Symmetrical bilateral phase-shifting PWM method of three-level isolation type direct-current converter

Abstract

The invention discloses a symmetrical bilateral phase-shifting PWM method for a three-level isolation type direct-current converter, and the method comprises the steps: generating an isosceles-triangle-shaped reference carrier according to a local clock of a controller, shifting the phase of the reference carrier leftwards by alpha/2 according to a phase-shifting angle instruction alpha, obtaining an advanced bridge arm carrier uc1, and obtaining uc2 after the phase of the uc1 is converted by 180 degrees; and shifting the phase of the reference carrier rightwards by alpha/2 to obtain a hysteresis bridge arm carrier uc3, converting the phase of the uc3 by 180 degrees to obtain uc4, calculating a modulated wave according to a conduction angle, comparing the modulated wave with the reference carrier to obtain a corresponding signal, and applying each signal to each power electronic power device to realize voltage modulation and power output of the isolation type direct-current converter. Firstly, the reference carrier is constructed, signals of leading and lagging bridge arms are symmetrically adjusted, positive and negative half-wave asymmetry of H-bridge output voltage during phase shift angle dynamic switching can be effectively suppressed, and saturation of a transformer core is further avoided.

Description

technical field [0001] The invention belongs to the field of power electronics, and in particular relates to a symmetrical bilateral phase-shift PWM modulation method for a three-level isolated DC converter. Background technique [0002] With the popularization and application of DC system in the field of power distribution, large-capacity DC converters have broad application prospects. The main circuit of the large-capacity isolated DC converter includes an H-bridge inverter unit, an isolation transformer, an uncontrolled rectifier, and an LCL filter. In the phase-shift modulation method of the H-bridge inverter unit, the H-bridge is usually divided into a leading bridge arm and a lagging bridge arm. In the traditional phase-shift modulation method, the phase of the leading bridge arm remains unchanged, and the phase of the lagging bridge arm changes in real time according to the phase-shift angle command, and then adjusts the output voltage of the H-bridge inverter unit t...

AI Technical Summary

Problems solved by technology

In the process of fast switching of the phase shift angle, the positive and negative half-waves of the H-bridge output voltage are asymmetrical, which may cause the iron core of the isolation transformer to be biased, and in severe cases, may cause the saturation of the transformer iron core and the overcurrent of the primary winding.

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