Control approach of a connected PV system under grid faults

Abstract

This paper proposes a flexible power control of a three-phase grid-connected PV system which fulfills the PV converter operations under normal conditions and symmetrical grid voltage sags. This control approach can be configured in the PV converters and flexibly change from one to another mode during operation. In normal operation mode, a Maximal Power Point Tracking (MPPT) algorithm and PQ-control loop have been designed around the converters. Their aim is to maximize the PV power and to inject into the grid a current with low harmonic distortion, as well as energy at unity power factor. Under grid voltage dips, the PQ-control strategy has been changed within the grid voltage sag levels and the inverter rating currents. The MPPT control is deactivated, and the PV power has been reduced to the target value delivered by the inverter at the Point of Common Coupling. Case studies with simulations and experimental results have verified the effectiveness and flexibilities of the proposed power control strategy to release the advanced features.