KR101567248B1 - Method and System for Measuring Impedance of Fuel Cell with Variable Signal Generation and Signal Collection Velocity - Google Patents

Abstract

The present invention relates to a fuel cell impedance measuring method and a system thereof which efficiently measure impedance of a fuel cell or the like of a vehicle at the optimized variable signal generating/signal collecting speed in order to reduce a load of a processor by reducing power consumption and the number of collected AC voltages and increasing accuracy in measurement by reducing interference between alternating currents. The fuel cell impedance measuring method comprises the following steps of: generating a plurality of alternating current signals and applying the alternating current signals to the fuel cell; and measuring a voltage generated in the fuel cell during corresponding application time and providing the voltage as impedance calculation information.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method and a system for measuring impedance of a fuel cell having variable signal generation and signal collection speed,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer electrolyte fuel cell (hereinafter referred to as " fuel cell ") impedance measuring method and system, and more particularly to a fuel cell Impedance measuring method and system.

The performance and lifetime of polymer electrolyte fuel cells (hereinafter referred to as fuel cells) are greatly influenced by the operating conditions of the fuel cell. The operating conditions of the fuel cell include current, temperature, amount of reactant, pressure of reactant, amount of coolant, and water content. In order to optimally control the fuel cell operating conditions based on the current state of the fuel cells, the industry conducts fuel cell state diagnosis in various ways.

Representative examples of fuel cell condition diagnosis include AC impedance measurement, current-voltage curve measurement, and catalyst area measurement. The AC impedance measurement is generally a method of applying an AC signal of several to several tens of frequency regions to a fuel cell and then measuring the impedance of each of them by measuring their respective voltage responses. As an effect obtained from the impedance measurement of the fuel cell, in the impedance measurement for a 100 Hz alternating current, in the measurement of the moisture content of the fuel cell (for example, the output decreases when the water content in the fuel cell is small) The measurement of the state and the impedance measurement for the 4 Hz alternating current include measurement of the state of the gas supply inside the fuel cell (for example, if the fuel cell is not supplied with the internal gas, the output and operation stability are degraded).

The impedance measurement of such a fuel cell generally uses a method of generating two or more alternating current signals to be applied to the fuel cell, measuring the alternating current voltage of the fuel cell, and calculating the impedance using the alternating current and the voltage.

However, in the conventional AC current generation and AC voltage collection methods, for example, as shown in FIG. 1, the generation of 20 Hz and 100 Hz alternating currents is maintained until one cycle of the slowest 4 Hz is completed. , The total current consumption for one period of 4 Hz (0.25 seconds) by the three signals is calculated by simple calculation as shown in Equation (1).

[Equation 1]

0.707A * 0.25 + 0.707A * 0.25 + 0.707A * 0.25 = 0.53A

The total AC voltage collection number for one cycle of 4 Hz (0.25 s) is 2000 * 0.25 = 500, assuming 2000 samples / s is required to measure the highest frequency, 100 Hz, And the impedance measurement time is 0.25 sec / s.

In the conventional method of measuring the impedance of the fuel cell, not only the current consumption is high but also the number of the AC voltage collection is large and the load of the processor is large and the intermodal interference due to the interference between the three AC currents is large, There is a falling problem.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to improve the accuracy of measurement by reducing the current consumption and the number of AC voltage collectors to reduce the load on the processor and reduce the inter- The present invention provides a fuel cell impedance measurement method and system that can efficiently perform impedance measurement of a fuel cell of a vehicle with optimized variable signal generation and signal acquisition speed.

In accordance with another aspect of the present invention, there is provided a method of measuring impedance of a fuel cell using a plurality of ac current signals, the method comprising: generating a plurality of ac current signals having different frequencies using a signal generator; Generating the plurality of alternating current signals and applying the plurality of alternating current signals to the fuel cell so as to include one period or less of another signal within one period of the signal having the smallest frequency; And providing a voltage generated in the fuel cell in synchronization with a signal having a highest frequency in a period of at least two signal mixing periods of the plurality of alternating current signals during a corresponding application time and providing the measured voltage as impedance calculation information And the number of measurement samples per second in the measurement for each of the plurality of alternating current signals is determined to be the same multiple of the frequency of each of the plurality of alternating current signals. And the plurality of alternating current signals are generated such that the peak portions do not overlap with each other.

According to another aspect of the present invention, there is provided a method of measuring impedance of a fuel cell using a plurality of alternating current signals, comprising: generating a plurality of alternating current signals having different frequencies in succession by one cycle or less, step; And providing a voltage generated in the fuel cell in synchronization with the application of each of the generated alternating current signals during a corresponding application time and providing the resulting voltage as impedance calculation information, And the number of samples per second is determined to be the same multiple of the frequency of each of the plurality of alternating current signals.

The drain value may be 20 times or more, and the plurality of alternating current signals may include three signals selected from 1 to 10 Hz sections, 10 to 100 Hz sections, and 100 to 1000 Hz sections, respectively.

A system for measuring impedance of a fuel cell using a plurality of alternating current signals according to another aspect of the present invention is a system for simultaneously generating a plurality of alternating current signals having different frequencies, A signal generator for generating the plurality of alternating current signals so as to include one cycle or less of the alternating current signals and applying the alternating current signals to the fuel cell; And a signal collector for measuring a voltage generated in the fuel cell in synchronism with a signal having a largest frequency in at least two signal mixing periods of the plurality of alternating current signals during a corresponding application time and providing the measured voltage as impedance calculation information And the number of measurement samples per second in the measurement for each of the plurality of alternating current signals is determined to be the same multiple of the frequency of each of the plurality of alternating current signals.

A system for measuring impedance of a fuel cell using a plurality of alternating current signals according to another aspect of the present invention includes a signal generator for generating a plurality of alternating current signals having different frequencies in succession, ; And a signal collector for measuring a voltage generated in the fuel cell in synchronism with the application of the generated alternating current signals for a corresponding application time and providing the resulting voltage as impedance calculation information, wherein in the measurement for each of the plurality of alternating current signals The number of samples per second is set to the same multiple of the frequency of each of the plurality of alternating current signals.

According to the method and system for measuring impedance of a fuel cell according to the present invention, the current consumption can be reduced by 55.6% or more, the load of the processor can be reduced by reducing the number of AC voltage collectors by 88.6% or more, The accuracy of the measurement can be improved. In addition, since the maximum values of the current signals of the multiple frequencies do not overlap, the stability of the fuel cell impedance measurement system can be improved.

1 is a signal waveform diagram for explaining a relation of a current signal for measuring a general fuel cell impedance.
2 is a view for explaining a fuel cell impedance measurement system according to an embodiment of the present invention.
3 is a flowchart for explaining an example of a method for measuring a fuel cell impedance of the present invention.
4 is a signal waveform diagram for explaining the relationship of current signals in the fuel cell impedance measuring method of FIG.
5 is a flow chart for explaining another example of the method for measuring the impedance of the fuel cell according to the present invention.
6 is a signal waveform diagram for explaining the relationship of current signals in the fuel cell impedance measuring method of FIG.
7 is a current signal waveform diagram for explaining AC current consumption in the fuel cell impedance measuring method of the present invention.
8 is a current signal waveform diagram for explaining AC current consumption in the conventional fuel cell impedance measuring method.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same components are denoted by the same reference symbols as possible. In addition, detailed descriptions of known functions and / or configurations are omitted. The following description will focus on the parts necessary for understanding the operation according to various embodiments, and a description of elements that may obscure the gist of the description will be omitted. Also, some of the elements of the drawings may be exaggerated, omitted, or schematically illustrated. The size of each component does not entirely reflect the actual size, and therefore the contents described herein are not limited by the relative sizes or spacings of the components drawn in the respective drawings.

2 is a view for explaining a fuel cell impedance measurement system 100 according to an embodiment of the present invention.

2, the fuel cell impedance measurement system 100 according to an embodiment of the present invention includes an AC current signal generator 110 and an AC voltage signal collector 120 for measuring impedance of the fuel cell 10 .

3 and 4, the signal generator 110 generates a plurality of alternating current signals having different frequencies (for example, 4 Hz, , 20 Hz, and 100 Hz) are generated at the same time, but within one cycle of the signal having the smallest frequency, the plurality of alternating currents (1, 2, 3, A signal can be generated and applied to the fuel cell 10. At this time, the signal collector 120 preferentially synchronizes with the signal having the largest frequency in two or more signal mixing periods of the plurality of alternating current signals, measures the voltage generated in the fuel cell 10 during the applicable time, Information can be provided.

5 and 6, the signal generator 110 sequentially generates a plurality of alternating current signals having different frequencies (for example, 4 Hz, 20 Hz, and 100 Hz) As shown in FIG. At this time, the signal collector 120 outputs a voltage generated in the fuel cell 10 in synchronism with the application of the generated alternating current signals for a predetermined period of time (for example, 1 cycle, 1/2 cycle, or 1/3 cycle) And can be provided as impedance calculation information.

Here, the number of samples per second for each measurement of a plurality of alternating current signals (e.g., 4 Hz, 20 Hz, 100 Hz) can be determined by the same multiple of the frequency of each of the alternating current signals (e.g., 20 times or more) have. For example, with a multiple of 20, it could be 80 samples per second for a 4 Hz signal, 400 samples per second for a 20 Hz signal, and 2000 samples per second for a 100 Hz signal. Here, the number of the plurality of alternating current signals may be two or more according to the purpose of measurement, and the drain value is described as being 20 times, but may be set to a higher multiple for high resolution if necessary. The frequency of the plurality of alternating current signals is 4 Hz, 20 Hz, and 100 Hz. However, the frequency of the alternating current signals is not limited thereto, and may be selected from 1 to 10 Hz, 10 to 100 Hz, and 100 to 1000 Hz, It can be composed of three signals.

The impedance of the fuel cell 10 can be calculated from the applied alternating current and the measured alternating voltage. As an effect obtained from the impedance measurement of the fuel cell, for example, in the impedance measurement for the alternating current of 100 Hz, Measurement of moisture content (eg, output degradation when water content inside the fuel cell is low), measurement of fuel cell durability for impedance measurement at 20 Hz alternating current, impedance measurement for 4 Hz alternating current, And if the internal gas supply is not desired, the output and operational safety deteriorate).

Hereinafter, the generation and collection of signals for the impedance measurement of the fuel cell 110 of the fuel cell impedance measurement system 100 according to an embodiment of the present invention will be described in more detail with reference to FIGS. 3 to 8. FIG.

3 is a flowchart for explaining an example of a method for measuring a fuel cell impedance of the present invention.

For example, the signal generator 110 can simultaneously generate a plurality of alternating current signals having different frequencies (e.g., 4 Hz, 20 Hz, and 100 Hz) and apply the same to the fuel cell 10 as shown in FIG. 4 (S 10). At this time, the signal generator 110 may be configured to apply alternating current signals (e.g., 4 Hz, 20 Hz, and 100 Hz) simultaneously starting from the same phase as shown in FIG. 4, but the present invention is not limited thereto, The authorization start time need not be the same. That is, one cycle (e.g., one cycle, one half cycle, or one third cycle) of the other signal (e.g., 20 Hz or 100 Hz) is included within one cycle of the signal having the smallest frequency The AC current signals can be generated and applied to the fuel cell 10.

At this time, the signal collector 120 preferentially synchronizes with the signal having the highest frequency in any two or more signal mixing periods among the alternating current signals, so that the voltage generated in the fuel cell 10 is applied for a predetermined time (for example, one cycle) (S11). ≪ tb > < / TABLE > In the example of FIG. 4, the voltage is measured at a sampling rate of 2000 samples per second for the applicable application time in synchronism with 100 Hz in the signal mixing period '1'. In the signal mixing period '2' The voltage can be measured at 400 samples per second for a period of time and the data can be collected by measuring the voltage at a rate of 80 samples per second for a 4 Hz signal. Similarly, when the signal intensities are at different positions, the voltage is measured at a rate of 2000 samples per second for the applicable time for 100 Hz, the voltage is measured at a rate of 400 samples per second for the duration of 20 Hz, Data can be collected by measuring the voltage at a rate of 80 samples per second for the signal.

As the signal collector 120 collects the measured voltage sample data, the impedance can be calculated by dividing the measured voltage by the applied current, using software executed by the processor or the computer (S12) . At this time, the influence of the signals having different frequencies in the signal incorporation period can be removed by using a predetermined filter and the impedance can be calculated.

When the application time (for example, 1 cycle, 1/2 cycle, or 1/3 cycle) is completed irrespective of the frequency (or speed) of the signal as described above, the signal generation is stopped and 0.707 A is consumed for generation of each signal , The total current consumption during one period (0.25 seconds) of 4 Hz by the three signals is as shown in Equation (2) by simple calculation. This means that the current consumption is reduced by 55.6% compared to the prior art (in the case of the conventional technique, 0.53A in Equation 1).

&Quot; (2) "

0.707A * 0.25 + 0.707A * 0.05 + 0.707A * 0.01 = 0.235A

In addition, the number of collecting AC voltage sample data is reduced by 89.6% as compared with the 500 samples of the prior art because a total of 52 sample data is collected during one period (0.25 second) of 4 Hz by three signals as shown in [Equation 3] It is effective.

&Quot; (3) "

2000 * 0.01 + 400 * 0.04 + 80 * 0.2 = 52

Also, since the impedance measurement time is 0.25 sec / s and the intermodal interference due to the interference between the AC current signals occurs only for 0.05 second, the measurement noise is reduced by 80.4% or more compared with the prior art.

5 is a flow chart for explaining another example of the method for measuring the impedance of the fuel cell according to the present invention.

For example, the signal generator 110 may sequentially output a plurality of alternating current signals having different frequencies (e.g., 4 Hz, 20 Hz, and 100 Hz) by one cycle or less 1/3 period) and can be applied to the fuel cell 10. Although FIG. 6 shows a method of first applying a signal having a large frequency, it is not limited thereto, and may include any method of applying the signal in a different order depending on the case.

At this time, the signal collector 120 outputs a voltage generated in the fuel cell 10 in synchronism with the application of the generated alternating current signals for a predetermined period of time (for example, 1 cycle, 1/2 cycle, or 1/3 cycle) And can be provided as impedance calculation information.

That is, in the example of FIG. 6, the signal collector 120 acquires sample data (S20) by measuring a voltage at a sampling rate of 2000 samples per second for the corresponding signal application time in synchronization with 100 Hz, (S21) by measuring the voltage at a sampling rate of 400 samples per second for the applicable application time, and then collecting the sample data by measuring the voltage at a rate of 80 samples per second for the subsequently applied 4 Hz signal (S22).

As the signal collector 120 collects the measured voltage sample data, the impedance can be calculated by dividing the measured voltage by the applied current, using software executed by the processor or the computer (S23) .

In the above method, since signal generation is stopped when the applicable time (for example, 1 cycle, 1/2 cycle, or 1/3 cycle) ends regardless of the frequency (or speed) of the signal, 0.707A If consumed, the total current consumption for one period (0.25 seconds) of 4 Hz by the three signals is as shown in Equation (2) by simple calculation. This means that the current consumption is reduced by 55.6% compared to the prior art (in the case of the conventional technique, 0.53A in Equation 1).

In addition, the number of collecting AC voltage sample data is reduced by 89.6% as compared with the 500 samples of the prior art because a total of 52 sample data is collected during one period (0.25 second) of 4 Hz by three signals as shown in [Equation 3] It is effective.

Also, the impedance measurement time is 0.31 sec / s, which is slightly increased. However, the measurement is not time-consuming because of a short time. Instead, the interference phenomenon between alternating current signals is completely eliminated.

7 is a current signal waveform diagram for explaining AC current consumption in the fuel cell impedance measuring method of the present invention. 8 is a current signal waveform diagram for explaining AC current consumption in the conventional fuel cell impedance measuring method.

In the present invention, when the signal generator 110 generates a plurality of alternating current signals, the peak portions are generated so as not to overlap each other as shown in FIG. 7 (in particular, in the scheme of FIG. 4) The maximum-minimum range of the current can be reduced. For example, in the present invention, the current sum values of the three AC current signals as shown in FIG. 7A are lower than the maximum-minimum range as shown in FIG. 7B, When the three AC current signals are simultaneously generated and applied in the entire range of the signal having the lowest frequency, the current sum value shows a high maximum-minimum range as shown in FIG. 8 (b). For example, under the condition that the alternating current is applied to the fuel cell 10 in the range of -3A to 3A maximum-minimum in the conventional method, according to the method of the present invention, the range of -1.064A to 1.327A in the maximum- It can be confirmed that an AC current is applied to the fuel cell 10. As described above, the system of the present invention can reduce the maximum-minimum range of the AC current application by 60.1% or more, thereby reducing the change in the operating characteristic due to the high current of the fuel cell 10, So that the system stability can be improved.

As described above, the present invention has been described with reference to particular embodiments, such as specific elements, and specific embodiments and drawings. However, it should be understood that the present invention is not limited to the above- Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the essential characteristics of the invention. Therefore, the spirit of the present invention should not be construed as being limited to the embodiments described, and all technical ideas which are equivalent to or equivalent to the claims of the present invention are included in the scope of the present invention .

In the fuel cell 10,
AC current signal generator 110,
Collectors of ac ... (120)

Claims (7)

1. A fuel cell impedance measuring method using a plurality of alternating current signals,
The plurality of alternating current signals having different frequencies are simultaneously generated using a signal generator so that the plurality of alternating current signals are generated within one period of the signal having the smallest frequency so as to include one period or less of the other signals, step; And
And a step of preferentially synchronizing a frequency of the signal having the largest frequency in at least two signal mixing periods of the plurality of alternating current signals to measure the voltage generated in the fuel cell during the applicable time period and providing the measured voltage as the impedance calculating information,
Wherein the number of measurement samples per second in the measurement for each of the plurality of alternating current signals is determined to be a multiple of the same multiple of the frequency of each of the plurality of alternating current signals. 1. A fuel cell impedance measuring method using a plurality of alternating current signals,
Generating a plurality of alternating current signals having different frequencies in succession by one or less cycles using a signal generator and applying the alternating current signals to the fuel cell; And
Measuring the voltage generated in the fuel cell in synchronism with the application of the generated alternating current signals during the application time and providing the measured voltage as the impedance calculation information,
Wherein the number of measurement samples per second in the measurement for each of the plurality of alternating current signals is determined to be a multiple of the same multiple of the frequency of each of the plurality of alternating current signals. 3. The method according to claim 1 or 2,
Wherein the drainage value is 20 times or more. 3. The method according to claim 1 or 2,
Wherein the plurality of alternating current signals include three signals each selected from a range of 1 to 10 Hz, a range of 10 to 100 Hz, and a range of 100 to 1000 Hz. 3. The method according to claim 1 or 2,
Wherein the plurality of alternating current signals are generated such that peak portions do not overlap with each other. 1. A system for measuring impedance of a fuel cell using a plurality of alternating current signals,
A signal generator for generating the plurality of alternating current signals and applying the plurality of alternating current signals to the fuel cell so that a plurality of alternating current signals having different frequencies are simultaneously generated but not more than one period of other signals within one period of the signal having the smallest frequency; And
And a signal collector for measuring a voltage generated in the fuel cell in synchronization with a signal having a largest frequency in a period in which two or more signals of the plurality of alternating current signals are mixed during a corresponding application time and providing the measured voltage as impedance calculation information ,
Wherein the number of measurement samples per second in the measurement for each of the plurality of alternating current signals is determined to be a multiple of the same value for the frequency of each of the plurality of alternating current signals. 1. A system for measuring impedance of a fuel cell using a plurality of alternating current signals,
A signal generator for sequentially generating a plurality of alternating current signals having different frequencies in less than one cycle and applying the generated alternating current signals to the fuel cell; And
And a signal collector for measuring a voltage generated in the fuel cell in synchronism with the application of the generated alternating current signals for a corresponding application time and providing the measured voltage as impedance calculation information,
Wherein the number of measurement samples per second in the measurement for each of the plurality of alternating current signals is determined to be a multiple of the same multiple of the frequency of each of the plurality of alternating current signals.

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