Sliding mode control of neutral point clamped PWM rectifier

A sliding mode controlled single-phase neutral point clamped rectifier is proposed to achieve bi-directional power flow, regulate dc bus voltage, reduce line current distortion and obtain nearly unity power factor. Based on the neutral point clamped topology, the voltage stress of the power devices is clamped to half dc bus voltage instead of full dc link voltage in the conventional PWM rectifier. The line current tracking, dc link voltage regulation and neutral point voltage compensation are performed by the inner loop current controller, the outer loop voltage controller and voltage balance compensator, respectively. Based on the proposed control scheme, the rectifier can draw a clean sinusoidal line current with unity input power factor. The experimental results are presented to verify the effectiveness of the proposed control scheme.