High frequency link DC/AC converter with PWM cycloconverter

A high-frequency link DC/AC converter developed for flexible, compact, and high-efficiency uninterruptible power supply (UPS) systems is discussed. The DC/AC converter consists of a 50% duty ratio rectangular voltage output inverter, a high-frequency transformer, a pulse-width modulation (PWM) cycloconverter, and an LC filter. For this converter, a three-phase output DC/AC converter can be easily realized with only one inverter and one three-phase cycloconverter. Conversion efficiency is inherently high because the inverter can utilize zero-current switching to minimize the switching loss. Output waveform control is improved because the dead time in the cycloconverter PWM can be eliminated. The main circuit configuration, the PWM method of the cycloconverter used to obtain a sinusoidal output voltage and the switching method of the inverter are described. The experimental results of a 1 kVA DC/AC converter using a high-frequency link of 20 kHz in both single-phase and three-phase output are discussed. >