Unbalanced current analysis of three‐phase AC–DC converter with power factor correction function based on integrated transformer

Abstract

Three-phase AC–DC converter based on integrated transformer is a novel converter which is capable of handling high power levels and can realise power factor correction function. Owing to different parameter tolerances of the primary windings, grid current could be unbalanced, which usually could not be solved through traditional control methods. To handle this problem, a current balancing method is adopted in this study to improve former current control loop. Meanwhile, based on the principle of instantaneous power balance, a dual loop control strategy with an outer voltage loop and an inner current loop is designed. Besides, load current feedforward control is introduced to enhance the dynamic response. Moreover, phase-shift control is employed as the modulation method, in which duty ratios change along with sinusoidal signals. Simulation and experimental results show that the control strategy could make the three-phase current of the converter sinusoidal and balanced.