Average modeling and control for three-phase three-level non-regenerate rectifier with unbalanced DC loads

This paper proposes a new average model and a control approach for the three-phase three-level non-regenerate rectifier (Vienna-type rectifier) with unbalanced dc load. State space analysis is first carried out to achieve the relationship between the voltage unbalance, load conditions and the control duty cycle. With the implementation of an optimum zero-sequence component, a simplified average model for the dc output stage with unbalanced load is obtained. Based on the developed model, a new control approach and the criteria of control parameter selection are presented. The simulation and experiment results validate the proposed control scheme.