Controlling trilevel center-split power quality compensator by 3-dimensional space vector modulation

In the past researches, strategies based on hysteresis control are proposed for controlling trilevel 3-leg center-split inverter, which can be used as a shunt power quality compensator for three-phase four-wire system. In this paper, results indicate that the complicated 3-dimensional (3D) space vector allocation of the trilevel center-split inverter can be simplified into six space vector regions of two-level center-split inverter. Thus, based on the 3D space vector modulation (3DSVM) control strategy for two-level center-split inverter, the novel 3DSVM control strategy for trilevel 3-leg center-split inverter is proposed. Different from the conventional 2-dimensional space vector modulation (2DSVM), the zero-axis component should be of a major concern in this novel 3DSVM since 3D space vectors are located in different horizontal planes and each vector contributes to zero-axis compensation. When the zero-axis component is considered, the neutral current of the three-phase four-wire system can be compensated simultaneously with three-phase current harmonics. Simulation results are given to show the validity of the proposed control strategy.