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A single-phase half-bridge switching mode rectifier is presented to draw a sinusoidal line current, to achieve power factor correction and to maintain the DC-link voltage constant. Four active switches are used in the proposed rectifier to generate a unipolar pulse width modulation (PWM) voltage waveform on the AC terminal voltage. There is no clamping diode in the proposed rectifier (as compared with the neutral point clamped (NPC) converter) so as to achieve three-level PWM operation. Two control loops are used in the proposed control scheme. In the outer control loop, a proportional integral voltage controller is used to regulate the DC-link voltage. A phase lock loop circuit is adopted to generate a sinusoidal waveform in phase with mains voltage to achieve power factor correction. In the inner control loop, a carrier-based current controller is used to track the line current command. To compensate the neutral point voltage due to the load variation, a neutral point voltage compensator is used in the control scheme. Three voltage levels are generated on the AC terminal of the adopted rectifier. Computer simulations and experimental results are presented to verify the effectiveness of the proposed control algorithm.
Date of Publication: 7 July 2004