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A novel single-phase AC/DC/AC converter with capacitor clamped topology is presented to achieve a power factor correction in the AC/DC converter and to generate a sinusoidal voltage in the DC/AC inverter to the critical load. A three-leg configuration, which has a common leg between the AC/DC and DC/AC converters, is adopted to reduce the number of switching devices compared with the conventional three-level AC/DC/AC system. The AC/DC converter is operated to draw a sinusoidal line current with a nearly unity power factor from the AC source and to keep the DC-link voltage constant. The DC/AC inverter is controlled to provide a stable sinusoidal voltage to the critical load. A three-level pulse-width modulated scheme is used to reduce the voltage harmonics in the input and output sides of the proposed system. The carrier-based control scheme is adopted in the system to track line current command and output voltage reference. The capacitor clamped topology is used in the adopted circuit to reduce the voltage stress of power devices. The system model and control algorithm are described and analysed. Experimental results based on a laboratory prototype are provided to verify the effectiveness of the proposed control strategy.
Date of Publication: May 2005