JP4702592B2 - Fuel cell system and operation method thereof - Google Patents

Description

  The present invention relates to a fuel cell system and an operation method thereof.

In an electric vehicle, a fuel cell power generation system, and the like, in general, the insulation resistance of various devices is measured during maintenance and the state of insulation deterioration is monitored. As a method for measuring such an insulation resistance, for example, a method described in Patent Document 1 can be cited. This conventional method is intended to realize the measurement of the insulation resistance of the object to be measured without DC grounding. Specifically, an LC resonance circuit that is capable of maintaining oscillation by an AC power source or the like is connected to a measurement object such as an electric vehicle via a capacitor connected in series with the circuit, and the voltage of the LC resonance circuit is set. By measuring, the insulation resistance between the object to be measured and the ground is obtained.
JP-A-8-160082

  Incidentally, a high voltage circuit provided in a fuel cell system mounted on a fuel cell vehicle or the like is usually insulated from the ground in order to ensure safety. However, due to the structure of the fuel cell, the electrode to which the pipe is connected via the manifold is inevitably electrically connected to the ground with a resistance value determined by the conductivity of the generated water and cooling water flowing through the pipe. Will be. In such a situation, when the electrical conductivity increases due to a change in the components of the generated water or the deterioration of the cooling water, the resistance value decreases, thereby deteriorating the insulation between the fuel cell and the ground. .

  In order to detect such a decrease in insulation, even if the conventional insulation deterioration detection method described above is applied, the change in the resistance value caused by the component change or deterioration of the generated water or cooling water flowing in the pipe is accurately measured. It is difficult to do. In addition, it is necessary to newly add a complicated oscillation device including an LC resonance circuit, an AC power source, and the like. Further, as described in Patent Document 1, an operation of adjusting the frequency of the AC power supply in accordance with the change in the capacitance between the ground between the fuel cell as the object to be measured and the ground is also required. Therefore, the cost tends to increase and the control operation becomes complicated.

  Therefore, the present invention has been made in view of such circumstances, and it is possible to accurately and easily detect a decrease in insulation between the fuel cell and the ground caused by the generated water or cooling water of the fuel cell. It is an object of the present invention to provide a fuel cell system and an operation method thereof.

In order to solve the above problems, a fuel cell system according to the present invention includes a fuel cell, a power source provided to apply a voltage to the fuel cell via a discharge resistor, and a first voltage for measuring the voltage of the fuel cell. A voltage measuring unit, a second voltage measuring unit for measuring the voltage of the power source, a third voltage measuring unit for measuring a voltage between the fuel cell and the ground, and between the discharge resistance and the fuel cell and the ground. The relationship between the current flowing through each of the insulation resistances, the relationship between the voltage of the fuel cell and the voltage drop due to the discharge resistance and the insulation resistance, and the relationship between the power supply voltage and the voltage drop due to the discharge resistance and the insulation resistance are mathematically expressed. voltage, the voltage of the power supply, and the voltage between the fuel cell and the ground, and based on the known resistance value of the discharge resistor, calculation unit for calculating the resistance value of the insulation resistance between the fuel cell and the ground It is equipped with

  In the fuel cell system configured as described above, a closed circuit loop is configured in which a power source is connected to the fuel cell via a resistor and the fuel cell is connected to the ground via an insulation resistor. When this is expressed by an equivalent circuit, the relationship between the current flowing through the resistance and the insulation resistance, the relationship between the voltage of the fuel cell and the voltage drop due to the resistance and the insulation resistance, and the relationship between the power supply voltage and the voltage drop due to the resistance and the insulation resistance Can be mathematically expressed. Then, by solving these mathematical expressions, the resistance value of the insulation resistance can be expressed as a resistance value of the resistance and a relational expression of the power supply voltage, the fuel cell voltage, and the fuel cell / ground voltage. Among these, the resistance value of the resistor is known, and each voltage value is actually measured by the first voltage measuring unit, the second voltage measuring unit, and the third voltage measuring unit, respectively.

  Therefore, the resistance value of the insulation resistance is calculated by substituting the predetermined value and the actual measurement value into the relational expression representing the resistance value of the insulation resistance in the calculation unit. Accordingly, since the resistance value of the insulation resistance can be measured without using a complicated oscillation device or the like, a change in insulation between the fuel cell and the ground can be detected accurately and easily.

  More specifically, the fuel cell system according to the present invention includes open circuit means (switches, diodes, etc.) that operate to open a connection line between the fuel cell and the power source. Are preferably connected to each other through the open circuit means, and voltage measurement is preferably performed in a closed circuit loop formed with the open circuit means open.

  In addition, it is preferable to include a determination unit that determines that the fuel cell system is abnormal when the calculated resistance value (insulation resistance value) between the fuel cell and the ground is less than a preset reference value. is there. As a reference value, the insulation between the fuel cell and the ground can be sufficiently secured to prevent significant leakage.

  If such an abnormality determination is made, the fuel cell system is stopped following the determination, or the operator, operator, driver, or the like is notified that such an abnormality has occurred. Control can be performed. In this way, it is possible to reliably avoid inconvenient situations such as electric leakage and electric shock due to deterioration of insulation resistance.

In addition, after the voltage of the fuel cell has dropped below the voltage of the power source , the arithmetic unit determines whether the fuel cell is grounded based on the voltage of the fuel cell, the power source voltage, and the voltage between the fuel cell and ground. It is preferable that the resistance value is calculated. Furthermore, it is more preferable that the predetermined value is the voltage of the power source.

The fuel cell system operating method according to the present invention is a method for effectively operating the fuel cell system according to the present invention, that is, a fuel cell system including a fuel cell and a power source connected to the fuel cell. And a voltage applying step for applying a voltage to the fuel cell via a discharge resistor, a first voltage measuring step for measuring the voltage of the fuel cell, and a second voltage measuring step for measuring the voltage of the power source. A third voltage measuring step for measuring the voltage between the fuel cell and the ground, the relationship between the discharge resistance and the current flowing through the insulation resistance between the fuel cell and the ground, the voltage of the fuel cell, the discharge resistance and the insulation resistance, respectively the relationship between the voltage drop due to, as well, and formulas of the relationship between the voltage drop due to the power supply voltage and the discharge resistance and the insulation resistance, voltage of the fuel cell, the voltage of the power supply, and the fuel cell and ah Based voltage and the known resistance value of the discharge resistor between, and a calculation step of calculating a resistance value of the insulation resistance between the fuel cell and ground.

  Furthermore, it is preferable to provide a determination step of determining that the fuel cell system is abnormal when the calculated resistance value (insulation resistance value) between the fuel cell and ground is less than a preset reference value.

Furthermore, it is preferable to provide a voltage reduction step for reducing the voltage of the fuel cell to a voltage lower than that of the power source prior to the calculation step. At this time, it is more preferable that the predetermined value is the voltage of the power source.

  According to the fuel cell system of the present invention and the operation method thereof, since the voltage is applied to the fuel cell via a resistor and the voltage at a predetermined part is measured, the insulation resistance between the fuel cell and the ground can be measured. It becomes possible to accurately and easily detect a decrease in insulation or a poor insulation between the high voltage circuit and the ground due to the generated water or cooling water of the fuel cell.

  Hereinafter, embodiments of the present invention will be described in detail. In addition, the same code | symbol is attached | subjected to the same element and the overlapping description is abbreviate | omitted. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

  FIG. 1 is a circuit block diagram showing a preferred embodiment of a fuel cell system according to the present invention. The fuel cell system 1 is a system mounted on, for example, a fuel cell vehicle, and includes a fuel cell 2 connected to a load H of the vehicle or the like, and constitutes a high voltage circuit. The fuel cell 2 is connected to an auxiliary power source 3 which is a direct current power source via a switch 4 provided between the cathodes 2a and 3a and via discharge resistors 51 and 52 connected in series with each other. ing. That is, the discharge resistors 51 and 52 are connected so as to connect a portion between the switch 4 and the cathode 3a of the auxiliary power source 3 and a portion between the anodes 2b and 3b of both the fuel cell 2 and the auxiliary power source 3. . With such a configuration, the voltage from the auxiliary power source 3 is applied to the fuel cell 2 via the discharge resistors 51 and 52 in a state where the connection line provided with the switch 4 is opened.

  As the discharge resistors 51 and 52, resistors for discharging charges accumulated in a capacitor (not shown) provided in the high voltage circuit can be used, and the resistance is sufficiently larger than the resistance value of the auxiliary power supply 3. It is desirable to have a value. Furthermore, the discharge resistors 51 and 52 are connected to, for example, a ground E (ground potential; body ground) of the vehicle body, and the electrode of the fuel cell 2 and the ground E have an insulation resistance 6 having a sufficiently large resistance value therebetween. Is in an equivalent state as formed, and is substantially insulated.

  Furthermore, the fuel cell system 1 includes a voltmeter 11 (first voltage measuring unit) and a voltmeter 12 (second voltage measuring unit) for measuring the voltages of the fuel cell 2 and the auxiliary power supply 3. ing. Furthermore, the voltmeter 13 (third voltage measuring unit) is connected to a portion between the cathode 2 a of the fuel cell 2 and the switch 4 and a portion between the discharge resistors 51 and 52. The voltmeter 13 measures the voltage between the fuel cell 2 and the ground E, that is, the voltage (potential difference) at both ends of the insulation resistor 6.

  Moreover, the voltmeters 11, 12, and 13 are connected to the calculation unit 8 provided in the control system or the like, and the voltage value signals acquired by the voltmeters 11, 12, and 13 are output to the calculation unit 8, An operation for obtaining the resistance value of the insulation resistor 6 is performed. The calculation unit 8 is connected to the determination unit 9 and performs a comparison calculation between the calculated resistance value of the insulation resistance 6 and a preset reference value, and based on the result, abnormality such as the occurrence of an insulation failure is calculated. Presence / absence is determined.

  An example of a procedure for carrying out the operation method of the fuel cell system according to the present invention using the fuel cell system 1 configured as described above will be described. First, the operation of the fuel cell 2 is stopped (the current drawing to the load H is stopped), and the switch 4 is opened. Thereby, a high voltage is applied from the auxiliary power source 3 to the fuel cell 2 via the discharge resistors 51 and 52 (voltage application step). Then, the voltage measurement by each voltmeter 11, 12, 13 is performed continuously or intermittently, and each voltage value signal is output to the calculation unit 8 (first to third voltage measurement steps).

  Further, the supply of fuel gas (hydrogen gas) and oxidant gas (air) to the fuel cell 2 is stopped, and power generation in the fuel cell 2 is stopped. As a result, the voltage in the fuel cell 2 decreases and eventually the voltage of the fuel cell 2 becomes smaller than the voltage of the auxiliary power supply 3 (voltage reduction step). After satisfying such conditions, the calculation unit 8 calculates the resistance value of the insulation resistor 6 as exemplified below.

Here, FIG. 2 is an equivalent circuit diagram of a circuit loop including the fuel cell 2 and the auxiliary power supply 3 in the fuel cell system 1 when the switch 4 is opened. In the equivalent circuit 10 shown in the figure, the voltages of the fuel cell 2 and the auxiliary power source 3 are V _FC and V _Bat , respectively, and the resistance values of the discharge resistors 51 and 52 are R _A and R _B , respectively. The respective current values flowing are I ₁ and I ₂ , the resistance value of the insulation resistance 6 to be measured is R _X , the current value flowing therethrough is I ₃ , and the voltage between both ends is V _LLC .

  Then, the equivalent circuit 10 satisfies the relationships represented by the following formulas (1) to (3).

From the equations (1) and (2), the relationship represented by the following equation (4) can be obtained by eliminating I ₂ .

Further, from the equations (1) and (3), the relationship represented by the following equation (5) is obtained by eliminating I ₂ .

Furthermore, the following formula (6) is obtained by multiplying the formula (4) by (R _A + R _B ).

Furthermore, to obtain multiplied by R _B in the formula (5), the following equation (7).

Next, when the equation (7) is subtracted from the equation (6) and further solved for I ₃ , the relationship represented by the following equation (8) is obtained.

  Here, in the insulation resistance 6, the relationship represented by the following formula (9) is satisfied.

  By substituting equation (8) into equation (9), the relationship represented by equation (10) below is obtained.

Furthermore, in Equation (10), when R _A and R _B are equal (R _A = R _B ), and further solving for R _X , the relationship represented by the following Equation (11) is obtained.

Substituting the known values R _A and the measured values of V _Bat , V _FC , and V _LLC into Equation (11), the resistance value R _X of the insulation resistance 6 is calculated (calculation step). Further, the obtained resistance value R _X is output to the determination unit 9. The determination unit 9 performs a comparison operation between the input resistance value R _X and a preset reference value R _th, and if the resistance value R _X is less than the reference value R _th , the system caused by insulation failure It is determined that an abnormality has occurred (determination step). On the other hand, when the resistance value R _X is equal to or greater than the reference value R _th , the insulation between the fuel cell 2 and the ground E is sufficiently secured, and the process is terminated. Alternatively, each voltage measurement by the voltmeters 11, 12, 13, the calculation of the resistance value R _X of the insulation resistance 6 in the calculation unit 8, and the comparison calculation with the reference value R _th in the determination unit 9 are repeated to generate an abnormality. This detection may be continued.

According to the fuel cell system 1 configured as described above and the operation method thereof, a predetermined high voltage is applied to the fuel cell 2 from the auxiliary power source 3 via the discharge resistors 51 and 52. The voltages V _FC , V _Bat and V _LLC between the power source 3 and the fuel cell 2 and the ground E are actually measured. Then, using these measured values and the resistance values of the discharge resistors 51 and 52, specifically, the resistance value R _X of the insulation resistor 6 is calculated in the calculation unit 8 based on the relationship represented by the above formula (11). be able to.

  Therefore, a change (insulation deterioration) in the insulation resistance value between the fuel cell 2 and the ground E can be detected accurately and easily without providing a conventional complicated oscillation device or the like. Therefore, in the fuel cell system 1, the conductivity increases due to the component change or deterioration of the generated water and cooling water in the fuel cell 2, and even if the insulation deteriorates undesirably due to this, The presence or absence of such an abnormality can be detected accurately and quickly. Therefore, it is possible to reliably suppress a leakage accident and an electric shock accident, and it is possible to prevent erroneous determination of system abnormality and unnecessary system stoppage. In addition, since the apparatus configuration is not complicated and the insulation resistance value can be easily calculated, it is possible to improve operability and operation controllability and to prevent an increase in cost.

  In addition, this invention is not limited to embodiment mentioned above, A various deformation | transformation is possible in the limit which does not change the summary. For example, instead of the switch 4, a member capable of forming another open circuit, for example, a diode may be provided. Further, in order to lower the voltage in the fuel cell 2, the supply of the fuel gas and the oxidant gas to the fuel cell 2 is stopped and the remaining gas in the gas supply pipe is consumed by the power generation of the fuel cell 2. Alternatively, the inert gas may be supplied to the supply pipes while the gas supply is stopped.

  The fuel cell system and the operation method thereof according to the present invention can measure the insulation resistance value between the fuel cell and the ground based on the voltage measurement result of a predetermined portion by applying a voltage to the fuel cell via the resistance. It is possible to accurately and easily detect a decrease in insulation caused by generated water or cooling water. Therefore, it can be widely used for devices, motives, facilities, and the like that are equipped with a fuel cell system such as a fuel cell vehicle and power generation facilities.

1 is a circuit block diagram showing a preferred embodiment of a fuel cell system according to the present invention. 2 is an equivalent circuit diagram of a circuit loop including a fuel cell 2 and an auxiliary power supply 3 in the fuel cell system 1 when a switch 4 is opened. FIG.

Explanation of symbols

  H: Load, 1 ... Fuel cell system, 2a, 3a ... Cathode, 2b, 3b ... Anode, 2 ... Fuel cell, 3 ... Auxiliary power supply (power supply), 4 ... Switch, 6 ... Insulation resistance, 8 ... Calculation unit, 9 Determining unit, 10 ... Equivalent circuit, 11 ... Voltmeter (first voltage measuring unit), 12 ... Voltmeter (second voltage measuring unit), 13 ... Voltmeter (third voltage measuring unit), 51, 52: Discharge resistance, E: Ground.

Claims (6)

A fuel cell;
A power source provided to apply a voltage to the fuel cell via a discharge resistor;
A first voltage measuring unit for measuring a voltage of the fuel cell;
A second voltage measuring unit for measuring the voltage of the power source;
A third voltage measuring unit for measuring a voltage between the fuel cell and ground;
The discharge resistance and relationship between the current flowing through each insulation resistance between the fuel cell and the ground, the relationship between the voltage drop due to voltage and the discharge resistor and the insulation resistance of the fuel cell, as well as the power supply voltage and the discharge resistance and insulation resistance And the voltage of the fuel cell, the voltage of the power source, the voltage between the fuel cell and the ground, and the known resistance value of the discharge resistance. A calculation unit for calculating a resistance value of an insulation resistance between the ground and the ground;
A fuel cell system comprising: A determination unit that determines that the fuel cell system is abnormal when the calculated resistance value between the fuel cell and the ground is less than a preset reference value;
The fuel cell system according to claim 1. After the voltage of the fuel cell has dropped below the voltage of the power source, the arithmetic unit is configured to determine the fuel cell based on the voltage of the fuel cell, the voltage of the power source, and the voltage between the fuel cell and ground. A resistance value between the ground and the ground,
The fuel cell system according to claim 1 or 2. A method of operating a fuel cell system comprising a fuel cell and a power source connected to the fuel cell,
A voltage application step of applying a voltage to the fuel cell via a discharge resistor;
A first voltage measuring step for measuring a voltage of the fuel cell;
A second voltage measuring step for measuring the voltage of the power source;
A third voltage measuring step for measuring a voltage between the fuel cell and ground;
The discharge resistance and relationship between the current flowing through each insulation resistance between the fuel cell and the ground, the relationship between the voltage drop due to voltage and the discharge resistor and the insulation resistance of the fuel cell, as well as the power supply voltage and the discharge resistance and insulation resistance And the voltage of the fuel cell, the voltage of the power source, the voltage between the fuel cell and the ground, and the known resistance value of the discharge resistance. A calculation step of calculating a resistance value of an insulation resistance with respect to the ground;
A method for operating a fuel cell system comprising: A determination step of determining that the fuel cell system is abnormal when the calculated resistance value between the fuel cell and the ground is less than a preset reference value;
The operation method of the fuel cell system according to claim 4. Prior to the calculation step, a voltage reduction step of reducing the voltage of the fuel cell to a voltage equal to or lower than the voltage of the power source is provided.
The operation method of the fuel cell system according to claim 4 or 5.

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