Local protective relays distributed across power systems are prone to misoperate in interconnected microgrids integrated with Distributed Energy Resources (DERs) mainly due to the changes in the power flow pattern, fault current level, and difficulty in protection coordination. This paper presents a non-traditional Centralized Intelligent Station-Level Protection (CISP) approach in the simultaneous protection of multiple electric power apparatuses in interconnected (networked) microgrids. A new dynamic Protection Zone Selection (PZS) algorithm is proposed to account for the dynamic behavior of such microgrids, various operating topologies (grid-connected and islanded modes), and various system operating scenarios. Also, three new protective relaying algorithms are proposed for the protection of the electric power apparatuses in the zones determined by the PZS algorithm. Furthermore, the PZS algorithm intelligently determines the protection zones in MATLAB using graph theory, and communicates the results to the CISP algorithms implemented in the RTDS® simulator. The inputs to the CISP algorithms are wide area IEC 61869-9 Sampled Values (SVs) from the RTDS GT-FPGA and IEC 61860 GOOSE binary signals from the GTNET card. The modified IEEE 13-node distribution feeder integrated with DERs is modelled in RSCAD and was used in testing the proposed CISP approach in real-time. Results obtained are promising and showed that the centralized protection performed its intended function.
Adeyemi Adewole, University of Manitoba