Bi-directional AC/DC converter based on neutral point clamped

A single-phase bi-directional AC/DC converter based on neutral point diode clamped configuration is proposed to draw a clean sinusoidal line current with nearly unity input power factor and to achieve DC bus voltage regulation. Based on the neutral point diode clamped scheme, the voltage stress of the power devices is clamped to half DC bus voltage instead of full DC link voltage in the conventional half and full bridge PWM rectifier. The line current command tracking, voltage regulation and balanced neutral point voltage are performed by the inner loop current controller, the outer loop voltage controller and voltage balance compensator, respectively. To generate a three-level PWM pattern on the AC terminal of the AC/DC converter, a region detector of the mains voltage is employed. The effectiveness of the proposed control scheme is confirmed by the experimental results.