Simulation of PV based Grid connected Inverter with fuzzy based Unified control strategy

Abstract

Distributed generation (DG) is emerging as a viable alternative when renewable or nonconventional energy resources are available, such as wind turbines, photovoltaic arrays, fuel cells, micro turbines. Most of these resources are connected to the utility through power electronic interfacing converters, i.e., three-phase inverter. DG is a suitable form to offer high reliable electrical power supply, as it is able to operate either in the grid-tied mode or in the islanded mod. In the grid-tied operation, DG deliveries power to the utility and the local critical load. The proposed control strategy composes of an inner inductor current loop, and a novel voltage loop in the synchronous reference frame. The inverter is regulated as a current source just by the inner inductor current loop in grid-tied operation, and the voltage controller is automatically activated to regulate the load voltage upon the occurrence of islanding. To create a stable mode when different kinds of loads are connected locally or when working under contingency, the step-up converter must regulate the dc link voltage, allowing the VSI to stabilize its terminal voltage. PI and fuzzy controllers are used to regulate voltages and currents, while a phase-locked loop algorithm is used to synchronize the grid and DG.
Index Terms— Unified Power Quality Conditioner; Three Phase Inverter; Distributed generation (DG); islanding; load current; seamless transfer