CN115201563A - Multi-harmonic source positioning method and system based on joint entropy - Google Patents

Abstract

The invention discloses a multi-harmonic source positioning method and a multi-harmonic source positioning system based on joint entropy, which comprises the following steps: acquiring the number of harmonic sources in the system and harmonic voltages of each measurement node; obtaining harmonic times and each harmonic current estimation value of each harmonic source through a harmonic voltage and harmonic state model of each measurement node; constructing a joint entropy matrix between harmonics with different times and harmonic sources according to harmonic voltage and harmonic times of each measurement node in the system and each harmonic current estimation value of each harmonic source based on a joint entropy method; collecting the joint entropy matrixes between all harmonics with different times and harmonic sources to obtain a joint entropy matrix set; and obtaining a harmonic source positioning result by combining the entropy matrix set, the harmonic times, the number of harmonic sources and the number of measurement nodes. The harmonic sources can be located without the need for prior knowledge of the system harmonic impedance and topology.

Description

A method and system for multi-harmonic source localization based on joint entropy

technical field

The present invention relates to the technical field of harmonic source location, in particular to a method and system for multi-harmonic source location based on joint entropy.

Background technique

The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

With the large-scale use of source loads based on power electronic devices such as photovoltaic inverters, electric vehicle charging piles, and new nonlinear household loads, the harmonic level in the power system has deteriorated, and the background harmonic content has increased significantly. The interaction between them is also increasing. If the amount of harmonic injection in the system exceeds a certain range, some power electronic devices will not work properly, and even lead to accelerated aging of the equipment. In addition, excessive harmonics can also lead to increased harmonic losses in the system. In order to reduce the harm caused by harmonics and improve the power quality, it is the primary task to accurately estimate the location of the harmonic source, which can provide effective reference information for power quality control such as harmonic control, filter installation and location selection.

At present, the harmonic source localization methods are divided into two categories based on equivalent circuit model and harmonic state estimation methods. The location method based on the equivalent circuit model is based on the Thevenin or Norton equivalent circuit analysis method, combined with the power direction method, the critical impedance method and the voltage-current ratio method, to determine the location of the harmonic source; the active power direction method is used by The proof cannot be used to accurately locate the dominant harmonic source from the system or user side, and the critical impedance method of reactive power to detect the location of the harmonic source, in this method, assuming the system and user side impedances are known, However, these two impedances are difficult to obtain in practice, so the concepts of voltage-to-current ratio difference and current-to-voltage ratio difference are proposed to locate the dominant harmonic voltage and harmonic current sources, respectively. When there are multiple harmonic sources, it is necessary to model each node in the system equivalently and analyze them one by one. Misjudgments may occur, limiting the use of such methods.

SUMMARY OF THE INVENTION

In order to solve the above problems, the present invention proposes a method and system for locating multi-harmonic sources based on joint entropy. It does not need to know the power grid parameters and topology structure of the system in advance, and only obtains the number of harmonic sources in the system and each measurement node The harmonic voltage can be located by analyzing the harmonic voltage data, which is easy to use in the actual power grid.

To achieve the above object, the present invention adopts the following technical solutions:

In the first aspect, a joint entropy-based multi-harmonic source localization method is proposed, including:

Obtain the number of harmonic sources in the system and the harmonic voltage of each measurement node;

Obtain the harmonic order and the estimated value of each harmonic current of each harmonic source through the harmonic voltage and harmonic state model of each measurement node;

Based on the joint entropy method, according to the harmonic voltage and harmonic order of each measurement node in the system and the estimated value of each harmonic current of each harmonic source, the joint entropy matrix between different order harmonics and harmonic sources is constructed. ;

Assemble the joint entropy matrices between all different harmonics and harmonic sources to obtain a joint entropy matrix set;

Through the joint entropy matrix set, the harmonic order, the number of harmonic sources and the number of measurement nodes, the harmonic source location results are obtained.

In the second aspect, a joint entropy-based multi-harmonic source localization system is proposed, including:

The data acquisition module is used to acquire the number of harmonic sources in the system and the harmonic voltage of each measurement node;

The harmonic current estimated value acquisition module is used to obtain the harmonic order and each harmonic current estimated value of each harmonic source through the harmonic voltage and harmonic state model of each measurement node;

The joint entropy matrix acquisition module is used to construct different orders of harmonics and harmonics based on the joint entropy method, according to the harmonic voltage and harmonic order of each measurement node in the system and the estimated value of each harmonic current of each harmonic source. Joint entropy matrix between wave sources;

The joint entropy matrix set acquisition module is used to collect the joint entropy matrices between all harmonics of different orders and harmonic sources to obtain the joint entropy matrix set;

The harmonic source location module is used to obtain the harmonic source location result by combining the entropy matrix set, the harmonic order, the number of harmonic sources and the number of measurement nodes.

In a third aspect, an electronic device is proposed, including a memory and a processor, and computer instructions stored in the memory and running on the processor, the computer instructions being executed by the processor to complete a joint entropy-based multivibration method The steps described in the wave source localization method.

In a fourth aspect, a computer-readable storage medium is provided for storing computer instructions that, when executed by a processor, complete the steps of a joint entropy-based multi-harmonic source localization method.

Compared with the prior art, the beneficial effects of the present invention are:

1. Aiming at the power system with multiple harmonic sources, the present invention proposes a method for locating harmonic sources based on joint entropy, which can only obtain the harmonics in the system without knowing the harmonic impedance and topology of the system in advance. The number of wave sources and the harmonic voltage of each measurement node, and the data of harmonic voltage can be analyzed to achieve accurate and fast positioning of multiple harmonic sources. This method can also find the location of unknown harmonic sources in the power system. , compared with the existing harmonic source localization method, it is necessary to ensure that at least one harmonic source in the system interacts with the system. This method can be generalized and applicable to any power grid structure. It is necessary to ensure the accurate location of the harmonic source in the power system. significant.

Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will become apparent from the description which follows, or may be learned by practice of the invention.

Description of drawings

The accompanying drawings that form a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application and do not constitute improper limitations on the present application.

1 is a flow chart of the method disclosed in Embodiment 1;

Fig. 2 is a test chart for verifying the validity and accuracy of the disclosed method of embodiment 1;

FIG. 3 is a graph showing the result of positioning of two harmonic sources using the method disclosed in Embodiment 1 when injecting harmonics at different times.

Detailed ways:

The present invention will be further described below with reference to the accompanying drawings and embodiments.

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural as well, furthermore, it is to be understood that when the terms "comprising" and/or "including" are used in this specification, it indicates that There are features, steps, operations, devices, components and/or combinations thereof.

Example 1

In this embodiment, a joint entropy-based multi-harmonic source localization method is disclosed, as shown in FIG. 1 , including:

S1: Obtain the number of harmonic sources in the system and the harmonic voltage of each measurement node.

S2: Obtain the harmonic order and the estimated value of each harmonic current of each harmonic source through the harmonic voltage and harmonic state model of each measurement node, including: preprocessing the harmonic voltage of each measurement node , obtain the preprocessed voltage of each measurement node;

According to the preprocessed voltage and harmonic state models of each measurement node, the harmonic order and the estimated value of each harmonic current of each harmonic source are obtained.

Among them, the harmonic order is determined according to the preprocessed voltage of each measurement node.

The harmonic voltage of each measurement node is preprocessed by moving average filtering method.

The construction process of the harmonic state model is as follows:

For the hth harmonic, the harmonic state equation is established, and the specific expression is (1):

表征第j个谐波源的第h次谐波电流估测值，

为获取的第i个测量节点的第h次谐波电压，Z_ij为第j个谐波源与第i个测量节点之间的谐波阻抗，h表示谐波次数，i表示测量节点的个数，i＝1，2，…，N；j表示谐波源的个数，j＝1，2，…，M。in,

is the estimated value of the h-th harmonic current characterizing the j-th harmonic source,

is the obtained h-th harmonic voltage of the i-th measurement node, Z _ij is the harmonic impedance between the j-th harmonic source and the i-th measurement node, h represents the harmonic order, and i represents the number of measurement nodes. number, i=1, 2,...,N; j represents the number of harmonic sources, j=1, 2,...,M.

In order to estimate the harmonic current matrix, obtain the harmonic current estimated value matrix, transform the harmonic state equation (1), and obtain the harmonic state model, the specific expression is (2):

和

分别为获取的谐波电压矩阵，谐波电流估测值矩阵和分离系数矩阵。in,

and

are the obtained harmonic voltage matrix, harmonic current estimated value matrix and separation coefficient matrix, respectively.

Substitute the harmonic voltage of each measurement node into the harmonic state model (2), and analyze it based on the iterative method to obtain the estimated value matrix of the harmonic current. The iterative expression is:

Among them, W is the pre-processed voltage data matrix after moving average filtering, f is a nonlinear function, k is the number of iterations, and Y _k is the separation coefficient matrix of the k-th iteration.

S3: Based on the joint entropy method, according to the harmonic voltage and harmonic order of each measurement node in the system, and the estimated value of each harmonic current of each harmonic source, construct the joint between different order harmonics and harmonic sources. Entropy matrix, specifically:

Obtain the amplitude of the harmonic voltage of each measurement node and the amplitude of each harmonic current estimated value of each harmonic source;

The amplitude of the harmonic voltage of each measurement node and the amplitude of the estimated value of each harmonic current of each harmonic source are formed into a variable set;

According to the variable set, construct the joint entropy matrix between different order harmonics and harmonic sources.

与第i个测量节点的谐波电压的幅值V_i，并组成变量集为

构建联合熵表示为式(4)：For the estimated value of the h-th harmonic current of the j-th harmonic source and the harmonic voltage of the i-th measurement node, obtain the amplitude of the estimated value of the h-th harmonic current of the j-th harmonic source

and the amplitude V _i of the harmonic voltage of the i-th measurement node, and form a variable set as

The construction of joint entropy is expressed as formula (4):

为变量集的联合概率分布值，L为变量长度。为简化表示式(4)，其联合熵值可表示为：

in

is the joint probability distribution value of the variable set, and L is the variable length. To simplify expression (4), its joint entropy value can be expressed as:

构成h次谐波与谐波源之间的联合熵矩阵为式(5)：By joint entropy value

The joint entropy matrix that constitutes the h-th harmonic and the harmonic source is equation (5):

S4: Assemble the joint entropy matrices between all harmonics of different orders and harmonic sources to obtain a joint entropy matrix set.

For all order harmonics considered in the system, the joint entropy matrix set {S ₁ , S ₂ , ..., S _H } formed by them is:

S5: Analyze the set of joint entropy matrices, the harmonic order, the number of harmonic sources and the number of measurement nodes through the multi-harmonic source localization algorithm to obtain the harmonic source localization result. When all the joint entropy matrices corresponding to a certain measurement node are When the joint entropy value of , is less than the set value, the node is the result of harmonic source location.

Specifically:

1) Input into the joint entropy matrix set {S ₁ , S ₂ ,..., S _H }: S ₁ , S ₂ ,..., S _H , M, N, H.

2) Loop 1: Suppose i=1,...,M

3) Loop 2: Suppose j=1,...,N

4) Loop 3: Suppose h=1,...,H

均小于设定阈值λ_thr，则第i个节点确定为高概率谐波源注入节点；反之为低概率谐波注入节点。5) If the joint entropy value of all harmonic orders is

are smaller than the set threshold λ _thr , the i-th node is determined as a high-probability harmonic source injection node; otherwise, it is a low-probability harmonic injection node.

6) End loop 3.

7) Loop 4: Suppose h=1,...,H-1

均小于设定阈值λ_thr，则第i个节点确定为中概率谐波源注入节点；反之为低概率谐波注入节点8) If the joint entropy value of all harmonic orders is

are smaller than the set threshold λ _thr , then the i-th node is determined as a medium-probability harmonic source injection node; otherwise, it is a low-probability harmonic injection node

9) End loop 4.

10) End loops 1 and 2.

11) Output the high-probability harmonic source injection node data set K _HS , which is the harmonic source localization result.

A joint entropy-based multi-harmonic source localization method disclosed in this embodiment is verified. Construct the single-line wiring diagram shown in Figure 2, select three different harmonic sources of office, residential and commercial types, and connect them to nodes 9, 20 and 36 respectively. The harmonic source can also be accurately located under time-varying conditions. The above three types of harmonic sources are selected as the harmonic injection system at two different times. The harmonic spectrum is shown in the table below.

The joint entropy calculated based on the harmonic source locating method proposed by the present invention at the above two different times can accurately locate the harmonic sources of three different nodes in the system, namely nodes 9, 20 and 36. The joint entropy calculation The results are shown in Figure 3. Figure 3 (a) is the harmonic source location result after the harmonics are injected into the system at 12:00; Figure 3 (b) is the harmonics after the harmonics are injected into the system at 18:00. Wave source location results.

It can be seen that the multi-harmonic source localization method based on joint entropy proposed in this embodiment can only use the measured harmonic voltage as the input quantity without needing to know the harmonic impedance and topology of the system in advance, that is, Accurate and fast positioning of multiple harmonic sources can be achieved, and the method can also find the location of unknown harmonic sources in the power system. Compared with the existing harmonic source positioning methods, it is necessary to ensure that there is at least one harmonic source in the system and the system There is interaction, the method can be generalized and applicable to any grid structure, which is of great significance to ensure the accurate location of harmonic sources in the power system.

Example 2

In this embodiment, a joint entropy-based multi-harmonic source localization system is disclosed, including:

The data acquisition module is used to acquire the number of harmonic sources in the system and the harmonic voltage of each measurement node;

The harmonic current estimated value acquisition module is used to obtain the harmonic order and each harmonic current estimated value of each harmonic source through the harmonic voltage and harmonic state model of each measurement node;

The joint entropy matrix acquisition module is used to construct different orders of harmonics and harmonics based on the joint entropy method, according to the harmonic voltage and harmonic order of each measurement node in the system and the estimated value of each harmonic current of each harmonic source. Joint entropy matrix between wave sources;

The joint entropy matrix set acquisition module is used to collect the joint entropy matrices between all harmonics of different orders and harmonic sources to obtain the joint entropy matrix set;

The harmonic source location module is used to obtain the harmonic source location result by combining the entropy matrix set, the harmonic order, the number of harmonic sources and the number of measurement nodes.

Example 3

In this embodiment, an electronic device is disclosed, which includes a memory, a processor, and computer instructions stored in the memory and executed on the processor. When the computer instructions are executed by the processor, one of the methods disclosed in Embodiment 1 is completed. The steps described in a joint entropy-based multi-harmonic source localization method.

Example 4

In this embodiment, a computer-readable storage medium is disclosed for storing computer instructions, and when the computer instructions are executed by a processor, a joint entropy-based multi-harmonic source localization method disclosed in Embodiment 1 is completed. the steps described.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the present invention can still be Modifications or equivalent replacements are made to the specific embodiments of the present invention, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (10)

1. A multi-harmonic source positioning method based on joint entropy is characterized by comprising the following steps:

acquiring the number of harmonic sources in the system and harmonic voltages of each measurement node;

obtaining harmonic times and each harmonic current estimation value of each harmonic source through a harmonic voltage and harmonic state model of each measurement node;

constructing a joint entropy matrix between harmonics with different times and harmonic sources according to harmonic voltage and harmonic times of each measurement node in the system and each harmonic current estimation value of each harmonic source based on a joint entropy method;

collecting the joint entropy matrixes between all harmonics with different times and harmonic sources to obtain a joint entropy matrix set;

and obtaining a harmonic source positioning result through the joint entropy matrix set, the harmonic times, the number of the harmonic sources and the number of the measurement nodes.

2. The joint entropy-based multi-harmonic source positioning method according to claim 1, wherein harmonic voltages of the measurement nodes are preprocessed to obtain preprocessed voltages of the measurement nodes;

and obtaining the harmonic times and each harmonic current estimation value of each harmonic source according to the voltage and harmonic state model after pretreatment of each measurement node.

3. The method as claimed in claim 1, wherein the harmonic frequency and each harmonic current estimation value of each harmonic source are obtained based on an iterative principal component analysis method based on a harmonic voltage and harmonic state model of each measurement node.

4. The joint entropy-based multi-harmonic source positioning method of claim 1, wherein the harmonic state model is constructed by:

for the h harmonic, establishing a harmonic state equation, wherein the specific expression is (1):

wherein,

an estimated value of the h harmonic current characterizing the j harmonic source,

for obtaining the h-th harmonic voltage, Z, of the i-th measurement node _ij The harmonic impedance between the jth harmonic source and the ith measurement node is represented by h, the harmonic frequency is represented by h, the number of the measurement nodes is represented by i =1,2, …, N; j represents the number of harmonic sources, j =1,2, …, M;

converting the harmonic state equation (1) to obtain a harmonic state model, wherein the specific expression is (2):

wherein,

and

respectively an obtained harmonic voltage matrix, a harmonic current estimation value matrix and a separation coefficient matrix.

5. The method for locating the multi-harmonic source based on the joint entropy as claimed in claim 1, wherein the construction process of the joint entropy matrix between the harmonic source of different times and the harmonic source is as follows:

obtaining the amplitude of the harmonic voltage of each measurement node and the amplitude of each harmonic current estimation value of each harmonic source;

combining the amplitude of the harmonic voltage of each measurement node and the amplitude of each harmonic current estimation value of each harmonic source to form a variable set;

and constructing a joint entropy matrix between the harmonic waves of different times and the harmonic wave source according to the variable set.

6. A joint entropy based multi-harmonic source localization method according to claim 1, wherein the obtained joint entropy matrix set { S } ₁ ，S ₂ ，…，S _H The method is as follows:

is the joint entropy value of the joint entropy matrix.

7. The method as claimed in claim 1, wherein when the joint entropy values of all joint entropy matrices corresponding to a certain measurement node are smaller than a set value, the node is a harmonic source positioning result.

8. A joint entropy based multi-harmonic source localization system, comprising:

the data acquisition module is used for acquiring the number of harmonic sources in the system and the harmonic voltage of each measurement node;

the harmonic current estimation value acquisition module is used for acquiring harmonic times and each harmonic current estimation value of each harmonic source through the harmonic voltage and harmonic state model of each measurement node;

the joint entropy matrix acquisition module is used for constructing a joint entropy matrix between harmonic waves of different times and harmonic sources according to the harmonic voltage and the harmonic times of each measurement node in the system and each harmonic current estimation value of each harmonic source based on a joint entropy method;

the joint entropy matrix set acquisition module is used for collecting joint entropy matrixes between all harmonics with different times and harmonic sources to obtain a joint entropy matrix set;

and the harmonic source positioning module is used for obtaining a harmonic source positioning result through the joint entropy matrix set, the harmonic times, the number of the harmonic sources and the number of the measurement nodes.

9. An electronic device comprising a memory and a processor, and computer instructions stored on the memory and executed on the processor, wherein the computer instructions, when executed by the processor, perform the steps of a joint entropy based multiple harmonic source localization method of any one of claims 1-7.

10. A computer readable storage medium storing computer instructions which, when executed by a processor, perform the steps of a joint entropy based multi-harmonic source localization method of any one of claims 1 to 7.

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