A fast island detection method for distributed grid-connected power generation system

Abstract

The invention discloses a rapid detection island method of a distributed grid-connected generation system. A power grid, a circuit breaker, a transformer, a gird-connected inverter and a local load are included. The power grid is connected in series with the circuit breaker through an electric wire and one side of the circuit breaker is connected in series with the transformer. The transformer is connected to the gird-connected inverter and the local load. The local load is arranged on one side of the gird-connected inverter. When a photovoltaic system operates normally, a reactive power disturbance mode is set and a modulation wave commutation period is detected and output. If a rate of change of the commutation period exceeds a threshold value, it is possible to generate an island in the power grid, at this time, the system memorizes a current voltage amplitude and a frequency and simultaneously the set is changed into an active disturbance mode. A photovoltaic system MPP point is actively deviated so that the system does not match with load power. Through comparing the voltage amplitudes and the frequencies memorized by the system, whether the island is generated is determined. By using the island detection method, when the island is generated, rapidity and accuracy of detection are increased.

Description

technical field [0001] The invention relates to an island detection method for a grid-connected power generation system, in particular to a method for rapidly detecting an island in a distributed grid-connected power generation system, and belongs to the technical field of electric power detection applications. Background technique [0002] With the widespread use of new energy sources such as solar energy and fuel cells, inverter power stations are becoming more and more common in power grid transmission and distribution, and inverter power stations are connected to the grid for transmission of electric energy, requiring various comprehensive protection measures , such as power device overcurrent, overtemperature, drive signal undervoltage, etc. For the grid-connected system, it is also necessary to prevent the islanding phenomenon. The distributed grid-connected power generation system at the terminal fails to detect the power failure in real time and cuts itself off from ...

AI Technical Summary

Problems solved by technology

[0003] The current island detection methods are mainly divided into active and passive detection. The passive detection method is simple but has blind spots. There are many active detection methods, which mainly break the balance of the island system by adding different interference signals, so that the voltage or frequency of the island system exceeds the network access standard. This method has high reliability, but the introduction of interference signals will cause distortion of the output current of the inverter and affect the power quality. According to this, the occurrence of islanding can be detected quickly and accurately, and the power quality can be avoided. The impact of the distributed grid-connected power generation system to quickly detect the islanding method will be widely used

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