Study Of Centralized Anti-islanding Scheme For Renewable Energy Base With Large-scale Wind Power

China's new energy development is currently on a large scale, centralized and long-distance-transmission mode. At present, China has achieved some million-kilowatts renewable energy bases, and some 10-million-kilowatts renewable energy bases are under construction. Under the impact of grid fault, the transient process of large renewable energy base is very complicated. An important aspect of the safety issues is islanding. Islanding problem research mainly studied in distribution network, but for large-scale renewable energy base, there is very few research.This paper is mainly on the islanding issue of renewable energy base. The formation mechanism were studied, and a centralized anti islanding protection schemes is proposed.First, based on the consideration of the fault protection principles of renewable energy bases, the criteria of stability control devices, and the characteristics of fault ride-through of wind power generation, the mechanism and the process of the islanding of renewable energy bases are analyzed. Then a switch model of DFIG and a system model are built in PSCAD, to analyze the process of island and the overvoltage in an island, under different fault types, e.g. single-phase fault and three-phase fault, and under different fault locations, e.g. feeder fault and bus fault.In the following part, the drawbacks of the existing mainstream anti-islanding protection strategys are discussed when applied in new energy bases. Therefore, a centralized anti-islanding protection scheme is proposed, and the criterios, implementation scheme, operation sequence and constructability of the proposed scheme is elaborated. However, this scheme is not advisible when the grid structure is complex. Finally, in order to solve the problem of the determination of islanding in a complex network structure, two algorithms are proposed, which are virtual node communication method and virtual node search method. The two algorithms can be applied to the determination of islanding in different operation mode, and under complex network structures.