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Method for distinguishing island phenomenon from grid-side voltage transient disturbance phenomenon

A grid-side voltage and transient disturbance technology, applied to AC network circuits, photovoltaic power generation, electrical components, etc., can solve problems such as operational conflicts and achieve practical and feasible results

Active Publication Date: 2021-01-29
ZHEJIANG UNIV +2
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Problems solved by technology

[0024] The purpose of the present invention is to solve the operation conflict problem between island protection and low voltage ride-through in photovoltaic grid-connected systems. According to the difference in the change characteristics of PCC harmonic voltage before and after the island and before and after the grid side voltage drop, a method for distinguishing the island phenomenon from the grid side is proposed. The method of voltage transient disturbance phenomenon, so as to provide the basis for the grid-connected controller to perform the next step operation

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  • Method for distinguishing island phenomenon from grid-side voltage transient disturbance phenomenon
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  • Method for distinguishing island phenomenon from grid-side voltage transient disturbance phenomenon

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Embodiment Construction

[0040] The principle of the present invention will be described in detail below according to the accompanying drawings.

[0041] Harmonic Characteristics of Two Faults

[0042] Such as figure 1As shown, the local load is an RLC parallel constant impedance load. For the convenience of analysis, it is temporarily assumed that the background harmonics of the main grid are 0. It is easy to know the load impedance Z of the h order harmonic h The value is:

[0043]

[0044] In the formula: R, L, C are parallel load parameters, ω 0 = 2πf 0 is the angular frequency corresponding to the power frequency.

[0045] In the case of grid-connected operation of the system, the circuit breaker is closed, and the h-order harmonic voltage and harmonic current of PCC satisfy the following relationship:

[0046]

[0047] In the formula: and are the h-order harmonic phasor (effective value) corresponding to the PCC voltage and load current in the grid-connected state, L S is the e...

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Abstract

The invention provides a method for distinguishing an island phenomenon from a grid-side voltage transient disturbance phenomenon. The method is suitable for a photovoltaic grid-connected system faultdetection technology. According to the method, change characteristics of a harmonic voltage before and after different faults are taken as a main basis, and the influence of main power grid background harmonic and spectrum leakage on harmonic detection is comprehensively considered. According to the method, a harmonic voltage threshold setting formula is specifically provided, the island phenomenon and the voltage transient disturbance phenomenon can be effectively distinguished, interference of frequency spectrum leakage and the main power grid background harmonic is avoided, and the methodhas practical feasibility.

Description

technical field [0001] The invention relates to a method for distinguishing the islanding phenomenon and the network side voltage transient disturbance phenomenon, which belongs to the fault detection technology in the field of new energy. Background technique [0002] (1) The necessity of distinguishing the islanding phenomenon from the voltage transient disturbance phenomenon [0003] When the photovoltaic grid-connected system fails, voltage drops will occur. There are two reasons for this phenomenon. One is that the grid-side short circuit breaker causes the system to be in an island state, and the other is that the system is still in the grid-connected state and the grid There is a transient disturbance in the side voltage due to other reasons. According to GB / T 19964-2012, IEEE Std.1547.1-2020 and other domestic and foreign standards (references [1-9]), when a point of common coupling (PCC) voltage drop is detected, the system needs to Perform island protection and l...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J3/38H02J3/01G01R31/08G01R23/16
CPCH02J3/388H02J3/381H02J3/01G01R31/086G01R23/16H02J2300/24Y04S10/52Y02E10/56Y02E40/40
Inventor 于淼赵禹灿孙铭徽孙福寿姜旭宋晓喆丁浩刘家岩王鼎葛路明陈宁曲立楠
Owner ZHEJIANG UNIV
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