A Current Source Three-Phase AC-AC Converter using Current Unfolding and Active Damping Principles

This paper proposes a new current source three-phase AC to AC converter based on current unfolding and active damping principles. The proposed converter consists of two bidirectional three-phase AC/DC converters connecting in a Back-To-Back (BTB) configuration. Each of them is similar to a bidirectional SWISS rectifier but operating in current source mode with current unfolding and active damping techniques and thus does not need to employ passive ac filter and damping resistor. Comparing to a conventional BTB current source three-phase converter, this approach requires a total of 32 switches but only eight of them are operated at high frequency, thus resulting in a significant reduction in switching losses. The other 24 switches only operate at low frequency, and therefore have negligible switching losses, long life-time and can be parallel easily to reduce conduction losses. As a result, the proposed converter is expected to deliver high efficiency at small volume. This paper discusses the basic operating principle and control method for the converter. Simulation study confirms stable operation of the proposed inverter during both transient and steady states.