A new control scheme for single-phase PWM multilevel rectifier with power-factor correction

A new control scheme for a single-phase bridge rectifier with three-level pulsewidth modulation is proposed to achieve high power factor and low current distortion. The main circuit consists of a diode-bridge rectifier, a boost inductor, two ac power switches, and two capacitors. According to the proposed control scheme based on a voltage comparator and hysteresis current control technique, the output capacitor voltages are balanced and the line current will follow the supply current command. The supply current command is derived from a dc-link voltage regulator and an output power estimator. The major advantage of using a three-level rectifier is that the blocking voltage of each ac power device is clamping to half of the de-link voltage and the generated harmonics of the three-level rectifier are less than those of the conventional two-level rectifier, There are five voltage levels (0, +/-V-dc/2, +/-V-dc) on the ac side of the diode rectifier. The high power factor and low harmonic currents at the input of the rectifier are verified by software simulations and experimental tests.