Relay Protection Schemes for Medium-Voltage Microgrids with Grid-Forming/Grid-Following Generators and Energy Storage System

This paper first investigates the equivalent models and fault characteristics of GFM/GFL DGs and ESSs, considering their control strategies. A corresponding fault analysis model for medium-voltage microgrids is established for both grid-connected and islanded modes, and a fault current calculation method is proposed. Subsequently, a smart IoT-based architecture for medium-voltage microgrid protection is constructed. Based on this architecture, the principles, configuration schemes, and setting criteria for adaptive pilot protection, adaptive current protection, and adaptive zero-sequence protection are proposed. Finally, a real-time digital simulator (RTDS) platform for a medium-voltage microgrid with GFM/GFL DGs and ESSs is developed. The proposed protection schemes were embedded in feeder protection devices

(FPDs) and feeder automation terminals (FTUs), and validated through hardware-in-the-loop

(HIL) testing. The test results demonstrate that the proposed microgrid protection system can effectively address the challenges posed by complex fault characteristics resulting from highpenetration distributed generation integration, providing key technical support for building a secure and reliable new power system.