CN116660623A - A method and system for detecting harmonics in distribution network with distributed power - Google Patents

Abstract

The invention belongs to the technical field of distribution network fault detection, and specifically relates to a method and system for detecting harmonics of a distribution network containing distributed power sources, including: performing harmonic control partitions on the distribution network containing distributed power sources; The detection active filter is connected to the partitioned distribution network, and the sensitivity matrix of the distribution network is calculated; with the goal of minimizing the sum of voltage harmonic distortion rates of all nodes in the distribution network, a distribution network harmonic detection is constructed The model is used to complete the harmonic detection of distribution network including distributed power generation; among them, the harmonic detection model of distribution network constructed adopts the joint harmonic detection method combining window interpolation algorithm and wavelet packet transform.

Description

A method and system for detecting harmonics in a distribution network with distributed power

technical field

The invention belongs to the technical field of distribution network fault detection, and in particular relates to a method and system for detecting harmonics of a distribution network including distributed power sources.

Background technique

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

Distributed power is flexibly connected to the distribution network through converters. Large-capacity distributed power is connected to the distribution network through a 10kV or 35kV busbar, and small-capacity distributed power, especially photovoltaic power generation, is directly connected to the user side through a converter. Due to the decentralization, uncertainty and extensiveness of distributed power access to the distribution network, as the proportion of distributed power access in the distribution network increases year by year, the harmonic superposition effect generated by a large number of distributed power cannot be ignored. May cause harmonic amplification. For this reason, the harmonic problem of high-proportion distributed power access to distribution network is becoming increasingly severe and complex, and harmonic control has become an urgent problem to be solved.

Harmonic control has always been a research hotspot in the field of power systems. In the traditional distribution network, there are few distributed power sources, and the harmonics are mainly generated by special users, which are relatively concentrated, and point-to-point harmonic control can be carried out. When the number of harmonic sources is small, the current detection active filter can be used to achieve effective governance. With the large-scale access of distributed power sources, the number of harmonic sources in the distribution network is large and widely dispersed, and the decentralized point-to-point governance scheme only makes decisions based on the amount of local information, resulting in the gap between multiple harmonic control devices. Unable to coordinate, poor governance effect. At the same time, the cost of point-to-point decentralized governance is high, so comprehensive governance should be carried out from the perspective of the entire power grid, and it is necessary to study systematic harmonic governance from the perspective of the power grid.

Contents of the invention

In order to solve the above problems, the present invention proposes a method and system for detecting harmonics of a distribution network with distributed power sources. Aiming at the inaccurate detection of unsteady state harmonics by power harmonics, the Blackman window interpolation algorithm and db44 The joint harmonic detection method combined with wavelet packet transform improves the detection accuracy of distribution network harmonics.

According to some embodiments, the first solution of the present invention provides a method for detecting harmonics in a distribution network with distributed power sources, which adopts the following technical solution:

A method for detecting harmonics in a distribution network including distributed power sources, comprising:

Carry out harmonic control divisions for distribution networks with distributed power sources;

The voltage detection active filter is connected to the partitioned distribution network, and the sensitivity matrix of the distribution network is calculated;

With the goal of minimizing the sum of voltage harmonic distortion rates of all nodes in the distribution network, a distribution network harmonic detection model is constructed to complete the distribution network harmonic detection including distributed power generation;

Among them, the constructed distribution network harmonic detection model adopts the joint harmonic detection method combining window interpolation algorithm and wavelet packet transform.

As a further technical limitation, in the process of harmonic control division, the harmonic sensitivity is used as the configuration voltage detection active filter, and the node harmonic voltage is controlled by controlling the increment of node branch conductance.

Further, the harmonic sensitivity Sh _,j,i is Among them, h is the dominant harmonic order, j, i are nodes, U _{h, j} is the hth harmonic voltage of node j, G _{h, i} is the equivalent conductance of node i.

As a further technical limitation, the sensitivity matrix S is Among them, n is a distribution network node, m is a distribution network node configured with a voltage detection active filter, and the number of controlled nodes is nm.

As a further technical limitation, the goal is to minimize the sum of the voltage harmonic distortion rates of all nodes in the power grid. Considering that different electrical equipment has different requirements for power quality, in the optimization process of the target voltage distortion rate, by setting The weighting factor considers the degree of difference in the requirements of different voltage nodes for voltage harmonic levels.

Further, taking the weight coefficient of the node as μ _j , the objective function of the distribution network harmonic detection model is Among them, μ _j is the weight coefficient of node j; U _THD,j is the voltage distortion rate of node j, U _1,j is the fundamental voltage amplitude.

As a further technical limitation, the joint algorithm of Blackman window Fourier transform and db44 wavelet packet transform is used to analyze the transient harmonics, and the transient harmonics are decomposed and reconstructed by db44 wavelet packet transform to obtain the fundamental and The waveform of each harmonic component is analyzed by adding Blackman window Fourier transform to obtain the frequency and amplitude of the fundamental wave and each harmonic component, and complete the harmonic detection.

According to some embodiments, the second solution of the present invention provides a distribution network harmonic detection system including distributed power supply, which adopts the following technical solution:

A distribution network harmonic detection system including distributed power supply, including:

a zoning module configured to perform harmonic control zoning on a distribution network containing distributed power;

A calculation module, which is configured to connect the voltage detection active filter into the partitioned distribution network, and calculate the sensitivity matrix of the distribution network;

The detection module is configured to aim at the minimum sum of voltage harmonic distortion rates of all nodes in the distribution network, construct a distribution network harmonic detection model, and complete the distribution network harmonic detection including distributed power supply;

Among them, the constructed distribution network harmonic detection model adopts the joint harmonic detection method combining window interpolation algorithm and wavelet packet transform.

According to some embodiments, the third solution of the present invention provides a computer-readable storage medium, adopting the following technical solution:

A computer-readable storage medium, on which a program is stored, and when the program is executed by a processor, the steps in the method for detecting harmonics of a distribution network including distributed power sources as described in the first solution of the present invention are implemented.

According to some embodiments, the fourth solution of the present invention provides an electronic device, which adopts the following technical solution:

An electronic device, including a memory, a processor, and a program stored on the memory and operable on the processor. When the processor executes the program, the distributed power supply configuration as described in the first solution of the present invention is realized. Steps in the grid harmonic detection method.

Compared with prior art, the beneficial effect of the present invention is:

Aiming at the inaccurate detection of unsteady-state harmonics in current electric harmonic detection, the present invention adopts a joint harmonic detection method combining Blackman window interpolation algorithm and db44 wavelet packet transformation to improve the distribution network containing distributed power The accuracy of detection can effectively control the harmonics of the power grid and reduce the voltage harmonic distortion rate.

Description of drawings

The accompanying drawings constituting a part of this embodiment are used to provide a further understanding of this embodiment, and the schematic embodiments and descriptions of this embodiment are used to explain this embodiment and do not constitute an improper limitation to this embodiment.

FIG. 1 is a flow chart of a method for detecting harmonics of a distribution network containing distributed power sources in Embodiment 1 of the present invention;

FIG. 2 is a flowchart of a joint harmonic detection method in Embodiment 1 of the present invention;

Fig. 3 is a structural block diagram of a distribution network harmonic detection system including distributed power sources in Embodiment 2 of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

It should be pointed out that the following detailed description is exemplary and is intended to provide further explanation to the present application. Unless defined otherwise, 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 here is only for describing specific embodiments, and is not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof.

In the case of no conflict, the embodiments and the features in the embodiments of the present invention can be combined with each other.

Embodiment one

Embodiment 1 of the present invention introduces a method for detecting harmonics in a distribution network including distributed power sources.

As shown in Figure 1, a method for detecting harmonics in a distribution network with distributed power sources includes:

Carry out harmonic control divisions for distribution networks with distributed power sources;

The voltage detection active filter is connected to the partitioned distribution network, and the sensitivity matrix of the distribution network is calculated;

With the goal of minimizing the sum of voltage harmonic distortion rates of all nodes in the distribution network, a distribution network harmonic detection model is constructed to complete the distribution network harmonic detection including distributed power generation;

Among them, the constructed distribution network harmonic detection model adopts the joint harmonic detection method combining window interpolation algorithm and wavelet packet transform.

In this embodiment, in the process of harmonic control zoning, harmonic sensitivity is used as a configuration voltage detection active filter, and node harmonic voltage control is performed by controlling the increment of node branch conductance.

The harmonic sensitivity Sh _,j,i is Among them, h is the dominant harmonic order, j, i are nodes, U _{h, j} is the h harmonic voltage of node j, G _{h, i} is the equivalent conductance of node i; the sensitivity matrix S is Among them, n is a distribution network node, m is a distribution network node configured with a voltage detection active filter, and the number of controlled nodes is nm.

The goal is to minimize the sum of voltage harmonic distortion rates of all nodes in the power grid. Considering that different electrical equipment has different requirements on power quality, in the process of optimizing the target voltage distortion rate, by setting weight coefficients, different voltages are considered. The degree to which nodes vary in their requirements for voltage harmonic levels. Taking the weight coefficient of the node as μ _j , the objective function of the distribution network harmonic detection model is Among them, μ _j is the weight coefficient of node j; U _THD,j is the voltage distortion rate of node j, /> U _1,j is the fundamental voltage amplitude.

Even if the Blackman Fourier transform algorithm has the advantages of simple implementation, high detection accuracy and convenient use, it cannot extract features from transient signals, while wavelet packet transform can detect transient signals, but for steady-state signals, it cannot The frequency and amplitude information of each steady-state signal cannot be obtained as accurately as the Fourier transform. The joint harmonic detection method combined with Blackman window Fourier transform algorithm and wavelet packet transform is used to detect transient power harmonics. Two parts, the transient component is included in the high-frequency detail part, and the steady-state components are in the low-frequency approximation part. The wavelet packet transform is used to analyze this part to obtain the characteristic information of the transient component. The decomposed steady-state components are analyzed using the Blackman window interpolation algorithm to obtain the frequency and amplitude of the steady-state components; the flow chart of the combined harmonic detection method in this embodiment is shown in Figure 2.

The joint harmonic detection algorithm combined with Blackman window interpolation algorithm and wavelet packet transform used in this embodiment is feasible. The principle is to use the time-frequency characteristics of the wavelet packet transform. After the signal is decomposed by the wavelet packet transform, the attenuation component is included in the decomposed high-frequency part, so as to determine the moment when the signal attenuates. The wavelet packet transform can be used to observe well to the attenuation component of the signal. But the wavelet packet transform does not have the characteristics of Fourier transform, and it is impossible to obtain accurate frequency and amplitude information for the analysis of the steady-state limit signal. Therefore, after the wavelet packet transformation, the low-frequency part containing the steady-state components of each order is analyzed by adding the Blackman window interpolation algorithm to obtain accurate frequency and amplitude information of each order of steady-state. Through the combined algorithm of Blackman window interpolation algorithm and wavelet packet transform, the moment of signal attenuation can be determined, and the frequency and amplitude of each steady-state signal can be obtained accurately.

In this embodiment, aiming at the inaccurate detection of unsteady-state harmonics in the current power harmonic detection, a joint harmonic detection method combining Blackman window interpolation algorithm and db44 wavelet packet transformation is adopted to improve the harmonic detection of distributed power distribution network. The accuracy of wave detection can effectively control the harmonics of the power grid and reduce the voltage harmonic distortion rate.

Embodiment two

Embodiment 2 of the present invention introduces a harmonic detection system of a distribution network including a distributed power supply.

As shown in Figure 3, a distribution network harmonic detection system with distributed power supply includes:

a zoning module configured to perform harmonic control zoning on a distribution network containing distributed power;

A calculation module, which is configured to connect the voltage detection active filter into the partitioned distribution network, and calculate the sensitivity matrix of the distribution network;

The detection module is configured to aim at the minimum sum of voltage harmonic distortion rates of all nodes in the distribution network, construct a distribution network harmonic detection model, and complete the distribution network harmonic detection including distributed power supply;

Among them, the constructed distribution network harmonic detection model adopts the joint harmonic detection method combining window interpolation algorithm and wavelet packet transform.

The detailed steps are the same as the method for detecting harmonics of a distribution network including distributed power sources provided in Embodiment 1, and will not be repeated here.

Embodiment three

Embodiment 3 of the present invention provides a computer-readable storage medium.

A computer-readable storage medium, on which a program is stored. When the program is executed by a processor, the steps in the method for detecting harmonics of a distribution network including distributed power sources according to Embodiment 1 of the present invention are implemented.

The detailed steps are the same as the method for detecting harmonics of a distribution network including distributed power sources provided in Embodiment 1, and will not be repeated here.

Embodiment four

Embodiment 4 of the present invention provides an electronic device.

An electronic device includes a memory, a processor, and a program stored in the memory and operable on the processor. When the processor executes the program, the distributed power supply configuration as described in Embodiment 1 of the present invention is realized. Steps in the grid harmonic detection method.

The detailed steps are the same as the method for detecting harmonics of a distribution network including distributed power sources provided in Embodiment 1, and will not be repeated here.

The above descriptions are only preferred embodiments of this embodiment, and are not intended to limit this embodiment. For those skilled in the art, various modifications and changes may be made to this embodiment. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this embodiment shall be included in the protection scope of this embodiment.

Claims (10)

1. The utility model provides a distribution network harmonic detection method that contains distributed power supply which characterized in that includes:

carrying out harmonic treatment partition on a power distribution network containing a distributed power supply;

the voltage detection type active filter is connected into the partitioned power distribution network, and a sensitivity matrix of the power distribution network is calculated;

constructing a harmonic detection model of the power distribution network by taking the minimum sum of voltage harmonic distortion rates of all nodes in the power distribution network as a target, and finishing the harmonic detection of the power distribution network containing the distributed power supply;

the constructed power distribution network harmonic detection model adopts a combined harmonic detection method combining a windowing interpolation algorithm and wavelet packet transformation.

2. The method for detecting harmonic waves of a power distribution network with a distributed power supply according to claim 1, wherein in the process of harmonic wave treatment and partitioning, harmonic wave sensitivity is adopted as a configuration voltage detection type active filter, and node harmonic wave voltage treatment is performed by controlling the increment of node branch circuit conductance.

3. A method for harmonic detection in a power distribution network including a distributed power source as claimed in claim 2, wherein said harmonic sensitivity S _h,j,i Is thatWherein h is the dominant harmonic frequency, j, i are nodes, U _h,j For the h-order harmonic voltage of node j, G _h,i Is the equivalent conductance of node i.

4. A method for harmonic detection in a power distribution network including a distributed power source as claimed in claim 1, wherein said sensitivity matrix S isAnd n is a power distribution network node, m is a power distribution network node for configuring the voltage detection type active filter, and the number of controlled nodes is n-m.

5. The method for detecting harmonic waves of a power distribution network with a distributed power supply according to claim 1, wherein the method is characterized in that the sum of voltage harmonic distortion rates of all nodes in the power distribution network is taken as a target, different requirements of different electric equipment on electric energy quality are considered, and in the process of optimizing the voltage distortion rates as the target, the degree of difference of the voltage harmonic level requirements of different voltage nodes is considered by setting weight coefficients.

6. The method for detecting harmonic waves of power distribution network with distributed power supply as claimed in claim 5, wherein the weighting coefficient of the node is μ _j The objective function of the harmonic detection model of the power distribution network is thatWherein mu _j The weight coefficient of the node j; u (U) _THD,j For the voltage distortion rate of node j, +.>U _1,j Is the fundamental voltage amplitude.

7. The method for detecting harmonic waves of a power distribution network with a distributed power supply according to claim 1, wherein a combination algorithm of Blackman window Fourier transform and db44 wavelet packet transform is adopted to analyze transient harmonic waves, the transient harmonic waves are decomposed and reconstructed through db44 wavelet packet transform to obtain waveforms of fundamental wave and sub-harmonic components, and then Blackman window Fourier transform is adopted to analyze the fundamental wave and the sub-harmonic components to obtain frequencies and amplitudes of the fundamental wave and the sub-harmonic components, so that harmonic wave detection is completed.

8. A power distribution network harmonic detection system including a distributed power source, comprising:

a partitioning module configured to perform harmonic remediation partitioning of a power distribution network including a distributed power source;

the calculation module is configured to access the voltage detection type active filter into the partitioned power distribution network and calculate a sensitivity matrix of the power distribution network;

the detection module is configured to construct a harmonic detection model of the power distribution network by taking the minimum sum of voltage harmonic distortion rates of all nodes in the power distribution network as a target, so as to complete the harmonic detection of the power distribution network containing the distributed power supply;

the constructed power distribution network harmonic detection model adopts a combined harmonic detection method combining a windowing interpolation algorithm and wavelet packet transformation.

9. A computer readable storage medium having stored thereon a computer program, which when executed by a processor, implements the steps of a method for harmonic detection of a power distribution network comprising a distributed power supply as claimed in any one of claims 1 to 7.

10. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements the steps of the method for harmonic detection of a power distribution network comprising a distributed power supply as claimed in any one of claims 1 to 7 when the program is executed by the processor.