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ABSTRACT

This paper proposed an improved topology for a high efficiency PWM DC-AC grid-connected PV inverter that utilizes a zero-voltage-transition (ZVT) auxiliary network to provide soft-switching condition. In this paper, a soft-switching method using ZVT technique is presented to increase the efficiency of the single-phase grid-connected photovoltaic (PV) power generation system. ZVT technique employs a resonant auxiliary circuit that is connected in parallel with the main power path to achieve the soft-switching conditions for the active and passive switches in PV inverter, without increasing their voltage and current stresses. The auxiliary circuit will be activated just before the main switch is turned on and ceases after the softswitching condition has been achieved. The operation principle, soft-switching conditions and parameter design consideration of the ZVT network for DC-AC Inverter are analyzed in detail. Mathematical modeling and simulated validation of the proposed PV system is thoroughly presented based on 500 W prototype. The proposed method contributed to switching loss reduction as well as to minimization of the stress on power semiconductor switches. These results demonstrate that the proposed dc-ac inverter with ZVT technique can achieve high efficiency while maintaining stable current injection to the grid with unity power factor. The efficiency of the proposed inverter is improved by about 4% at full load condition. It is confirmed that the ZVT technique is effective in improving circuit performance in term of efficiency. HIGH-EFFICIENCY PWM DC-AC INVERTER FOR SMALL PV POWER GENERATION SYSTEM