A Novel Single-Phase Three-Level PWM Rectifier With Asymmetrical Legs

To draw a sinusoidal line current and to achieve high power factor and low voltage stress of power switches, Some single-phase three-level switching mode unidirectional rectifiers with power diodes have been presented. But there is an inherited disadvantage of imbalance of the DC-link voltage, which is difficult to be solved only by control method. A novel three-level rectifier with asymmetrical legs is proposed in this paper, it can maintain the DC-link voltage constant and draw a sinusoidal line current with nearly unity power factor. The working states are analyzed in detail, and the mathematic model of the rectifier is derived. To track the fine current command derived from a voltage controller and a phase-locked loop circuit, predictive current control and SVPWM method are used in the inner loop control. A capacitor voltage compensator is employed to achieve the balanced neutral point voltage. Simulation results are provided to verify the performance of the control scheme.