Analysis, Synthesis and Implementation of a Direct Current Control Strategy for Three-Phase Grid Connected Converter

This work presents the analysis, synthesis and implementation of a direct current control strategy for a three-phase Grid connected Converter (GcC). The considered control strategy is aimed to control the grid current vector in the d-q reference frame. For that, two switching functions linked to the d-q components of the grid current vector were defined. These switching functions were utilized to deduce rules that allow an appropriate selection of the GcC voltage vector for the control of the grid current vector components during full and low loads, during transients and steady-state operation. In order to show the performances of the developed control strategy, simulation tests were carried out and compared with the results of two direct current control strategies: A three-Hysteresis Controllers (3HC), and a two-Hysteresis Controllers using six-Sectors Switching Table (2HC-6SST). The obtained results confirmed that the proposed control strategy decreases the switching frequency while maintaining a good value of the Total Harmonic Distortion factor (THD) of the grid currents. Also, the DC-link voltage fluctuations during severe and sudden change of the transferred active power are reduced.