Multiterminal Hybrid Protection of Microgrids Over Wireless Communications Network

Communications network plays a key role in the next-generation microgrid protection schemes, as the protective relays need to communicate with each other to dynamically track their tripping currents due to the time-varying nature of the loads and the distributed generation (DG) outputs. Hence, communications cost and reliability are some of the key factors that need to be considered before deploying a microgrid protection scheme. In this paper, we introduce the concept of a hybrid microgrid protection system, which implements traditional differential protection scheme along with an adaptive microgrid protection scheme. While the differential scheme is more sensitive, yet relies on extensive communications, the adaptive scheme is less sensitive but has low communications load. The joint deployment of these two schemes has the potential to increase the accuracy and precision of the whole protection scheme, while reducing the overall communications cost. Moreover, we propose a preemptive switching algorithm for the microgrid relays, which ensures a seamless transition from differential protection to adaptive protection based on the bit error rate of the communications links. Some illustrative results are provided based on an IEEE 802.16/WiMAX network to justify the proposed hybrid protection scheme.