OC/OL Protection of Droop-Controlled and Directly Voltage-Controlled Microgrids Using TMF/ANN-Based Fault Detection and Discrimination

In this article, we propose a generalized overcurrent (OC) and overload (OL) protection scheme for the droop-controlled and directly voltage-controlled (DVC) inverter-interfaced distributed energy resources (IIDERs) to be used for the protection studies of the alternating-current (ac)-islanded (autonomous) microgrids, and provide a management strategy during and after short circuit (SC) and consequent OLs. The fault is detected, and its type is discriminated by a new method that takes the advantages of both artificial neural networks (ANNs) and transient monitoring function (TMF). By using the proposed strategy, the output current magnitudes of the distributed energy resource (DER) units are limited, and after fault clearance, the microgrid is restored to its normal operating conditions. The proposed OC/OL protection scheme limits the output power of the DERs. In this regard, a generalized fault model is presented, which considers the effect of the control system of the IIDERs. This model exploits a current-limiting strategy (CLS) that can be implemented in different reference frames to enhance the microgrid fault ride-through (FRT) capability. Finally, to demonstrate effectiveness, accuracy, authenticity, and feasibility of the proposed OC/OL protection scheme along with the TMF/ANN-based fault detection method and their desirable performance, offline digital time-domain simulations are done in MATLAB/Simulink environment, and the results are experimentally verified by using the OPAL-RT real-time digital simulator (RTDS).