Multilevel AC/DC power converting method and converter device thereof

摘要

A multilevel AC/DC power converter device includes a high-frequency power converter including a first AC port and a low-frequency power converter including a second AC port and a DC port. A power converting method includes: serially connecting the first AC port of the high-frequency power converter and the second AC port of the low-frequency power converter; operating frequency of the low-frequency power converter synchronized with frequency of an AC power source and operating the high-frequency power converter with high-frequency PWM to generate a multilevel AC voltage; and controlling the multilevel AC voltage to obtain a current of an input AC port being sinusoidal and in a same phase with a voltage of the AC power source. Accordingly, the input power factor approaches unity and the low-frequency power converter supplies a DC voltage to a load via a DC output port.

主权项

1. A multilevel AC/DC power converting method consisting of:
connecting a high-frequency power converter and a low-frequency power converter between an AC power source and a load in a three-phase three-wire power converter; providing a first AC port of the high-frequency power converter and a second AC port of the low-frequency power converter in the three-phase three-wire power converter, and serially connecting the first AC port of the high-frequency power converter to the second AC port of the low-frequency power converter to form a cascade bridge-type multilevel rectifier structure, wherein the high-frequency power converter consists of two single-phase full-bridge power converters and two DC capacitors provided in the three-phase three-wire power converter, with each of the two single-phase full-bridge power converters including an AC terminal performed as the first AC port, with the AC terminal comprising a first terminal point and a second terminal point, wherein the second AC port of the low-frequency power converter includes a first terminal point, a second terminal point and a third terminal point, with the first terminal point and the second terminal point of the second AC port of the low-frequency power converter selectively connecting with the second terminal points of the AC terminals of the single-phase full-bridge power converters while the third terminal point of the second AC port of the low-frequency power converter selectively connecting with the AC input port via a filter circuit; operating the low-frequency power converter with a frequency of the AC power source; operating the high-frequency power converter with high-frequency PWM to generate a multilevel AC voltage from a serial connection of the low-frequency power converter and the high-frequency power converter; controlling the multilevel AC voltage for a current of an AC input port approaching to a sinusoidal waveform and identical with a phase of a voltage of the AC power source, thereby operating a power factor approach to unity; controlling a DC voltage output from the low-frequency power converter to supply to the load via a DC output port.