KR101051017B1 - Super capacitor performance evaluation method and parametric measurement device for super capacitor performance evaluation. - Google Patents

Abstract

Disclosed are a method of evaluating a supercapacitor performance and a parameter measuring apparatus for evaluating supercapacitor performance. According to this technique, a step of receiving impedance information on a supercapacitor; And generating a parameter for the equivalent circuit using the impedance information and the equivalent circuit of the supercapacitor, wherein the impedance information is an impedance value at a plurality of preset frequencies, wherein the parameter is the equivalent circuit. A method for evaluating supercapacitor performance is provided, which is equivalent series resistance value or electrode impedance value.

Supercapacitors, impedance

Description

METHOD FOR PERFORMANCE EVALUATION OF SUPERCAPACITOR AND APPARATUS FOR PARAMETER MEASUREMENT EVALUATION FOR PERFORMANCE EVALUATION OF THE SUPERCAPACITOR}

The present invention relates to a super capacitor performance evaluation method and a parameter measuring apparatus for super capacitor performance evaluation.

Supercapacitors have high power density and long cycle life. Due to the characteristics of these supercapacitors, supercapacitors are widely used in applications requiring dynamic power compensation or instantaneous high output of renewable energy sources. And in high-capacity systems such as wind power generation, electric vehicles, railways, and UPS systems, supercapacitors are used as modules containing multiple cells.

If a supercapacitor whose performance is not uniform is used in the module, the performance of the supercapacitor module may not be optimized, and it may cause a failure of the supercapacitor module when the supercapacitor module is used later. Therefore, it is very important to select and exclude the poor supercapacitors in the production stage of the supercapacitors and to release only the supercapacitors having uniform performance.

Representative factors that determine the performance of a supercapacitor include natural discharge rate, capacitance, and equivalent series resistance (ESR). Charge the supercapacitor up to 100% of SOC (State of Charge), and measure the terminal capacitor voltage of the supercapacitor by leaving it for 24 hours, and measure the natural discharge rate of the supercapacitor. IEC (International Electrotechnical Commission) 62391-1 regulations Based on this, the supercapacitor may be discharged to a constant current so that the SOC becomes 80% to 40%, and the capacitance value of the supercapacitor may be calculated by measuring the voltage change of the supercapacitor due to the constant current discharge. In addition, in the case of equivalent series resistance, which is one of the important evaluation factors, the equivalent series resistance value at a specific frequency can be measured by using a separate device such as a measuring instrument.

However, when evaluating the performance of the supercapacitor according to the above-described method, there is a problem that the evaluation time is considerably long, and at the same time, the performance of the supercapacitor may be reduced because various performance evaluation factors cannot be obtained.

The present invention has been proposed to solve the above problems, and an object thereof is to provide a supercapacitor performance evaluation method for evaluating the performance of a supercapacitor in a shorter time while maintaining the accuracy of the supercapacitor performance measurement.

In addition, an object of the present invention is to provide a parameter measuring apparatus for evaluating the performance of the supercapacitor, which can reduce the time according to the evaluation of the supercapacitor performance.

The present invention for achieving the above object is a step of receiving the impedance information on the supercapacitor; And generating a parameter for the equivalent circuit using the impedance information and the equivalent circuit of the supercapacitor, wherein the impedance information is an impedance value at a plurality of preset frequencies, wherein the parameter is the equivalent circuit. The present invention provides a method for evaluating supercapacitor performance which is equivalent series resistance value or electrode impedance value.

In addition, the present invention for achieving the above object is a measurement unit for measuring the current value and the voltage value for each of the plurality of supercapacitors using a plurality of supercapacitors in which perturbation current is induced; And a transmission unit which transmits the measured current value and the voltage value to a supercapacitor performance evaluation device, wherein the supercapacitor performance evaluation device uses the measured current value and the voltage value to represent an impedance for each of the plurality of supercapacitors. The present invention provides a parameter measuring apparatus for evaluating supercapacitor performance for generating redundancy information and generating an equivalent series resistance value or an electrode impedance value for the equivalent circuit using the impedance information and the equivalent circuit of the supercapacitor.

According to the present invention, the performance of the supercapacitor can be evaluated in a shorter time while maintaining the accuracy of the supercapacitor performance measurement by using the impedance information for the supercapacitor and the equivalent circuit for the supercapacitor.

In addition, according to the present invention, by measuring the current value and the voltage value for the plurality of supercapacitors at one time, it is possible to measure the parameters necessary for evaluating the supercapacitor performance in a shorter time.

DETAILED DESCRIPTION Hereinafter, the most preferred embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. The above objects, features, and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, and in describing the present invention, a detailed description of well-known technology related to the present invention may unnecessarily obscure the subject matter of the present invention. If it is determined that the detailed description thereof will be omitted.

1 is a view for explaining a supercapacitor performance evaluation system 100 according to a first embodiment of the present invention.

As shown in FIG. 1, the supercapacitor performance evaluation system 100 according to the present invention includes a supercapacitor 101, an impedance measuring device 103, and a supercapacitor performance evaluation device 105.

The impedance measuring device 103 is a device for measuring the impedance of the supercapacitor 101, and may measure the impedance of the supercapacitor 101 using, for example, electrochemical impedance spectroscopy. Electrochemical Impedance Spectroscopy is a method of measuring impedance by applying a small alternating current signal of different frequency to a target material.

The supercapacitor performance evaluation apparatus 105 generates parameters for the equivalent circuit using the impedance information measured by the impedance measuring apparatus 103 and the equivalent circuit of the supercapacitor 101.

The equivalent circuit of the supercapacitor 101 reflecting the physical characteristics of the supercapacitor 101 may generally be composed of an equivalent series resistance and an electrode impedance of the supercapacitor 101. Since the equivalent circuit and the impedance reflect the physical characteristics of the supercapacitor 101, the equivalent series resistance value and the electrode impedance value of the equivalent circuit can be calculated using the impedance information of the supercapacitor 101. Here, the parameters are equivalent series resistance values and electrode impedance values of the equivalent circuit. The electrode impedance represents the constant phase element (CPE) of the electrode, and the performance of the supercapacitor 101 may be measured and evaluated through the parameters of the equivalent circuit.

That is, the supercapacitor performance evaluation apparatus 105 according to the present invention uses the first impedance information of the supercapacitor 101 and the equivalent circuit of the supercapacitor 101 to determine an equivalent circuit which is a factor of measuring the performance of the supercapacitor 101. You can create parameter values. As a result, according to the present invention, since the performance of the supercapacitor can be evaluated without the charge / discharge and natural discharge experiments on the supercapacitor, the time required for measuring the supercapacitor performance can be shortened, and the super By effectively selecting capacitors, the failure rate of the products shipped can be lowered.

Meanwhile, a detailed method for generating the parameter by the supercapacitor performance evaluation apparatus 105 will be described in more detail with reference to FIGS. 3 to 6.

2 is a view for explaining a supercapacitor performance evaluation method according to an embodiment of the present invention. In FIG. 2, the supercapacitor performance evaluation method of the supercapacitor performance evaluation apparatus 105 of FIG. 1 is described as an embodiment.

As shown in Fig. 2, the method for evaluating supercapacitor performance according to the present invention starts from step S201.

In step S201, the supercapacitor performance evaluation apparatus 105 receives, i.e., receives, impedance information about the supercapacitor. The impedance information is an impedance value at a plurality of preset frequencies, and may receive impedance information from the impedance measuring apparatus 103 of FIG. 1.

In operation S203, the supercapacitor performance evaluation apparatus 105 generates a parameter for the equivalent circuit by using the impedance information and the equivalent circuit of the supercapacitor. The parameter for the equivalent circuit is the equivalent series resistance value of the equivalent circuit or the electrode resistance and the CPE value of the electrode impedance. As described above, the parameter for the equivalent circuit is an element capable of evaluating the performance of the supercapacitor.

According to the present invention, to evaluate the performance of the supercapacitor, by measuring the capacitance by charging and discharging the supercapacitor for a long time, or by measuring the equivalent series resistance value using a measuring instrument, by using the impedance information on the supercapacitor By extracting and analyzing the parameters of the equivalent circuit, charge and discharge losses and natural discharge rates due to equivalent series resistance can be measured by computer simulation. Therefore, the time required for evaluating supercapacitor performance can be reduced.

In this case, the equivalent series resistance value or the electrode impedance value of the generated equivalent circuit may be provided with high accuracy in the measurement result, as described below with reference to FIGS. 3 to 6 by using the impedance information and the equivalent circuit.

Hereinafter, specific embodiments according to the present invention will be described with reference to FIGS. 3 to 6. Hereinafter, a method of evaluating the performance of the supercapacitor of the 2.7V 2600F standard by the supercapacitor performance evaluation apparatus 105 of FIG. 1 will be described as an embodiment.

First, the impedance information may be generated in the impedance measuring apparatus 103 by electrochemical impedance spectroscopy as impedance values at a plurality of preset frequencies. More specifically, it is possible to charge and discharge the supercapacitor and connect voltage perturbation to the supercapacitor by connecting Potentiostat and Bipolar Power Supply to both ends of the supercapacitor to be measured. At this time, perturbation current is induced in the supercapacitor and impedance values at a plurality of preset frequencies can be obtained. At this time, the magnitude of the perturbation voltage applied to guarantee the linearity of the impedance measuring apparatus 103 may be limited to 2% or less of the charge amount of the supercapacitor. Potentiostat and Bipolar Power Supply may be included in the impedance measuring device 103 or may be configured as a separate device.

The supercapacitor performance evaluation apparatus 105 may curve-fit the first impedance information input from the impedance measuring apparatus 103 to the supercapacitor equivalent circuit illustrated in FIG. 3 to generate parameters for the equivalent circuit. In FIG. 3, R _s denotes an equivalent series resistance, Z _pore denotes an electrode impedance, and total impedance Z _SC for the supercapacitor equivalent circuit is expressed by Equation 1 below.

In Equation 1, R _e is an electrode resistance R _e included in the electrode impedance Z _pore , and 1 / (jw) ^d Q _d is a constant phase element (CPE). Here, 'd' is a rational number between 0 and 1, and according to 'd', the CPE may include resistance and capacitance values.

That is, the supercapacitor performance evaluation apparatus 105 may generate a parameter for the equivalent circuit by curve fitting the impedance information to the equivalent circuit using Equation (1). In general, the equivalent series resistance (R _s ) is shown in the Nyquist impedance spectrum near 50 Hz, and the capacitance can be calculated for each frequency by using Equation 2 described below. Converge.

4 and 5 are diagrams for comparing the conventional supercapacitor performance evaluation method and the supercapacitor performance evaluation method according to the present invention. More specifically, in FIG. 4, the solid line represents the result of the natural discharge experiment by the left after charging the supercapacitor, and the red dotted line is the result of calculating the natural discharge rate using the parameters for the equivalent circuit obtained in the evaluation method according to the present invention. Indicates. In FIG. 5, the solid line represents the result of the supercapacitor charge / discharge experiment, and the red dotted line represents the charge / discharge loss result obtained using the parameters for the equivalent circuit obtained in the evaluation method according to the present invention.

As shown in FIG. 4 and FIG. 5, the solid line and the red dotted line almost match, and thus the accuracy of the supercapacitor performance evaluation method according to the present invention is not different from the conventional method. On the other hand, in the general capacitor supercapacitor discharge experiment, the capacitance of the supercapacitor is calculated using the SOC 80% to 40% discharge curve, so that the capacitance value at about SOC 60% is calculated on average. Therefore, the impedance information used in FIGS. 4 and 5 is, for example, impedance information according to electrochemical impedance spectroscopy performed when the SOC of the supercapacitor is 60%.

As described above, the supercapacitor performance evaluation apparatus 105 may generate the parameters for the equivalent circuit through curve fitting the impedance information to the equivalent circuit. In this case, the preset frequency used to generate the impedance information may include a low frequency of a predetermined section of 0.01 Hz or less. According to a further embodiment described below, parameters for the equivalent circuit are generated in a geometrical manner using only impedance information for two or more specific frequencies within a preset range from characteristic frequencies of the supercapacitor. Due to the characteristics of low frequency, the measurement of impedance in the low frequency region requires a considerable time, but the embodiments described below can further evaluate the performance of the supercapacitor by overlapping two or more specific frequency components at once and calculating the impedance. It can be shortened. That is, according to the present invention, the impedance for each of the frequencies can be measured at once by filtering the impedances obtained through two or more overlapping specific frequency components according to the frequency using a filter. As the filter, for example, a digital lock-in amplifier may be used.

FIG. 6 is a diagram for explaining a further embodiment, in which a Nyquist impedance spectrum of a supercapacitor and a red straight line obtained according to the further embodiment are shown together.

According to the impedance spectrum of FIG. 6, the impedance value in the high frequency region around the characteristic frequency (the frequency where the impedance characteristic curve of the supercapacitor porous electrode and the characteristic curve of the CPE intersect) is about 45 ° asymptote. In the low frequency region, the impedance value converges to an asymptote of about 90 °. Therefore, the supercapacitor performance evaluation apparatus 105 according to the embodiment of FIG. 6 is within a preset frequency range from the characteristic frequency of the supercapacitor, and has two or more first sample frequencies higher than the characteristic frequency and two or more lower than the characteristic frequency. By using the impedance information on the second sample frequency, a parameter for the equivalent circuit may be generated.

In FIG. 6, two first sample frequencies H1 and H2 and two second sample frequencies L1 and L2 are used, and the lowest of four frequencies is a common multiple of another frequency in order to increase the accuracy of measurement and calculation. The case is described as an embodiment.

The intersection of the first straight line and the real axis obtained from the impedance values for the first sample frequencies H1 and H2 and the first sample frequencies H1 and H2 has an equivalent series resistance R _s that does not include an imaginary value among the impedance values. Indicates. Here, the first straight line represents a straight line generated by using an impedance value with respect to the first sample frequency. That is, the first straight line may be an approximated impedance value of a preset frequency range generated using only an impedance value for the first sample frequency.

The intersection of the second straight line and the real axis obtained from the impedance values for the second sample frequencies L1 and L2 and the second sample frequencies L1 and L2 represents R _s + R _e / 3. In the above Equation 1, when the coth function is expanded to the Taylor series to take the second term, the real component may be R _s + R _e / 3. Here, the second straight line is a straight line generated by using an impedance value with respect to the second sample frequency, and may be an approximated impedance value of a preset frequency range. That is, the second straight line represents an approximated impedance value generated by using an impedance value for the second sample frequency, and may be an approximated impedance value of a preset frequency range. Since the equivalent series resistance R _s can be obtained using the first sample frequencies H1 and H2, the electrode resistance value R _e included in the electrode impedance value can be obtained.

In addition, 'd' of Equation 1 can be obtained from the angle between the second straight line and the 90 ° asymptote obtained from the impedance values for the second sample frequencies L1 and L2 and the second sample frequencies L1 and L2. . In addition, CPE (Z _L2 ) can be obtained by using Equation 2 representing the capacitance information of the lowest frequency L2 and the impedance of the electrode impedance.

As a result, since equivalent series resistance (R _s ), electrode resistance value (R _e ), 'd' and CPE (Z _L2 ) can be obtained, the impedance information of the supercapacitor can be known by [Equation 1]. Equation 3] can calculate the capacitance of the supercapacitor.

That is, according to the present invention, the parameters for the equivalent circuit can be generated by a geometric method using only impedance information for four specific frequencies.

According to an embodiment described in FIG. 6, the supercapacitor performance evaluation method of step S203 of FIG. 2 is described in more detail as follows.

The supercapacitor performance evaluation apparatus 105 generates an approximated first impedance value of the preset frequency range by using an impedance value for a first sample frequency, and uses an approximated first impedance value to produce an equivalent series resistance. Create a (R _s ) value. In this case, the impedance information of step S201 is an impedance value at a plurality of preset frequencies, and the plurality of preset frequencies exist within a preset frequency range from a characteristic frequency of the supercapacitor, and at least two first samples higher than the characteristic frequency. Include frequency.

In addition, the supercapacitor performance evaluation apparatus 105 generates an approximated second impedance value of a preset frequency range by using an impedance value for the second sample frequency, and uses an equivalent series resistance value and an approximated second impedance value. By, the electrode resistance value contained in the electrode impedance value is generated. In this case, the plurality of preset frequencies exist within a preset range from the characteristic frequency of the supercapacitor and include two or more second sample frequencies lower than the characteristic frequency.

In addition, the supercapacitor performance evaluation apparatus 105 generates the capacitance of the supercapacitor using the equivalent series resistance value, the electrode resistance value, and the approximated second impedance value.

7 is a diagram for describing a supercapacitor performance evaluation system 700 according to a second embodiment of the present invention.

As shown in FIG. 7, the supercapacitor performance evaluation system 700 according to the present invention includes a Potentiostat and Bipolar Power Supply 701, a parameter measuring device 703, and a supercapacitor performance evaluation device 705.

The parameter measuring device 703 uses a plurality of supercapacitors SC1 to SCn from which perturbation current is induced, and a measuring unit measuring current and voltage values for each of the plurality of supercapacitors, and measured current and voltage values. It includes a transmission unit for transmitting to the supercapacitor performance evaluation apparatus 705. That is, the parameter measuring device 703 may receive parameters for a plurality of supercapacitors simultaneously from a plurality of supercapacitors in which perturbation current is induced by the potentiostat and the bipolar power supply 701. Therefore, since the performance of a plurality of supercapacitors can be simultaneously measured by the supercapacitor performance evaluation apparatus 705 described later, the performance measurement time can be further reduced.

At this time, it is preferable that the measurement unit measures the current value and the voltage value from both ends of each of the plurality of supercapacitors connected in series due to the characteristics of the capacitor. The transmitter may sample the measured current and voltage values and transmit the measured current and voltage values to the supercapacitor performance evaluation apparatus 705 in the form of a digital signal.

The supercapacitor performance evaluator 705 generates impedance information for each of the plurality of supercapacitors using the measured current value and the voltage value, and uses the impedance information and the equivalent circuit of the supercapacitor to provide parameters for the equivalent circuit. That is, an equivalent series resistance value or electrode impedance value for an equivalent circuit is generated. That is, unlike the supercapacitor performance evaluation apparatus 105 of FIG. 1, the supercapacitor performance evaluation apparatus 705 of FIG. 7 uses a plurality of measured current and voltage values received from the parameter measuring device 703. The parameters of the equivalent circuit for the supercapacitor can be further generated. The supercapacitor performance measuring apparatus 705 may generate impedance information and generate an impedance spectrum after extracting a signal of a test frequency band using a digital lock-in amplifier.

Meanwhile, the supercapacitor performance evaluation apparatus 105 of FIG. 1 may also receive impedance information about each of a plurality of supercapacitors connected in series, and generate an equivalent circuit parameter for each of the plurality of supercapacitors using the impedance information. can do.

Although the present invention has been described in terms of process, each step constituting the method for evaluating the performance of the supercapacitor according to the present invention can be easily understood from the viewpoint of device. Therefore, each step included in the supercapacitor performance evaluation method according to the present invention may be understood as a component included in the supercapacitor performance evaluation apparatus.

That is, the apparatus for evaluating a supercapacitor according to the present invention includes an information input unit for receiving impedance information on the supercapacitor and an information generator for generating a parameter for the equivalent circuit using the impedance information and the equivalent circuit of the supercapacitor. Here, the impedance information is an impedance value at a plurality of preset frequencies, and the parameter for the equivalent circuit is an equivalent series resistance value or electrode impedance value of the equivalent circuit.

Meanwhile, the method of evaluating the supercapacitor performance according to the present invention as described above can be prepared by a computer program. And the code and code segments constituting the program can be easily inferred by a computer programmer in the art. In addition, the written program is stored in a computer-readable recording medium (information storage medium), and read and executed by a computer to implement the method of the present invention. And the recording medium includes all types of recording media (intangible medium such as a carrier wave as well as tangible media such as CD and DVD) readable by a computer.

Although the present invention has been described by means of limited embodiments and drawings, the present invention is not limited thereto and is intended to be equivalent to the technical idea and claims of the present invention by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible.

1 is a view for explaining a supercapacitor measuring system according to a first embodiment of the present invention;

2 is a view for explaining a supercapacitor measuring method according to an embodiment of the present invention;

3 is a diagram showing an equivalent circuit of a supercapacitor;

4 and 5 are views for comparing the conventional supercapacitor performance measurement method and the supercapacitor performance measurement method according to the present invention,

6 is a diagram showing a Nyquist impedance spectrum of a supercapacitor and a red straight line obtained according to a further embodiment;

7 is a view for explaining a super capacitor measuring system according to a second embodiment of the present invention.

Claims (10)

Receiving impedance information including impedance values at a plurality of preset frequencies for the supercapacitor; And Generating a parameter including an equivalent series resistance value or an electrode impedance value of the equivalent circuit by using the impedance information and the equivalent circuit of the supercapacitor, The preset plurality of frequencies It exists within a predetermined range from the characteristic frequency of the supercapacitor, and includes two or more first sample frequencies higher than the characteristic frequency, and two or more second sample frequencies lower than the characteristic frequency, Generating the parameter An approximated first impedance value of a preset frequency range is generated using an impedance value of the first sample frequency, and an approximated second impedance value of a preset frequency range is generated using an impedance value of a second sample frequency. Generating; And Generating the equivalent series resistance value using the first impedance value, and generating an electrode resistance value included in the electrode impedance value using the second impedance value Supercapacitor performance evaluation method comprising a. The method of claim 1, Generating the parameter Curve fitting the impedance information to the equivalent circuit to generate the parameter How to evaluate supercapacitor performance. 3. The method of claim 2, The impedance information is Information generated by electrochemical spectroscopy, How to evaluate supercapacitor performance. delete delete The method of claim 1, Generating the parameter Generating the capacitance of the supercapacitor using the equivalent series resistance value, the electrode resistance value and the approximated second impedance value How to evaluate supercapacitor performance. The method of claim 1, Each of the impedance values for the first and second sample frequencies is Impedance values generated by filtering the impedance values for the overlapping first and second sample frequencies How to evaluate supercapacitor performance. The method of claim 1, The step of receiving the impedance information Receives impedance information about each of the plurality of supercapacitors connected in series. Generating the parameter Generating an equivalent circuit parameter for each of the plurality of supercapacitors How to evaluate supercapacitor performance. delete delete

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