Step response identification method for characteristic parameters of supercapacitor

Abstract

The invention discloses a step response identification method for characteristic parameters of a super capacitor, which comprises the following steps of: acquiring the current of the super capacitor by using a current acquisition system, initializing the super capacitor to be detected to be in a zero state, applying a direct-current voltage source with constant amplitude to the super capacitor to be detected, sampling the current of the super capacitor and storing a sample; calculating a basic coefficient and an average basic coefficient, calculating an estimation coefficient, an estimation factor and an average estimation coefficient, and calculating a resistance value and a capacitance value of the supercapacitor; according to the invention, the super capacitor is used as a monitoring object, the working state of the internal components of the super capacitor is monitored in real time, verification is carried out in an experimental mode, and the result is analyzed; according to the identification method provided by the invention, the feasibility and the accuracy of the method for identifying the characteristic parameters of the internal components of the supercapacitor by monitoring the output current of the supercapacitor in real time can be confirmed, and the method has the outstanding characteristics of high timeliness of acquired data, high accuracy of the acquired data and no damage to the supercapacitor.

Description

Technical Field

[0001] The present invention relates to the technical field of supercapacitors, and in particular to a step response identification method of characteristic parameters of a supercapacitor. Background Art

[0002] In order to have a greener and more environmentally friendly living and working environment, people have accelerated the process of using renewable energy sources such as wind energy and solar energy. Among them, as an important energy storage device, supercapacitor energy storage system is favored in electric vehicles, buses, subways, rail trains and new energy power generation due to its high power density, large instantaneous charge and discharge current, and long cycle life, and plays an increasingly important role.

[0003] The performance of supercapacitors in storing electrical energy, charging, and discharging depends on the resistance R and capacitance C of their basic components. Changes in these characteristic parameters R and C will affect the supercapacitor's ability to store electrical energy, its reliability and safety, and its power loss and efficiency during the charging and discharging process. Therefore, it is critical to accurately obtain these characteristic parameters. However, supercapacitors as products are usually well packaged, and it is very difficult to directly test these characteristic parameters. Therefore, people have conducted research on monitoring the characteristic parameters of supercapacitors.

[0004] The performance of a supercapacitor actually depends on its basic internal components, namely resistance R and capacitance C. The size of these components determines its performance in a specific application. The charging speed of a supercapacitor is related to the time constant, and the time constant is related to its characteristic parameters R and C. For example, the smaller R is, the faster it charges and discharges. The larger C is, the more electrical energy is stored and the stronger the storage capacity. Therefore, changes in these characteristic parameters will affect its electrical energy storage capacity, charging and discharging performance, and also involve the reliability and safety of the capacitor in a specific circuit. The equivalent circuit model of a traditional supercapacitor is as follows: Figure 1 As shown in the figure, the supercapacitor is composed of two components: resistor R and capacitor C. Assume that the input voltage of the supercapacitor is u i (t), the capacitor voltage is u c (t), and the current is i1(t), then:

[0005]

[0006] With input step voltage signal u i (t) is used to analyze the internal characteristic parameters of the supercapacitor, namely:

[0007]

[0008] Before working, make the supercapacitor u i(t) and i1(t) are both zero, that is, the supercapacitor to be tested is in the zero state. By combining equations (1.1), (1.2), and (1.3) and combining them in the zero state, we can obtain u c (t) and i1(t), which are closely related to the characteristic parameters R and C. In engineering, it is necessary to measure the u of a well-packaged supercapacitor without disassembly or damage. c (t), very difficult.

[0009] In the prior art, most of the methods for identifying the characteristic parameters of supercapacitors have the problems of complicated procedures and poor anti-interference ability, and some identification methods can only estimate the parameter information of the capacitance value. Its equivalent resistance will also have an impact in actual work and will change with temperature, etc., resulting in inaccurate measurement of the supercapacitor. In addition, some identification methods do not consider the influence of resistance, resulting in inaccurate capacitance value measurement. Therefore, the present invention proposes a step response identification method for the characteristic parameters of supercapacitors to solve the problems existing in the prior art. Summary of the invention

[0010] In view of the above problems, the purpose of the present invention is to propose a step response identification method for supercapacitor characteristic parameters, so as to solve the problems that most of the existing methods for identifying supercapacitor characteristic parameters have complex processes, poor anti-interference ability and low accuracy.

[0011] In order to achieve the purpose of the present invention, the present invention is implemented by the following technical scheme: a step response identification method of a supercapacitor characteristic parameter comprises the following steps:

[0012] Step 1: Prepare a current acquisition system and a current with an amplitude of U a A constant voltage DC voltage source of 100 volts is used to initialize the supercapacitor to be tested to a zero state, and the current of the capacitor is collected by a current collection system;

[0013] Step 2: Connect the constant voltage DC voltage source prepared in step 1 to the input end of the supercapacitor to be tested, and use the current acquisition system prepared in step 1 to sample the current of the supercapacitor to be tested, and save the collected samples, and record SCU(j) as the jth sample, indicating the current collected in the jth sampling period, j = 1, 2, 3, ..., N, N is the number of samples, and the sampling period is T;

[0014] Step 3: According to the sample SCU(j) saved in step 2, calculate the basic coefficient FirstPara(j) respectively, and then calculate the average basic coefficient MulParaAv according to the basic coefficient FirstPara(j), where j = 1, 2, 3, ..., m, 1 <m≤N;

[0015] Step 4: Calculate the estimated coefficient SecondPara(j) according to the average basic coefficient MulParaAv calculated in step 3, then calculate the average estimated coefficient SecondParaAv according to the estimated coefficient SecondPara(j), and then calculate the estimated factor ThirdPara according to the average basic coefficient MulParaAv, where j = 1, 2, 3, ..., m, 1 <m≤N+1;

[0016] Step 5: Calculate the resistance value R of the supercapacitor according to the average estimated coefficient SecondParaAv calculated in step 4;

[0017] Step 6: Calculate the capacitance C of the supercapacitor according to the average estimated coefficient SecondParaAv and the estimated factor ThirdPara calculated in step 4.

[0018] A further improvement is that in step 1, the supercapacitor to be tested is initialized to a zero state by grounding its input and output ports, and when the current remains at zero for a preset time, the supercapacitor to be tested is initialized to a zero state.

[0019] A further improvement is that in step 3, the calculation formula of the basic coefficient FirstPara(j) is:

[0020]

[0021] A further improvement is that in step 3, the calculation formula of the average basic coefficient MulParaAv is:

[0022]

[0023] A further improvement is that in step 4, the calculation formula of the estimated coefficient SecondPara(j) is:

[0024]

[0025] A further improvement is that in step 4, the calculation formula of the average estimation coefficient SecondPar aAv is:

[0026]

[0027] A further improvement is that in step 4, the calculation formula of the estimated factor ThirdPara is:

[0028] ThirdPara=ln(MulParaAv).

[0029] A further improvement is that in step 5, the calculation formula of the resistance value R of the supercapacitor is:

[0030]

[0031] A further improvement is that in step 6, the calculation formula of the capacitance value C of the supercapacitor is:

[0032]

[0033] The beneficial effects of the present invention are as follows: the present invention takes the supercapacitor as the monitoring object, performs real-time monitoring of the working status of its internal components, and based on the MATALB / Simulink platform, conducts experimental verification on the supercapacitor circuit model and the method for identifying the characteristic parameters of the internal components of the supercapacitor and analyzes the results, confirming that the identification method proposed in the present invention can identify the characteristic parameters of the internal components of the supercapacitor by real-time monitoring of the supercapacitor output current without disassembling or damaging the supercapacitor device. The method has the outstanding characteristics of strong timeliness of data acquisition, high accuracy of data acquisition, and no damage to the supercapacitor, and provides basic work for more timely and accurate dynamic monitoring of the working status of the supercapacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 It is a schematic diagram of an equivalent circuit model of a traditional supercapacitor in the background technology of the present invention;

[0036] Figure 2 It is a schematic flow chart of a method for identifying a step response of characteristic parameters of a supercapacitor according to the present invention;

[0037] Figure 3 Schematic diagram of a supercapacitor circuit model in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] See also Figure 2 , Figure 3 In this embodiment, a circuit model of a supercapacitor is established in Simulink under the Matlab environment, and an experiment is carried out on the circuit model for verification. The specific steps are as follows:

[0040] Step 1: First, establish a supercapacitor circuit model, such as Figure 3 As shown, the capacitor C = 10.3125F, the resistor R = 0.1008Ω, the gain of the white noise is 0, that is, there is no noise interference input, and the step signal with an amplitude of 768 controls the controlled voltage source to generate U a =768V step voltage source u i (t) is for the supercapacitor, the current sensor collects the supercapacitor current i1(t), and the voltage across the capacitor is initialized to 0V, that is, the supercapacitor is initialized to zero state;

[0041] Step 2: Set the sampling period T = 2.5 × 10 -3 seconds, the sampling time is 1s (through a lot of experimental research, it is found that supercapacitors can eliminate oscillations in a very short time. In order to maximize the experimental accuracy and reduce the simulation time, the sampling time is determined to be 1s), start the simulation, u i (t) is connected to the input terminal of the supercapacitor. At the same time, the current sensor collects i1(t) and saves it. SCU(j) = i1(jT) represents the jth sampling value, j = 1, 2, 3, ..., N, when N = 4 × 10 2 When SCU(j) changes very little, the experiment ends, the sampling ends, and the following Table 1 shows the sample information collected;

[0042] Table 1 Current samples collected

[0043] Sampling time t <![CDATA[Output current value i1(t)]]> 0 0 0.0025 7604.81044256058 0.0050 7586.54283077621 0.0075 7568.31909985420 …… …… 0.9925 2934.09790151373 0.9950 2927.04986766633 0.9975 2920.01876399059 1 2913.00454981831

[0044] Step 3: Calculate the basic coefficient based on the sample SCU(j) saved in step 2 Its FirstPara(j) value is shown in Table 2 below;

[0045] Table 2: FirstPara(j) value table analyzed

[0046] Serial number FirstPara(j) 1 0.99759788729 2 0.99759788729 3 0.99759788729 4 0.99759788729 …… …… 396 0.99759788729 397 0.99759788729 398 0.99759788729 399 0.99759788729

[0047] The average basic coefficient MulParaAv is calculated from the above table as follows:

[0048]

[0049] Step 4: According to the average basic coefficient MulParaAv calculated in step 3, calculate the estimated coefficient SecondPara(j), as follows:

[0050]

[0051] Wherein, j = 1, 2, 3, ..., 399, and its SecondPara (j) value is shown in Table 3 below;

[0052] Table 3 SecondPara(j) value table

[0053]

[0054] The average estimated coefficient SecondParaAv can be calculated from the above table as follows:

[0055]

[0056] The estimated factor ThirdPara is calculated based on the average basic coefficient MulParaAv as follows:

[0057] ThirdPara=ln(MulParaAv)=ln(0.99759788729)=-0.002405002;

[0058] Step 5: According to the average estimated coefficient SecondParaAv calculated in step 4, calculate the resistance value R of the supercapacitor as follows:

[0059]

[0060] Step 6: According to the average estimated coefficient SecondParaAv and the estimated factor ThirdPara calculated in step 4, the capacitance C of the supercapacitor is calculated as follows:

[0061]

[0062] From the calculation results of the above steps 5 and 6, it can be seen that in the non-interference state, the capacitance C=10.3180148F and the resistance R=0.1007461Ω identified by the method proposed by the present invention have relative errors of 0.053% and 0.053% respectively. It can be seen that in the non-interference state, the identification error is small and very close to the true values ​​of the characteristic parameters C and R.

[0063] The above situation is the identification of characteristic parameters of supercapacitors without interference signals. However, in actual work, the current i1(t) of the energy storage capacitor is mixed with interference signals i d (t), that is, SCu(j)=i1(jT)+i d (jT).id (t) is generally expressed as white noise. Therefore, in order to verify the anti-interference performance of the method of the present invention, the above experimental steps from step 1 to step 6 are repeated. The difference is that in step 1, the parameters of the random white noise module and the gain module need to be set to simulate the interference in the project. The variance of the white noise is 0.1, and the gain is taken as 5, 10, 15, 20, 25, and 30, a total of six groups. Multiple experiments were carried out, and the experimental results are shown in Table 4 below.

[0064] Table 4 Characteristic parameter identification when there is interference

[0065]

[0066] As can be seen from Table 4 above, the estimation error of R is less than the estimation error of C when the identification method proposed in the present invention is used to estimate the characteristic parameters R and C of the supercapacitor. For example, when the signal-to-noise ratio is 2.6%, the estimated relative errors of R and C are 3.720% and 4.292% respectively. As the interference increases, the estimated error of the parameters increases. For example, when the signal-to-noise ratio is 0.65%, the estimated relative errors of R and C are 0.211% and 0.292 respectively; when the signal-to-noise ratio is 3.9%, the estimated relative errors of R and C reach 8.441% and 10.962% respectively. These results show that the identification method proposed in the present invention can effectively and reliably identify the characteristic parameters of the supercapacitor, has strong anti-interference ability and high identification accuracy.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A step response identification method for characteristic parameters of a supercapacitor, characterized in that: The following steps are involved: Step 1: Prepare a current acquisition system and a current with an amplitude of U a A constant voltage DC voltage source of 100 volts is used to initialize the supercapacitor to be tested to a zero state, and the current of the capacitor is collected by a current collection system; Step 2: Connect the constant voltage DC voltage source prepared in step 1 to the input end of the supercapacitor to be tested, and use the current acquisition system prepared in step 1 to sample the current of the supercapacitor to be tested, and save the collected samples, and record SCU(j) as the jth sample, indicating the current collected in the jth sampling period, j = 1, 2, 3, ..., N, N is the number of samples, and the sampling period is T; Step 3: According to the sample SCU(j) saved in step 2, calculate the basic coefficient FirstPara(j) respectively, and then calculate the average basic coefficient MulParaAv according to the basic coefficient FirstPara(j), where j = 1, 2, 3, ..., m, 1 <m≤N; Step 4: Calculate the estimated coefficient SecondPara(j) according to the average basic coefficient MulParaAv calculated in step 3, then calculate the average estimated coefficient SecondParaAv according to the estimated coefficient SecondPara(j), and then calculate the estimated factor ThirdPara according to the average basic coefficient MulParaAv, where j = 1, 2, 3, ..., m, 1 <m≤N+1; Step 5: Calculate the resistance value R of the supercapacitor according to the average estimated coefficient SecondParaAv calculated in step 4; Step 6: Calculate the capacitance C of the supercapacitor according to the average estimated coefficient SecondParaAv and the estimated factor ThirdPara calculated in step 4.

2. The method for identifying the step response of characteristic parameters of a supercapacitor according to claim 1, characterized in that: In the step 1, the supercapacitor to be tested is initialized to a zero state by grounding the input and output ports of the supercapacitor to be tested. When the current remains at zero for a preset time, the supercapacitor to be tested is initialized to a zero state.

3. The method for identifying the step response of characteristic parameters of a supercapacitor according to claim 1, characterized in that: In the step 3, the calculation formula of the basic coefficient FirstPara(j) is:

4. The method for identifying the step response of characteristic parameters of a supercapacitor according to claim 1, characterized in that: In the step 3, the calculation formula of the average basic coefficient MulParaAv is:

5. The method for identifying the step response of characteristic parameters of a supercapacitor according to claim 1, characterized in that: In the step 4, the calculation formula of the estimated coefficient SecondPara(j) is:

6. The method for identifying the step response of characteristic parameters of a supercapacitor according to claim 1, characterized in that: In the step 4, the calculation formula of the average estimated coefficient SecondParaAv is:

7. The method for identifying the step response of characteristic parameters of a supercapacitor according to claim 1, characterized in that: In the step 4, the calculation formula of the estimated factor ThirdPara is: ThirdPara=ln(MulParaAv).

8. The method for identifying the step response of characteristic parameters of a supercapacitor according to claim 1, characterized in that: In the step 5, the calculation formula of the resistance value R of the supercapacitor is:

9. The method for identifying the step response of characteristic parameters of a supercapacitor according to claim 1, characterized in that: In step 6, the calculation formula of the capacitance value C of the supercapacitor is:

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