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Solutions for the Distributed Photovoltaic Access Distribution Network Relay Protection

The high penetration distributed generation (DG) access to the distribution network caused the distribution network protection to be extremely complicated. Based on the analysis of the impact of distributed power grid connection on the fault current of the distribution network, a protection scheme based on operating conditions was proposed. In the scheme, some signals including voltage, current and frequency which collected during the island detection process of the distributed photovoltaic distribution network are used to determine whether the grid-connected distributed photovoltaic power generation system is in the state of equal power or under power or over power through the principle of power conservation. Further, according to the magnitude of the sudden change in the voltage and current on the grid-connected side and the output power, voltage, and current of the photovoltaic array side, a determination is made as to whether a fault and a fault occurrence area occur. The solution requires low accuracy of voltage, current, frequency and other information, and is simple and reliable, and does not require the high communication channels and speeds. Various data are collected during the island detection process, which saves sensors and is good economy for the distribution network.