JP2011014284A - Fuel cell internal state detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell internal state detecting device for controlling an incorrect detection of an internal state caused by disturbance.SOLUTION: The fuel cell internal state detection device to detect an internal state of a plurality of fuel cell modules constituting a fuel cell stack 10 includes: a current impression means 52 to impress AC current on the fuel cell stack 10; a voltage detection means S11 to detect response voltages at a predetermined frequency of each fuel cell modules in current impression; a condition determination means S13 to determine whether internal state detection condition is satisfied or not by comparing the response voltages of each fuel cell modules at the predetermined frequency and reference values at the frequency; and an internal state detection means S14 to detect the internal state by each of the fuel cell modules based on the response voltages of each fuel cell modules at the predetermined frequency in the internal state detection condition completion.

Description

  The present invention relates to an apparatus for detecting the internal state of a fuel cell.

  In a fuel cell serving as a power source for an electric vehicle or a hybrid vehicle, the power generation performance may be lowered depending on the state of the electrolyte membrane, the fuel electrode, and the oxidant electrode (hereinafter referred to as “internal state”). When the power generation performance of the fuel cell deteriorates, it is important to return the fuel cell to a normal state or to operate according to the state of the fuel cell. Therefore, in the fuel cell system, it is necessary to detect the internal state of the fuel cell.

  Patent Document 1 discloses an internal state detection device that detects an internal state of a fuel cell by applying an alternating current to the fuel cell after power generation of the fuel cell is stabilized and obtaining an alternating current impedance of the fuel cell. Yes. Since the internal state of the fuel cell is detected after stabilizing the power generation state of the fuel cell, the internal state can be detected without being affected by disturbance.

JP 2007-18741 A

  In the fuel cell system, it is necessary to detect the internal state at times other than when the power generation is stable. However, when the internal state detection device described in Patent Document 1 is applied at times other than when the power generation is stable, switching of the drive motor control inverter is performed. There is a possibility that the internal state of the fuel cell is erroneously detected due to the influence of disturbances such as noise caused by the control.

  Accordingly, the present invention has been made paying attention to such problems, and an object thereof is to provide a fuel cell internal state detection device capable of suppressing erroneous detection of an internal state caused by a disturbance. .

  The present invention solves the above problems by the following means.

  The present invention is a fuel cell internal state detection device that detects internal states of a plurality of fuel cell modules constituting a fuel cell stack. The fuel cell internal state detection device includes a current application unit that applies an alternating current to the fuel cell stack, a voltage detection unit that detects a response voltage at a predetermined frequency of each fuel cell module when the current is applied, and a predetermined unit for each fuel cell module. A condition determining means for comparing the response voltage at the frequency with a reference value at the frequency to determine whether or not the internal state detection condition is satisfied; and a response at a predetermined frequency of each fuel cell module when the internal state detection condition is satisfied An internal state detecting means for detecting the internal state of each fuel cell module based on the voltage is provided.

  According to the present invention, the internal state of each cell module is detected based on the response voltage of each cell module at a predetermined frequency only when the internal state detection condition is satisfied. Even if it exists, the internal state of the cell module is not erroneously detected.

1 is a system configuration diagram showing an example of a fuel cell system to which a fuel cell internal state detection device according to the present invention can be applied. It is a schematic block diagram of a voltage detection apparatus. It is a figure which shows the alternating current applied by an electric current application part. It is a figure which shows the frequency-gain characteristic of a filter part. It is a figure which shows the response voltage in the nth cell module of a fuel cell stack. It is a flowchart which shows the internal state detection control of the cell module which a controller performs. It is a flowchart which shows a low frequency internal state detection control. It is a flowchart which shows medium frequency internal state detection control. It is a flowchart which shows high frequency internal state detection control. It is a figure explaining an example of the internal state detection control of a cell module when there is no disturbance. It is a figure explaining an example of the internal state detection control of a cell module in case there exists a disturbance of a high frequency. It is a figure which shows the relationship between the output electric power of a fuel cell stack, and the coefficient used for reference voltage value calculation. It is a flowchart which shows the low frequency internal state detection control in 2nd Embodiment. It is a flowchart which shows the intermediate frequency internal state detection control in 2nd Embodiment. It is a flowchart which shows the high frequency internal state detection control in 2nd Embodiment. It is a figure which shows the relationship between the output electric power of a fuel cell stack, and a dispersion | variation reference value. It is a flowchart which shows the internal state detection control and disturbance frequency internal state detection control in 3rd Embodiment. It is a figure explaining an example of the internal state detection control of a cell module when the response voltage in a disturbance frequency is detected.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a system configuration diagram showing an example of a fuel cell system to which a fuel cell internal state detection device according to the present invention can be applied.

  The fuel cell system 100 is a fuel cell system for a vehicle, and includes a fuel cell stack 10, a hydrogen intake / exhaust mechanism 20, an air intake / exhaust mechanism 30, a drive motor control device 40, a voltage detection device 50, a controller 60, and the like. Is provided.

  The fuel cell stack 10 includes n cell modules each including at least one fuel cell that generates power using hydrogen as an anode gas and air as a cathode gas. The fuel cell stack 10 generates electric power necessary for driving the vehicle.

  The hydrogen intake / exhaust mechanism 20 includes a high-pressure hydrogen tank 21, a hydrogen supply passage 22, a hydrogen supply valve 23, a hydrogen offgas discharge passage 24, and a hydrogen offgas discharge valve 25.

  The high-pressure hydrogen tank 21 stores hydrogen supplied to the fuel cell stack 10 in a high-pressure state.

  One end of the hydrogen supply passage 22 is connected to the high-pressure hydrogen tank 21, and the other end is connected to the hydrogen supply hole of the fuel cell stack 10.

  The hydrogen supply valve 23 is provided in the hydrogen supply passage 22 and adjusts the flow rate of hydrogen supplied from the high-pressure hydrogen tank 21 to the fuel cell stack 10.

  One end of the hydrogen off-gas discharge passage 24 is connected to the hydrogen off-gas discharge hole of the fuel cell stack 10, and the other end opens to the outside.

  The hydrogen off gas discharge valve 25 is provided in the hydrogen off gas discharge passage 24 and adjusts the flow rate of the hydrogen off gas discharged to the outside.

  The air intake / exhaust mechanism 30 includes an air supply passage 31, a compressor 32, an air off-gas discharge passage 33, and an air off-gas discharge valve 34.

  One end of the air supply passage 31 forms an air intake port, and the other end is connected to the air supply hole of the fuel cell stack 10.

  The compressor 32 is provided in the air supply passage 31, pressurizes air taken from outside, and supplies the pressurized air to the fuel cell stack 10.

  The air off-gas discharge passage 33 has one end connected to the air off-gas discharge hole of the fuel cell stack 10 and the other end opened to the outside.

  The air off gas discharge valve 34 is provided in the air off gas discharge passage 33 and adjusts the flow rate of the air off gas discharged to the outside.

  The drive motor control device 40 includes a DC / DC converter 41, a battery 42, an inverter 43, and a drive motor 44.

  The DC / DC converter 41 increases or decreases the DC voltage between the fuel cell stack 10 and the battery 42 that is a chargeable / dischargeable secondary battery.

  The inverter 43 converts a direct current from the fuel cell stack 10 and the battery 42 into an alternating current and supplies the alternating current to the drive motor 44. The drive motor 44 is a three-phase AC motor and is a main power source of the vehicle.

  The voltage detection device 50 applies an alternating current to the fuel cell stack 10 during internal state detection control, and detects a response voltage in each cell module. The response voltage signal detected by the voltage detection device 50 is output to the controller 60.

  The controller 60 is configured by a microcomputer including a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). In addition to the response voltage signal from the voltage detection device 50, the controller 60 also receives signals from various sensors. Based on these input signals, the controller 60 detects the internal state of each cell module of the fuel cell stack 10 and controls the switching elements of the inverter 43.

  With reference to FIG. 2, the structure of the voltage detection apparatus 50 is demonstrated.

  The voltage detection device 50 is electrically connected to each cell module of the fuel cell stack 10 via the connection line 51. The voltage detection device 50 includes a current application unit 52, a filter unit 53, a voltage measurement unit 54, an isolator 55, and a voltage processing unit 56.

  The current application unit 52 applies an alternating current to the fuel cell stack 10 during internal state detection control. When an alternating current is applied to the fuel cell stack 10 in this way, a response voltage is generated in each cell module of the fuel cell stack 10. The current application unit 52 may be installed in the DC / DC converter 41 instead of being provided in the voltage detection device 50.

  The alternating current applied by the current applying unit 52 is an alternating current including three different frequencies f1 to f3 as shown in FIGS. 3 (A) and 3 (B). The low frequency f1 is a frequency of about 0.01 to 1 Hz. The middle frequency f2 is a frequency of about 20 to 40 Hz. The high frequency f3 is a frequency of about 5 to 10 kHz.

Returning to FIG. 2, the filter unit 53 is provided in the voltage detection device 50 for each cell module. As shown in FIG. 4, the filter unit 53 is a band-pass filter that passes a response voltage in a predetermined frequency band among the response voltages of the cell modules. The cut-off frequency f _CH on the high pass side of the filter unit 53 is set to be smaller than the low frequency f 1 of the alternating current applied by the current application unit 52. The cut-off frequency f _CL on the low pass side of the filter unit 53 is set larger than the low frequency f3 of the alternating current applied by the current application unit 52.

  The filter unit 53 shown in FIG. 2 removes the DC voltage component of the response voltage and lowers the input voltage, so that the durability of the voltage measurement unit 54 can be improved, and the high frequency component of the response voltage is removed, so that voltage measurement is performed. The occurrence of aliasing at the portion 54 can be suppressed.

  The same number of voltage measuring units 54 as the filter units 53 are provided. The voltage measurement unit 54 detects the filtered response voltage and converts the analog signal into a digital signal. The response voltage measured by the voltage measurement unit 54 is input to the voltage processing unit 56 via the isolator 55.

  The voltage processing unit 56 performs FFT processing on the response voltage of each cell module, and calculates a response voltage for each frequency in each cell module.

FIG. 5 shows the response voltage of the nth cell module of the fuel cell stack 10 detected by the voltage detection device 50. In the present embodiment, an alternating current including three frequencies f1, f2, and f3 is applied to the fuel cell stack 10, so that the response voltages V1 _n , V2 _n , and V3 _n corresponding to the respective frequencies are detected by the voltage detection device 50. The The response voltage V1 _n is a response voltage at the low frequency f1 in the nth cell module. The response voltage V2 _n is a response voltage at the medium frequency f2 in the nth cell module, and the response voltage V3n is a response voltage at the high frequency f3 in the nth cell module.

The controller 60 detects the internal state of each cell module based on the response voltages V1 ₁ to _n , V2 ₁ to _n , and V3 ₁ to _n for each frequency of each cell module. The controller 60 calculates the AC impedance of each cell module from the response voltage V1 ₁ ~ _n at low frequencies f1, detects abnormality of the reaction gas inlet portion of each cell modules on the basis of these AC impedance. The controller 60 calculates the AC impedance of each cell module from the response voltages V2 ₁ to _{n at} the medium frequency f2, and detects an abnormality in the fuel electrode and the oxidizer electrode of each cell module based on these AC impedances. Furthermore, the controller 60 calculates the AC impedance of each cell module from the response voltages V3 ₁ to _{n at} the high frequency f3, and detects an abnormality in the electrolyte membrane of each cell module based on these AC impedances.

  It is known in Japanese Patent Laid-Open No. 2005-332702 to detect different internal states of a cell module based on response voltages having different frequencies.

  By the way, the fuel cell internal state detection device of the conventional method can erroneously detect the internal state due to the influence of disturbance such as noise caused by switching control of the drive motor control inverter when detecting the internal state other than when the power generation is stable. There was sex.

Therefore, in the present embodiment, it is determined whether or not an internal state detection condition for performing no false detection is satisfied based on the response voltages V1 ₁ to _n , V2 ₁ to _n , and V3 ₁ to _n of each cell module. Sometimes, by detecting the internal state of each cell module, the internal state of each cell module is diagnosed without being affected by disturbance.

  The internal state detection control of the cell module executed by the controller 60 will be described with reference to the flowchart of FIG.

  FIG. 6 is a flowchart showing the main routine of the internal state detection control. This control is started when the power is turned on, and is repeatedly executed, for example, at a cycle of 10 milliseconds.

  In step S1, the controller 60 performs low frequency internal state detection control.

  In step S2, the controller 60 performs medium frequency internal state detection control.

  In step S3, the controller 60 performs high-frequency internal state detection control and ends the process.

  The low frequency internal state detection control will be described with reference to the flowchart of FIG.

In step S _< b _> 11, the controller 60 reads the response voltages V _< b _{> 1 1} to _n at the low frequency f _< b _{> 1} for each cell module detected by the voltage detection device 50.

In step S12, the controller 60 calculates the low frequency reference voltage value V1s from the equation (1) based on the low frequency response voltage average value V1 _AVE and the coefficient C1.

Here, the coefficient C1 is a value larger than 1. Coefficient C1 is in advance by experiment and is determined based on the variation of the response voltage V1 ₁ ~ _n of each cell module in a normal state.

In step S13, the controller 60 determines whether or not at least one of the response voltages V1 ₁ to _n of each cell module is greater than the low frequency reference voltage value V1s.

At least one of the response voltages V1 ₁ ~ _n is greater than the low-frequency reference voltage value V1s, the controller 60 determines that never erroneously detecting the internal state low frequency internal state detecting condition is satisfied Then, the process of step S14 is executed. If all the response voltage V1 ₁ ~ _n is smaller than the low frequency reference voltage value V1s, the controller 60, the low-frequency internal state detection condition is determined to be satisfied, to detect the internal state of each cell module The process is finished without.

In step S14, the controller 60 on the basis of the response voltage V1 ₁ ~ _n at low frequency f1 of each cell module, calculates the AC impedance of each cell module, the internal state of each cell modules on the basis of these AC impedance ( Abnormality of reaction gas introduction part) is detected.

  The medium frequency internal state detection control will be described with reference to the flowchart of FIG.

In step S _< b _> 21, the controller 60 reads the response voltages V _< b _{> 2 1} to _n at the medium frequency f _< b _{> 2} for each cell module detected by the voltage detection device 50.

In step S22, the controller 60 calculates the mid-frequency reference voltage value V2s from based on the medium-frequency response voltage average value V2 _AVE and the coefficient C2 (2) expression.

Here, the coefficient C2 is a value larger than 1. The coefficient C2 is determined based on the variation of the response voltages V2 ₁ to _n of each cell module in a normal state by a prior experiment.

In step S23, the controller 60 determines whether or not at least one of the response voltages V2 ₁ to _n of each cell module is greater than the medium frequency reference voltage value V2s.

When at least one of the response voltages V2 ₁ to _n is larger than the medium frequency reference voltage value V2s, the controller 60 determines that the medium frequency internal state detection condition that does not erroneously detect the internal state is satisfied. Then, the process of step S24 is executed. When all of the response voltages V2 ₁ to _n are smaller than the medium frequency reference voltage value V2s, the controller 60 determines that the medium frequency internal state detection condition is not satisfied, and detects the internal state of each cell module. The process is finished without.

In step S24, the controller 60 calculates the AC impedance of each cell module based on the response voltages V2 ₁ to _n at the medium frequency f2 of each cell module, and the internal state ( Abnormality of fuel electrode and oxidizer electrode) is detected.

  The high-frequency internal state detection control will be described with reference to the flowchart of FIG.

In step S31, the controller 60 reads the response voltages V3 ₁ to _n at the high frequency f3 for each cell module detected by the voltage detection device 50.

In step S32, the controller 60 calculates the medium frequency reference voltage value V3s from the equation (3) based on the high frequency response voltage average value V3 _AVE and the coefficient C3.

Here, the coefficient C3 is a value larger than 1. The coefficient C3 is determined based on the variation of the response voltages V3 ₁ to _n of each cell module in a normal state by a prior experiment.

In step S33, the controller 60 determines whether or not at least one of the response voltages V3 ₁ to _n of each cell module is greater than the high frequency reference voltage value V3s.

_If at least one of the response voltages V3 ₁ to _n is greater than the high-frequency reference voltage value V3s, the controller 60 determines that a high-frequency internal state detection condition that does not erroneously detect the internal state is satisfied, and the step The process of S34 is executed. When all of the response voltages V3 ₁ to _n are smaller than the high-frequency reference voltage value V3s, the controller 60 determines that the high-frequency internal state detection condition is not satisfied, and performs processing without detecting the internal state of each cell module. Exit.

In step S34, the controller 60 calculates the AC impedance of each cell module based on the response voltage V3 ₁ to _n at the high frequency f3 of each cell module, and based on these AC impedances, the internal state ( Detect abnormalities in electrolyte membrane).

  With reference to FIG. 10, an example of the internal state detection control of the cell module when there is no disturbance such as noise due to the switching control of the inverter 43 will be described. FIG. 10 is a diagram showing the relationship between the frequency and response voltage for each cell module detected when an alternating current is applied to the fuel cell stack 10.

Since the response voltages V1 ₁ to _n at the low frequency f1 of each cell module are substantially the same between the modules, all of the response voltages V1 ₁ to _n are smaller than the low frequency reference voltage value V1s, and are low. Since the frequency internal state detection condition is not satisfied (NO in step S13), the low frequency internal state detection control is not performed.

In addition, since the response voltages V2 ₁ to _n at the medium frequency f2 of each cell module are substantially the same between the modules, all of the response voltages V2 ₁ to _n are smaller than the medium frequency reference voltage value V2s. Since the medium frequency internal state detection condition is not satisfied (NO in step S23), the medium frequency internal state detection control is not performed.

On the other hand, only the response voltage V3 ₂ of the second cell module is extremely large at the response voltage V3 ₁ to _n at the high frequency f3 of each cell module. In such a case, the response voltage V3 ₂ becomes larger than the high frequency reference voltage value V3s, and the high frequency internal state detection condition is satisfied (YES in step S33). When there is a possibility of abnormality in the internal state of the cell module, the AC impedance of each cell module is calculated based on the response voltages V3 ₁ to _n, and the internal state of each cell module (abnormality of the electrolyte membrane) based on these AC impedances Is detected.

  Next, an example of the internal state detection control of the cell module when the noise or the like due to the switching control of the inverter 43 is a disturbance of the high frequency f3 will be described with reference to FIG. FIG. 11 is a diagram showing the relationship between the frequency and response voltage for each cell module detected when an alternating current is applied to the fuel cell stack 10.

Since the response voltages V1 ₁ to _n at the low frequency f1 and the response voltages V2 ₁ to _n at the medium frequency f2 of each cell module are approximately the same between the modules, the response voltage V1 ₁ to _n is low as in the case of FIG.・ Medium frequency internal state detection control is not implemented.

On the other hand, since the noise from the inverter 43 is a disturbance at the high frequency f3, the response voltages V3 ₁ to _n at the high frequency f3 of each cell module have a large value overall due to this disturbance.

When the response voltages V3 ₁ to _n increase in this way, the conventional fuel cell internal state detection device detects that the internal state has deteriorated in all the cell modules even though there is no abnormality in the internal state, There is a possibility of misdetecting the internal state.

In the present embodiment, even if the response voltages V3 ₁ to _n are increased including disturbances, if the response voltages V3 ₁ to _n are of the same level between modules, all of the response voltages V3 ₁ to _n are used. Becomes smaller than the high-frequency reference voltage value V3s, and the high-frequency internal state detection condition is not satisfied (NO in step S33), so the high-frequency internal state detection control is not performed. Therefore, even if a disturbance is included in the response voltages V3 ₁ to _n , the internal state of the cell module is not erroneously detected.

  As described above, in the fuel cell internal state detection device of the first embodiment, the following effects can be obtained.

  The fuel cell internal state detection device applies an alternating current to the fuel cell stack 10, detects a response voltage for each cell module corresponding to the frequency of the alternating current, and at least one of these response voltages is larger than a reference voltage value. In such a case, the internal state of each cell module is detected based on the response voltage of each cell module. Thereby, even if a disturbance is included in the response voltage, the internal state of the cell module is not erroneously detected, and the internal state detection accuracy can be improved.

  Further, since the alternating current applied to the fuel cell stack 10 includes three different frequencies f1, f2, and f3, a response voltage corresponding to each frequency can be detected for each cell module. Since the fuel cell internal state detection device performs internal state detection control based on response voltages of different frequencies, it is possible to detect different types of fuel cell internal states.

  In the first embodiment, the constants C1, C2, and C3 are used when calculating the low, medium, and high frequency reference voltage values V1s, V2s, and V3s. However, as shown in FIG. Coefficients C1, C2, and C3 that change according to the output power of 10 may be used. In this case, the coefficients C1, C2, and C3 are values larger than 1, and are set so as to decrease as the output power of the fuel cell stack 10 increases. Since the low, medium, and high frequency reference voltage values V1s, V2s, and V3s are changed according to the output power of the fuel cell stack 10, it is possible to detect the internal state that is optimal for the operating state of the fuel cell stack 10.

(Second Embodiment)
The fuel cell system 100 according to the second embodiment has substantially the same configuration as that of the first embodiment, but differs in the determination of the internal state detection condition in the low / medium / high frequency internal state detection control. Hereinafter, the difference will be mainly described.

  With reference to the flowchart of FIG. 13, the low frequency internal state detection control in 2nd Embodiment is demonstrated. The contents of steps S11 and S14 of FIG. 13 are the same as steps S11 and S14 of FIG. 7 in the first embodiment.

The controller 60 reads the response voltages V1 ₁ to _n at the low frequency f1 in step S11, and then executes the process of step S15.

In step S15, the controller 60, based on the low frequency response voltage average value V1 _AVE and response voltage V1 ₁ ~ _n of each cell module (4) equation, to calculate the standard deviation S1, which is indicative of variability.

In step S16, the controller 60 calculates the variation reference value S1s at the low frequency f1. Variation reference value S1s is in advance by experiment and is determined from the variation of the response voltage V1 ₁ ~ _n of each cell module in a normal state.

In step S17, the controller 60 determines whether or not the standard deviation S1 is greater than the variation reference value S1s indicating the variation of the response voltage V1 ₁ ~ _n.

  When the standard deviation S1 is larger than the variation reference value S1s, the controller 60 determines that the low frequency internal state detection condition is satisfied, and executes the process of step S14. When the standard deviation S1 is smaller than the variation reference value S1s, the controller 60 determines that the low-frequency internal state detection condition is not established, and ends the process without detecting the internal state of each cell module.

In step S14, the controller 60 calculates the AC impedance of each cell modules based on the response voltages V1 ₁ ~ _n at low frequency f1 of each cell module, the internal state (reaction of each cell modules on the basis of these AC impedance Abnormality of the gas introduction part) is detected.

  The medium frequency internal state detection control in the second embodiment will be described with reference to the flowchart of FIG. The contents of steps S21 and S24 in FIG. 14 are the same as steps S21 and S24 in FIG. 8 in the first embodiment.

The controller 60 reads the response voltages V2 ₁ to _n at the middle frequency f2 in step S21, and then executes the process of step S25.

In step S25, the controller 60 calculates a standard deviation S2 that serves as an index of variation from the equation (5) based on the response voltages V2 ₁ to _{n of} each cell module and the medium frequency response voltage average value _V2AVE .

In step S26, the controller 60 calculates the variation reference value S2s at the medium frequency f2. The variation reference value S2s is determined from variations in the response voltages V2 ₁ to _n of each cell module in a normal state by a prior experiment.

In step S27, the controller 60 determines whether or not the standard deviation S2 indicating the variation of the response voltages V2 ₁ to _n is larger than the variation reference value S2s.

  When the standard deviation S2 is larger than the variation reference value S2s, the controller 60 determines that the medium frequency internal state detection condition is satisfied, and executes the process of step S24. When the standard deviation S2 is smaller than the variation reference value S2s, the controller 60 determines that the medium frequency internal state detection condition is not satisfied, and ends the process without detecting the internal state of each cell module.

In step S24, the controller 60 calculates the AC impedance of each cell module based on the response voltages V2 ₁ to _n at the medium frequency f2 of each cell module, and the internal state ( Abnormality of fuel electrode and oxidizer electrode) is detected.

  Next, high-frequency internal state detection control in the second embodiment will be described with reference to the flowchart in FIG. The contents of steps S31 and S34 in FIG. 15 are the same as steps S31 and S34 in FIG. 9 in the first embodiment.

The controller 60, after reading the response voltage V3 ₁ ~ _n in a high frequency f3 at step S31, executes the process of step S35.

In step S35, the controller 60 calculates a standard deviation S3 that serves as an index of variation from the equation (6) based on the response voltages V3 ₁ to _{n of} each cell module and the high-frequency response voltage average value _V3AVE .

In step S36, the controller 60 calculates a variation reference value S3s at the high frequency f3. The variation reference value S3s is determined from variations in the response voltages V3 ₁ to _n of each cell module in a normal state by a prior experiment.

In step S37, the controller 60 determines whether or not the standard deviation S3 indicating the variation of the response voltages V3 ₁ to _n is larger than the variation reference value S3s.

  When the standard deviation S3 is larger than the variation reference value S3s, the controller 60 determines that the high-frequency internal state detection condition is satisfied, and executes the process of step S34. When the standard deviation S3 is smaller than the variation reference value S3s, the controller 60 determines that the high-frequency internal state detection condition is not satisfied, and ends the process without detecting the internal state of each cell module.

In step S34, the controller 60 calculates the AC impedance of each cell module based on the response voltage V3 ₁ to _n at the high frequency f3 of each cell module, and based on these AC impedances, the internal state ( Detect abnormalities in electrolyte membrane).

  As described above, the following effects can be obtained in the fuel cell internal state detection device of the second embodiment.

  The fuel cell internal state detection device applies an alternating current to the fuel cell stack 10, detects a response voltage for each cell module corresponding to the frequency of the alternating current, and a standard deviation calculated from these response voltages varies. When it becomes larger, the internal state of each cell module is detected based on the response voltage of each cell module. Thereby, even if disturbance is included in the response voltage, the internal state of the cell module is not erroneously detected, and the same effect as in the first embodiment can be obtained.

  In the second embodiment, the variation reference values S1s, S2s, and S3s are constant values. However, as shown in FIG. 16, the variation reference values S1s, S2s, and S3s are changed according to the output power of the fuel cell stack 10. You may do it. In this case, the variation reference values S1s, S2s, and S3s are set so as to decrease as the output power of the fuel cell stack 10 increases. Since the variation reference values S1s, S2s, and S3s are changed according to the output power of the fuel cell stack 10, the internal state detection that is optimal for the operating state of the fuel cell stack 10 can be performed.

(Third embodiment)
The fuel cell system 100 according to the third embodiment has substantially the same configuration as that of the first embodiment, but differs in detection of the internal state of the cell module. Hereinafter, the difference will be mainly described.

  When the noise or the like due to the switching control of the inverter 43 is a disturbance having a frequency different from the frequency of the alternating current applied to the fuel cell stack 10 (hereinafter referred to as “disturbance frequency”), the response at the disturbance frequency during the internal state detection control Voltage may be detected. Therefore, in the third embodiment, not only the internal state of each cell module is detected based on the response voltage at the low frequency f1 to the high frequency f3 as in the first embodiment, but also based on the response voltage at the disturbance frequency. The internal state of each cell module is detected.

  FIG. 17A is a flowchart showing the main routine of the internal state detection control of the third embodiment. The processes in steps S1 to S3 in FIG. 17 are the same as the processes in steps S1 to S3 in FIG. 6 of the first embodiment.

  In step S4 after step S3, the controller 60 performs disturbance frequency internal state detection control and ends the process.

  Next, disturbance frequency internal state detection control will be described with reference to the flowchart of FIG.

In step S41, the controller 60 reads the response voltage V4 ₁ ~ _n in disturbance frequency f4 of each cell module detected by the voltage detector 50.

In step S42, the controller 60 calculates the disturbance frequency reference voltage value V4s from the equation (7) based on the disturbance frequency response voltage average value V4 _AVE and the coefficient C4.

Here, the coefficient C4 is a value larger than 1. Coefficient C4 is in advance by experiment and is determined based on the variation of the response voltage V4 ₁ ~ _n of each cell module in a normal state. The coefficient C4 may be set so as to decrease as the output power of the fuel cell stack 10 increases.

In step S43, the controller 60 determines whether or not at least one of the response voltages V4 ₁ to _n of each cell module is greater than the disturbance frequency reference voltage value V4s.

When at least one of the response voltages V4 ₁ to _n is larger than the disturbance frequency reference voltage value V4s, the controller 60 determines that the disturbance frequency internal state detection condition is satisfied, and executes the process of step S44. When all of the response voltages V4 ₁ to _n are smaller than the disturbance frequency reference voltage value V4s, the controller 60 determines that the disturbance frequency internal state detection condition is not satisfied, and detects the internal state of each cell module. The process is finished without.

In step S44, the controller 60 calculates the AC impedance of each cell module based on the response voltages V4 ₁ to _n at the disturbance frequency f4 of each cell module, and determines the internal state of each cell module based on these AC impedances. To detect.

FIG. 18 illustrates an example of the internal state detection control of the cell module when the response voltages V4 ₁ to _n at the disturbance frequency f4 are detected.

Since the response voltages V1 ₁ to _{n to} V3 ₁ to _n at the low to high frequencies f1 to f3 of each cell module are substantially the same between the modules, the internal state of each cell module is not detected.

On the other hand, only the response voltage V4 ₂ of the second cell module is extremely large at the response voltages V4 ₁ to _n at the disturbance frequency f4 of each cell module. In such a case, response voltage V4 ₂ of the second cell module becomes larger than the disturbance frequency reference voltage value V4s, disturbance frequency internal state detecting condition is satisfied (YES at step S43). And disturbance frequency internal state detecting condition is satisfied, when it is determined that there is a possibility of internal state abnormality of the cell module calculates the AC impedance of each cell module based on response voltage V4 ₁ ~ _n, these AC impedance Based on this, the internal state of each cell module is detected.

  As described above, in the fuel cell internal state detection device of the third embodiment, the following effects can be obtained.

  The fuel cell internal state detection device detects not only the internal state of each cell module based on the response voltage at the low frequency f1 to the high frequency f3, but also the internal state of each cell module based on the response voltage at the disturbance frequency. Therefore, it becomes easier to detect a change in the state of the cell module than in the first embodiment.

  Note that the present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  In the first to third embodiments, the internal state of each cell module is detected based on the response voltage having a frequency corresponding to the frequency of the alternating current applied to the fuel cell stack 10, but the present invention is not limited to this. Absent. For example, the response voltage at the harmonic frequency with respect to the frequency of the alternating current applied to the fuel cell stack 10 is detected for each cell module, and the internal state of each cell module is detected based on the response voltage at the harmonic frequency. Also good.

DESCRIPTION OF SYMBOLS 100 Fuel cell system 10 Fuel cell stack 43 Inverter 44 Drive motor 50 Voltage detection apparatus 52 Current application part (current application means)
53 Filter unit 54 Voltage measurement unit 56 Voltage processing unit 60 Controller S11, S21, S31, S41 Voltage detection means S13, S23, S33, S43, S17, S27, S37 Condition determination means S14, S24, S34, S44 Internal state detection means

Claims (8)

In a fuel cell internal state detection device for detecting internal states of a plurality of fuel cell modules constituting a fuel cell stack,
Current application means for applying an alternating current to the fuel cell stack;
Voltage detecting means for detecting a response voltage at a predetermined frequency of each fuel cell module when applying current;
Condition determination means for comparing the response voltage at a predetermined frequency of each fuel cell module with a reference value at that frequency to determine whether an internal state detection condition is satisfied,
An internal state detecting means for detecting an internal state of each fuel cell module based on a response voltage at a predetermined frequency of each fuel cell module when the internal state detection condition is established;
A fuel cell internal state detection device comprising: The condition determining means is configured to determine whether at least one of the response voltages at a predetermined frequency of each fuel cell module is greater than the reference value calculated based on an average value of the response voltages at a predetermined frequency of each fuel cell module. Determining that the internal state detection condition is satisfied,
The fuel cell internal state detection device according to claim 1. The condition determination means determines that an internal state detection condition is satisfied when a standard deviation calculated from a response voltage at a predetermined frequency of each fuel cell module is larger than the reference value.
The fuel cell internal state detection device according to claim 1. The condition determining means sets the reference value from the variation in response voltage of each cell module in a normal state by a prior experiment.
The fuel cell internal state detection device according to claim 3. The condition determining means sets the reference value smaller as the output power of the fuel cell stack increases.
The fuel cell internal state detection device according to any one of claims 1 to 4, characterized in that: The voltage detecting means detects a response voltage at a frequency corresponding to the frequency of the alternating current;
The fuel cell internal state detection device according to any one of claims 1 to 5, characterized in that: The current application means applies an alternating current having a plurality of frequencies,
The voltage detection means detects a response voltage for each frequency in each fuel cell module,
The condition determination means compares the response voltage for each frequency of each fuel cell module and a reference value at those frequencies to determine whether an internal state detection condition for each frequency is satisfied,
The internal state detection means detects an internal state of each fuel cell module based on the response voltage at a frequency at which an internal state detection condition is established.
The fuel cell internal state detection device according to claim 6. The voltage detection means includes a band-pass filter that passes the response voltage of the predetermined frequency.
The fuel cell internal state detection device according to any one of claims 1 to 7, wherein

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