High-frequency link DC/AC converter with suppressed voltage clamp circuits-naturally commutated phase angle control with self turn-off devices

High-frequency (HF) link circuit topology is advantageous in realizing compact and light-weight power converters for UPS systems, new energy systems, etc. Among its several circuit configurations, the so called "cycloconverter type" DC/AC converter has its inherent merit of bidirectional power flow and fewer power conversion stages. But, without an additional voltage clamp circuit, a voltage surge occurs at the moment of PWM switching of the cycloconverter due to the stored energy in the leakage inductance at the HF transformer. In this paper, a new approach which adopts only natural-commutation phase angle control for the cycloconverter stage instead of PWM is proposed to remove such voltage clamp circuits. Experimental results of the prototype system which include the application as an AC active filter are also shown.