Mixed island detection method based on combination of slide mode frequency shift method and passive method

Abstract

The invention relates to a mixed island detection method based on a combination of a slide mode frequency shift method and a passive method. The method comprises that an inversion output current, a load current and related values are collected, and inversion output active power and reactive power and load consumption active power and reactive power of are calculated; according to a difference between the inversion output active power and the load consumption active power as well as a difference between the inversion output reactive power and the load consumption reactive power, an over / under frequency detection method in the passive method is used to obtain a reference current value, or the slide mode frequency shift method is used to obtain the reference current value. According to the invention, load change can be tracked, and different algorithms are switched in real time; switching mistakes of the island detection algorithms caused by instant voltage and current jump can be prevented; and blind detection areas can be reduced and the detection speed can be increased compared with those when the passive method is used independently, and THD of the power-grid current can be reduced compared with that only the slide-mode frequency shift method is used.

Description

technical field [0001] The invention belongs to the technical field of photovoltaic power generation. Background technique [0002] Island operation means that when the power grid is interrupted due to electrical failure, misoperation or natural factors, the photovoltaic micro-grid power supply system continues to output power to the grid and supply power to local loads as an independent power source, thus forming a self-sufficient power supply that the grid cannot control isolated island. When the distributed photovoltaic power generation system is operating in an isolated state, it may affect the power quality or even damage the electrical equipment, and may endanger the personal safety of maintenance personnel in severe cases. Therefore, no matter from the aspect of safety or reliability, the islanding operation status should be detected effectively in time, and the photovoltaic inverter should be disconnected from the point of common connection (PCC), which is the islan...

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to solve the problem that the active method causes the current THD of the grid-connected point to increase and the blind area of ​​the passive method to detect is large, and proposes a hybrid island detection method based on the combination of the synovial film frequency offset method and the passive method

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