Modulation method of a three-phase four-wire soft-switching rectifier with voltage equalization function

Abstract

The invention discloses a method for modulating a three-phase four-wire soft-switching rectifier having an equalizing function. The method comprises the steps of: fixing the switching frequencies of all main switching tubes and auxiliary switching tubes, and enabling the switching frequencies to be same; in each switching period, performing synchronization at the time of conversion from a diode toan complementary switching tube in four groups of bridge arms, turning off the auxiliary switching tube S<aux> before the synchronization time, and resonating the bus voltage at two ends of the fourgroups of bridge arms to zero; after conversion processes from all diodes to a main tube are ended, increasing a bridge arm through process according to the polarity of balanced inductive current, and, when the balanced inductive current outflows the midpoint of the fourth group of bridge arms, not increasing the bridge arm through process; and, when the balanced inductive current flows into the midpoint of the fourth group of bridge arms, increasing the bridge arm through process, and, after resonating the voltage on a resonant capacitor C<raux> to zero, performing zero-voltage switching of the auxiliary switching tube S<aux>. By means of the method in the invention, the reverse recovery current of a main switch anti-parallel diode can be effectively inhibited; the switching loss is low;and the efficiency and the power density are easily increased.

Description

technical field [0001] The invention relates to the technical field of rectifiers, in particular to a modulation method of a three-phase four-wire soft-switching rectifier with a voltage equalizing function. Background technique [0002] A traditional three-phase four-wire rectifier with a voltage equalizing function includes four sets of half-bridge arms, and each set of bridge arms is composed of two series-connected fully-controlled main switch tubes containing anti-parallel diodes. The middle points of the first group of half-bridge arms, the second group of half-bridge arms, and the third group of half-bridge arms are connected to the three-phase grid through three AC side filter inductors, and the midpoint of the three-phase grid is connected to the DC side series capacitor group The points are directly connected to form a three-phase four-wire AC-DC converter; the midpoint of the fourth group of half-bridge arms is connected to the midpoint of the DC side series capac...

AI Technical Summary

Problems solved by technology

The first group of half-bridge arms, the second group of half-bridge arms, and the third group of half-bridge arms of the traditional three-phase four-wire rectifier circuit with voltage equalization function are controlled by sine wave pulse width modulation. The bridge arms of the group half bridge are controlled by pulse width modulation, and the circuit works in a hard switching state. The switching devices and diodes in the circuit generate a large switching loss and diode reverse recovery loss respectively, which limits the increase in operating frequency. As a result, the size of the filter in the circuit is large and the power density is not high

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