A Modulation Compensation Scheme to Reduce Input Current Distortion in GaN-Based High Switching Frequency Three-Phase Three-Level Vienna-Type Rectifiers

摘要

Wide bandgap semiconductors are gradually being adopted in high power-density high efficiency applications, providing faster switching and lower loss, and at the same time imposing new challenges in control and hardware design. In this paper, a gallium nitride-based Vienna-type rectifier with SiC diodes is proposed to serve as the power factor correction stage in a high-density battery charger system targeting for aircraft applications with 800 Hz ac system and 600 V level dc link, where power quality is required according to DO160E standard. To meet the current harmonic requirement, PWM voltage distortion during the turn-off transient, is studied as the main harmonics contributor. The distortion mechanism caused by different junction capacitances of the switching devices is presented. A mitigation scheme considering the nonlinear voltage-dependent characteristics of these capacitances is proposed and then simplified from a pulse-based turn-off compensation method to a general modulation scheme. Simulation and experimental results with a 450 kHz Vienna-type rectifier demonstrate the performance of the proposed approach, showing a THD reduction from 10% to 3% with a relatively low-speed controller.