Fault Current Hierarchical Limitation Strategy for Fault Ride-Through Scheme of Microgrid

Abstract

With the growing penetration of grid-connected microgrids (MGs), utility grid (UG) faces the challenge of high-level fault current during fault ride-through (FRT) of MGs. To tackle this challenge, a fault current hierarchical limitation (FCHL) strategy is proposed, which consists of four levels: 1) fault current primary limitation control (FCPLC) is based on the proportional-resonant (PR) current controller; 2) fault current secondary limitation control (FCSLC) is formulated for current generation of grid-connected inverters (GCIs) with peak fault current limitation; 3) fault current tertiary limitation control (FCTLC) is formulated for the phase angle shifting of MG’s fault current to neutralize its effect on UG’s fault current; and 4) fault current quartus limitation control (FCQLC) is developed for the coordinated operation of parallel GCIs within grid code requirement. Extensive tests have validated the effectiveness of proposed strategy with a successful FRT while the MG’s output fault current has a minute effect on the UG’s fault current amplitude.