A single-phase switching mode multilevel rectifier is presented in order to improve the power factor, reduce current harmonics and regulate the DC-bus voltage. The adopted rectifier can achieve a bi-directional power-flow capability. The sinusoidal line current with fewer harmonics can be drawn from the AC mains. Six active switches are used in the proposed rectifier to achieve three-level pulse-width modulated operation. Two rectifier legs are used in the adopted rectifier. The rectifier's leg-a is operated at the carrier frequency and the rectifier's leg-b is operated at the line frequency. With using an appropriate control scheme, three voltage levels and two voltage levels are generated on the rectifier's leg-a and leg-b, respectively. Two control loops are adopted in the control scheme to achieve line current command tracking and DC-link voltage regulation. The carrier-based current controller is adopted in the inner loop to draw a sinusoidal line current form the ac source. A voltage controller based on a proportional-integral scheme is used in the outer loop to obtain a constant DC-link voltage. A neutral point voltage compensator is adopted in the system to balance the capacitor voltages on the DC side. Based on the proposed control scheme, a three-level pulse-width modulated waveform is generated on the AC terminal of the rectifier. Computer simulation and experimental results are provided to verify the performance of the control scheme.
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