Overcurrent and Overload Protection of Directly Voltage-Controlled Distributed Resources in a Microgrid

This paper presents two add-on features for the voltage control scheme of directly voltage-controlled distributed energy resource units (VC-DERs) of an islanded microgrid to provide overcurrent and overload protection. The overcurrent protection scheme detects the fault, limits the output current magnitude of the DER unit, and restores the microgrid to its normal operating conditions subsequent to fault clearance. The overload protection scheme limits the output power of the VC-DER unit. Off-line digital time-domain simulation studies, in the EMTDC/PSCAD software environment, demonstrate the feasibility and desirable performance of the proposed features. Real-time case studies based on an RTDS system verifies performance of the hardware-implemented overload and overcurrent protection schemes in a hardware-in-the-loop environment.