Seamless Control of Grid-Connected Inverter during Single Phase Disconnection after Single Phase Fault in a Weak Grid

Abstract

With the increasing penetration of renewable energy in power systems, the requirement of fault ride through (FRT) capability becomes imperative for the stability of the grid. However, the topology and operation of the power system during the fault and fault clearance, especially during single phase disconnection, is seldom taken into account in most existing control schemes for grid-connected inverters. In this paper, a novel seamless positive-sequence current control method based on phase voltage with equal 120 degree dephasing and zero-sequence voltage decomposition is proposed. It realizes a smooth and rapid transition between normal operation, single phase fault, single phase disconnection without mode change, and injects no negative-sequence current to the grid during single phase disconnection which may last long and cause dangerous overheating of the rotor of conventional generators in a power system. The results obtained from the simulation and experiment demonstrate the effectiveness of the proposed method.