A regenerative active clamp circuit for DC/AC converters with high-frequency isolation in photovoltaic systems

Abstract

DC/AC converters with high-frequency isolation and bidirectional power flow are extensively used in photovoltaic power systems and small isolated power converters at low and medium power ranges. The main disadvantages of these circuits are: high freewheeling loss of the primary leakage current, limited ZVS range for the lagging leg switches, the effects of the parasitic elements of the systems and others. To avoid these losses an energy recovery circuit based on an active voltage clamper is presented. The control circuit is designed having a number of soft switching transitions. The system has been verified by simulation and a prototype is being tested. In this paper we present an energy recovery system and a modulation sequence for the cycloconverter. The energy recovery system is based on an active voltage clamper; the voltage peaks energy is returned to the source. Furthermore, the presented modulation sequence is designed to have a maximum number of soft-switching transitions independent of the electric variables; which means minimum losses and independence on measurement systems limitations for modulation.