Single-phase three-level converter for power factor correction

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 with voltage stress of half dc bus voltage are used in the proposed rectifier to generate a unipolar PWM voltage waveform on the ac terminal voltage. There is no clamping diode in the proposed rectifier compared with the neutral point clamped converter 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. The experimental results are presented to verify the effectiveness of the proposed control algorithm.