JP4600642B2 - Abnormality judgment device for fuel cell stack - Google Patents

Description

  The present invention relates to an abnormality determination device for determining a power generation abnormality of a fuel cell stack, and more particularly to an improved technique for appropriately determining the degree of power generation abnormality.

A fuel cell has a stack structure in which cells are stacked in series, and generates electric power using an electrochemical reaction between a fuel gas supplied to an anode electrode and an oxidizing gas supplied to a cathode electrode. Since water is generated in the battery reaction, the effective electrode area of the cell is reduced due to condensation of the water, and there is a possibility that the fuel gas is not uniformly supplied to each cell. In such a situation, a voltage distribution occurs between the cells, the current density becomes non-uniform, the output decreases, and the cell with the lowest voltage may reach 0 V or less to be overdischarged. If an electric current continues to flow in an overdischarged state, the electrolyte membrane may be damaged. Therefore, it is necessary to determine the power generation abnormality of the fuel cell stack in advance. As means for determining power generation abnormality of a fuel cell stack, Japanese Patent Application Laid-Open No. 2003-297407 compares a cell voltage with a plurality of reference voltages for each cell constituting the fuel cell stack, Techniques for early determination of power generation abnormality have been proposed.
JP 2003-297407 A

  However, since power generation abnormality is conventionally determined by simple comparison between cell voltage and reference voltage, how much abnormal current is flowing for how long, that is, how much is power generation abnormality? Could not be determined accurately.

  Therefore, an object of the present invention is to propose an abnormality determination device that can appropriately determine the degree of power generation abnormality of a fuel cell stack.

  An abnormality determination apparatus according to the present invention is an apparatus for determining a power generation abnormality of a fuel cell stack formed by stacking a plurality of cells, and firstly determines whether or not a cell voltage has dropped below a predetermined threshold voltage. Secondary determination means, and secondary determination means for secondary determination of the degree of power generation abnormality based on the integrated output value of the cells, taking into account the elapsed time since it was determined in the primary determination that the cell voltage has fallen below the threshold voltage With. By determining the degree of power generation abnormality based on the integrated output value of the cell taking into account the elapsed time since it was determined that the cell voltage has fallen below the threshold voltage, it is possible to appropriately determine power generation abnormality.

  Here, the integrated output value of the cell used for the secondary determination is, for example, an integrated current value obtained by integrating the cell current over the elapsed time after the determination that the cell voltage has dropped below the threshold voltage in the primary determination. desirable. By using the integrated current value, it is possible to reflect the magnitude and duration of the cell current that flowed during power generation abnormality in the abnormality determination, so it is possible to grasp how much abnormal state has continued, The degree of power generation abnormality can be determined appropriately.

  In addition, as the output integrated value of the cell used for the secondary determination, for example, an integrated voltage value obtained by integrating the cell voltage over the elapsed time since it was determined in the primary determination that the cell voltage has fallen below the threshold voltage. But you can. By using the integrated voltage value, the degree of power generation abnormality and its duration can be reflected in the abnormality judgment, so it is possible to grasp how much abnormal state has continued and how much power generation abnormality has occurred. It can be determined appropriately.

  In addition to the above-described configuration, the abnormality determination device of the present invention may further include a control unit that controls output limitation or operation stop of the fuel cell stack based on the secondary determination. With this configuration, damage to the fuel cell stack due to power generation abnormality can be avoided.

  According to the present invention, an appropriate determination of power generation abnormality is made by determining the degree of power generation abnormality based on the integrated output value of the cell taking into account the elapsed time since it was determined that the cell voltage has fallen below the threshold voltage. Is possible.

  The abnormality determination device of the present embodiment is a device that determines a power generation abnormality of a fuel cell stack formed by stacking a plurality of cells, and primarily determines whether or not the cell voltage has dropped below a predetermined threshold voltage. Based on the primary determination means and the output integrated value (integrated current value or integrated voltage value) of the cell taking into account the elapsed time since it was determined in the primary determination that the cell voltage has dropped below the threshold voltage, Secondary determination means for secondary determination of the degree. By determining the degree of power generation abnormality based on the output integrated value of the cell taking into account the elapsed time since it was determined that the cell voltage has fallen below the threshold voltage, how much abnormal state continued how much It becomes possible to grasp and the degree of power generation abnormality can be determined appropriately.

  FIG. 1 is a main configuration diagram of a fuel cell system 10 provided with an abnormality determination device of the present embodiment. The fuel cell system 10 is mainly a fuel cell in which a predetermined number of cells, each having an anode electrode and a cathode electrode facing each other on both sides of a solid polymer electrolyte membrane and sandwiched outside by a pair of separators, are connected in series. The stack 20, a fuel gas supply device 51 that supplies fuel gas to the anode electrode of the fuel cell stack 20, an oxidizing gas supply device 52 that supplies oxidizing gas to the cathode electrode of the fuel cell stack 20, and the fuel cell stack 20 are configured. A cell voltage detecting means 41 for detecting an output voltage (cell voltage) of each cell, a cell current detecting means 42 for detecting an output current (cell current) of the fuel cell stack 20, and a controller 30 for performing system control. Configured.

  The fuel gas supply device 51 is, for example, a high-pressure hydrogen tank or hydrogen storage tank filled with hydrogen gas, or a reforming material that reforms reforming raw materials (hydrocarbon raw fuel and water such as methanol or natural gas) into hydrogen-rich gas. It is composed of a quality device. The oxidizing gas supply device 52 is composed of, for example, an air compressor (air compressor) that pumps oxygen in the atmosphere. The control unit 30 functions as a control unit 33 that controls battery operation, and the flow rate of the fuel gas supplied from the fuel gas supply device 51 and the oxidizing gas supply so that the power generation amount of the fuel cell stack 20 matches the required power generation amount. The flow rate of the oxidizing gas supplied from the device 52 is adjusted. The electric power generated by the fuel cell stack 20 is consumed by the load 60. When the system 10 is mounted as a power supply device for a fuel cell vehicle or the like, the load 60 includes, for example, a traction motor for driving the vehicle, an inverter that supplies AC power to the traction motor, and other in-vehicle accessories. . When the system 10 is used as a stationary power generator, a commercial inverter or the like corresponds to the load 60, for example. The power system of the fuel cell stack 20 is provided with a diode 61 for suppressing reverse current and a switch (fuel cell output switch) 62 that electrically connects the fuel cell stack 20 and the load 60.

  In addition to functioning as a system controller that controls battery operation, the control unit 30 functions as an abnormality determination device including determination means 31 and 32 that determine power generation abnormality of the fuel cell stack 20. The primary determination means 31 performs a primary determination as to whether or not the cell voltage detected by the cell voltage detection means 41 has dropped below a predetermined threshold voltage V0. The cell voltage detecting means 41 is preferably means for detecting the output voltage of each cell for each cell, but may be means for detecting the output voltage for every predetermined number of cells. Further, the threshold voltage V0 used for the primary determination is not particularly limited as long as it is a voltage value that serves as a guideline for determining a cell voltage drop due to power generation abnormality, but is preferably about 0.3 V, for example. (The output voltage of each cell during normal power generation is about 0.6V.) As shown in FIG. 3, the secondary determination means 32 has elapsed time (abnormal power generation time) after it is determined in the primary determination that the cell voltage has dropped below the threshold voltage V0 (that is, power generation abnormality has occurred). Is calculated as a time integral value (integrated current value IT) of the cell current, and the degree of power generation abnormality is secondarily determined based on the integrated current value IT. The integration time of the integrated current value IT is an elapsed time after it is determined in the primary determination that the cell voltage has dropped below the threshold voltage V0. The time integration of the cell current is performed on condition that the cell voltage is equal to or lower than the threshold voltage V0.

  The control means 33 controls the load 60 so that the output of the fuel cell stack 20 is suppressed as the integrated current value IT (degree of power generation abnormality) calculated in the secondary determination increases, and accordingly, The fuel gas supply device 51 and the oxidizing gas supply device 52 are controlled to limit the output of the fuel cell stack 20. When the integrated current value IT becomes a value within a range in which the fuel cell stack 20 may be damaged, the control means 33 stops the supply of the reaction gas (fuel gas, oxidizing gas) to the fuel cell stack 20. At the same time, the switch 62 is opened to stop battery operation (power generation).

  FIG. 2 shows a processing routine for determining a power generation abnormality of the fuel cell stack and controlling the battery operation. The above description will be described again with reference to the processing routine. The primary determination means 31 acquires the sensor signal output from the cell voltage detection means 41, and monitors each cell voltage (S11). When the cell voltage V is equal to or higher than the threshold voltage V0 (S12; NO), since the power generation state is normal, the process returns to S11. When the cell voltage V becomes equal to or lower than the threshold voltage V0 (S12; YES), since the power generation state is abnormal, the secondary determination unit 32 performs time integration of the cell current detected by the cell current detection unit 42 (S13). When the integrated current value IT is less than the predetermined value W1 (S14; NO), the control means 33 performs the output limitation of the fuel cell stack 20 (S15). The control unit 30 stores map data such as the limiting rate of the load 60 and the reaction gas supply amount in accordance with the integrated current value IT in advance, and the control means 33 refers to this map data, and the fuel cell stack 20. The output restriction is implemented. The output of the fuel cell stack 20 may be limited by feedback of the integrated current value IT. On the other hand, when the integrated current value IT is equal to or greater than the predetermined value W1 (S14; YES), the control means 33 stops the battery operation (S16) in order to prevent the fuel cell stack 20 from being damaged.

  According to the present embodiment, by integrating (accumulating) the amount of current that has flown at the time of power generation abnormality, the magnitude of the cell current that has flowed at the time of power generation abnormality and its duration can be reflected in the abnormality determination. It is possible to grasp how long the state has continued, and it is possible to appropriately determine the degree of abnormality of the fuel cell stack 20.

  FIG. 2 is a main configuration diagram of the fuel cell system 11 including the abnormality determination device of the present embodiment. The devices having the same reference numerals as those in FIG. 1 indicate the same devices and the like, and detailed description thereof is omitted. In this embodiment, the cell current detection means 42 is omitted, and the above-described primary determination and secondary determination are performed based on the cell voltage detected by the cell voltage detection means 41. Similar to the first embodiment, the primary determination unit 31 performs a primary determination as to whether or not the cell voltage detected by the cell voltage detection unit 41 has decreased to a predetermined threshold voltage V0 or less. As shown in FIG. 6, the secondary determination means 32 is a time integral value (integrated voltage value VT) of the cell voltage taking into account the elapsed time since it was determined in the primary determination that the cell voltage has fallen below the threshold voltage V0. And the degree of power generation abnormality is secondarily determined based on the integrated voltage value VT. The integration time of the integrated voltage value VT is an elapsed time after it is determined in the primary determination that the cell voltage has dropped below the threshold voltage V0. The time integration of the cell voltage is performed on condition that the cell voltage is equal to or lower than the threshold voltage V0.

  FIG. 5 shows a processing routine for determining the power generation abnormality of the fuel cell stack and controlling the battery operation. The above description will be described again with reference to the processing routine. The primary determination means 31 acquires the sensor signal output from the cell voltage detection means 41, and monitors each cell voltage (S21). If the cell voltage V is equal to or higher than the threshold voltage V0 (S22; NO), the power generation state is normal, and the process returns to S21. When the cell voltage V becomes equal to or lower than the threshold voltage V0 (S22; YES), since the power generation state is abnormal, the secondary determination means 32 performs time integration of the cell voltage detected by the cell voltage detection means 41 (S23). When the integrated voltage value VT is less than the predetermined value W2 (S24; NO), the control means 33 performs output limitation of the fuel cell stack 20 (S25). The control unit 30 stores in advance map data such as the limiting rate of the load 60 and the reaction gas supply amount in accordance with the integrated voltage value VT, and the control means 33 refers to this map data to store the fuel cell stack 20. The output restriction is implemented. Further, the output of the fuel cell stack 20 may be limited by feedback of the integrated voltage value VT. On the other hand, when the integrated voltage value VT is equal to or greater than the predetermined value W2 (S24; YES), the control means 33 stops the battery operation to prevent the fuel cell stack 20 from being damaged (S26).

  According to the present embodiment, by integrating (accumulating) the cell voltage at the time of power generation abnormality, the degree of power generation abnormality and its duration can be reflected in the abnormality determination. This makes it possible to determine whether or not the fuel cell stack 20 is abnormal. Further, since the cell current detecting means 42 is unnecessary, the system configuration can be simplified.

1 is a main configuration diagram of a fuel cell system of Example 1. FIG. It is an electric power generation abnormality determination processing routine of Example 1. FIG. It is explanatory drawing of the time integration of the cell current of Example 1. FIG. 4 is a main configuration diagram of a fuel cell system of Example 2. 7 is a power generation abnormality determination processing routine according to a second embodiment. It is explanatory drawing of the time integration of the cell voltage of Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 11 ... Fuel cell system 20 ... Fuel cell stack 30 ... Control part 31 ... Primary determination means 32 ... Secondary determination means 33 ... Control means 41 ... Cell voltage detection means 42 ... Cell current detection means 51 ... Fuel gas supply apparatus 52 ... Oxidizing gas supply device 60 ... Load 61 ... Diode 62 ... Switch

Claims (4)

  An apparatus for determining a power generation abnormality of a fuel cell stack formed by stacking a plurality of cells, wherein primary determination means for primarily determining whether or not a cell voltage has dropped below a predetermined threshold voltage; and the primary Secondary determination means for secondary determination of the degree of power generation abnormality based on the integrated output value of the cell taking into account the elapsed time since it was determined in the determination that the cell voltage has dropped below the threshold voltage; Abnormality judgment device. A malfunction determining device according to claim 1, the output integrated value of the cell is the integral of the cell current over elapsed time since it is determined that the cell voltage in the primary determining drops below the threshold voltage An abnormality determination device that is an integrated current value. 2. The abnormality determination device according to claim 1 , wherein the integrated output value of the cell is obtained by integrating the cell voltage over an elapsed time after it is determined in the primary determination that the cell voltage has decreased below the threshold voltage. An abnormality determination device that is an integrated voltage value. The abnormality determination device according to any one of claims 1 to 3 , further comprising a control unit that controls output limitation or shutdown of the fuel cell stack based on the secondary determination. Judgment device.

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