Phase-staggered multiple ZVS inverters for grid-connected PV systems

Power switches in many DC/AC inverter designs are hard switched, which generates EMI noise and losses in the inverter. A relatively low switching frequency may be used to increase the inverter efficiency; however, this imposes a compromise in the size of the inverter components. In this paper, switching losses have been minimized by incorporating Zero Voltage Switching (ZVS) in a full-bridge topology, at switch turn-on and an adaptive Variable Dead-time Control at switch turn-off. Since the soft switching technique is based on control algorithms, there is no additional cost and size involved with the use of any extra auxiliary circuits. Further, the size of the output filter is reduced without increasing the switching frequency, by connecting multiple grid-tied inverters in parallel. This interleaving technique also improves the quality of the current fed into the utility grid. The proposed method was implemented on a 250W micro-inverter prototype to validate the superior performance of the proposed concept and to compare the experimental results with those of the existing methods of soft switching.