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A wind farm anti-islanding identification method and system based on harmonic impedance matrix

A technology of harmonic impedance and identification method, used in wind power generation, measurement of electricity, electrical components, etc., can solve the problems of online identification of islands and failures, and achieve the effect of good engineering practical application significance, high reliability, and reduced impact.

Active Publication Date: 2021-08-06
CHINA ELECTRIC POWER RES INST +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] In order to solve the deficiencies in the above-mentioned prior art, the object of the present invention is to provide a wind farm anti-islanding identification method based on harmonic impedance matrix and its system, which solves the problems of the single-unit islanding identification method when multiple machines are running in parallel due to different Wind turbines use different parameters and lead to the failure of island online identification

Method used

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  • A wind farm anti-islanding identification method and system based on harmonic impedance matrix
  • A wind farm anti-islanding identification method and system based on harmonic impedance matrix
  • A wind farm anti-islanding identification method and system based on harmonic impedance matrix

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Embodiment 1

[0062] The present invention provides a wind farm anti-islanding identification method based on harmonic impedance matrix, the flow chart of which is as follows image 3 and 7 As shown, by collecting the voltage and current of the grid-connected point of the wind farm, analyzing the magnitude of each harmonic impedance, calculating the modulus of the harmonic impedance matrix, and judging whether there is islanding in the wind farm, the island protection of the wind farm is realized. The present invention mainly involves key technologies such as wind farm grid-connected point voltage and current collection, fast Fourier transform, diagonal harmonic impedance matrix and island criterion, and the adopted technical scheme is as follows:

[0063] (1) With a certain sampling frequency f s Real-time collection of wind farm grid-connected point voltage and current data. The three-phase circuit diagram and equivalent circuit diagram of N wind farms are as follows: figure 1 and 2 s...

Embodiment 2

[0071] According to the wind farm power generation system built to illustrate the implementation of the method, such as Figure 4 shown. There are 7 wind farms in the figure. Table 1 is the statistical table of wind farm capacity. The total capacity is 357MW. Each wind farm is upgraded to 35kV through 690 / 35kV transformers. The 7 wind farms are collected through 35kV and connected to public grid. The sampling frequency is 5000Hz, and the time interval ΔT=0.4s.

[0072] Table 1

[0073] wind farm Number of wind turbines Total capacity (MW) 1 24 36 2 28 42 3 24 36 4 28 42 5 28 42 6 48 72 7 58 87

[0074] (1) Analyze the current and voltage harmonic components at the low-voltage side of the wind turbine outlet during the grid-connected operation of the full-power variable frequency wind turbine. The voltage and current spectrum diagrams are as follows: Figure 5 and Figure 6 shown. Among them, the current signal c...

Embodiment 3

[0082] Based on the same inventive concept, the present invention also provides a wind farm island identification system based on harmonic impedance matrix, including:

[0083] The calculation module is used to calculate the diagonal harmonic impedance matrix modulus according to the collected voltage and current of the grid-connected point of the wind farm;

[0084] The judging module is used to judge whether islanding occurs in the wind farm according to the modulus value of the diagonal harmonic impedance matrix;

[0085] The island protection action module is used for anti-islanding protection action when the wind farm enters the island state; otherwise, re-collect the grid-connected point voltage and current of the wind farm, and calculate the diagonal harmonic impedance matrix modulus.

[0086] Further: the computing module further includes:

[0087] The acquisition unit is used to collect the voltage and current of the grid-connected point of the wind farm in real time...

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Abstract

The invention relates to a wind farm anti-islanding identification method and system based on a harmonic impedance matrix. By collecting the voltage and current of the grid-connected point of the wind farm, analyzing the magnitude of each harmonic impedance, calculating the harmonic impedance matrix modulus, and judging wind power Whether there is an island in the wind farm, so as to realize the island protection of the wind farm. Islanding is identified by using the change of circuit impedance at the grid-connected point before and after the grid is disconnected. Under grid-connected conditions, the system impedance is equivalent to the parallel connection of wind farm impedance and grid impedance. Since the main grid is close to an ideal voltage source, the system impedance is very small. After the island occurs, the main grid circuit is disconnected, and the system impedance is equal to the power station system impedance, and its value is generally much greater than the impedance when connected to the grid, so that the island state can be identified.

Description

technical field [0001] The invention relates to a passive anti-islanding method and system, in particular to a method for identifying anti-islanding in a wind farm based on a harmonic impedance matrix and a system thereof. Background technique [0002] The island phenomenon refers to the state in which a part of the power grid including loads and power sources continues to operate in isolation after being separated from the main grid. Islands can be divided into unplanned islands and planned islands. The planned island is mostly used in the distribution network. When the distribution network fails, it will be transformed into a planned island operation mode to minimize the power failure loss of the distribution network. At the same time, planned island operation can effectively play the positive role of distributed power. Islands formed by accidental factors such as fault trips are called unplanned islands. Unplanned island operation may cause serious damage to the power ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/38G01R31/00
CPCG01R31/00H02J3/386H02J3/388Y02E10/76
Inventor 刘纯何国庆孙文文冯凯辉李光辉王淼
Owner CHINA ELECTRIC POWER RES INST
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