Two stage resonant inverter for AC distributed power supply

This paper describes the topology aspects of a two-stage high frequency resonant inverter consisting of a buck converter and a half bridge series/parallel resonant inverter. The resonant inverter has the advantages of better waveform quality, zero voltage switching adaptability to both inductive and capacitive load, and high efficiency. Most importantly, the phase angle of this resonant inverter can be controlled independently from the voltage magnitude control, allowing for multiple module operation in parallel. The design of high efficiency, fast dynamics first stage converter is the key of the whole system performance. In this paper, a zero voltage transition (ZVT) based two-switch buck converter is proposed. By using an auxiliary circuit consisting of auxiliary switch, inductor and capacitor, the current transition from the lower switch to the upper switch can be accomplished with zero voltage. Prior to turning on the upper switch, the auxiliary circuit Is turned on with zero current switching. The upper switch flows negative current as the auxiliary circuit current exceeds the buck inductor current, therefore the anti-parallel diode conducts before the gate signal applies to the upper switch. The lower switch has zero voltage switching naturally. The interaction of the ripples of the fist stage buck converter with the second stage output voltage harmonics of the inverter Is also investigated.