An Innovative VSI Controller for the Generation of Balanced Voltage in Spite of the Presence of Unbalanced Loads

The aim of this paper is to present an innovative controller for a four-leg voltage source inverter (VSI) which allows generating a balanced voltage under unbalanced load conditions. The designed innovative controller contains four differentiated part. The first part decomposes three-phase unbalanced signals in three three-phase balanced signals. The second part projects these signals on to a rotating reference frame fixed to the voltage phasor. Then, the third part consists on the regulation of the voltage and current components represented in this frame by cascade control systems and PI controllers. Finally the outputs of the PIs are processed by a 3D space vector modulation algorithm to generate the duty cycles corresponding to the desired output VSI voltage. Some results of trials realized in steady and transient load conditions show the effectiveness of the innovative controller compared to a classical one.