Adaptive overcurrent protection scheme for distribution networks with connection of mobile energy storage devices

Abstract

The increasing penetration of renewable energy sources in distribution networks has caused great challenges to the reliable operation of the conventional overcurrent protection schemes. In particularly, serious underreach and overreach problems of protection scope may occur under the ever growing application of mobile energy storage (MES) devices. To improve the adaptability to the connection of MES devices under distribution networks, this paper proposes an adaptive overcurrent protection scheme, which can avoid the unfavorable effects caused by infeed currents and out flowing currents. Firstly, the effects of MES device on the protection scope of the overcurrent protection strategy are investigated, considering the charging, discharging, and backup operation modes of MES device. Secondly, to adapt to the different operation modes, the equivalent impedance of MES device is calculated, and then it is introduced to determine the adaptive settings of fast current protection and time-critical fast current protection. Finally, the constructed adaptive overcurrent protection scheme can adapt to varied fault conditions, including different operation modes and output power of MES device, connection locations, fault locations, and fault types. Large amounts of simulation results show that the proposed adaptive overcurrent method can overcome the underreach and overreach problems of protection scope, demonstrating its good application prospects.