Converter impedance measurement method and apparatus, electronic device, and medium

Abstract

A converter impedance measurement method and apparatus, an electronic device, and a medium, applied to the field of converter data computation and processing. The present application comprises: superimposing a positive-sequence current disturbance at a current sampling value of a converter and a positive-sequence voltage disturbance to obtain a first disturbed current value, a first disturbed voltage value, a second disturbed current value and a second disturbed voltage value; determining a first impedance value for measurement and a transfer function on the basis of the obtained values; on the basis of the first impedance value for measurement, the transfer function, a filter equivalent impedance value and relevant parameters of the converter, determining a second impedance value for measurement, and determining an initial impedance value; and determining a final target impedance value of the converter on the basis of the initial impedance value and a decoupling coefficient determined on the basis of the transfer function and the filter equivalent impedance value at a secondary disturbance frequency. Thus, the present application involves a simple operation process, requires no addition and change of devices, and achieves low overall engineering cost. Moreover, the effects of both grid impedance value and line impedance value are considered to obtain a realistic and accurate converter impedance value.

Description

A method, device, electronic device and medium for measuring current transformer impedance

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on April 2, 2024, with application number 202410396063.7 and invention name “A method, device, electronic device and medium for measuring impedance of a current transformer”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of converter data calculation and processing, and in particular to a converter impedance measurement method, device, electronic equipment and medium. Background Art

[0003] Converters, as electrical devices that can modify the voltage, frequency, number of phases, and other electrical quantities or characteristics of a power system, are widely used in real-world scenarios. During use, the converter's impedance, a key parameter, influences the quality of these changes. Based on the converter's specific structure and related parameters, the converter's impedance can be calculated using a theoretical model of the converter's AC-side positive-sequence impedance. However, since the converter's specific structure and related parameters are often unknown, actual measurement of the converter's impedance is necessary.

[0004] Actual measurements fall into two categories: primary-side measurement and secondary-side measurement. The primary-side measurement method based on a converter specifically involves connecting a disturbance voltage source in series or a disturbance current source in parallel at the port of the converter under test, and calculating the broadband impedance characteristics of the port based on the output current or port voltage of the converter under test, as shown in Figure 1. This method is the most commonly used and highly accurate, but in actual engineering, it is costly and difficult to transport. Connecting the disturbance power source to the actual primary-side main circuit is complex. Furthermore, the primary-side disturbance power source's switching speed is slow, resulting in long time intervals between different frequency points. Furthermore, the capacity of the disturbance power source varies for converters of different capacities, requiring the design of separate main circuits, control parameters, and protection devices. This method has limited universal applicability. The secondary-side measurement method based on a converter specifically involves injecting disturbances into the converter's control loop to measure the converter's impedance. Some of the current existing disturbance injection methods include: superimposing a sine wave at a specific disturbance frequency at the voltage and current sampling points of the converter grid-connected point, and at the same time artificially changing the equivalent impedance of the grid in the main circuit before measurement, that is, connecting a small inductor in series, or injecting disturbances at two locations: the reference voltage generation point of the converter and the phase-locked loop sampling voltage output, and finally obtaining the impedance value of the converter by calculation. However, the premise of using this method is that the impedance measurement personnel can know the basic control structure of the converter and can modify the loop in the converter controller to achieve disturbance injection. Otherwise, the method fails. At the same time, in this method, the control loops (feedforward loop, phase-locked loop loop) are measured independently and separately, and the influence of grid impedance is not considered, which is a defect of this method.

[0005] In view of the above technology, seeking a method for measuring the impedance of a current transformer is an urgent problem to be solved by those skilled in the art.

[0006] Summary of the Invention

[0007] The purpose of this application is to provide a method, device, electronic device, and medium for measuring transformer impedance. This method can address the problems of existing primary-side measurement methods, such as high cost, difficult transportation, and complex operation, as well as the secondary-side measurement method, which requires the manufacturer to disclose the entire controller design and does not consider the grid impedance.

[0008] To solve the above technical problems, the present application provides a method for measuring the impedance of a current transformer, comprising:

[0009] Superimposing a positive sequence current disturbance on a current sampling value of the converter to obtain a first disturbance current value and a first disturbance voltage value;

[0010] Superimposing a positive sequence voltage disturbance on the voltage sampling value of the converter to obtain a second disturbance current value and a second disturbance voltage value;

[0011] Determining a first impedance value to be measured and a transfer function according to the first disturbance current value, the first disturbance voltage value, the second disturbance current value, and the second disturbance voltage value;

[0012] Determining a second impedance value to be measured based on the transfer function, the equivalent impedance value of the filter with coupled grid impedance influence, and relevant parameters of the converter; wherein the relevant parameters of the converter include an inductance value, a capacitance value, and a frequency domain operator;

[0013] determining an initial impedance value according to the first impedance value to be measured and the second impedance value to be measured;

[0014] Determine the decoupling coefficient based on the filter equivalent impedance value and transfer function affected by the grid impedance at the secondary disturbance frequency;

[0015] The target impedance value of the converter is determined according to the decoupling coefficient and the initial impedance value.

[0016] Preferably, the expression of the first disturbance current value is:

[0017] Among them, i g1 is the first disturbance current value, v p1 is the first disturbance voltage value generated by superimposing the positive sequence current disturbance on the current sampling value of the converter, Z'1(s) is the first impedance value to be measured, Δi t is the virtual disturbance current corresponding to the positive sequence current disturbance superimposed on the current sampling value of the converter, G c is the transfer function.

[0018] Preferably, the expression of the second disturbance current value is:

[0019] Among them, i g2 is the second disturbance current value, v p2 is the second disturbance voltage value generated by superimposing the positive sequence voltage disturbance on the voltage sampling value of the converter, Z'1(s) is the first impedance value to be measured, Δv t It is the virtual disturbance voltage corresponding to the positive sequence voltage disturbance superimposed on the voltage sampling value of the converter.

[0020] Preferably, the expression of the second impedance value to be measured is:

[0021] Among them, Z'0(s) is the second impedance value to be measured, Z' filter G is the equivalent impedance of the filter with coupled grid impedance. c is the transfer function, L1 is the inductance value, C f is the capacitance value, and s is the frequency domain operator.

[0022] Preferably, the expression of the initial impedance value is:

[0023] Among them, Z'1(s) is the first impedance value to be measured, Z'0(s) is the second impedance value to be measured, and Z' p (s) is the initial impedance value.

[0024] Preferably, the decoupling coefficient is determined based on the filter equivalent impedance value and transfer function affected by the grid impedance at the secondary disturbance frequency. The expression of the decoupling coefficient is:

[0025] Among them, K' is the decoupling coefficient, Z' filter is the equivalent impedance of the filter with coupled grid impedance, Z filter G is the equivalent impedance of the filter without the influence of coupled grid impedance. c is the transfer function; where Z' filter and Z filter Both are equivalent impedance values ​​of the filter based on the influence of grid impedance at the secondary disturbance frequency;

[0026] The target impedance value of the converter is determined based on the decoupling coefficient and the initial impedance value. The expression of the target impedance value is: Z p (s) = K′Z′ p (s);

[0027] Among them, Z' p (s) is the initial impedance value, Z p (s) is the target impedance value.

[0028] To solve the above technical problems, the present application also provides a current transformer impedance measurement device, comprising:

[0029] A current disturbance module, configured to superimpose a positive sequence current disturbance on the current sampling value of the converter to obtain a first disturbance current value and a first disturbance voltage value;

[0030] A voltage disturbance module is used to superimpose a positive sequence voltage disturbance on the voltage sampling value of the converter to obtain a second disturbance current value and a second disturbance voltage value;

[0031] A first determining module, configured to determine a first impedance value to be measured and a transfer function according to the first disturbance current value, the first disturbance voltage value, the second disturbance current value, and the second disturbance voltage value;

[0032] a second determination module, configured to determine a second impedance value to be measured based on the transfer function, an equivalent impedance value of the filter with coupled grid impedance influence, and relevant parameters of the converter; wherein the relevant parameters of the converter include an inductance value, a capacitance value, and a frequency domain operator;

[0033] a third determining module, configured to determine an initial impedance value according to the first impedance value to be measured and the second impedance value to be measured;

[0034] a fourth determining module, configured to determine a decoupling coefficient based on an equivalent impedance value of a filter affected by grid impedance at a secondary disturbance frequency and a transfer function;

[0035] The fifth determining module is configured to determine a target impedance value of the converter according to the decoupling coefficient and the initial impedance value.

[0036] To solve the above technical problems, the present application further provides an electronic device, comprising a memory for storing a computer program;

[0037] The processor is configured to implement the steps of the above-mentioned method for measuring the impedance of a current transformer when executing a computer program.

[0038] To solve the above technical problems, the present application also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the above-mentioned converter impedance measurement method are implemented.

[0039] The present application provides a method for measuring the impedance of a converter, comprising: superimposing a positive-sequence current disturbance on the current sampling value of the converter to obtain a first disturbance current value and a first disturbance voltage value; superimposing a positive-sequence voltage disturbance on the voltage sampling value of the converter to obtain a second disturbance current value and a second disturbance voltage value; determining a first impedance value to be measured and a transfer function based on the first disturbance current value, the first disturbance voltage value, the second disturbance current value and the second disturbance voltage value; determining a second impedance value to be measured based on the transfer function, an equivalent impedance value of a filter with coupled grid impedance influence and relevant parameters of the converter; wherein the relevant parameters of the converter include inductance value, capacitance value and frequency domain operator; determining an initial impedance value based on the first impedance value to be measured and the second impedance value to be measured; determining a decoupling coefficient based on the equivalent impedance value of the filter with grid impedance influence at a secondary disturbance frequency and the transfer function; and determining a target impedance value of the converter based on the decoupling coefficient and the initial impedance value. It can be seen that the present application injects a virtual secondary-side disturbance at the sampling point of the voltage and current of the converter, that is, superimposes the positive-sequence current disturbance and the positive-sequence voltage disturbance respectively. During the operation, there is no need to add an actual disturbance power supply, nor to change the primary-side circuit elements. The overall engineering cost is low and the actual operation is simple. At the same time, the calculation of the target impedance value of the present application does not require the manufacturer of the converter to open the parameters and structure of its controller, which expands the scope of use of the present application as a whole. In addition, the present application takes into account the influence of the grid impedance value and the line impedance value in the calculation of the target impedance value, and performs decoupling before obtaining the final target impedance value, thereby removing the influence of the grid equivalent impedance and obtaining a true and accurate impedance value of the converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0041] FIG1 is a block diagram of a primary side measurement method in the prior art;

[0042] FIG2 is a flow chart of a method for measuring impedance of a current transformer provided in an embodiment of the present application;

[0043] FIG3 is a main circuit topology diagram of a converter provided in an embodiment of the present application;

[0044] FIG4 is a block diagram of a grid-side output current closed-loop control of a converter according to an embodiment of the present application;

[0045] FIG5 is a block diagram of a phase-locked loop control in a converter according to an embodiment of the present application;

[0046] FIG6 is a complete flow chart of a method for measuring impedance of a current transformer provided in an embodiment of the present application;

[0047] FIG7 is a first comparison diagram provided in an embodiment of the present application;

[0048] FIG8 is a second comparison diagram provided in an embodiment of the present application;

[0049] FIG9 is a current transformer impedance measurement device provided by another embodiment of the present application;

[0050] FIG10 is a structural diagram of an electronic device provided in another embodiment of the present application. DETAILED DESCRIPTION

[0051] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0052] The core of this application is to provide a method, device, electronic equipment and medium for measuring the impedance of a converter.

[0053] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0054] To solve the above technical problems, the present application provides a method for measuring the impedance of a current transformer, as shown in FIG2 , comprising the following steps:

[0055] S10: Superimposing a positive sequence current disturbance on the current sampling value of the converter to obtain a first disturbance current value and a first disturbance voltage value.

[0056] S11: Superimposing a positive-sequence voltage disturbance on the voltage sampling value of the converter to obtain a second disturbance current value and a second disturbance voltage value.

[0057] In a specific embodiment, the main circuit topology of the converter is shown in FIG3 , wherein the circuit topology shown in FIG3 is a three-phase circuit topology, a, b, and c are three-phase voltages; L 1a 、L 1b 、L 1c 、L 2a 、L 2b , L 2c , L ga 、L gb 、L gc is the inductance (where L 1a 、L 1b 、L 1c The inductance value is the same, its inductance value is L1; L 2a 、L 2b , L 2c The inductance value is the same as L2; ​​L ga 、L gb , L gc The inductance value is the same as L g );C fa 、C fb 、C fc is the capacitance (where C fa 、C fb 、C fc The capacitance values ​​are the same, C f );i 1a 、i 1b 、i 1c 、i 2a 、i 2b 、i 2c 、i ca 、i cb 、i cc is the current; v ca 、v cb 、v cc is the capacitor voltage; R da 、R db 、R dc is the resistance (where R da 、R db 、R dc The resistance value is the same, and its resistance value is R d). In this process, the corresponding grid-side output current closed-loop control block diagram is shown in Figure 4, where the current I on the d-axis coordinate system is 2ref and the reference current i on the d-axis coordinate system 2d Through the current loop G in the controller i , which is the voltage v at the PCC in Figure 1 in the d-axis coordinate gd Combined, the current 0 on the q-axis coordinate system and the reference current i on the q-axis coordinate system 2q Through the current loop parameter G in the controller i , which is the voltage v at the PCC in Figure 1 in the q-axis coordinate gq The result of the two combinations is transformed into the coordinate system dq-αβ, and the voltage is (U dc Based on the voltage at the power supply end), space vector pulse width modulation (SVPWM) conversion is performed to obtain the required trigger pulse (Pulse width modulation, PWM). The phase-locked loop control block diagram in this process is shown in Figure 5, where the voltage at PCC in Figure 1 is converted to v in the abc coordinate system. ga 、v gb and v gc Convert the coordinate system abc-dq to get the voltage V d and V q , then the voltage V q Enter the PID control system for initial calculation (that is, Among them, Kp pll and are all phase-locked loop controller parameters), and then pass the angular velocity ω, operator The calculation of the phase angle θ is used to obtain the final result. On this basis, the theoretical model of the AC transformer positive sequence impedance is as follows:

[0058] in,

[0059] Where M is the intermediate variable, V1 is the voltage amplitude, Z p (s) is the impedance value (model), s is the frequency domain operator, L1 and L2 are the inductance values, C f is the capacitance value, R d is the resistance parameter, K PWM is the voltage gain of the converter, G i is the current loop coefficient in the controller, f1 is the grid frequency (50Hz), T p (s) is the phase-locked loop function, I1 is the current amplitude, is the angle vector, K f is the voltage feedforward coefficient, G id is the output current sampling delay value, G vd It is the voltage sampling delay value of PCC point.

[0060] As can be seen, the impedance value of the converter can be calculated using the above formula based on the knowledge of the converter's complete structure and relevant parameters. However, in actual applications, manufacturers may not disclose the converter's complete structure, so the above formula is not practical. However, in actual applications, the converter's main function is known. In other words, regardless of the converter type, its main circuit topology is basically the same, as shown in Figure 3.

[0061] On this basis, the current sampling value points and voltage sampling value points of the converter are determined, and the positive sequence current disturbance is superimposed on the current sampling values ​​of the converter to obtain a first disturbance current value and a first disturbance voltage. The positive sequence voltage disturbance is superimposed on the voltage sampling values ​​of the converter to obtain a second disturbance current value and a second disturbance voltage. The injection of the current disturbance will cause the controller of the converter to generate disturbances, thereby outputting a certain disturbance current (i.e., the first disturbance current). The first disturbance current includes two parts: one part is a part of the first disturbance current output by the current loop due to the injection of current disturbance, and the other part is due to the existence of line impedance and grid equivalent impedance. The output disturbance current excites a disturbance voltage at the same frequency at the grid-connected point of the converter, and the disturbance voltage causes the phase-locked loop and feedforward circuit of the converter to use the voltage at the grid-connected point as input to control its loop circuit to generate disturbance, thereby outputting another part of the first disturbance current. The sum of the two parts of the first disturbance current is the final first disturbance current, and then the corresponding first disturbance current value is determined according to the first disturbance current, wherein the first disturbance current value and the first disturbance voltage can be directly obtained through measurement. The injection of voltage disturbances also stimulates the converter's controller to generate disturbances, thereby outputting a disturbance current. However, unlike current disturbances, the disturbance current output by this voltage disturbance only includes one component: the disturbance voltage causes disturbances in the converter's phase-locked loop and feedforward current control loops, which use the grid-connected voltage as input, thereby outputting a second disturbance current. The corresponding second disturbance current value is then determined based on the second disturbance current. The second disturbance current value and the second disturbance voltage can be directly measured.

[0062] The injected voltage disturbance or current disturbance may be a pulse wave signal, a random binary sequence, or various broadband signals, etc., which is not limited in this application.

[0063] S12: Determine a first impedance value to be measured and a transfer function according to the first disturbance current value, the first disturbance voltage value, the second disturbance current value, and the second disturbance voltage value.

[0064] S13: Determine a second impedance value to be measured according to the transfer function, the equivalent impedance value of the filter with coupled grid impedance influence, and relevant parameters of the converter; wherein the relevant parameters of the converter include inductance value, capacitance value, and frequency domain operator.

[0065] S14: Determine the initial impedance value according to the corresponding relationship between the first impedance value to be measured, the second impedance value to be measured, and the initial impedance value.

[0066] In an embodiment of the present application, in the above steps, a measurement method is used to determine the first disturbance current value, the first disturbance voltage value, the second disturbance current value, and the second disturbance voltage value of known specific values, but the determination of the first disturbance current value and the second disturbance current value also has a certain formula corresponding relationship, and under this corresponding relationship, the first impedance value to be measured and the transfer function can be preliminarily determined, and then the second impedance value to be measured can be determined according to the transfer function, the equivalent impedance value of the filter with the coupled grid impedance effect and the relevant parameters of the converter, and finally the initial impedance value is determined according to the corresponding relationship between the first impedance value to be measured and the second impedance value to be measured and the initial impedance value. In simple terms, in a clear corresponding relationship, there are input quantities and output quantities, and the corresponding output quantity can be obtained based on the known input quantity, and the input quantity can be inferred based on the known output quantity. The first disturbance current value, the first disturbance voltage value, the second disturbance current value and the second disturbance voltage value in this step are the output quantities of the first group of corresponding relationships, and the transfer function and the first impedance value to be measured are the input quantities of the first group of corresponding relationships; the transfer function, the equivalent impedance value of the filter with coupled grid impedance influence and the relevant parameters of the converter are the input quantities of the second group of corresponding relationships, and the second impedance value to be measured is the output quantity of the second group of corresponding relationships; the first impedance value to be measured and the second impedance value to be measured are the input quantities of the third group of corresponding relationships, and the initial impedance value finally obtained is the output quantity of the third group of corresponding relationships.

[0067] It should be noted that the sources of the first impedance value to be measured and the second impedance value to be measured are: first rewriting the above-mentioned AC positive sequence impedance theoretical model of the AC device, and the rewritten impedance theoretical model is as follows;

[0068] That is to say, this application splits the original AC positive sequence impedance theoretical model and divides the impedance value Z p(s) is split into Z1(s) and Z0(s). Based on this splitting principle and the above-mentioned corresponding relationship, the first impedance value to be measured, the transfer function and the second impedance value to be measured are determined according to the first disturbance current value, the first disturbance voltage, the second disturbance current value, the second disturbance voltage, the filter equivalent impedance value affected by the grid impedance, and the relevant parameters of the converter, and finally the initial impedance value is obtained.

[0069] S15: Determine a decoupling coefficient based on the filter equivalent impedance value and transfer function affected by the grid impedance at the secondary disturbance frequency.

[0070] S16: Determine a target impedance value of the converter according to the decoupling coefficient and the initial impedance value.

[0071] In an embodiment of the present application, when the impedance value of the converter is measured after injecting current disturbance and voltage disturbance, the grid impedance in the circuit is actually connected in series with the grid-side inductance of the filter, thereby changing the impedance of the original filter. Therefore, when obtaining the final target impedance value, it is necessary to remove the influence of the line impedance and the grid impedance in the measurement, that is, at the secondary disturbance frequency (current disturbance and voltage disturbance), the decoupling coefficient is determined according to the obtained grid line impedance value and the transfer function determined in the above steps. The decoupling coefficient represents the influence of the line impedance and the grid impedance in the measurement, and finally the target impedance value of the converter is determined according to the decoupling coefficient and the initial impedance value.

[0072] The present application provides a method for measuring the impedance of a converter, comprising: superimposing a positive-sequence current disturbance on the current sampling value of the converter to obtain a first disturbance current value and a first disturbance voltage value; superimposing a positive-sequence voltage disturbance on the voltage sampling value of the converter to obtain a second disturbance current value and a second disturbance voltage value; determining a first impedance value to be measured and a transfer function based on the first disturbance current value, the first disturbance voltage value, the second disturbance current value and the second disturbance voltage value; determining a second impedance value to be measured based on the transfer function, an equivalent impedance value of a filter with coupled grid impedance influence and relevant parameters of the converter; wherein the relevant parameters of the converter include inductance value, capacitance value and frequency domain operator; determining an initial impedance value based on the first impedance value to be measured and the second impedance value to be measured; determining a decoupling coefficient based on the equivalent impedance value of the filter with grid impedance influence at a secondary disturbance frequency and the transfer function; and determining a target impedance value of the converter based on the decoupling coefficient and the initial impedance value. It can be seen that the present application injects a virtual secondary-side disturbance at the sampling point of the voltage and current of the converter, that is, superimposes the positive-sequence current disturbance and the positive-sequence voltage disturbance respectively. During the operation, there is no need to add an actual disturbance power supply, nor to change the primary-side circuit elements. The overall engineering cost is low and the actual operation is simple. At the same time, the calculation of the target impedance value of the present application does not require the manufacturer of the converter to open the parameters and structure of its controller, which expands the scope of use of the present application as a whole. In addition, the present application takes into account the influence of the grid impedance value and the line impedance in the calculation of the target impedance value, and performs decoupling before obtaining the final target impedance value, thereby removing the influence of the grid equivalent impedance and obtaining a true and accurate impedance value of the converter.

[0073] Based on the above embodiment, as a preferred embodiment, the expression of the first disturbance current value is:

[0074] Among them, i g1 is the first disturbance current value, v p1 is the first disturbance voltage value generated by superimposing the positive sequence current disturbance on the current sampling value of the converter, Z'1(s) is the first impedance value to be measured, Δi t is the virtual disturbance current corresponding to the positive sequence current disturbance superimposed on the current sampling value of the converter, G c is the transfer function.

[0075] As a preferred embodiment, the expression of the second disturbance current value is:

[0076] Among them, i g2 is the second disturbance current value, v p2 is the second disturbance voltage value generated by superimposing the positive sequence voltage disturbance on the voltage sampling value of the converter, Z'1(s) is the first impedance value to be measured, Δv tIt is the virtual disturbance voltage corresponding to the positive sequence voltage disturbance superimposed on the voltage sampling value of the converter.

[0077] As a preferred embodiment, the expression of the second impedance value to be measured is:

[0078] Among them, Z'0(s) is the second impedance value to be measured, Z' filter G is the equivalent impedance of the filter with coupled grid impedance. c is the transfer function, L1 is the inductance value, C f is the capacitance value, and s is the frequency domain operator.

[0079] As a preferred embodiment, the expression of the initial impedance value is:

[0080] Among them, Z'1(s) is the first impedance value to be measured, Z'0(s) is the second impedance value to be measured, and Z' p (s) is the initial impedance value.

[0081] In a specific embodiment, according to the above-mentioned theoretical model of the AC positive-sequence impedance measurement of the AC converter, two impedance values ​​Z1(s) and Z0(s) are obtained. The specific numerical values ​​in this application are substituted into the rewritten impedance value formula to obtain the first impedance value to be measured Z'1(s) and the second impedance value to be measured Z'0(s) in this application.

[0082] The specific steps are: determining the first impedance value to be measured and the transfer function according to the first disturbance current value, the first disturbance voltage value, the second disturbance current value and the second disturbance voltage value. That is, when the expressions of the first disturbance current value and the second disturbance current value are as shown above, the expression of the first impedance value to be measured is as follows:

[0083] The expression of the transfer function is as follows:

[0084] Wherein, the expression of the second impedance value to be measured is the filter equivalent impedance value Z' with the coupled grid impedance effect. filter The specific expression is:

[0085] Among them, L'2 is the equivalent resistance value, due to i g1 (measured and known), v p1 (measured and known), Δi t (the injected disturbance is known), i g2 (measured and known), v p2 (measured and known), Δv t (injected disturbance is known), s (known), L1 (known), L2 (known), Lg (known), C f (known), R d (known), so Z' filter , Z'1(s) and G c are all known, and the known initial impedance value Z' can be obtained p (s).

[0086] It should be noted that this application is only one possible implementation method, but is not limited to this implementation method and can be set up according to user needs.

[0087] The present application provides a specific process for obtaining the initial impedance value, and also provides a calculation formula required in the process. Under this formula, the voltage and current in the circuit are obtained through measurement, and the relevant parameters of the converter (filter parameters) are obtained through the component nameplate, while the control parameters of the converter do not need to be known. This expands the scope of use of the present application as a whole, while ensuring the accuracy of the initial impedance value.

[0088] Based on the above embodiment, as a preferred embodiment, the decoupling coefficient is determined based on the filter equivalent impedance value and transfer function affected by the grid impedance at the secondary disturbance frequency. The expression of the decoupling coefficient is:

[0089] Among them, K' is the decoupling coefficient, Z' filter is the equivalent impedance of the filter with coupled grid impedance, Z filter G is the equivalent impedance of the filter without the influence of coupled grid impedance. c is the transfer function; where Z' filter and Z filter Both are equivalent impedance values ​​of the filter based on the influence of grid impedance at the secondary disturbance frequency;

[0090] The target impedance value of the converter is determined based on the decoupling coefficient and the initial impedance value. The expression of the target impedance value is: Z p (s) = K′Z′ p (s);

[0091] Among them, Z' p (s) is the initial impedance value, Z p (s) is the target impedance value.

[0092] In a specific embodiment, when the impedance value of the converter is measured after injecting current disturbance and voltage disturbance, the grid impedance in the circuit is actually connected in series with the grid-side inductance of the filter, thereby changing the impedance of the original filter. Therefore, when obtaining the final target impedance value, it is necessary to remove the influence of the line impedance and the grid impedance in the measurement, that is, at the secondary disturbance frequency (current disturbance and voltage disturbance), obtain the grid line impedance value and the transfer function determined in the above steps to determine the decoupling coefficient. The decoupling coefficient represents the influence of the line impedance and the grid impedance in the measurement. Finally, the target impedance value of the converter is determined based on the decoupling coefficient and the initial impedance value.

[0093] The expression for the decoupling coefficient and the expression for the target impedance value are determined as follows:

[0094] The complete calculation formula for the target impedance value is as follows:

[0095] Where,

[0096] therefore,

[0097] Furthermore, Z p (s) = K′Z′ p (s);

[0098] It can be seen that the present application injects a virtual secondary-side disturbance at the sampling point of the voltage and current of the converter, that is, superimposes the positive-sequence current disturbance and the positive-sequence voltage disturbance respectively. During the operation, there is no need to add an actual disturbance power supply, nor to change the primary-side circuit elements. The overall engineering cost is low and the actual operation is simple. At the same time, the calculation of the target impedance value of the present application does not require the manufacturer of the converter to open the parameters and structure of its controller, which expands the scope of use of the present application as a whole. In addition, the present application takes into account the influence of the grid impedance value and the line impedance value in the calculation of the target impedance value, and performs decoupling before obtaining the final target impedance value, thereby removing the influence of the grid equivalent impedance and obtaining a true and accurate impedance value of the converter.

[0099] From the above embodiments, it can be seen that a complete flow chart of a method for measuring the impedance of a current transformer is shown in FIG6 , which includes the following steps:

[0100] S20: Start.

[0101] S21: The first injection of current disturbance.

[0102] S22: Delay.

[0103] S23: Recording the voltage and current waveforms and the disturbance waveforms at the grid connection point to obtain a first disturbance current value.

[0104] S24: Determine whether the recording is completed. If not, return to step S23; if so, proceed to step S25.

[0105] S25: Second injection of voltage disturbance.

[0106] S26: Delay.

[0107] S27: Recording the voltage and current waveforms and the disturbance waveforms at the grid connection point to obtain a second disturbance current value.

[0108] S28: Determine whether the recording is completed. If not, return to step S27; if so, proceed to step S29.

[0109] S29: Calculate the initial impedance value and decoupling coefficient.

[0110] S30: Calculate the target impedance value of the converter.

[0111] S31: Determine whether the calculation is completed, if not, return to step S29.

[0112] S32: Change the frequency of the injected disturbance.

[0113] S33: Determine whether the impedance measurement is completed. If not, proceed to step S21; if so, proceed to step S34.

[0114] S34: End.

[0115] The first time this application injects current disturbance is to superimpose a single-frequency sinusoidal disturbance with the current sampling value at the actual converter grid-connected point; the second time is voltage disturbance, which is the same as the first disturbance injection. After the secondary side disturbance injection is realized, after a certain delay, the voltage and current waveforms at the converter grid-connected point and the corresponding injected disturbance waveforms are recorded respectively, and the disturbance component corresponding to the disturbance frequency is calculated by Fourier analysis and transformed into the positive and negative sequence coordinate system. The target impedance value of the converter at the frequency point to be measured is calculated by the above formula. This process includes the calculation of the initial impedance value and the decoupling of the initial impedance value to obtain the target impedance value. After one process is completed, the frequency of the injected sinusoidal disturbance is changed to the next frequency point to be measured, and the above steps are repeated.

[0116] The results of the present application are compared with those obtained by the primary side measurement method, and the comparison results are shown in Figures 7 and 8. Among them, the impedance results of the present application and the primary side measurement and the theoretical value are basically consistent, which shows the accuracy of the present application.

[0117] In summary, the method provided in this application has the following beneficial effects:

[0118] 1. A virtual secondary-side disturbance is injected into the sampling point of the voltage and current at the grid-connected point of the converter, without adding an actual disturbance power supply or changing the primary-side circuit components. Therefore, the engineering cost of this application is low and the actual operation is simple.

[0119] 2. Injecting a virtual secondary-side disturbance at the sampling point of the voltage and current at the grid-connected point of the converter does not require changing the controller of the original converter. Therefore, in actual impedance measurement, even if the converter manufacturer does not open its controller, this application can still achieve impedance value measurement.

[0120] 3. This application takes into account the influence of the equivalent impedance of the line and the grid, and removes the influence of the equivalent impedance of the grid in the calculation. Therefore, this application can measure the impedance value of the converter under strong and weak grids, and the measurement frequency band covers the range of 10Hz to 4kHz.

[0121] In the above embodiment, a method for measuring the impedance of a current transformer is described in detail. This application also provides a corresponding embodiment of a current transformer impedance measurement device. It should be noted that this application describes the embodiments of the device from two perspectives: one from the perspective of functional modules and the other from the perspective of hardware.

[0122] FIG9 is a module diagram of a current transformer impedance measurement device provided by another embodiment of the present application, comprising:

[0123] The current disturbance module 11 is configured to superimpose a positive sequence current disturbance on the current sampling value of the converter to obtain a first disturbance current value and a first disturbance voltage value;

[0124] The voltage disturbance module 12 is used to superimpose a positive sequence voltage disturbance on the voltage sampling value of the converter to obtain a second disturbance current value and a second disturbance voltage value;

[0125] A first determining module 13, configured to determine a first impedance value to be measured and a transfer function according to the first disturbance current value, the first disturbance voltage value, the second disturbance current value, and the second disturbance voltage value;

[0126] a second determination module 14, configured to determine a second impedance value to be measured based on the transfer function, the equivalent impedance value of the filter with coupled grid impedance influence, and relevant parameters of the converter; wherein the relevant parameters of the converter include an inductance value, a capacitance value, and a frequency domain operator;

[0127] A third determining module 15 is configured to determine an initial impedance value according to the first impedance value to be measured and the second impedance value to be measured;

[0128] A fourth determining module 16 is configured to determine a decoupling coefficient based on an equivalent impedance value of a filter affected by grid impedance at a secondary disturbance frequency and a transfer function;

[0129] The fifth determining module 17 is configured to determine a target impedance value of the converter according to the decoupling coefficient and the initial impedance value.

[0130] Since the embodiments of the apparatus part correspond to the embodiments of the method part, please refer to the description of the embodiments of the method part for the embodiments of the apparatus part, and they will not be repeated here.

[0131] FIG10 is a structural diagram of an electronic device provided by another embodiment of the present application. As shown in FIG10 , the electronic device includes: a memory 20 for storing computer programs;

[0132] The processor 21 is configured to implement the steps of the current transformer impedance measurement method mentioned in the above embodiment when executing the computer program.

[0133] The electronic device provided in this embodiment may include but is not limited to a smart phone, a tablet computer, a laptop computer, or a desktop computer.

[0134] Among them, the processor 21 may include one or more processing cores, such as a 4-core processor, an 8-core processor, etc. The processor 21 can be implemented in at least one hardware form of a digital signal processor (DSP), a field programmable gate array (FPGA), and a programmable logic array (PLA). The processor 21 may also include a main processor and a coprocessor. The main processor is a processor for processing data in the awake state, also known as a central processing unit (CPU); the coprocessor is a low-power processor for processing data in the standby state. In some embodiments, the processor 21 may be integrated with a graphics processing unit (GPU), which is responsible for rendering and drawing the content to be displayed on the display screen. In some embodiments, the processor 21 may also include an artificial intelligence (AI) processor, which is used to process computing operations related to machine learning.

[0135] The memory 20 may include one or more computer-readable storage media, which may be non-transitory. The memory 20 may also include a high-speed random access memory and a non-volatile memory, such as one or more disk storage devices and flash memory storage devices. In this embodiment, the memory 20 is used to store at least the following computer program 201, wherein, after the computer program is loaded and executed by the processor 21, it can implement the relevant steps of the transformer impedance measurement method disclosed in any of the aforementioned embodiments. In addition, the resources stored in the memory 20 may also include an operating system 202 and data 203, etc., and the storage method may be temporary storage or permanent storage. Among them, the operating system 202 may include Windows, Unix, Linux, etc.

[0136] In some embodiments, the electronic device may further include a display screen 22 , an input / output interface 23 , a communication interface 24 , a power supply 25 , and a communication bus 26 .

[0137] Those skilled in the art will appreciate that the structure shown in FIG10 does not limit the electronic device and may include more or fewer components than shown in the figure.

[0138] The electronic device provided in an embodiment of the present application includes a memory and a processor. When the processor executes the program stored in the memory, it can implement the above-mentioned converter impedance measurement method and have the same beneficial effects.

[0139] Finally, the present application also provides an embodiment corresponding to a computer-readable storage medium. The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps described in the above method embodiment.

[0140] It is understandable that if the method in the above embodiment is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium and executes all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0141] The above is a detailed introduction to a method, device, electronic device and medium for measuring the impedance of a current transformer provided by the present application. The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of this application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of this application.

[0142] It should also be noted that, in this specification, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.

Claims

1. A method for measuring impedance of a current transformer, characterized in that: include: Superimposing a positive sequence current disturbance on the current sampling value of the converter to obtain a first disturbance current value and a first disturbance voltage value; Superimposing a positive sequence voltage disturbance on the voltage sampling value of the converter to obtain a second disturbance current value and a second disturbance voltage value; determining a first impedance value to be measured and a transfer function according to the first disturbance current value, the first disturbance voltage value, the second disturbance current value, and the second disturbance voltage value; Determining a second impedance value to be measured based on the transfer function, the equivalent impedance value of the filter with coupled grid impedance influence, and relevant parameters of the converter; wherein the relevant parameters of the converter include an inductance value, a capacitance value, and a frequency domain operator; determining an initial impedance value according to the first impedance value to be measured and the second impedance value to be measured; Determining a decoupling coefficient based on a filter equivalent impedance value affected by grid impedance at a secondary disturbance frequency and the transfer function; A target impedance value of the converter is determined according to the decoupling coefficient and the initial impedance value.

2. The method for measuring the impedance of a current transformer according to claim 1, wherein: The expression of the first disturbance current value is: Among them, i g1 is the first disturbance current value, v p1 is the first disturbance voltage value generated by superimposing the positive sequence current disturbance on the current sampling value of the converter, Z′1(s) is the first impedance value to be measured, Δi t G is the virtual disturbance current corresponding to the positive sequence current disturbance superimposed on the current sampling value of the converter, c is the transfer function.

3. The method for measuring the impedance of a current transformer according to claim 1, wherein: The expression of the second disturbance current value is: Among them, i g2 is the second disturbance current value, v p2 is the second disturbance voltage value generated by superimposing the positive sequence voltage disturbance on the voltage sampling value of the converter, Z′1(s) is the first impedance value to be measured, Δv t A virtual disturbance voltage corresponding to the positive sequence voltage disturbance is superimposed on the voltage sampling value of the converter.

4. The method for measuring the impedance of a current transformer according to claim 1, wherein: The expression of the second impedance value to be measured is: Wherein, Z′0(s) is the second impedance value to be measured, Z′ filter is the equivalent impedance value of the filter with the coupled grid impedance effect, G c is the transfer function, L1 is the inductance value, C f is the capacitance value, and s is the frequency domain operator.

5. The method for measuring the impedance of a current transformer according to claim 1, wherein: The expression of the initial impedance value is: Wherein, Z′1(s) is the first impedance value to be measured, Z′0(s) is the second impedance value to be measured, and Z′ p (s) is the initial impedance value.

6. The method for measuring the impedance of a current transformer according to any one of claims 1 to 5, characterized in that: The decoupling coefficient is determined based on the filter equivalent impedance value affected by the grid impedance at the secondary disturbance frequency and the transfer function. The expression of the decoupling coefficient is: Wherein, K′ is the decoupling coefficient, Z′ filter is the equivalent impedance of the filter with coupled grid impedance, Z filter G is the equivalent impedance of the filter without the influence of coupled grid impedance. c is the transfer function; where Z′ filter and Z filter are all equivalent impedance values ​​of the filter based on the influence of the grid impedance at the secondary disturbance frequency; The target impedance value of the converter is determined according to the decoupling coefficient and the initial impedance value, and the expression of the target impedance value is: Z p (s)=K′Z′ p (s); Among them, Z′ p (s) is the initial impedance value, Z p (s) is the target impedance value.

7. A current transformer impedance measuring device, characterized in that: include: A current disturbance module, configured to superimpose a positive sequence current disturbance on the current sampling value of the converter to obtain a first disturbance current value and a first disturbance voltage value; A voltage disturbance module, configured to superimpose a positive sequence voltage disturbance on the voltage sampling value of the converter to obtain a second disturbance current value and a second disturbance voltage value; a first determining module, configured to determine a first impedance value to be measured and a transfer function according to the first disturbance current value, the first disturbance voltage value, the second disturbance current value, and the second disturbance voltage value; a second determination module, configured to determine a second impedance value to be measured based on the transfer function, an equivalent impedance value of the filter with coupled grid impedance influence, and relevant parameters of the converter; wherein the relevant parameters of the converter include an inductance value, a capacitance value, and a frequency domain operator; a third determining module, configured to determine an initial impedance value according to the first impedance value to be measured and the second impedance value to be measured; a fourth determining module, configured to determine a decoupling coefficient based on an equivalent impedance value of a filter affected by grid impedance at a secondary disturbance frequency and the transfer function; A fifth determining module is configured to determine a target impedance value of the converter according to the decoupling coefficient and the initial impedance value.

8. An electronic device, characterized in that: including a memory for storing a computer program; A processor, configured to implement the steps of the method for measuring the impedance of a current transformer according to any one of claims 1 to 6 when executing the computer program.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the current transformer impedance measurement method according to any one of claims 1 to 6 are implemented.

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