Comparative Evaluation of Three-Phase AC-AC Voltage/Current-Source Converter Systems Employing Latest GaN Power Transistor Technology

Abstract

The emergence of monolithic bidirectional GaN power transistors sparks renewed interest in AC-AC current source converters (CSCs) as an alternative to AC-AC voltage source converters (VSCs) for motor drive applications. This paper compares the two approaches with the CSC utilizing novel 600 V, 140 m Omega monolithic bidirectional CaN transistors. Aiming for a comparison of next-generation plug-and-play motor drives, both systems must fulfill the same EMI limits that cover an extended frequency range from 9 kHz to 30MHz at the grid and at the motor interface. Designing both systems with roughly the same total chip area for the same AC-AC efficiency of 97 % at a nominal power of 1.4 kW (200 V nominal line-to-line RMS voltage, 4A nominal RMS current), we identify a suitable switching frequency of 72 kHz, and we discuss efficiency characteristics over the motor current (torque) and voltage (speed) ranges. A comparison of the total magnetic component volumes finds advantages for the VSC system, which disappear if motor-integration (voiding the need for a motor-side differential-mode EMI filter) is considered.