Photovoltaic grid connected inverter island detection method based on negative sequence current injection

A negative-sequence current, islanding detection technology, applied in photovoltaic power generation, measuring electrical variables, instruments, etc., can solve problems such as large harmonics, failure, difficulty, etc.

Active Publication Date: 2013-11-27
NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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Problems solved by technology

While operating in an isolated island, on the one hand, the nonlinear loads in the island, such as distribution transformers, will be highly distorted in voltage under the excitation of current harmonics, usually the third harmonic; large loads, making V PCC produce large harmonics
Therefore, in theory, a THD-based islanding detection method can be constructed by selecting an appropriate threshold, but there are difficulties i

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  • Photovoltaic grid connected inverter island detection method based on negative sequence current injection
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  • Photovoltaic grid connected inverter island detection method based on negative sequence current injection

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[0078] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0079] An islanding detection method for photovoltaic grid-connected inverters based on negative-sequence current injection, figure 1 Schematic diagram of the principle structure of the grid for island detection, such as figure 1 As shown, the electric energy generated by the photovoltaic cell array undergoes DC / DC conversion to make the converted DC voltage meet the grid-connection requirements. At the same time, the maximum power tracking control (MPPT) of the conductance incremental method is adopted in the DC / DC conversion. Through the inverter Convert direct current to alternating current and connect to the grid, and adopt unit power factor current control when PV is connected to the grid. Among them, R f , L f is the resistance and inductance of the AC side filter of the inverter, R s , L s The equivalent resistance and inductance of...

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Abstract

The invention provides a photovoltaic grid connected inverter island detection method based on negative sequence current injection, belonging to the technical field of power system relay protection and automatic control. According to the method, an inverter is started to inject negative sequence current when a voltage harmonic distortion rate is larger than a fixed value, common connection point voltage unbalanced degree and voltage harmonic distortion rate are detected, when both the common connection point voltage unbalanced degree and the voltage harmonic distortion rate are larger than the respective fixed value and the duration time exceeds a set time, the generation of island is determined, and the rapid detection of the island is realized. According to the method, the setting difficulty of a criterion is reduced, the improvement of the detection speed is facilitated, the interference on a power grid is reduced as much as possible in the condition that the normal operation is ensured, the influence of a power grid asymmetrical fault is avoided, and there is no detection blind area. The simulation verification is carried out in the condition that the island detection is most not facilitated, and an island operation state still can be rapidly and accurately detected according to the method. A good method is provided for the operation withdrawal of a distributed power supply in the island or the turning of power grid connected operation into island operation control mode power system safe operation and the detection.

Description

technical field [0001] The invention relates to a photovoltaic grid-connected inverter island detection method based on negative-sequence current injection, and belongs to the technical field of relay protection and automatic control of power systems. Background technique [0002] With the aggravation of global environmental pollution and the gradual depletion of conventional energy sources, the development and utilization of new energy sources has gradually become a current research hotspot. As one of the important forms of power generation, photovoltaic power generation (Photovoltaic, PV) still has three main problems: maximum power tracking control, grid-connected technology and islanding detection. The island effect means that when the power grid is interrupted due to electrical failure, misoperation or natural factors, the distributed generation (Distributed Generation, DG) system fails to detect the power outage and breaks away from the grid, and still provides power t...

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Application Information

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IPC IPC(8): G01R31/00H02J3/38
CPCY02E10/563Y02E10/56
Inventor 戴志辉
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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