Harmonic analysis method and system for power distribution network

Abstract

The invention relates to a power distribution network harmonic analysis method and system, and the method comprises the steps: constructing a digital twinborn model of a power distribution network region, and selecting transformers in the region as analysis objects one by one; for each analysis object, various working conditions are simulated by changing the transformation ratio of the analysis object in a digital twin model, and voltage and current waveforms are collected and subjected to Fourier decomposition to obtain harmonic phasors; thirdly, performing phase reduction on the phasor data, separating a real part from an imaginary part to construct a matrix, and solving a harmonic coefficient matrix by using a least square method to realize error minimization; separating linear and nonlinear parts of the harmonic current, and calculating a harmonic emission capability parameter and a harmonic current risk parameter for quantitative evaluation; according to the method, all transformers are traversed and analyzed, and systematic harmonic evaluation of the whole power distribution network area is finally realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power distribution network, and particularly relates to a power distribution network harmonic analysis method and system. BACKGROUND

[0002] With the wide application of power electronic devices such as energy storage and photovoltaic and nonlinear loads, the harmonic pollution problem of power distribution network is increasingly serious, which not only threatens the stable operation of power system and the safety of equipment, but also interferes with the protection device and aggravates the risk of power grid. Under this background, the high requirement of users on power quality and the urgent demand of safe operation of power grid make it necessary to effectively control harmonic pollution. The basis of all control strategies is to accurately identify the harmonic source in the comprehensive load, which not only needs to qualitatively judge the existence of harmonic source, but also more importantly needs to quantitatively analyze the proportion of linear and nonlinear components in the load and their dynamic changes, so as to provide a scientific basis for realizing fine load characteristic evaluation, harmonic responsibility division and comprehensive control. SUMMARY

[0003] The present application relates to the technical field of power distribution network, and particularly relates to a power distribution network harmonic analysis method and system.

[0004] To achieve the above-mentioned purpose, according to the first aspect of the present application, a power distribution network harmonic analysis method is provided, comprising the following steps: Step S1, a digital twin model is constructed for the power distribution network area to be analyzed, and a transformer to be analyzed is selected as a current analysis object; Step S2, the voltage waveform and current waveform of the current analysis object under different variable ratios are recorded in the digital twin model, and the voltage waveform and current waveform under different variable ratios are subjected to Fourier decomposition to obtain voltage phasor representation and current phasor representation of the fundamental wave and hth harmonic under different variable ratios; h is the harmonic order; Step S3, the voltage phasor representation and current phasor representation of the fundamental wave and hth harmonic under different variable ratios are reduced to a reference point with the fundamental wave voltage phase being 0, and the real part and imaginary part of the voltage and current of hth harmonic under different variable ratios are separated, respectively, and the voltage matrix and current matrix are constructed according to the real part and imaginary part of the voltage and current of hth harmonic under different variable ratios; Step S4, based on the least square method, the voltage matrix and current matrix are used to solve the harmonic coefficient matrix, so that the sum of squares of real part and imaginary part of harmonic current error is minimized; Step S5, the linear part and nonlinear part of hth harmonic current are calculated according to the harmonic coefficient matrix, and the harmonic emission capability parameter and harmonic current risk of the current analysis object are calculated according to the nonlinear part; Step S6: Determine if there are any unanalyzed transformers. If so, select the next transformer to be analyzed as the current analysis object and repeat steps S2 to S6. If not, end the process.

[0005] In some embodiments, step S3, constructing the voltage matrix and current matrix based on the real and imaginary parts of the voltage and current of the h-th harmonic under different turns ratios, includes: The voltage matrix is ​​represented as follows: , in ; The current matrix includes a real part matrix and an imaginary part matrix; The real part matrix of the current is represented as: ; The imaginary part matrix of the current is represented as: ; in, Let be the harmonic matrix corresponding to the voltage waveform of the nth turns ratio, where N is the number of different turns ratios, α represents the real part, and β represents the imaginary part. Let T denote the fundamental frequency, and T denote the matrix transpose.

[0006] In some embodiments, in step S4, the harmonic coefficient matrix includes: ; ; in, The harmonic coefficient matrices are calculated using the least squares method. The coefficients in; The harmonic coefficient matrices are calculated using the least squares method. The coefficients in.

[0007] In some embodiments, step S5, calculating the linear and nonlinear portions of the h-th harmonic current based on the harmonic coefficient matrix, includes:

[0008]

[0009] Among them, I h For the h-th harmonic current, I hL For the linear component of the h-th harmonic current, I hNonL V represents the nonlinear component of the h-th harmonic current. h For the h-th harmonic voltage, Y hα and Y hβ It represents the real and imaginary parts of the h-th harmonic admittance matrix for the linear load component, where h ≥ 2.

[0010] In some embodiments, the harmonic emission capability parameter in step S5 is: .

[0011] In some embodiments, the harmonic current risk in step S5 is: S N The rated capacity of the object being analyzed.

[0012] According to a second aspect of the present invention, a power distribution network harmonic analysis system is provided, comprising a module for performing the method described in the first aspect of the present invention.

[0013] According to a third aspect of the present invention, an electronic device is provided, comprising: A communication interface used for communicating with other electronic devices; Memory is used to store computer program instructions; A processor for executing the computer program instructions to support the electronic device in implementing the method according to the first aspect of the invention.

[0014] According to a fourth aspect of the present invention, a computer program product is provided, comprising computer program instructions that instruct a computer device to perform an operation corresponding to the method described in the first aspect of the present invention.

[0015] The present invention has the following beneficial effects: By sampling multiple sets of data using digital twin technology, the difficult and arduous on-site measurement operations in the actual power grid are completely avoided, significantly reducing workload and implementation difficulty. Simultaneously, digital twin technology can simulate various operating states, generating massive amounts of simulated data, providing a rich data foundation for harmonic analysis. This effectively overcomes the problems of limited monitoring points and insufficient historical data in actual distribution networks, thereby improving the accuracy and reliability of the final analysis results. The calculation of harmonic coefficients based on the least squares method considers the coupling relationship between different harmonics, enabling more precise separation of linear and nonlinear components in the load, thus significantly improving the accuracy of the harmonic model. The "harmonic emission capability parameter" and "harmonic risk parameter" can quantitatively assess the potential of each transformer as a harmonic source and its actual risk to the power grid, making the harmonic situation of the entire area readily apparent. This facilitates maintenance personnel in quickly identifying key harmonic sources and developing mitigation strategies. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings required in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of a power distribution network harmonic analysis method according to an embodiment of the present invention. Detailed Implementation

[0018] The detailed description of the accompanying drawings is intended to illustrate the present embodiments of the invention and is not intended to represent only the forms in which the invention can be implemented. It should be understood that the same or equivalent functions can be accomplished by different embodiments intended to be included within the spirit and scope of the invention.

[0019] like Figure 1 As shown, one embodiment of the present invention provides a method for harmonic analysis of a power distribution network, comprising the following steps: Step S1: Construct a digital twin model for the distribution network area to be analyzed, and select a transformer to be analyzed as the current analysis object; Specifically, a digital twin model is created based on the distribution network area to be analyzed. Information such as the line topology, equipment parameters, and load status of the area is input into the platform to build an overall calculation example and construct a digital twin model of the area. All transformers in the area are numbered k=1,2,3...n, and the kth transformer is selected for analysis. Step S2: Record the voltage and current waveforms of the current analysis object under different turns ratios in the digital twin model, and perform Fourier decomposition on the voltage and current waveforms under different turns ratios to obtain the voltage phasor representation and current phasor representation of the fundamental wave and h-th harmonic under different turns ratios; h is the harmonic order. Specifically, the current and voltage waveforms of the k-th transformer are recorded in the digital twin model. Fourier decomposition of the current and voltage waveforms can be performed to obtain the amplitude and phase of the fundamental wave (voltage + current) and the h-th harmonic (voltage + current). Based on the above method, the transformer turns ratio can be modified to measure N sets of current and voltage waveforms, and Fourier decomposition can be performed on each to obtain N sets of data. Each set of data includes the voltage phasor representation and current phasor representation of the fundamental wave and the h-th harmonic. The voltage phasor representation and the current phasor representation are denoted as: ; Where n represents the nth transformation ratio, and h represents the harmonic order. Let v represent phase, v represent voltage, and i represent current. Step S3: The voltage phasor representations and current phasor representations of the fundamental wave and the h-th harmonic under different turns ratios are reduced to the reference point where the phase of the fundamental wave voltage is 0, and the real and imaginary parts of the voltage and current of the h-th harmonic under different turns ratios are separated respectively. The voltage matrix and current matrix are constructed based on the real and imaginary parts of the voltage and current of the h-th harmonic under different turns ratios. Specifically, the voltage and current vectors mentioned above are reduced to their values ​​when the fundamental voltage phase is 0 using the formula. The real and imaginary parts are then separated, with the real part represented by α and the imaginary part by β, as follows:

[0020]

[0021]

[0022]

[0023] Where n represents the nth transformation ratio, and h represents the harmonic order. Let v represent phase, v represent voltage, and i represent current. Indicates the phase of the fundamental voltage; Step S4: Based on the least squares method, solve the harmonic coefficient matrix using the voltage matrix and current matrix to minimize the sum of squares of the errors of the real and imaginary parts of the harmonic current. Specifically, the method in this embodiment uses the least squares principle to solve the harmonic coefficient matrix. By substituting the voltage matrix and current matrix constructed in step S3 into a specific least squares formula, an optimal set of harmonic coefficients is calculated. This set of coefficients can ensure that the sum of squared errors between the real and imaginary parts of the harmonic current calculated by the model and the actual measured values ​​(in the digital twin model) is minimized, thereby achieving accurate fitting of the harmonic characteristics of the system.

[0024] Least squares is a classic mathematical optimization method. Its core idea is to find the best function fit for data by minimizing the sum of squares of errors. When a set of observation data exists, least squares attempts to find a mathematical model that minimizes the sum of squares of the deviations (i.e., errors) between the model's predicted values ​​and the actual observed values. This method is particularly suitable for processing actual measurement data containing noise or uncertainty, because squaring can amplify the influence of large errors, making the fitting results more sensitive to outliers and improving the overall robustness of the fit.

[0025] In this embodiment, the least squares method is used to calculate the harmonic coefficient matrix. The goal is to find an optimal set of harmonic coefficients that minimizes the sum of squared errors between the harmonic currents (including real and imaginary parts) calculated based on these coefficients and the harmonic currents actually measured (simulated) through a digital twin model. In this way, the linear and nonlinear components in the load can be accurately separated, thereby achieving accurate modeling and analysis of the harmonic state of the distribution network and improving the accuracy of harmonic analysis.

[0026] Step S5: Calculate the linear and nonlinear components of the h-th harmonic current based on the harmonic coefficient matrix, and calculate the harmonic emission capability parameters and harmonic current risk of the current analysis object based on the nonlinear component. Specifically, step S5 aims to quantify the harmonic impact of the current analysis object. First, using the harmonic coefficient matrix calculated in step S4, the h-th harmonic current is precisely decomposed into linear and nonlinear parts. Then, based on the magnitude of the nonlinear part, two key evaluation indicators are defined and calculated: one is the harmonic emission capability parameter, which characterizes the transformer's ability to generate harmonics; the other is the harmonic current risk parameter, which assesses the actual risk level to the power grid by normalizing the nonlinear current according to the transformer capacity.

[0027] Step S6: Determine if there are any unanalyzed transformers. If so, select the next transformer to be analyzed as the current analysis object and repeat steps S2 to S6. If not, end the process.

[0028] Specifically, step S6 is a loop control step that ensures a comprehensive analysis of the entire power distribution network area. This step determines whether there are any unanalyzed transformers in the area (i.e., whether k equals N). If there are (k is less than N), the next transformer is selected as the new current analysis object (at this time k = k + 1), and the complete analysis process from step S2 to step S5 is repeated until all transformers have been analyzed, thereby achieving a systematic assessment of the harmonic status of the entire area.

[0029] As described above, the method in this embodiment uses digital twin technology to sample multiple sets of data, completely avoiding the difficult and arduous on-site measurement operations in the actual power grid, significantly reducing workload and implementation difficulty. Simultaneously, digital twin technology can simulate various operating states, generating massive amounts of simulated data, providing a rich data foundation for harmonic analysis, effectively overcoming the problems of few monitoring points and insufficient historical data in actual distribution networks, thereby improving the accuracy and reliability of the final analysis results. The calculation of harmonic coefficients based on the least squares method considers the coupling relationship between each harmonic, enabling more precise separation of linear and nonlinear components in the load, thus significantly improving the accuracy of the harmonic model. The "harmonic emission capability parameter" and "harmonic risk parameter" can quantitatively assess the potential capability of each transformer as a harmonic source and its actual risk to the power grid, making the harmonic status of the entire area readily apparent, facilitating maintenance personnel to quickly identify key harmonic sources and formulate mitigation strategies.

[0030] In some embodiments, step S3, constructing the voltage matrix and current matrix based on the real and imaginary parts of the voltage and current of the h-th harmonic under different turns ratios, includes: The voltage matrix is ​​represented as follows: , in ; The current matrix includes a real part matrix and an imaginary part matrix; The real part matrix of the current is represented as: ; The imaginary part matrix of the current is represented as: ; in, Let be the harmonic matrix corresponding to the voltage waveform of the nth turns ratio, where N is the number of different turns ratios, α represents the real part, and β represents the imaginary part. Let T denote the fundamental frequency, and T denote the matrix transpose.

[0031] In some embodiments, in step S4, the harmonic coefficient matrix includes: ; ; in, The harmonic coefficient matrices are calculated using the least squares method. The coefficients in; The harmonic coefficient matrices are calculated using the least squares method. The coefficients in.

[0032] In some embodiments, step S5, calculating the linear and nonlinear portions of the h-th harmonic current based on the harmonic coefficient matrix, includes:

[0033]

[0034] Among them, I h For the h-th harmonic current, I hL For the linear component of the h-th harmonic current, I hNonL V represents the nonlinear component of the h-th harmonic current. h For the h-th harmonic voltage, Y hα and Y hβ It represents the real and imaginary parts of the h-th harmonic admittance matrix for the linear load component, where h ≥ 2.

[0035] In some embodiments, the harmonic emission capability parameter in step S5 is: .

[0036] Specifically, the nonlinear current proportion of all transformers in the analysis region is calculated and analyzed one by one. The proportion of the h-th harmonic nonlinear current of the k-th transformer is denoted as... The harmonics are statistically classified according to their order of harmonics and sorted in descending order. For example, when h=3, the focus is on the 3rd harmonic in the analysis area. The harmonic source with the largest proportion of 3rd harmonics in the analysis area is the one that needs to be focused on. The magnitude of represents the ability of the k-th transformer harmonic source to generate h-th harmonics. When the load on the transformer increases, the harmonic current of the corresponding order will increase accordingly.

[0037] In some embodiments, the harmonic current risk in step S5 is: S N The rated capacity of the object being analyzed.

[0038] Specifically, the nonlinear current magnitudes of all transformers in the analysis region are calculated one by one, and normalized according to the transformer capacity. The calculated result of the h-th order nonlinear current normalization parameter of the k-th transformer is denoted as... , This characterizes the current harmonic current risk of the k-th transformer, when When the harmonic current is relatively small, the impact of the transformer's harmonic current on the power grid is minimal; conversely, when it is relatively large, the impact is greater and requires close monitoring.

[0039] Another embodiment of the present invention provides a power distribution network harmonic analysis system, including a module for performing the power distribution network harmonic analysis method described in the above embodiments.

[0040] It should be noted that the system provided in this embodiment can be used to execute the methods described in the above embodiments. Therefore, the contents not described in detail in this embodiment can be obtained by referring to the contents of the methods in the above embodiments, and will not be repeated here.

[0041] Another embodiment of the present invention provides an electronic device, comprising: A communication interface used for communicating with other electronic devices; Memory is used to store computer program instructions; A processor is configured to execute the computer program instructions to support the electronic device in implementing the methods described in the embodiments above.

[0042] In this embodiment, the memory mainly includes a program storage area and a data storage area. The program storage area can store the operating device, applications required for at least one function, etc., and the data storage area can store related data, etc. Furthermore, the memory can be a high-speed random access memory, or a non-volatile memory, such as a plug-in hard disk, a smart media card (SMC), a secure digital card (SD), and a flash card, or other volatile solid-state storage devices.

[0043] The processor can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor, or the processor can be any conventional processor. The processor is the control center of the electronic device and uses various interfaces and lines to connect the various parts of the electronic device.

[0044] Another embodiment of the present invention provides a computer program product including computer program instructions that instruct a computer device to perform operations corresponding to the methods described in the above embodiments.

[0045] Specifically, the computer program product includes a series of computer program instructions, which are codes written in a computer program. These instructions define how to perform specific operations. These instructions are designed to be loaded onto a computer device and instruct the device to perform specific operations, which refer to the various steps in the power distribution network harmonic analysis method described in the above embodiments. In this way, the computer program product of this embodiment provides a complete software solution that can run on various computer devices to implement the power distribution network harmonic analysis method described in the above embodiments.

[0046] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method of power distribution network harmonic analysis, characterized by, The method comprises the following steps: Step S1, constructing a digital twin model for a power distribution network region to be analyzed, and selecting a transformer to be analyzed as a current analysis object; Step S2, recording voltage waveforms and current waveforms of the current analysis object under different transformation ratios in the digital twin model, and performing Fourier decomposition on the voltage waveforms and current waveforms under the different transformation ratios to obtain voltage phasor representations and current phasor representations of fundamental waves and hth harmonics under the different transformation ratios; h is the harmonic order; Step S3, reducing the voltage phasor representations and current phasor representations of the fundamental waves and hth harmonics under the different transformation ratios to a reference point with a fundamental voltage phase of 0, and separating real parts and imaginary parts of the hth harmonic voltages and currents under the different transformation ratios, respectively, and constructing a voltage matrix and a current matrix according to the real parts and imaginary parts of the hth harmonic voltages and currents under the different transformation ratios; Step S4, based on the least square method, using the voltage matrix and the current matrix to solve a harmonic coefficient matrix, so that the sum of squares of real parts and imaginary parts of harmonic currents is minimized; Step S5, calculating a linear part and a nonlinear part of hth harmonic currents according to the harmonic coefficient matrix, and calculating a harmonic emission capability parameter and a harmonic current risk of the current analysis object according to the nonlinear part; Step S6, determining whether there is an unanalyzed transformer, if yes, selecting a next transformer to be analyzed as a current analysis object, and repeating steps S2 to S6, if not, ending.

2. The method of claim 1, wherein, In the step S3, the voltage matrix and the current matrix are constructed according to the real parts and imaginary parts of the hth harmonic voltages and currents under the different transformation ratios, which comprises: The voltage matrix is represented as: , wherein ; The current matrix comprises a current real part matrix and a current imaginary part matrix; The real part of the current matrix is represented as: ; The current imaginary matrix is expressed as: ; wherein, is the harmonic matrix corresponding to the voltage waveform of the nth ratio, N is the number of different ratios, a represents the real part and β represents the imaginary part, denotes the fundamental, and T denotes the matrix transpose.

3. The method of claim 2, wherein, In the step S4, the harmonic coefficient matrix comprises: ； ； wherein are coefficients in the harmonic coefficient matrix are coefficients in the harmonic coefficient matrix are coefficients in the harmonic coefficient matrix are coefficients in the harmonic coefficient matrix 4. The method of claim 3, wherein, In the step S5, the linear part and the nonlinear part of the hth harmonic currents are calculated according to the harmonic coefficient matrix, which comprises: where I h is the hth harmonic current, I hL is the linear part of the hth harmonic current, I hNonL is the nonlinear part of the hth harmonic current, V h is the hth harmonic voltage, Y hα and Y hβ are the real and imaginary parts of the hth harmonic admittance matrix of the linear load part, h≥2.

5. The method of claim 4, wherein, In the step S5, the harmonic emission capability parameter is: .

6. The method of claim 5, wherein, The step S5, the harmonic current risk is: where S N is the rated capacity of the current analysis object.

7. A power distribution network harmonic analysis system characterized by, The method comprises a module for executing the method of any one of claims 1 to 6.

8. An electronic device, comprising: The method comprises: a communication interface for communicating with other electronic devices; a memory for storing computer program instructions; a processor for executing the computer program instructions to support the electronic device to implement the method according to any one of claims 1 to 6.

9. A computer program product, characterised in that, The computer program instructions instruct a computer device to perform operations corresponding to the method of any one of claims 1 to 6. The computer program instructions instruct a computer device to perform operations corresponding to the method of any one of claims 1 to 6.

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