Research on regional centralized protection scheme for distribution network integrated with electric vehicles

Abstract

In view of the difficulty in balancing between selectivity and sensitivity of current protection in distribution networks integrated with electric vehicles, a regional current protection method applicable to distribution networks with large-scale electric vehicle penetration is proposed. First, considering the effect of the converter control strategy of electric vehicle chargers, a theoretical analysis is made to determine the expression of the short circuit current that the electric vehicle charger provides when faults occur on feeders. On this basis, according to the minimum short circuit current, the current protection criterion that meets the requirement of sensitivity alone is established. And then, combining multiple start-up signals of the criterion on the fault line and multiple-level neighboring lines after fault occurs, the regional current protection scheme for distribution network is constructed. Finally, simulation tests conducted in Real-Time Digital Simulator (RTDS) of IEEE 33-bus system verify that the proposed method can effectively avoid mal-cooperation between different protection zones which is common in traditional current protection. Besides, the proposed scheme is not affected by factors such as the charging capacity of electric vehicles, the number and the location of charging facilities, etc., and can accurately identify the fault location even when the information is partly missing or in error.