Improved Carrier-Based DPWM for Vienna Rectifier Considering Oscillated and Unbalanced Neutral-Point Voltages

Discontinuous pulse width modulation (DPWM) has been widely used in three-level Vienna rectifiers due to its higher efficiency. However, for dual output load applications, vector synthesis error will be introduced by oscillated and unbalanced neutral-point (NP) voltages after using conventional DPWM without NP balance control, which results in extra input current distortion. In this article, an improved carrier-based discontinuous pulse width modulation (ICB-DPWM) scheme for the Vienna rectifier is provided. Then, zero-sequence components (ZSCs) with optimized clamping modes considering oscillated and unbalanced components are investigated. Thus, operation characteristics with reduced low-frequency current harmonics and no zero-crossing distortion are realized simultaneously. Under balanced and unbalanced load conditions, the proposed ICB-DPWM can operate stably without regulating clamping modes, so the switching losses are reduced effectively. Furthermore, it features an almost 52% runtime reduction under oscillated and unbalanced NP voltage conditions compared with the DPWM based on the asymmetrical space vector diagrams. Finally, simulation and experimental results of the Vienna rectifier verify the correctness and advantages of the proposed ICB-DPWM scheme.