the first embodiment. Therefore, a voltage corresponding to the minimum voltage of the fuel cells FC1 to FC4 is held in the capacitor C155, and the MCU 180 Is output.

  On the other hand, in the maximum value detection operation of the voltage monitoring system 120, in response to a signal from the CPU 90, the switches SW11 to SW14 and the switch SW16 are turned off, and the switches SW21 to SW24 and the switch SW26 are turned on. As a result, the connection relationship of the maximum / minimum value detection circuit 150 is the same as that of the maximum value detection circuit 60 of the first embodiment. Therefore, a voltage corresponding to the maximum voltage of the fuel cells FC1 to FC4 is held in the capacitor C155, and the MCU 180 Is output. In this way, the voltage monitoring system 120 selectively detects the minimum value and the maximum value by switching the switches SW11 to SW14, SW21 to SW24, SW16, and SW16.

  The voltage monitoring system 120 having such a configuration achieves the same effects as those of the first embodiment by performing the abnormality determination process described above. In the abnormality determination process, the minimum value or the maximum value may be selectively detected according to the operating state determined in step S111. In addition, since the maximum / minimum value detection circuit 150 selectively detects the minimum value and the maximum value by switching the switch circuit, the MCU 180 only needs to have one input port and one output port. It is not necessary to separately provide capacitors for maximum value detection and minimum value detection, and the apparatus configuration can be simplified.

C. Third embodiment:
C-1. Schematic configuration of the voltage monitoring system 220:
The voltage monitoring system 220 according to the third embodiment differs from the voltage monitoring system 120 according to the second embodiment described above only in the configuration of the voltage monitoring circuit. A schematic configuration of the voltage monitoring system 220 is shown in FIG. In FIG. 4, the same components as those in the second embodiment are denoted by the same reference numerals as those in FIG. As shown in FIG. 4, the voltage monitoring system 220 includes a voltage monitoring circuit 225, an operational amplifier 70, an MCU 180, and a CPU 90. The voltage monitoring circuit 225 includes a maximum / minimum value detection circuit 250 instead of the maximum / minimum value detection circuit 150 of the second embodiment. The maximum / minimum value detection circuit 250 is a circuit that selectively detects the maximum value and the minimum value among the outputs of the fuel cells FC1 to FC4.

  In the maximum / minimum value detection circuit 250, the outputs of the operational amplifiers 41 to 44 are all connected to diodes 51 to 54 whose rectification directions can be switched by a switch circuit. Similarly to the second embodiment, the output of the operational amplifiers 41 to 44 is connected to a capacitor C155 having one end connected to the ground, and further via the switch SW16 and the resistor 58 via the power source 57 and the switch SW26. A resistor 68 is connected.

  A configuration for switching the rectifying directions of the diodes 51 to 54 will be described. In the maximum / minimum value detection circuit 250, switches SW 31 and 41 are connected before and after the diode 51. The switch SW31 is configured so that the output of the operational amplifier 41 can be selectively connected to either the output terminal a1 of the diode 51 or the terminal b1 connected to the input terminal a2. The switch SW41 is configured such that the capacitor C155 can be selectively connected to either the input terminal a2 of the diode 51 or the terminal b2 connected to the output terminal a1. If the switch SW31 is connected to the terminal a1 and the switch SW41 is connected to the terminal a2, the output of the operational amplifier 41 is connected to the diode 51 in the reverse direction. On the other hand, if the switch SW31 is connected to the terminal b1 and the switch SW41 is connected to the terminal b2, the output of the operational amplifier 41 is connected to the forward diode 51. Although description is omitted, the diodes 52 to 54 are also connected to the outputs of the operational amplifiers 42 to 44 so that the rectification direction can be switched by the switches SW32 to SW34 and SW42 to 44, similarly to the diode 51.

C-2. Minimum / maximum value detection operation:
The minimum value detection operation and maximum value detection operation of the voltage monitoring system 220 will be described. In the minimum value detection operation of the voltage monitoring system 220, upon receiving a signal from the CPU 90, the switch SW31 is connected to the terminal a1, the switch SW41 is connected to the terminal a2, and the switch SW16 is turned on and the switch SW26 is turned on. Set to OFF. As a result, the connection relationship of the maximum / minimum value detection circuit 250 is the same as that of the minimum value detection circuit 50 of the first embodiment. Therefore, a voltage corresponding to the minimum voltage of the fuel cells FC1 to FC4 is held in the capacitor C155, and the MCU 180 Is output.

  On the other hand, in the minimum value detection operation of the voltage monitoring system 220, upon receiving a signal from the CPU 90, the switch SW31 is connected to the terminal b1, the switch SW41 is connected to the terminal b2, and the switch SW16 is turned off. Switch SW26 is turned on. As a result, the connection relationship of the maximum / minimum value detection circuit 250 is the same as that of the maximum value detection circuit 60 of the first embodiment. Therefore, a voltage corresponding to the maximum voltage of the fuel cells FC1 to FC4 is held in the capacitor C155, and the MCU 180 Is output.

  The voltage monitoring system 220 having such a configuration exhibits the same effect as that of the second embodiment by performing the abnormality determination process. In addition, since the maximum / minimum value detection circuit 250 can switch the rectification direction of the diodes 51 to 54 by the switches SW31 to SW34 and SW41 to 44, the number of diodes is reduced compared to the second embodiment, and the device configuration is reduced. It can be simplified.

D. Fourth embodiment:
A fourth embodiment of the present invention will be described. The voltage monitoring system according to the fourth embodiment differs from the voltage monitoring system 20 according to the first embodiment described above only in the configuration of the voltage transmission circuit. Hereinafter, the voltage monitoring system according to the fourth embodiment will be described only with respect to differences from the first embodiment. FIG. 5 is an explanatory diagram showing the configuration of the voltage transmission circuit 340 as the fourth embodiment. The voltage transmission circuit 340 includes resistors 311 to 314 and current sensors 341 to 344. That is, the voltage transmission circuit 340 includes resistors 311 to 314 and current sensors 341 to 344 instead of the resistors 31 to 34 and the operational amplifiers 41 to 44 of the voltage transmission circuit 40 according to the first embodiment. Is different from the first embodiment.

  A resistor 311 and a current sensor 341 are connected in series between the anode and cathode of the fuel cell FC1. Similarly, for the fuel cells FC2 to FC4, resistors 312 to 314 and current sensors 342 to 344 are connected in series.

  The current sensors 341 to 344 are non-contact type DC current sensors, and have the same value as the output voltage of the fuel cells FC1 to FC4 according to the current flowing through the resistors 311 to 314 while being insulated from the fuel cells FC1 to FC4. Is output. In the present embodiment, Hall element type magnetic sensors are used as the current sensors 341 to 344. That is, the voltage transmission circuit 340 is configured so that the output of the current sensors 341 to 344 is 0 V when there is a poor connection between any of the fuel cells FC1 to FC4 and the voltage transmission circuit 340. The voltage transmission circuit 340 having such a configuration can perform the minimum value detection operation and the maximum value detection operation based on the same principle as in the first embodiment. In such a voltage monitoring system, by performing the above-described abnormality determination process, the same effects as in the first embodiment can be obtained. Of course, the voltage monitoring system can selectively detect the minimum value and the maximum value in the same manner as in the second or third embodiment.

  The current sensors 341 to 344 may have any of the functions described above. For example, various magnetic sensors and current sensors such as a mag-amp type and a magnetic multivibrator type can be used. In the case where the current sensors 341 to 344 adopt a type in which the output does not become 0 V even if there is a poor connection between any of the fuel cells FC1 to FC4 and the voltage transmission circuit 340, as in the first embodiment, A resistor may be interposed between the anode and the cathode of the fuel cells FC1 to FC4. In addition, a current transformer can be used as the current sensors 341 to 344 as long as the fuel cells FC1 to FC4 need to output only when there is a sudden change in output.

E. Example 5:
A fifth embodiment of the present invention will be described.
E-1. General configuration of the voltage monitoring system 420:
A schematic configuration of a voltage monitoring system 420 as a fifth embodiment is shown in FIG. In addition, about the structure similar to 1st Example, the same code | symbol as FIG. 1 is attached | subjected and description is abbreviate | omitted, and only a structure different from 1st Example is demonstrated below. As shown in the figure, the voltage monitoring circuit 425 constituting the voltage monitoring system 420 as the fifth embodiment includes switch circuits 441 to 444, a transformer 440, a maximum / minimum value detection circuit 460, and an operational amplifier 472.

  Each of the switch circuits 441 to 444 is basically the same circuit, and when viewed from the fuel cells FC1 to FC4, capacitors C401 to C404 are interposed between the anode and the cathode, and the switches SW51 to SW51 are parallel to this. SW 54 and windings 451 to 454 are connected in series. Thus, one switch circuit 441 to 444 is provided for each of the fuel cells FC1 to FC4 constituting the fuel cell stack FC.

  The switches SW51 to SW54 are relays that receive a signal from the CPU 90 and switch ON / OFF of the conduction state between the anode side and the cathode side of the fuel cells FC1 to FC4. The transformer 440 is a transformer in which the windings 451 to 454 are input side windings and the winding 457 is an output side winding. When the switches SW51 to SW54 are all OFF, the capacitors C401 to C404 are charged by the fuel cells FC1 to FC4. The capacitors C401 to C404 do not consume power once they are charged. In this state, when any one of the switches SW51 to SW54 is turned on, the power stored in the capacitor corresponding to the switch that is turned on among the capacitors C401 to C404 is transferred to the input side winding of the transformer 440. Flows in. Since the change in current is extremely large, an output voltage corresponding to the input voltage appears at both ends of the winding 457 that is the output side winding of the transformer 440 according to the mutual inductance between the input and output of the transformer 440. If any one of the switches SW51 to SW54 is turned on, current flows also from the corresponding fuel cells FC1 to FC4. However, since the fuel cells FC1 to FC4 have internal resistance, a large rush occurs in a short time. Current cannot flow. For this reason, inrush current is caused to flow through the windings 451 to 454 that are the input side windings of the transformer 440 using the capacitors C401 to C404. Such capacitors C401 to C404 are so-called speed-up capacitors. The switch circuits 441 to 444 and 440 correspond to the voltage transmission circuit 40 of the first embodiment.

  The maximum / minimum value detection circuit 460 is a circuit common to the fuel cells FC1 to FC4, and includes capacitors C411 and C412, diodes 463 and 464, and switches SW61 and SW62. The maximum / minimum value detection circuit 460 receives a signal from the CPU 90, and when the switch SW61 is turned on and the switch SW62 is turned off, the maximum value detection circuit in which the maximum value of the output voltage of the transformer 440 is held in the capacitor C412. Works as. The maximum / minimum value detection circuit 460 receives the signal from the CPU 90, and when the switch SW61 is OFF and the switch SW62 is ON, the minimum value of the output voltage of the transformer 440 is the minimum value held in the capacitor C412. Operates as a detection circuit. Thus, the circuit configuration can be simplified by adopting a configuration in which the maximum value detection circuit and the minimum value detection circuit can be switched by the switch. Of course, the maximum value detection circuit and the minimum value detection circuit may be provided separately. Details of the operation of the maximum / minimum value detection circuit 460 will be described later.

  The operational amplifier 472 is a voltage follower. The operational amplifier 472 outputs the maximum voltage or the minimum voltage held by the capacitor C412 to the MCU 180 having one input port and one output port at a predetermined timing.

E-2. Maximum value detection operation:
The maximum value detection operation of the voltage monitoring system 420 will be described. Such an operation is realized by a switch ON / OFF operation via the CPU 90. In the maximum value detection operation of this embodiment, first, the switch SW61 is turned on and the switch SW62 is turned off. Then, the switch SW51 of the switch circuit 441 is turned on with the switches SW52 to SW54 of the switch circuits 442 to 444 being turned off. Then, the voltage V1 of the fuel cell FC1 is input to the transformer 440, and the output V1 is applied to the capacitor C411. Then, the voltage V <b> 1 is held at C <b> 412 via the diode 463.

  Next, the switch SW51 is turned off, and the switch SW52 of the switch circuit 442 is turned on. Then, the voltage V2 of the fuel cell FC2 is input to the transformer 440, and the output V2 is applied to the capacitor C411. At this time, if the voltage V2 is equal to or lower than the voltage V1, the diode 463 is reverse-biased, and thus the voltage V1 is held in the capacitor C412. On the other hand, if the voltage V2 is greater than the voltage V1, the diode 463 is forward biased, so that the charges of the capacitor C411 and the capacitor C412 are leveled through the diode 463. In this state, by repeatedly turning ON / OFF the switch SW52, when the voltage V2 is larger than the voltage V1, the voltage V2 is finally held in the capacitor C412.

  If this operation is also performed for the switch circuits 442 to 444, the maximum voltage Vmax that is the maximum value of the voltages of the fuel cells FC1 to FC4 is finally held in the capacitor C412. The maximum voltage Vmax detected in this way is output to the MCU 180 via the operational amplifier 472.

E-3. Minimum value detection operation:
The minimum value detection operation of the voltage monitoring system 420 will be described. Such an operation is realized by a switch ON / OFF operation via the CPU 90. In the minimum value detection operation of this embodiment, first, a predetermined initial voltage V0 is applied in advance to the capacitor C412 with the switches SW61 and SW62 being OFF. Here, the initial voltage V0 is a voltage that is assumed to be surely higher than the minimum value of the voltages of the fuel cells FC1 to FC4. In the present embodiment, the larger one of the voltages V1 and V2 is applied as the initial voltage V0 to the capacitor C412 by the same operation as the operation for detecting the voltages V1 and V2 described above. For example, a circuit configuration for application may be added.

  Then, the switch SW51 of the switch circuit 441 is turned on with the switches SW52 to SW54 of the switch circuits 442 to 444 being turned off. Then, similarly to the maximum value detection operation, the voltage V1 is held in the capacitor C411. Thereafter, the switch SW62 is turned on. Then, if the voltage V1 is equal to or higher than the voltage V0, the diode 464 is reverse-biased, so that the capacitor C412 holds V0. On the other hand, if the voltage V1 is smaller than the voltage V0, the diode 464 is forward biased, and the charges of the capacitor C411 and the capacitor C412 are leveled through the diode 464. By repeating ON / OFF of the switch SW51 many times in this state, when the voltage V1 is smaller than the voltage V0, the voltage V1 is finally held in the capacitor C412. In addition, since a back electromotive force is generated when the switch SW51 is turned off, it is necessary to turn off the switch SW62 once in advance.

  If such an operation is also performed for the switch circuits 442 to 444, the minimum voltage Vmin that is the minimum value of the voltages of the fuel cells FC1 to FC4 is finally held in the capacitor C412. The minimum voltage Vmin detected in this way is output to the MCU 180 via the operational amplifier 472.

  The voltage monitoring system 420 having such a configuration achieves the same effect as that of the first embodiment by executing the abnormality determination process described above. In the voltage monitoring system 420, the fuel cells FC <b> 1 to FC <b> 1 are disconnected from the terminals for outputting the outputs of the fuel cells FC <b> 1 to FC <b> 4 to the capacitors C <b> 401 to C <b> 404 without using a resistor between the anode and the cathode. When starting the power generation operation of FC4, the capacitors C401 to C404 are not charged. As a result, even if the switches SW51 to SW54 are turned on, no current flows through the windings 451 to 454. Therefore, the transformer 440 outputs 0 V by the minimum value detection operation, and abnormality determination can be made based on the determination in step S112. It is. However, a resistor may be interposed between the anode and the cathode. By doing this, after the start of the power generation operation of the fuel cells FC1 to FC4, even when the terminal for outputting the output of the fuel cells FC1 to FC4 to the capacitors C401 to C404 is disconnected, until the capacitors C401 to C404 wait for self-discharge. However, the transformer 440 outputs 0 V by the minimum value detecting operation, and the determination accuracy can be improved.

F. Modifications:
A modification of the above embodiment will be described.
F-1. Modification 1:
In the above-described embodiment, the configuration in which the voltage monitoring system determines abnormality of the voltage transmission circuit by the two methods according to the operation state of the fuel cells FC1 to FC4 has been described. However, these two methods are not necessarily performed. It is not necessary to use it, and abnormality determination may be performed using only one of the methods. Of course, in such a case, only one of the maximum value and the minimum value may be detected. In this way, it is possible to perform the abnormality determination more simply.

F-2. Modification 2:
In the above-described embodiment, the minimum value and the total voltage are determined using the detected overall voltage Vtotal of the fuel cells FC1 to FC4 and the maximum value Vmax of the output of the fuel cells FC1 to FC4 in the determination in step S114 of the abnormality determination process. However, instead of the detected maximum value Vmax, a previously assumed maximum value may be used. The assumed maximum value may be a maximum value that can be output (for example, 0.9 V) in consideration of the performance of the fuel cell. In this way, even when the reliability of the maximum value Vmax is doubtful, a certain determination accuracy can be ensured. Further, the present invention can be applied even when the voltage monitoring system detects only the minimum value and the total voltage among the maximum value, the minimum value, and the total voltage.

Further, as described above in the determination in step S114, the voltage range that can be assumed by the entire voltage should be equal to or greater than Vmax. Therefore, if the following equation (2) is not satisfied, either Vmax or Vtotal Can be determined to be an abnormal value. In such a case, it is possible to determine that any one of the operational amplifiers 41 to 44 is abnormal, the operational amplifier 70 is abnormal, or the operational amplifier 70 and the fuel cell stack FC are poorly connected.
Vmax ≦ Vtotal (2)

  Further, when both of the expressions (1) and (2) are not satisfied, in the determination of step S114, as described above, instead of the detected maximum value Vmax, a determination is made using a previously assumed maximum value. You may try again. In this way, when the maximum value Vmax is an abnormal value, it is possible to perform determination while eliminating the influence. Furthermore, if a resistor is interposed in the two input lines to the operational amplifier 70 and the operational amplifier 70 that outputs the entire voltage, the operational amplifier 70 can be used when a connection failure between the operational amplifier 70 and the fuel cell stack FC occurs. Since 0V is output with certainty, abnormal locations can be further narrowed down depending on whether or not the detected Vtotal is 0.

  Of course, the determination in step S114 may be omitted, and if the detected minimum value is 0V (step S112: YES), it may be determined that the voltage transmission means is abnormal. In this way, the determination can be performed more simply.

F-3. Modification 3:
The configuration of the voltage transmission means and the detection circuit in the voltage monitoring system of the present invention is not limited to the above-described embodiment, and can be realized by replacing with an equivalent circuit having an equivalent function. For example, instead of the diodes 51 to 54 in the first embodiment, a transistor may be used.

  The embodiment of the present invention has been described above, but the present invention is not limited to such an example, and it is needless to say that the present invention can be implemented in various modes without departing from the gist of the present invention. For example, the present invention is not limited to the polymer electrolyte fuel cell shown in the embodiments, but can be applied to various fuel cells such as a direct methanol fuel cell and a phosphoric acid fuel cell.

20, 120, 220, 420 ... voltage monitoring system 25, 125, 225, 425 ... voltage monitoring circuit 31-34, 58, 68, 311-314 ... resistor 40, 340 ... voltage transmission circuit 41-44, 70, 472 ... Operational amplifier 46 ... Power supply 50 ... Minimum value detection circuit 51-54, 463, 464 ... Diode 57 ... Power supply 60 ... Maximum value detection circuit 61-64 ... Diode 80 ... MCU
90 ... CPU
DESCRIPTION OF SYMBOLS 91 ... Operation state acquisition part 92 ... Abnormality determination part 150,250,460 ... Maximum / minimum value detection circuit 341-344 ... Current sensor 440 ... Transformer 441-444 ... Switch circuit 451-454,457 ... Winding 463,464 ... Diode SW11 to SW14, SW16, SW21 to SW24, SW26, SW31 to SW34, SW41 to SW44, SW51 to SW54, SW61, SW62 ... switches C55, C65, C155, C401, C411, C412 ... capacitors TE1, TE2, a1, a2, b1, b2 ... terminals FC1 to FC4 ... fuel cells

Claims (9)

A voltage monitoring system for a fuel cell stack in which a plurality of fuel cells are stacked,
A voltage transmission means provided for each of the plurality of fuel cells, the voltage of each of the fuel cells taken out from the fuel cell and output in an insulated state;
Specific detection means for collecting the voltages of the plurality of fuel cells output by the voltage transmission means and detecting at least one of a minimum value and a maximum value of the output voltages;
Obtaining means for obtaining an operating state of the fuel cell;
A voltage monitoring system comprising: determination means for determining an abnormality of the voltage transmission means based on at least one of the detected minimum value and maximum value and the acquired operating state of the fuel cell. The voltage monitoring system according to claim 1,
The specific detection means detects at least the maximum value,
The determination means is that the voltage transmission means is abnormal when the acquired operating state is stopped or open and the detected maximum value is equal to or greater than a predetermined threshold. Judgment voltage monitoring system. The voltage monitoring system according to claim 1 or 2,
Furthermore, it comprises a whole detecting means for detecting the whole voltage of the plurality of fuel cells,
The voltage transmission means is configured to have an output of 0 volt when there is a connection failure between any of the plurality of fuel cells and the voltage transmission means,
The specific detection means detects at least the minimum value;
The determination means, when the acquired operation state is under load operation, the detected minimum value is 0 volts, and the minimum value and the detected overall voltage are contradictory, A voltage monitoring system that determines that the voltage transmission means is abnormal. The voltage monitoring system according to claim 1 or 2,
The voltage transmission means is configured to have an output of 0 volt when there is a connection failure between any of the plurality of fuel cells and the voltage transmission means,
The specific detection means detects at least the minimum value;
The determination unit determines that the voltage transmission unit is abnormal when the acquired operation state is under load operation and the detected minimum value is 0 volts. A voltage monitoring system according to any one of claims 1 to 4,
The voltage transmission means includes a differential amplifier connected to the anode side and the cathode side of the plurality of fuel cells,
The specific detection means includes a diode provided in the same direction for each output of the differential amplifier, and a capacitor interposed between the diode and the ground. The voltage monitoring system according to claim 5,
The specific detection means includes
Detecting the minimum value and the maximum value;
A first circuit comprising: a first diode provided in a first direction for each output of the differential amplifier; and a first capacitor interposed between the first diode and the ground; ,
For each output of the differential amplifier, a second diode provided in a second direction opposite to the first direction, and a second diode interposed between the second diode and the ground. In parallel with a second circuit comprising two capacitors,
The determination unit determines the abnormality based on the detected minimum value or maximum value according to the acquired operating state. The voltage monitoring system according to claim 5,
The specific detection means includes
Detecting the minimum value and the maximum value;
A first diode provided in a first direction for each output of the differential amplifier;
For each output of the differential amplifier, a second diode provided in a second direction opposite to the first direction;
Connection switching means for switching a connection between the differential amplifier and any one of the first diode and the second diode by a switch circuit;
A capacitor interposed between the first diode and the second diode and the ground,
The determination unit determines the abnormality based on the detected minimum value or maximum value according to the acquired operating state. The voltage monitoring system according to claim 5,
The specific detection means includes
Detecting the minimum value and the maximum value;
A diode provided in the same direction for each output of the differential amplifier;
A capacitor interposed between the diode and ground;
The direction of the diode can be switched by a first switch circuit interposed between the differential amplifier and the diode and a second switch circuit interposed between the diode and the capacitor. Direction switching means, and
The determination unit determines the abnormality based on the detected minimum value or maximum value according to the acquired operating state. An abnormality determination method for determining an abnormality in a voltage monitoring system of a fuel cell stack in which a plurality of fuel cells are stacked,
The voltage monitoring system includes:
A voltage transmission means provided for each of the plurality of fuel cells, the voltage of each of the fuel cells taken out from the fuel cell and output in an insulated state;
Specific detection means for collecting the voltages of the plurality of fuel cells output by the voltage transmission means and outputting at least one of a minimum value and a maximum value of the output voltages;
An abnormality determination method for a voltage monitoring system, wherein an abnormality of the voltage transmission means is determined based on at least one of the detected minimum value and maximum value and an operating state of the fuel cell.

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