Novel Three-Layer Discontinuous PWM Method for Mitigating Resonant Current and Zero-Crossing Distortion in Vienna Rectifier With an LCL Filter

Vienna rectifier is widely employed in the electric vehicle charging system and wind turbine system due to its higher efficiency and lower total harmonic distortion. However, the Vienna rectifier with the
LCL
filter has the challenge of resonant current mitigation, current zero-crossing distortion elimination, neutral point (NP) voltage balance and switching loss reduction. Moreover, these problems are mutually coupled. To overcome these issues, the causes of resonant current with the conventional discontinuous pulsewidth modulation (PWM) (DPWM) method is analyzed, which reveals that the abrupt change of reference voltage has a wide range harmonics band and easily induces the resonant current at resonant frequency. Then, based on the analysis, a novel three-layer DPWM method with three offset voltages injection is proposed. In the first layer, the NP voltage balance is realized by injecting the first offset voltage. In the second layer, the second offset voltage, which makes the discontinuous reference voltages smooth is presented to reduce the losses and suppress the resonant current. In the third layer, the third offset voltage is elaborated to eliminate current zero-crossing distortion caused by different power factor and the
LCL
filter. Based on the proposed method, resonant current mitigation, current zero-crossing distortion elimination, NP voltage balance are realized simultaneously with reduced switching losses. The effectiveness and performance of the proposed method are verified by simulation and experiment.