SVPWM Strategy With Neutral Point Voltage Balance Capability for Electrolytic Capacitorless Vienna Rectifier

The neutral point (NP) voltage fluctuation is an inherent problem of the three-level converter, which is generally solved by increasing the capacitance value. However, electrolytic capacitors will cause problems such as short lifetime and low power density. Using film capacitors on the DC side of Vienna rectifiers instead of electrolytic capacitors can solve these problems. However, the reduction of the capacitance value will bring about the NP voltage fluctuation, which will further affect the quality of the grid-side current. In this paper, a modulation strategy based on SVPWM with redundant vector distribution is proposed, which can suppress NP voltage fluctuations and improve input current quality for Vienna rectifier. In order to reduce the NP voltage fluctuation, the influence of each vector on the NP current is analyzed. By assigning the action time of the redundant small vector, the NP current is zero in a switching cycle, which suppresses the fluctuation of the neutral point voltage and reduces the input current harmonics. Finally, the proposed modulation algorithm is compared with the traditional modulation algorithm on the electrolytic capacitorless Vienna rectifier platform, and the feasibility of the algorithm is verified.