A three-port series resonant converter for three-phase unfolding inverters

Isolated grid-connected inverters are typically constructed of two stages, namely a voltage-source inverter stage and an isolated bidirectional dc-dc converter stage. Recently, two dual-bridge isolated series resonant dc-dc converters are used to synthesize segments of the line current and reconstruct the complete sinusoidal line currents using a three-phase unfolder. The unfolder technique synthesizes high quality waveforms, but at the expense of additional switches. This paper proposes a three-port series resonant converter topology with reduced number of switches. With the proposed topology, advantages associated with the high frequency isolation and construction of high quality waveforms are maintained, but two switches and associated gate-drive circuits are removed by using a common leg of a converter. A control method interleaving the two resonant tank currents is presented to reduce rms switch currents in the common leg. Analysis and simulation results are presented to demonstrate benefits of interleaved control in the proposed topology, by reducing rms currents in the common leg and input capacitor up to 20% and 40%, respectively.