Design of a command scheme for grid connected PV systems using classical controllers

This paper proposes an approach of a grid connected PV control scheme, that provides optimal PV power and high quality of current injected into the grid and, therefore, high power quality. The control scheme combines current control and power control loops. To analyze the dynamic behavior and the design of the control strategy, a conventional two-stage energy conversion is selected and briefly modeled. The command developed around the first stage will raise the relatively low solar voltage to a suitable level corresponds to the optimal photovoltaic power. Around the second stage a voltage and current loops have been designed to regulate respectively the dc link voltage and the output inverter current. The aim of this command is to inject energy into the grid at unity power factor and a current with low harmonic distortion. All command loops of the grid connected photovoltaic system is based on classical controllers which are composed of proportional-integral (PI) regulators. The choice of control variables and the design of command loops are discussed. The proposed global model is simulated with the help of Matlab-Simulink, by considering a 3 kWc solar generator.