Improved Control for Three Phase dual-Stage Grid-Connected PV Systems Based on Predictive Control Strategy

Abstract

This paper focuses on the control of three phase dual-stage grid connected photovoltaic (PV) system. The control objective is to extract the maximum power delivered by PV array under irradiation variations and to inject it into the network, as well as, the reactive power requested by grid operator while providing high grid currents quality. A fast and accurate control method based on variable step size incremental conductance and predictive current control is proposed and applied to the first stage (DC-DC Boost converter) in order to achieve a fast maximum power point tracking MPPT with less oscillations. Furthermore, a voltage oriented control based on both predictive control strategy and space vector modulation SVM (PS-VOC) is applied to the second stage (Two-level inverter) in order to control the d-q axis grid currents. The proposed system is simulated using Matlab/Simulink and simpower system packages. As results, the proposed MPPT provides a fast and accurate tracking with significant oscillation reduction around the MPP in comparison with conventional methods under irradiation changes. Besides, the injection of the extracted PV power and reactive power requested by the grid operator is provided with high current quality due to the capability of the proposed PS-VOC control method.