Development of a single-phase half-bridge neutral point clamped converter and its applications

A unity power factor converter using neutral point diode clamped scheme is proposed. Four power switches are used in the proposed single-phase half-bridge converter. The voltage stress of each power switch in the proposed converter is equal to half of DC bus voltage instead of full DC link voltage in the conventional switching mode rectifier. A hysteresis current comparator is used to track the line current command. The DC bus voltage is controlled by a voltage controller to maintain a constant reference value. The applications of the proposed control algorithm also cover the active power filter (APF) and uninterruptible power supply (UPS). The system model and control algorithm are described and analyzed. The experimental results based on a laboratory prototype were performed to verify the effectiveness of the proposed control strategies.