An analysis of current control method for grid connected front-end three phase AC-DC converter

This paper investigates a new approach in developing a current control method utilizing the grid virtual flux estimation technique for reducing the number of sensors and to enhance the control performance of the grid connected three phase ac-dc converter system. Accordingly, a virtual flux oriented control (VFOC) with the improvement of virtual flux estimation technique has been proposed in this work. The virtual flux components obtained from the grid virtual flux estimation technique is used to extract the grid voltage information from the converter switching states, the dc-link output voltage and the three phase input currents. The VFOC structure is developed by incorporating the grid virtual flux components in modeling the ac-dc converter. The steady state as well as the dynamic performances of the proposed VFOC are presented and analyzed by using Matlab/Simulink and experimentally verified in real-time. The results show that the ac-dc converter utilizing the proposed VFOC is able to produce a fixed switching frequency, almost sinusoidal with low total harmonic distortion of the line currents, unity power factor operation and adjustable dc-link output voltage.