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Generally, discontinuous pulsewidth modulation (DPWM) strategy used in single Vienna rectifier will result in large current ripple and neutral-point fluctuation. When applied in interleaved rectifier, the issue of neutral-point voltage still exists. Besides, the input current around zero-crossing point is distorted due to the characteristics of unidirectional topology. Hence, a novel hybrid DPWM (H-DPWM) strategy for parallel Vienna rectifier is proposed in this article to reduce the distortion, current ripple, and neutral-point fluctuation. In this article, the characteristics of current ripple and neutral-point fluctuation with traditional DPWM (T-DPWM) are clarified at first. Then, the quantitative analyses on current ripple and neutral-point fluctuation with T-DPWM, classical space vector modulation, and optimized DPWM (O-DPWM) are presented in detail. To solve the issue of current distortion, the H-DPWM is proposed based on O-DPWM. Furthermore, the switching losses of these modulations are evaluated. At last, the analyses and performance of the proposed H-DPWM are verified by the experiments. [ABSTRACT FROM AUTHOR]

In view of the large neutral-point (NP) voltage fluctuation and the high low-frequency harmonics in the input current of conventional discontinuous pulse width modulation (DPWM) for the Vienna rectifier, a hybrid DPWM (HDPWM) is proposed on the basis of three-level to two-level conversion. The proposed HDPWM combines the modulation degree of freedom, namely the vector synthesis direction and the equivalent zero vector distribution coefficient. Under the two-level modulation unit, the shift angles that satisfy the predefined NP balance requirement for HDPWM are accurately calculated. Compared with the continuous PWM and conventional DPWM, the proposed HDPWM could effectively suppress the zero-crossing distortion, reduce the NP fluctuation and the switching losses. Simulation and experiment results demonstrate that the proposed HDPWM could reduce the NP voltage fluctuation to 1/2 of the conventional DPWM with reduced input current low-frequency harmonics and no zero-crossing distortion. [ABSTRACT FROM AUTHOR]

This paper proposes a generalized design framework for three-phase Vienna rectifiers to handle the neutral point voltage balance issue. On the basis of the design framework, it is convenient to construct various neutral point voltage balancing methods with the guarantee of stability. As demonstration, three representative neutral point voltage balance approaches are presented by choosing different zero-sequence voltages. A comprehensive comparison among the three approaches is given in the aspects of input current quality, capacitor voltage fluctuation, and system efficiency. The comparison results provide guidance for constructing the most appropriate approach based on the specific requirement. Finally, simulation and experimental results verify the correctness and effectiveness of the presented approaches and the related performance analysis. [ABSTRACT FROM AUTHOR]