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

Discontinuous pulsewidth modulation (DPWM) has been widely used in the 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 pulsewidth modulation (ICB-DPWM) scheme for the Vienna rectifier is provided. Then, zero-sequence components 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, the simulation and experimental results of the Vienna rectifier verify the correctness and advantages of the proposed ICB-DPWM scheme.