Method and system for evaluating impedance / admittance theoretical error

Abstract

The invention relates to the technical field of impedance / admittance measurement, in particular to an impedance / admittance theoretical error evaluation method and system, and the method comprises the steps: carrying out the sweep frequency measurement of target equipment, and obtaining a response signal under each frequency through injecting a disturbance signal under each frequency; # imgabs0 #, # imgabs1 # and # imgabs2 # are calculated as transfer functions of a disturbance signal and a response signal; screening frequency bands of # imgabs3 # and # imgabs4 # which meet the '0-1' characteristic, and taking the frequency bands of # imgabs5 # and # imgabs6 # which meet the '0-1' characteristic as theoretical relative error evaluation frequency bands; and calculating the theoretical relative error in the theoretical relative error evaluation frequency band. According to the method, the transfer function characteristics are constructed through the sweep frequency response signal, the error evaluation frequency band is divided, theoretical error calculation under the coupling frequency is combined, dynamic quantitative evaluation of the impedance / admittance error and accurate definition of the applicable frequency band under the non-ideal power grid condition are achieved, and the accuracy of a stability analysis result is improved.

Description

Background Art

[0002] With the large-scale grid connection application of new energy power generation equipment, the stability analysis of power systems and the suppression of harmonic oscillations have become the focus of the industry. As an important tool for analyzing the dynamic characteristics of power grids, the measurement accuracy of impedance models directly affects the judgment of system stability and the formulation of optimal control strategies. Currently, obtaining the impedance characteristics of equipment through the frequency sweep method is the mainstream technical means. This method establishes an impedance model by injecting disturbance signals and collecting response signals, and has the advantages of simple operation and intuitive results.

[0003] Existing technologies generally use the decoupling method or the matrix inversion method to process frequency sweep data. Among them, the decoupling method simplifies the calculation by separating the positive-sequence and negative-sequence response signals. The positive-sequence and negative-sequence calculation processes are separated, avoiding the propagation of measurement errors and simplifying the calibration difficulty; while the matrix inversion method ensures the integrity of the model by jointly solving multiple disturbance signals, can accurately reflect the impedance characteristics, and there is no theoretical error. However, the matrix inversion method has complex calculations, the disturbance signals measured before and after need to satisfy linear independence, and the errors of the two measurements will propagate to each other and jointly affect the calculation results; while the decoupling method introduces theoretical errors and is difficult to correct due to ignoring the frequency coupling effect, and is not applicable to frequency bands with high theoretical errors.

[0004] In the existing technologies, the deficiencies of using the decoupling method to process frequency sweep data are mainly reflected in the lack of a theoretical error evaluation method: on the one hand, traditional methods lack a quantitative analysis of the error sources of the decoupling method and are difficult to define its applicable frequency band; on the other hand, the error evaluation depends on the assumption of an ideal source-side impedance and cannot adapt to actual scenarios where it cannot be ignored, resulting in a deviation between the evaluation result and the actual working conditions. In addition, the existing methods do not establish a direct correlation between the error characteristics and the frequency sweep response signals, and cannot dynamically correct the evaluation conclusion through measurement data, limiting the accuracy and practicality of the error evaluation. Summary of the Invention

[0005] Aiming at the technical problem that the existing method of using the decoupling method to process frequency sweep data lacks a theoretical error evaluation method and does not establish a quantitative correlation between the transfer function characteristics and the error, resulting in the inability to dynamically evaluate the theoretical error and applicable frequency band of the decoupling method under non-ideal source-side impedance conditions, this application provides a method and system for evaluating the theoretical error of impedance / admittance. By constructing the transfer function characteristics from the frequency sweep response signals and dividing the error evaluation frequency band, combined with the calculation of the theoretical error at the coupling frequency, the dynamic quantitative evaluation of the impedance / admittance error and the accurate definition of the applicable frequency band under non-ideal power grid conditions are realized, improving the accuracy of the stability analysis results.

[0006] In the first aspect, this application provides a method for evaluating the theoretical error of impedance / admittance, including the following steps: S1. Perform a frequency sweep measurement on the target device, by injecting each frequency The disturbance signals at different frequencies are used to obtain the response signals at various frequencies. The disturbance signals include voltage disturbance signals and current disturbance signals, and the response signals include voltage response signals and current response signals. The frequencies include positive sequence frequencies , negative sequence frequencies , and power frequency , where = 50 Hz; S2. Calculate and , where is the transfer function of the disturbance signal and the response signal, including the transfer function when injecting positive sequence disturbance and the transfer function when injecting negative sequence disturbance; S3. Screen the frequency bands where and satisfy the "0-1" characteristic, and use the frequency bands where and satisfy the "0-1" characteristic as the theoretical relative error evaluation frequency bands; Among them, and satisfying the "0-1" characteristic means that when the ratio of the source-side impedance to the device-side impedance approaches infinity, approaches 0 and approaches 1; when the ratio of the source-side impedance to the device-side impedance approaches zero, approaches 1 and approaches 0; S4. Calculate the theoretical relative error when calculating the SISO sequence impedance / admittance by the decoupling method in the theoretical relative error evaluation frequency bands.

[0007] It should be further noted that it also includes step S5: setting the allowable error standard, comparing the absolute value of the theoretical relative error with the allowable error standard, and using the frequency bands where the absolute value of the theoretical relative error is less than or equal to the absolute value of the allowable error standard as the applicable frequency bands of the decoupling method.

[0008] It should be further noted that in step S1, injecting the disturbance signals at different frequencies includes , , , , where: represents the positive sequence disturbance voltage phasor with an injection frequency of ; represents the negative sequence disturbance voltage phasor with an injection frequency of ; represents the injection frequency of Positive sequence disturbance current phasor; Indicates that the injection frequency is Negative sequence disturbance current phasor; The voltage response signal includes , , , , where: Indicates the positive sequence voltage phasor at frequency after injecting positive sequence disturbance voltage / current; The meaning of is: after injecting positive sequence disturbance voltage / current, if >0, it indicates the negative sequence voltage phasor at frequency ; if <0, it indicates the conjugate positive sequence voltage phasor at frequency Indicates the negative sequence voltage phasor at frequency after injecting negative sequence disturbance voltage / current; Indicates the positive sequence voltage phasor at frequency after injecting negative sequence disturbance voltage / current; The current response signal includes , , , , where: Indicates the positive sequence current phasor at frequency after injecting positive sequence disturbance voltage / current; The meaning of is: after injecting positive sequence disturbance voltage / current, if >0, it indicates the negative sequence current phasor at frequency ; if <0, it indicates the conjugate positive sequence current phasor at frequency Indicates the negative sequence current phasor at frequency after injecting negative sequence disturbance voltage / current; Indicates the positive sequence current phasor at frequency after injecting negative sequence disturbance voltage / current.

[0009] It should be further noted that in step S1, the frequency sweep measurement includes: Injecting positive sequence voltage disturbances and negative sequence voltage disturbances of multiple frequencies into the target device in series; Inject positive-sequence current disturbances and negative-sequence current disturbances of multiple frequencies into the target device in parallel.

[0010] Furthermore, it should be noted that in step S2, when the frequency sweep measurement is to inject positive-sequence voltage disturbances and negative-sequence voltage disturbances of multiple frequencies into the target device in series, is , and the expression is:

[0011] is , and the expression is: .

[0012] Furthermore, it should be noted that in step S2, when the frequency sweep injects positive-sequence current disturbances and negative-sequence current disturbances of multiple frequencies into the target device in parallel, is , and the calculation formula is:

[0013] is , and the calculation formula is: .

[0014] Furthermore, it should be noted that in step S3, the theoretical relative error evaluation frequency band Freq satisfies:

[0015] In the formula, ξ is the preset upper limit of the allowable measurement error.

[0016] Furthermore, it should be noted that in step S4, the theoretical relative errors in calculating the SISO sequence impedance / admittance by the decoupling method include: The theoretical relative error of the SISO positive-sequence admittance on the device side; The theoretical relative error of the SISO negative-sequence admittance on the device side; The theoretical relative error of the SISO positive-sequence to negative-sequence coupling admittance on the device side; The theoretical relative error of the SISO negative-sequence to positive-sequence coupling admittance on the device side; The theoretical relative error of the SISO positive-sequence impedance on the device side; The SISO negative sequence impedance on the device side The theoretical relative error of ; The SISO positive sequence-negative sequence coupling impedance on the device side The theoretical relative error of ; The SISO negative sequence-positive sequence coupling impedance on the device side The theoretical relative error of .

[0017] Further, it should be noted that when the frequency sweep measurement injects positive sequence voltage disturbances and negative sequence voltage disturbances of multiple frequencies into the target device in series, the calculation formula of the theoretical relative error includes:

[0018]

[0019]

[0020]

[0021] Among them, The calculation formula of

[0022] The calculation formula of

[0023] The calculation formula of

[0024] The calculation formula of .

[0025] Further, it should be noted that when the frequency sweep measurement injects positive sequence current disturbances and negative sequence current disturbances of multiple frequencies into the target device in parallel, the calculation formula of the theoretical relative error includes:

[0026]

[0027]

[0028] .

[0029] Further, it should be noted that it also includes step S6: Within the applicable frequency band of the decoupling method, the SISO sequence admittance is calculated using the decoupling method, and then the corresponding MIMO sequence admittance is calculated using the theoretical error compensation formula, which includes:

[0030]

[0031] wherein, is the MIMO positive sequence admittance; is the MIMO negative sequence admittance; is the MIMO positive sequence - negative sequence coupling admittance; is the MIMO negative sequence - positive sequence coupling admittance.

[0032] In a second aspect, the present application provides an evaluation system for impedance / admittance theoretical error, which is used to implement the evaluation method for impedance / admittance theoretical error of the above integrated energy system, including: A frequency - sweep measurement module, which is used to perform frequency - sweep measurement on the target device, and obtain the response signals at each frequency by injecting perturbation signals at each frequency; A transfer - function calculation module, which is used to calculate the transfer function of the perturbation signal and the response signal 、 and ; A frequency - band screening module, which is used to screen the frequency bands of and that meet the "0 - 1" characteristic, and use the frequency bands of and that meet the "0 - 1" characteristic as the theoretical relative - error evaluation frequency bands; A theoretical relative - error calculation module, which is used to calculate the theoretical relative error in the theoretical relative - error evaluation frequency bands.

[0033] In a third aspect, the present application provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. The processor is used to implement the steps of the above - mentioned impedance / admittance theoretical - error evaluation method when executing the computer program.

[0034] In a fourth aspect, the present application provides a storage medium, on which a computer program is stored. The computer program, when executed by a processor, implements the steps of the above - mentioned impedance / admittance theoretical - error evaluation method.

[0035] From the above technical solutions, it can be seen that the present application has the following advantages: 1. The present application obtains voltage and current response signals through multi - frequency sweep measurement, and combines with the calculation of the transfer function And its characteristic parameters realize the dynamic characterization of the impedance interaction relationship between the device side and the source side, solve the problem of distorted error evaluation caused by ignoring the actual situation in the traditional method, and can accurately reflect the impedance coupling effect under the actual working conditions.

[0036] 2. This application judges and the frequency band that satisfies the "0-1" characteristic, and divides the theoretical error evaluation frequency band based on this characteristic, solves the problem that the prior art cannot quantitatively define the applicable range of the decoupling method, can dynamically identify the error-acceptable frequency band, and avoid evaluation deviation caused by improper setting of the empirical threshold.

[0037] 3. This application directly calculates the theoretical relative error of admittance / impedance within the theoretical error evaluation frequency band, establishes an error quantization model based on the transfer function characteristics, solves the problem that the traditional method relies on ideal assumptions or complex matrix operations, realizes the direct association between the error evaluation process and the swept-frequency measurement data, and significantly improves the evaluation efficiency and result credibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of this application, the drawings required for description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of this application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0039] Figure 1 is a flowchart of an evaluation method for impedance / admittance theoretical error in an embodiment of this application.

[0040] Figure 2 is an embodiment of this application R g = 0.1Ω, schematic diagram of the relative error of impedance / admittance of the grid-forming converter.

[0041] Figure 3 is an embodiment of this application R g = 3Ω, schematic diagram of the relative error of impedance / admittance of the grid-forming converter.

[0042] Figure 4 is a schematic diagram of the impedance / admittance frequency coupling degree of the grid-forming converter in an embodiment of this application.

[0043] Figure 5 is an embodiment of this application R g = 0.1Ω, impedance schematic diagram of the grid-forming converter.

[0044] Figure 6 is an embodiment of this applicationR g Schematic diagram of the impedance of the network-forming converter when = 3Ω.

[0045] Figure 7 In one embodiment of the present application R g Schematic diagram of the admittance of the network-forming converter when = 0.1Ω.

[0046] Figure 8 In one embodiment of the present application R g Schematic diagram of the admittance of the network-forming converter when = 3Ω.

[0047] Figure 9 Schematic block diagram of an evaluation system for the theoretical error of impedance / admittance in one embodiment of the present application.

[0048] Figure 10 Schematic diagram of the hardware structure of an electronic device in one embodiment of the present application. Detailed implementation manners

[0049] To make the application purpose, features, and advantages of the present application more obvious and understandable, the technical solutions protected by the present application will be clearly and completely described below by using specific embodiments and the accompanying drawings. Obviously, the embodiments described below are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts belong to the scope protected by the present application.

[0050] The evaluation method for the theoretical error of impedance / admittance involved in the present application is mainly aimed at the field of impedance / admittance measurement technology. By obtaining voltage and current response signals through multi-frequency sweep measurement and combining the calculation of the transfer function and its characteristic parameters, the dynamic characterization of the impedance interaction relationship between the device side and the source side is realized, the problem of distorted error evaluation caused by ignoring the actual situation in the traditional method is solved, and the impedance coupling effect under the real working condition can be accurately reflected; by judging and the frequency bands that satisfy the "0-1" characteristic, and dividing the theoretical error evaluation frequency bands based on this characteristic, the problem that the prior art cannot quantitatively define the applicable range of the decoupling method is solved, the error acceptable frequency bands can be dynamically identified, and the evaluation deviation caused by improper setting of the empirical threshold can be avoided; by directly calculating the theoretical relative error of admittance / impedance within the theoretical error evaluation frequency bands, an error quantization model based on the characteristics of the transfer function is established, the problem that the traditional method relies on ideal assumptions or complex matrix operations is solved, the direct association between the error evaluation process and the sweep measurement data is realized, and the evaluation efficiency and the credibility of the results are significantly improved.

[0051] The evaluation method of impedance / admittance theoretical error involved in this application mainly has the technical problem that the existing method of using the decoupling method to process swept-frequency data lacks an evaluation method for theoretical error, and there is no quantitative correlation established between the transfer function characteristics and the error, resulting in the inability to dynamically evaluate the theoretical error of the decoupling method and the applicable frequency band under non-ideal source-side impedance conditions.

[0052] The evaluation method of impedance / admittance theoretical error involved in this application will be described in detail below. For the purpose of illustration rather than limitation, specific details such as specific system structures and technologies are proposed to thoroughly understand the embodiments of this application. However, those skilled in the art should clearly understand that this application can also be implemented in other embodiments without these specific details.

[0053] Statements such as "an embodiment" or "some embodiments" described in this application mean that the specific features, structures, or characteristics described in that embodiment are included in one or more embodiments of this application. Thus, statements such as "in an embodiment", "in some embodiments", "in other some embodiments", "in still other embodiments" that appear in different places in this application do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways.

[0054] The evaluation method of impedance / admittance theoretical error provided by the embodiments of this application is executed by a computer device. Correspondingly, the evaluation system of impedance / admittance theoretical error runs in the computer device.

[0055] The following are explanations of some nouns and concepts in this solution to facilitate a better understanding of this solution: Matrix inversion method: The matrix inversion method is to obtain the sequence impedance / admittance parameters by constructing a 2×2 impedance matrix describing the small-signal characteristics of new energy equipment and performing an inversion operation on it. The inversion method generally requires two measurements, one injecting a positive-sequence perturbation and the other injecting a negative-sequence perturbation, which is different from the decoupling method that injects positive-sequence and negative-sequence perturbations simultaneously in one measurement. Therefore, the measurement and calculation process of the inversion method is more complex than that of the decoupling method. What the inversion method calculates is the MIMO sequence admittance / impedance, and the MIMO sequence impedance matrix can be converted into the dq impedance matrix after frequency shift, so it is also called the accurate sequence impedance.

[0056] The inversion method calculates the MIMO sequence admittance as follows:

[0057] where represents the MIMO positive-sequence admittance, represents the MIMO negative-sequence admittance, represents the MIMO positive-sequence-negative-sequence coupling admittance, Represents the MIMO negative-sequence to positive-sequence coupling admittance, Represents the MIMO positive-sequence impedance, Represents the MIMO negative-sequence impedance, Represents the MIMO positive-sequence to negative-sequence coupling impedance, Represents the MIMO negative-sequence to positive-sequence coupling impedance. Represents the positive-sequence frequency, Represents the negative-sequence frequency, Represents the power frequency, i.e., 50 Hz. Represents the positive-sequence disturbance voltage / current with an injection frequency of After that, the positive-sequence disturbance frequency The positive-sequence voltage phasor at; Represents the positive-sequence disturbance voltage / current with an injection frequency of After that, if > 0, it represents The negative-sequence voltage phasor at the coupling frequency of If < 0, it represents The conjugate phasor of the positive-sequence voltage response signal at the coupling frequency of ; Represents the negative-sequence disturbance voltage / current with an injection frequency of After that, the negative-sequence disturbance frequency The negative-sequence voltage phasor at; Represents the negative-sequence disturbance voltage / current with an injection frequency of After that, The positive-sequence voltage phasor at the coupling frequency of ; Represents the positive-sequence disturbance voltage / current with an injection frequency of After that, the frequency The positive-sequence current phasor at; Represents the positive-sequence disturbance voltage / current with an injection frequency of After that, if > 0, it represents The negative-sequence current phasor at the coupling frequency of 1, if < 0, it represents The conjugate phasor of the positive-sequence current response signal at the coupling frequency of ; Represents the negative-sequence disturbance voltage / current with an injection frequency of After that, the frequency The negative-sequence current phasor at; Represents the negative-sequence disturbance voltage / current with an injection frequency of After that, it represents the frequency The positive-sequence current phasor at the coupling frequency of ;

[0058] Decoupling method: The decoupling method is a method used to simplify the calculation of small-signal impedance / admittance of new energy equipment. Its core idea is to decouple the 2×2 sequence impedance / admittance matrix into 4 SISO impedances / admittances. The decoupling method can achieve fast impedance calculation and can complete the impedance calculation through a single measurement. The result calculated by the decoupling method is the SISO sequence impedance / admittance, also known as the decoupled sequence impedance / admittance. A single measurement of the decoupling method means that only one disturbance voltage or current is injected during the measurement and the relevant response signals are measured. The decoupling method significantly reduces the complexity of measurement and calculation. Since the decoupled admittance / impedance includes the source-side admittance / impedance, it is also called the sequence admittance / impedance considering grid coupling. When using the decoupling method, disturbance signals of positive sequence frequency and negative sequence frequency are injected. To ensure that the disturbance signals do not affect each other, when injecting the disturbance signals using the decoupling method, the positive sequence frequency and the negative sequence frequency need to satisfy the following conditions:

[0059] The formula for calculating the SISO sequence admittance by the decoupling method is as follows:

[0060] where, represents the SISO positive sequence admittance, represents the SISO negative sequence admittance, represents the SISO positive sequence-negative sequence coupling admittance, represents the SISO negative sequence-positive sequence coupling admittance, represents the SISO positive sequence impedance, represents the SISO negative sequence impedance, represents the SISO positive sequence-negative sequence coupling impedance, represents the SISO negative sequence-positive sequence coupling impedance. The remaining variables are the same as those in the inversion method.

[0061] In practical applications, in order to simplify the complexity of measurement and calculation, the decoupling method is often used to calculate the SISO sequence impedance / admittance, and then the SISO sequence impedance / admittance is used to approximate the MIMO sequence impedance / admittance. However, due to the coupling of the grid impedance in the SISO sequence impedance / admittance, there is a theoretical error in this approximation process.

[0062] The theoretical error is the error caused by calculating the measurement result using an approximate formula or an approximate value. A variable containing a theoretical error can be written in the following form:

[0063] where, represents the approximate value, represents the theoretical value, Indicates the theoretical absolute error.

[0064] In the decoupling method, since impedance is mathematically complex, the theoretical error should consider both the magnitude error and the phase error . To reflect both the magnitude and phase errors with a single metric, the relative error is introduced for description:

[0065] Magnitude error , and phase error have the following relationship with the modulus of the relative error :

[0066] Through the conversion relationship between SISO sequence impedance / admittance and MIMO sequence impedance / admittance, the magnitude of the theoretical error of SISO sequence impedance / admittance can be analyzed. The conversion relationship is as follows:

[0067]

[0068] where is the positive-sequence frequency admittance of the grid side; is the negative-sequence frequency admittance of the grid side.

[0069] Thus, the theoretical absolute error when substituting MIMO sequence impedance with SISO sequence impedance by the inversion method is obtained as follows:

[0070]

[0071] represents the absolute error of substituting the MIMO positive-sequence admittance with the SISO positive-sequence admittance, represents the absolute error of the SISO negative-sequence admittance, represents the absolute error of the SISO positive-sequence to negative-sequence coupling admittance, represents the absolute error of the SISO negative-sequence to positive-sequence coupling admittance.

[0072] Furthermore, the relative error of substituting MIMO sequence admittance with SISO sequence admittance is obtained:

[0073]

[0074] The relative error of the coupling admittance is related to the positive and negative sequence SISO short-circuit ratios |λ| of the new energy equipment grid-connection model and takes the theoretical relative error of the SISO positive-sequence to negative-sequence coupling admittance of the equipment side as an example, which can be written as: When

[0075] ; when tends to 0, ; When it approaches 0, ; For , there is:

[0076] When there is no frequency coupling in the equipment , and satisfy:

[0077] When , as amplitude approaches infinity, tends to 0, and at the same time and tend to 0 and 1 respectively, which is the "0-1" characteristic of impedance-admittance.

[0078] However, in the neighborhood of (-1,j0), the relative errors of admittance and impedance will increase. At the same time, in actual analysis, due to the frequency coupling characteristics of the equipment, , but and still have this characteristic, which is the "0-1" characteristic of the impedance-admittance relative error.

[0079] The diagonal dominance degrees of the 2×2 sequence impedance / admittance matrix , , and reflect the impedance coupling characteristics, as shown in the following formula:

[0080] The relative error ratio between and is the same, and its magnitude is equal to the product of the frequency coupling strengths defined in this paper. The relative error ratio between

[0081]

[0082] Thus, the relationship between the relative error of the main diagonal elements, the frequency coupling strength index, and the network admittance can be further expressed as:

[0083] Because and are generally less than 1, the relative error of the main diagonal elements is generally less than that of the off-diagonal elements.

[0084] Combined with the above analysis, it can be seen that the relative error of the decoupling method is related to the short-circuit ratios of the positive and negative sequence SISO systems, the frequency coupling degree, and the final manifestation form ( Z or Y ): (1) The relative error of the off-diagonal elements is determined by the short-circuit ratios of the positive and negative sequence SISO systems, and the expression form of impedance / admittance has a great influence on the relative error, and the relative error shows the "0-1" characteristic.

[0085] (2) The ratio of the relative errors of the main diagonal elements to the off-diagonal elements of the positive and negative sequences is the same, equal to the product of the frequency coupling degrees . In addition, the coupling degree K is generally less than 1, so in most cases, the relative error of the main diagonal elements is less than that of the off-diagonal elements.

[0086] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application.

[0087] Figure 1 is a flowchart of an evaluation method for the theoretical error of impedance / admittance in an embodiment of the present application. Among them, Figure 1 The execution subject can be an evaluation system for the theoretical error of impedance / admittance. According to different requirements, the order of the steps in this flowchart can be changed, and some can be omitted.

[0088] As Figure 1 shown, the evaluation method for the theoretical error of impedance / admittance includes: Step S1, perform a swept-frequency measurement on the target device, and obtain the response signals at each frequency by injecting disturbance signals at each frequency . The disturbance signals include voltage disturbance signals and current disturbance signals, and the response signals include voltage response signals and current response signals. The frequency includes positive sequence frequency , negative sequence frequency , and power frequency , , = 50 Hz.

[0089] By injecting positive / negative sequence voltage and current disturbances at multiple frequencies and collecting response signals, the frequency coupling characteristics of the device impedance / admittance are comprehensively covered, providing a complete data basis for subsequent transfer function calculation and avoiding the missing of key frequency band information caused by single-frequency disturbance.

[0090] In some specific embodiments, the injected disturbance signals at each frequency include , , , , where: represents the positive sequence disturbance voltage phasor with an injection frequency of ; represents the negative sequence disturbance voltage phasor with an injection frequency of ; represents the positive sequence disturbance current phasor with an injection frequency of ; represents the negative sequence disturbance current phasor with an injection frequency of ; The voltage response signals include , , , , where: represents the positive sequence voltage phasor at frequency after injecting positive sequence disturbance voltage / current; means that after injecting positive sequence disturbance voltage / current, if >0, it represents the negative sequence voltage phasor at frequency ; if <0, it represents the conjugate of the positive sequence voltage phasor at frequency ; represents the negative sequence voltage phasor at frequency after injecting negative sequence disturbance voltage / current; represents the positive sequence voltage phasor at frequency after injecting negative sequence disturbance voltage / current; The current response signals include , , , , where: represents the positive sequence current phasor at frequency after injecting positive sequence disturbance voltage / current; The meaning is: After injecting positive-sequence disturbance voltage / current, if >0, it represents the negative-sequence current phasor at frequency ; if <0, it represents the conjugate phasor of the positive-sequence current at frequency ; represents the negative-sequence current phasor at frequency after injecting negative-sequence disturbance voltage / current; represents the positive-sequence current phasor at frequency after injecting negative-sequence disturbance voltage / current.

[0091] By refining the parameter definition of the voltage / current response signal, it ensures that the swept-frequency data contains complete frequency coupling information, provides high-precision input for transfer function calculation and error analysis, and reduces error distortion caused by noise interference.

[0092] In some specific embodiments, the swept-frequency measurement includes: Injecting positive-sequence voltage disturbances and negative-sequence voltage disturbances of multiple frequencies into the target device in series; Injecting positive-sequence current disturbances and negative-sequence current disturbances of multiple frequencies into the target device in parallel.

[0093] By injecting multi-frequency disturbance signals in series or parallel, it adapts to different device interface types (such as voltage-source type or current-source type devices), enhances the compatibility of the method with different measurement scenarios, and ensures the universality of the impedance / admittance model.

[0094] Step S2, calculate and , is the transfer function of the disturbance signal and the response signal, including the transfer function when injecting positive-sequence disturbance, and the transfer function when injecting negative-sequence disturbance.

[0095] Through the calculation of the positive-sequence / negative-sequence transfer function , it quantifies the influence of the impedance ratio between the source side and the device side on the error, provides the core criterion for the "0-1" characteristic frequency band division, and solves the problem of ignoring the impedance interaction in traditional error evaluation In some specific embodiments, when the swept-frequency measurement is injecting positive-sequence voltage disturbances and negative-sequence voltage disturbances of multiple frequencies into the target device in series, is , and the expression is:

[0096] is , and the expression is: 。

[0097] In some specific embodiments, when the frequency sweep injects positive-sequence current disturbances and negative-sequence current disturbances of multiple frequencies into the target device in a parallel manner, For , the calculation formula is:

[0098] For , the calculation formula is: 。

[0099] By designing the transfer function formulas for series injection of voltage disturbances and parallel injection of current disturbances, the error calculation process under complex working conditions can be simplified, and the evaluation efficiency can be improved.

[0100] Taking series voltage disturbance as an example, when ≈ 0, ≈ 0, ≈ , and then , And , There is the following relationship:

[0101] At the same time, from the "0-1" characteristic of the relative error, it can be known that: 。

[0102] When there is parallel current disturbance, combining the dual characteristics of impedance-admittance can directly obtain:

[0103] Therefore, whether it is positive-sequence or negative-sequence impedance, whether it is series voltage disturbance or parallel current disturbance, by calculating And Both can be used as criteria for evaluating the relative error of the sub-coupling admittance And the relative error of the coupling impedance . However, the prerequisite for estimating the relative error magnitude of the sub-diagonal elements through the transfer function Is that the measurement error of the main diagonal elements is very small.

[0104] S3. Screening And The frequency bands that satisfy the "0-1" characteristic are selected, and And The frequency bands that satisfy the "0-1" characteristic are used as the theoretical relative error evaluation frequency bands; Among them, and satisfying the "0-1" characteristic means that when the ratio of the source-side impedance to the device-side impedance approaches infinity, approaches 0 and approaches 1; when the ratio of the source-side impedance to the device-side impedance approaches zero, approaches 1 and approaches 0.

[0105] When the frequency coupling degree of the device does not exceed 1, the relative error of the main diagonal element is less than the relative error of the sub-diagonal element. Assuming that the upper limit of the allowable measurement error is ξ, and ξ is generally <<1. When estimating and the magnitudes of and and determining the form (admittance or impedance) and frequency range that satisfy being less than ξ, if the frequency coupling degree is less than 1, then the relative errors of the diagonal elements and must be less than the sub-diagonal elements and , so and must also satisfy the allowable error ξ. If the frequency coupling degree is greater than 1, it is still necessary to further calculate the frequency coupling degree to determine the relative error range of the main diagonal element. Even if there is a situation where the frequency coupling degree is greater than 1, if the error of the main diagonal element is greater than the error of the sub-diagonal element and affects 's effectiveness, will no longer satisfy the "0-1" error characteristic. Therefore, when the actual error of the main diagonal element is large, judging the magnitude of the sub-diagonal element error through and criteria will no longer be accurate, and there are two situations: (1) The frequency coupling degree >>1; (2) and are located in the neighborhood of (-1,j0).

[0106] For the first situation, because the frequency coupling degree >>1, the error of the main diagonal element is much larger than the error of the sub-diagonal element. However, in the case where the frequency coupling degree >>1, λ Y,n ( λ Z,n ) −1 's condition will no longer be satisfied, and the relative errors of impedance and admittance will no longer satisfy the "0-1" dual characteristic, and 's waveforms will no longer conform to the "0-1" dual characteristic.

[0107] For the second case, it shows that the sub-diagonal element error is very large. In this case, the relative errors of impedance and admittance increase simultaneously and do not conform to the "0-1" duality characteristic.

[0108] Therefore, regardless of the case, the judgment and The accuracy of the criterion lies in determining whether it conforms to the "0-1" duality characteristic.

[0109] Based on the "0-1" characteristic dynamic division theory error evaluation frequency band of the transfer function, the objective identification of the error acceptable range can be realized, avoiding misjudgment or missed judgment caused by the setting of empirical thresholds.

[0110] In some specific embodiments, the theoretical relative error evaluation frequency band Freq satisfies:

[0111] In the formula, ξ is the upper limit of the preset measurement allowable error.

[0112] By introducing the upper limit of the measurement allowable error ξ and constructing a segmented frequency band judgment formula, the allowable deviation range of the "0-1" characteristic is quantified, improving the objectivity and repeatability of the frequency band division and reducing the influence of subjective experience on the evaluation results.

[0113] Step S4, calculate the theoretical relative error when calculating the SISO sequence impedance / admittance by the decoupling method in the theoretical relative error evaluation frequency band.

[0114] Directly calculate the relative error when calculating the SISO sequence admittance / impedance by the decoupling method within the theoretical error evaluation frequency band, which is convenient for dynamically correcting the error model in combination with the coupled frequency response signal in the subsequent steps, ensuring that the evaluation result is consistent with the actual swept frequency data, and improving the accuracy and engineering applicability of the error quantification.

[0115] In some specific embodiments, the theoretical relative error includes: The theoretical relative error of the SISO positive sequence admittance on the device side ; ; The theoretical relative error of the SISO negative sequence admittance on the device side ; ; The theoretical relative error of the SISO positive sequence-negative sequence coupled admittance on the device side ; ; The theoretical relative error of the SISO negative sequence-positive sequence coupled admittance on the device side ; ; The SISO positive sequence impedance on the device side The theoretical relative error ; The SISO negative-sequence impedance on the device side The theoretical relative error ; The SISO positive-sequence to negative-sequence coupling impedance on the device side The theoretical relative error ; The SISO negative-sequence to positive-sequence coupling impedance on the device side The theoretical relative error .

[0116] By defining the types of theoretical relative errors of the positive-sequence / negative-sequence admittances, impedances and their coupling terms on the device side, it covers the multi-dimensional error sources of the impedance model and provides a comprehensive error evaluation framework for complex frequency coupling scenarios.

[0117] In some specific embodiments, when the swept-frequency measurement injects positive-sequence voltage perturbations and negative-sequence voltage perturbations of multiple frequencies into the target device in series, the calculation formula of the theoretical relative error includes:

[0118]

[0119]

[0120]

[0121] Among them, The calculation formula of

[0122] The calculation formula of

[0123] The calculation formula of

[0124] The calculation formula of .

[0125] In some specific embodiments, when the swept-frequency measurement injects positive-sequence current perturbations and negative-sequence current perturbations of multiple frequencies into the target device in parallel, the calculation formula of the theoretical relative error includes:

[0126]

[0127]

[0128] 。

[0129] Taking the positive sequence perturbation as an example, according to and , and The relationship between them is as follows:

[0130]

[0131] Define :

[0132] It can be deduced that:

[0133] Similarly, it can be defined as :

[0134] Then the relative error evaluation calculation of the positive sequence impedance is as follows:

[0135] For the error evaluation of the negative sequence admittance and impedance, only need to replace with , and change the subscript p in the remaining parameters to subscript n.

[0136] Since in the approximate equal relationship of the above relational expressions, the approximate value has a very small deviation from the actual value. For the convenience of calculation, the approximate equal sign is regarded as an equal sign in the calculation of this scheme.

[0137] By constructing a theoretical error calculation formula, the swept frequency data is directly mapped to the error quantization result, avoiding relying on idealized assumptions and ensuring the consistency of the evaluation process with the real measurement data In some specific embodiments, it further includes step S5: setting the allowable error standard, comparing the absolute value of the theoretical relative error with the absolute value of the allowable error standard, and taking the frequency band where the absolute value of the theoretical relative error is less than or equal to the absolute value of the allowable error standard as the applicable frequency band of the decoupling method.

[0138] By setting the allowable error standard and comparing it with the theoretical relative error, the applicable frequency band boundary of the decoupling method is clarified, providing a quantitative basis for the impedance model selection in actual engineering and avoiding the risk of misjudging stability caused by excessive errors.

[0139] In some specific embodiments, it further includes step S6: within the applicable frequency band of the decoupling method, calculate the SISO sequence admittance using the decoupling method, and then calculate the corresponding MIMO sequence admittance using the theoretical error compensation formula, where the theoretical error compensation formula includes:

[0140]

[0141] In the formula, is the MIMO positive sequence admittance; is the MIMO negative sequence admittance; is the MIMO positive sequence-negative sequence coupling admittance; is the MIMO negative sequence-positive sequence coupling admittance.

[0142] In a specific embodiment, the method for evaluating the impedance / admittance theoretical error includes: Step S1, perform a swept-frequency measurement on the target device, and obtain the response signals at each frequency by injecting perturbation signals at each frequency The perturbation signals include voltage perturbation signals and current perturbation signals, and the response signals include voltage response signals and current response signals. The frequencies include positive sequence frequencies , negative sequence frequencies , and power frequency , where = 50 Hz; Injecting the perturbation signals at each frequency includes , , , , , where: represents the positive sequence perturbation voltage phasor injected at the frequency ; represents the negative sequence perturbation voltage phasor injected at the frequency ; represents the positive sequence perturbation current phasor injected at the frequency ; represents the negative sequence perturbation current phasor injected at the frequency ; The voltage response signals include , , , , where: represents the positive-sequence voltage phasor at the frequency after injecting a positive-sequence disturbance voltage / current; The meaning of is: after injecting a positive-sequence disturbance voltage / current, if >0, it represents the negative-sequence voltage phasor at the frequency ; if <0, it represents the conjugate positive-sequence voltage phasor at the frequency represents the negative-sequence voltage phasor at the frequency after injecting a negative-sequence disturbance voltage / current; represents the positive-sequence voltage phasor at the frequency after injecting a negative-sequence disturbance voltage / current; The current response signal includes , , , , where: represents the positive-sequence current phasor at the frequency after injecting a positive-sequence disturbance voltage / current; The meaning of is: after injecting a positive-sequence disturbance voltage / current, if >0, it represents the negative-sequence current phasor at the frequency ; if <0, it represents the conjugate positive-sequence current phasor at the frequency represents the negative-sequence current phasor at the frequency after injecting a negative-sequence disturbance voltage / current; represents the positive-sequence current phasor at the frequency after injecting a negative-sequence disturbance voltage / current.

[0143] Step S2, calculate and , is the transfer function of the disturbance signal and the response signal, including the transfer function when injecting a positive-sequence disturbance and the transfer function when injecting a negative-sequence disturbance; When the frequency sweep measurement is to inject positive-sequence voltage disturbances and negative-sequence voltage disturbances of multiple frequencies into the target device in series, is , and the expression is:

[0144] For , the expression is: ; When the swept frequency injects positive-sequence current disturbances and negative-sequence current disturbances of multiple frequencies into the target device in parallel, For , the calculation formula is:

[0145] For , the calculation formula is: .

[0146] Step S3, screen and frequency bands that meet the "0-1" characteristic, and use and frequency bands that meet the "0-1" characteristic as the theoretical relative error evaluation frequency bands; Among them, and meeting the "0-1" characteristic means that when the ratio of the source-side impedance to the device-side impedance approaches infinity, approaches 0 and approaches 1; when the ratio of the source-side impedance to the device-side impedance approaches zero, approaches 1 and approaches 0; The theoretical relative error evaluation frequency band Freq meets:

[0147] In the formula, ξ is the preset upper limit of the measurement allowable error.

[0148] Step S4, calculate the theoretical relative error when calculating the decoupling method for SISO sequence impedance / admittance in the theoretical relative error evaluation frequency band, including: The theoretical relative error of the device-side SISO positive-sequence admittance ; The theoretical relative error of the device-side SISO negative-sequence admittance ; The theoretical relative error of the device-side SISO positive-sequence-negative-sequence coupling admittance ; The theoretical relative error of the device-side SISO negative-sequence-positive-sequence coupling admittance ; Theoretical relative error of the SISO positive sequence impedance on the device side ; ; Theoretical relative error of the SISO negative sequence impedance on the device side ; ; Theoretical relative error of the SISO positive sequence - negative sequence coupling impedance on the device side ; ; Theoretical relative error of the SISO negative sequence - positive sequence coupling impedance on the device side ; ; When the swept - frequency measurement injects positive - sequence voltage disturbances and negative - sequence voltage disturbances of multiple frequencies into the target device in series, the calculation formula for the theoretical relative error includes:

[0149]

[0150]

[0151]

[0152] When the swept - frequency measurement injects positive - sequence current disturbances and negative - sequence current disturbances of multiple frequencies into the target device in parallel, the calculation formula for the theoretical relative error includes:

[0153]

[0154]

[0155]

[0156] Among them, The calculation formula is:

[0157] The calculation formula is:

[0158] The calculation formula is:

[0159] The calculation formula is: ;

[0160] Step S5, set the allowable error standard, compare the absolute value of the theoretical relative error with the absolute value of the allowable error standard, and use the frequency band where the absolute value of the theoretical relative error is less than or equal to the absolute value of the allowable error standard as the applicable frequency band for the decoupling method.

[0161] Step S6, within the applicable frequency band of the decoupling method, calculate the SISO sequence admittance using the decoupling method, and then calculate the corresponding MIMO sequence admittance using the theoretical error compensation formula. The theoretical error compensation formula includes:

[0162]

[0163] In the formula, is the MIMO positive sequence admittance; is the MIMO negative sequence admittance; is the MIMO positive sequence-negative sequence coupling admittance; is the MIMO negative sequence-positive sequence coupling admittance.

[0164] In MATLAB, a grid-forming converter using virtual synchronous generator (VSG) control is measured by frequency sweeping. The parameters of the grid-forming converter are shown in Table 1: Table 1 Grid-forming Converter Parameter Table

[0165] Since the grid-forming converter cannot operate in an environment with an extremely low short-circuit ratio, an ideal voltage source in series with a resistor is adopted on the source side. After testing, this type of grid-forming converter can operate stably in the range of short-circuit ratio (SCR) = 0.5 - 15. Therefore, the short-circuit ratios of 1, 3, and 7 are selected for frequency sweeping and data comparison.

[0166] During simulation, multi-sine signals are injected by means of a series voltage harmonic source. The measurement process of the inverse method is as follows: During the first measurement, a positive sequence perturbation is injected. The three-phase positive sequence harmonic frequencies injected within the frequency band of 100 Hz are 5, 10... 95 Hz, with an interval of 5 Hz; the harmonics injected within the frequency band of 100 - 1000 Hz are 105, 144... 973 Hz, and the harmonic interval is 39 Hz. During the second measurement, a negative sequence perturbation is injected. The three-phase negative sequence harmonic frequencies injected within the frequency band of 100 Hz are , that is, -95, -90... -5 Hz. Since there is no negative frequency, in fact, a positive sequence perturbation of 95, 90... 5 Hz is injected; within the range of 100 - 1000 Hz, , that is, a negative sequence perturbation of 5, 44,... 873 Hz is injected. The positive sequence and negative sequence voltage perturbations are injected in two times, and the voltages , , and , the current , , and . Then calculate the MIMO impedance / admittance.

[0167] The decoupling method injects positive and negative sequence perturbations once. The injection of the positive sequence perturbation is the same as that of the inversion method. The negative sequence perturbation injects three-phase negative sequence harmonic frequencies -92, -87... -2Hz in the frequency band within 100Hz, and injects negative sequence perturbations of 8, 47,... 876Hz in the range of 100 - 1000Hz. Then calculate the SISO impedance / admittance.

[0168] Figure 2 It is a schematic diagram of the relative error of the impedance / admittance of the grid-forming converter when Rg = 0.1Ω. As Figure 2 shown, when Rg = 0.1Ω, except near the power frequency resonance peak (40~60Hz), the admittance error is generally less than the impedance error; except for the part near the power frequency resonance peak (40 - 60Hz), is greater than , generally tends to 1 while tends to 0. , The waveforms of , are consistent with those of , and , ;

[0169] Figure 3 It is a schematic diagram of the relative error of the impedance / admittance of the grid-forming converter when Rg = 3Ω. As Figure 3 shown, the impedance error is generally less than the admittance error. Except for the frequency band of 200 - 400Hz, tends to 1 while tends to 0.

[0170] Figure 4 It is a schematic diagram of the frequency coupling degree of the impedance / admittance of the grid-forming converter. Figure 5 It is a schematic diagram of the impedance of the grid-forming converter when Rg = 0.1Ω. Figure 6 It is a schematic diagram of the impedance of the grid-forming converter when Rg = 3Ω. Figure 7 It is a schematic diagram of the admittance of the grid-forming converter when Rg = 0.1Ω. Figure 8 It is a schematic diagram of the admittance of the grid-forming converter when Rg = 3Ω.

[0171] Comparing R g = 0.1Ω andR g For two operating conditions of = 3Ω, it can be known that R g when = 0.1Ω, the relative error of the admittance model is smaller than that of the impedance model, while R g when = 3Ω, the conclusion is opposite.

[0172] Using the evaluation method of impedance / admittance theoretical error in this embodiment to judge the effective frequency band of decoupled sequence impedance / admittance, setting 0.2 as the allowable error standard, corresponding to the upper bound of the absolute error of the amplitude ±1.58 dB and the upper bound of the absolute error of the phase ±11.48°, the frequency bands that meet the allowable error standard are shown in Table 2: Table 2 Frequency Bands Meeting the Allowable Error Standard

[0173] The following is an embodiment of the impedance / admittance theoretical error evaluation system provided by this application. The impedance / admittance theoretical error evaluation system and the impedance / admittance theoretical error evaluation methods in the above embodiments belong to the same inventive concept. For the details not described in detail in the embodiment of the impedance / admittance theoretical error evaluation system, reference can be made to the embodiments of the impedance / admittance theoretical error evaluation methods above.

[0174] Now, the mobile terminals implementing various embodiments of this application will be described with reference to the drawings. In the subsequent description, the suffixes such as "module", "component", or "unit" used to represent elements are only for the convenience of explaining the embodiments of this application, and they have no specific meaning themselves. Therefore, "module" and "component" can be used interchangeably.

[0175] As Figure 9 shown, the impedance / admittance theoretical error evaluation system includes: A sweep frequency measurement module, configured to perform sweep frequency measurement on a target device, and obtain response signals at various frequencies by injecting perturbation signals at various frequencies; A transfer function calculation module, configured to calculate the transfer function of the perturbation signal and the response signal 、 and ; A frequency band screening module, configured to screen and frequency bands that meet the "0-1" characteristic, and use and the frequency bands that meet the "0-1" characteristic as the theoretical relative error evaluation frequency bands; A theoretical relative error calculation module, configured to calculate the theoretical relative error in the theoretical relative error evaluation frequency band.

[0176] The impedance / admittance theoretical error evaluation system of this embodiment is used to implement the impedance / admittance theoretical error evaluation method, and the steps include: S1. Perform swept-frequency measurement on the target device. By injecting disturbance signals at various frequencies to obtain the response signals at various frequencies The disturbance signals include voltage disturbance signals and current disturbance signals, and the response signals include voltage response signals and current response signals. The frequencies include positive-sequence frequencies , negative-sequence frequencies and power-frequency frequencies , = 50 Hz; S2. Calculate and , is the transfer function of the disturbance signal and the response signal, including the transfer function when injecting positive-sequence disturbance ; S3. Screen and for frequency bands that satisfy the "0-1" characteristic, and use and the frequency bands that satisfy the "0-1" characteristic as the theoretical relative error evaluation frequency bands; Among them, and satisfying the "0-1" characteristic means that when the ratio of the source-side impedance to the device-side impedance tends to infinity, tends to 0 and tends to 1; when the ratio of the source-side impedance to the device-side impedance tends to zero, tends to 1 and tends to 0; S4. Calculate the theoretical relative error when calculating the SISO sequence impedance / admittance by the decoupling method in the theoretical relative error evaluation frequency band.

[0177] This application also provides an electronic device for implementing each embodiment of this application. The electronic device includes a memory, a processor, and a computer program stored on the memory and executable on the processor.

[0178] Those skilled in the art can understand that the structure of the electronic device involved in the embodiments of this application does not constitute a limitation on the electronic device. The electronic device may include more or fewer components than shown in the figure, or combine certain components, or have different component arrangements.

[0179] Figure 10 It is a schematic diagram of the hardware structure of an electronic device for implementing each embodiment of this application.

[0180] The electronic device includes, but is not limited to, components such as a processor, a memory, etc. Those skilled in the art can understand that the structure of the electronic device involved in the embodiments of the present application does not constitute a limitation on the electronic device. The electronic device may include more or fewer components than shown in the figure, or combine certain components, or have different component arrangements.

[0181] In the embodiments of the present application, the electronic device includes, but is not limited to, a laptop computer, a desktop computer, a workbench, a personal digital assistant, a server, a blade server, a mainframe computer, and other suitable computers. The electronic device may also represent various forms of mobile devices and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the embodiments of the present application described herein and / or claimed.

[0182] In the embodiments of the present application, the processor may be implemented by using at least one of an application specific integrated circuit (ASIC), a digital signal processor (DSP), a digital signal processing device (DSPD), a processor, a controller, a microcontroller, a microprocessor, and an electronic unit designed to execute the functions described herein. In some cases, such an implementation may be implemented in the controller. For a software implementation, an implementation such as a process or a function may be implemented with a separate software module that allows execution of at least one function or operation. The software code may be implemented by a software application (or program) written in any suitable programming language. The software code may be stored in the memory and executed by the controller.

[0183] In addition, the electronic device includes some functional modules not shown herein, which will not be elaborated herein.

[0184] Those skilled in the art to which the present application pertains can understand that various aspects of the electronic device provided by the present application can be implemented as a system, a method, or a program product. Therefore, various aspects of the present application can be specifically implemented in the following forms, namely: a complete hardware implementation, a complete software implementation (including firmware, microcode, etc.), or an implementation combining hardware and software aspects, which can be collectively referred to herein as "circuitry", "module", or "system".

[0185] The present application also provides a storage medium in which a program product capable of implementing the evaluation method for the theoretical error of impedance / admittance is stored. In some possible implementation manners, various aspects of the present application can also be implemented in the form of a program product, which includes program code. When the program product runs on a terminal device, the program code is used to cause the terminal device to execute the steps according to various exemplary embodiments of the present application described in the above "Exemplary Method" section of this specification.

[0186] The storage medium may adopt any combination of one or more readable media. The readable media may be a readable signal medium or a readable storage medium. The readable storage medium may, for example, but is not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the above. More specific examples (a non-exhaustive list) of the readable storage medium include: an electrical connection with one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0187] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An evaluation method for impedance / admittance theoretical errors, characterized in that, Including: S1. Perform a swept-frequency measurement on the target device. By injecting disturbance signals at various frequencies obtain the response signals at various frequencies . The disturbance signals include voltage disturbance signals and current disturbance signals, and the response signals include voltage response signals and current response signals. The frequencies include positive-sequence frequencies , negative-sequence frequencies and power-frequency frequencies, where = 50 Hz; S2. Calculate and , is the transfer function of the disturbance signal and the response signal, including the transfer function when a positive-sequence disturbance is injected, and the transfer function when a negative-sequence disturbance is injected; S3. Screening and screen the frequency bands that meet the "0-1" characteristic, and and take the frequency bands that meet the "0-1" characteristic as the theoretical relative error evaluation frequency bands; Among them, and satisfying the "0-1" characteristic means that when the ratio of the source-side impedance to the device-side impedance approaches infinity, approaches 0 and approaches 1; when the ratio of the source-side impedance to the device-side impedance approaches zero, approaches 1 and approaches 0; S4. Calculate the theoretical relative error when calculating the SISO sequence impedance / admittance by the decoupling method in the theoretical relative error evaluation frequency band.

2. The evaluation method according to claim 1, wherein It further includes step S5: Set the allowable error standard, compare the absolute value of the theoretical relative error with the absolute value of the allowable error standard, and use the frequency band with the absolute value of the theoretical relative error less than or equal to the absolute value of the allowable error standard as the applicable frequency band of the decoupling method.

3. The evaluation method according to claim 1, wherein In step S1, injecting the disturbance signals at each frequency includes , , , , where: Indicates the positive-sequence disturbance voltage phasor with an injection frequency of ; Indicates the negative sequence disturbance voltage phasor with an injection frequency of ; Indicates the positive-sequence disturbance current phasor with an injection frequency of ; Indicates the negative-sequence disturbance current phasor with an injection frequency of ; The voltage response signal includes , , , , where: Indicates the positive-sequence voltage phasor at the frequency after injecting a positive-sequence disturbance voltage / current under; Its meaning is: after injecting positive-sequence disturbance voltage / current, if > 0, it indicates the negative-sequence voltage phasor at ; if < 0, it indicates the conjugate phasor of the positive-sequence voltage at ; Indicates the negative-sequence voltage phasor at the frequency after injecting negative-sequence disturbance voltage / current; Indicates the positive-sequence voltage phasor at the frequency after injecting negative-sequence disturbance voltage / current; The current response signal includes , , , , where: Indicates the positive-sequence current phasor at the frequency after injecting a positive-sequence disturbance voltage / current ; The meaning is: after injecting the positive-sequence disturbance voltage / current, if > 0, it means the negative-sequence current phasor at ; if < 0, it means the conjugate phasor of the positive-sequence current at ; Indicates the negative-sequence current phasor at the frequency after injecting negative-sequence disturbance voltage / current; Indicates the positive-sequence current phasor at the frequency after injecting negative-sequence disturbance voltage / current.

4. The evaluation method according to claim 3, characterized in that, In step S1, the frequency sweep measurement includes: Inject positive-sequence voltage disturbances and negative-sequence voltage disturbances of multiple frequencies into the target device in series; Inject positive-sequence current disturbances and negative-sequence current disturbances of multiple frequencies into the target device in parallel.

5. The evaluation method according to claim 4, characterized in that In step S2, when the swept-frequency measurement injects positive-sequence voltage disturbances and negative-sequence voltage disturbances of multiple frequencies into the target device in series, is , and the expression is: For , the expression is: ； When the frequency sweep injects positive-sequence current disturbances and negative-sequence current disturbances of multiple frequencies into the target device in parallel, is , and the calculation formula is: For , the calculation formula is as follows: 。 6. The evaluation method according to claim 5, wherein In step S3, the theoretical relative error evaluation frequency band Freq satisfies: In the formula, ξ is the preset upper limit of the allowable measurement error.

7. The evaluation method according to claim 1, wherein In step S4, the theoretical relative error when calculating the SISO sequence impedance / admittance by the decoupling method includes: Device-side SISO forward admittance Theoretical relative error ; Device-side SISO negative-sequence admittance Theoretical relative error ; Device-side SISO positive-sequence - negative-sequence coupling admittance Theoretical relative error ; Device-side SISO negative-sequence to positive-sequence coupling admittance Theoretical relative error ; Device-side SISO positive-sequence impedance Theoretical relative error ; Device-side SISO negative-sequence impedance Theoretical relative error ; Device-side SISO positive-sequence - negative-sequence coupling impedance Theoretical relative error ; Device-side SISO negative-sequence to positive-sequence coupling impedance Theoretical relative error .

8. The evaluation method according to claim 7, wherein When the frequency sweep measurement is to inject positive-sequence voltage disturbances and negative-sequence voltage disturbances of multiple frequencies into the target device in series, the calculation formula of the theoretical relative error includes: Among them, The calculation formula is: The calculation formula is as follows: The calculation formula is as follows: The calculation formula is as follows: 。 9. The evaluation method according to any one of claims 2 or 8, characterized in that, It further includes step S6: Calculate the SISO sequence admittance using the decoupling method within the applicable frequency band of the decoupling method, and then calculate the corresponding MIMO sequence admittance using the theoretical error compensation formula. The theoretical error compensation formula includes: In the formula, is the MIMO forward admittance; is the MIMO negative-sequence admittance; is the MIMO forward - reverse coupling admittance; is the MIMO negative-sequence to positive-sequence coupling admittance.

10. An evaluation system for impedance / admittance theoretical error, characterized in that, For implementing the impedance / admittance theoretical error evaluation method as described in any one of claims 1-9, including: A frequency sweep measurement module for performing a frequency sweep measurement on the target device and obtaining response signals at each frequency by injecting disturbance signals at each frequency; Transfer function calculation module, used to calculate the transfer function of the disturbance signal and the response signal 、 and ; A frequency band screening module for screening and frequency bands that meet the "0-1" characteristic, and use and the frequency bands that meet the "0-1" characteristic as the theoretical relative error evaluation frequency bands; A theoretical relative error calculation module for calculating the theoretical relative error in the theoretical relative error evaluation frequency band.

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