Control of a high-efficiency PV inverter with power decoupling function

This paper presents a single-phase grid-connected inverter with a power decoupling circuit which enables longer lifetime and high conversion efficiency. In the single-phase grid connected inverter, a power pulsation with twice the grid frequency is appeared in the input dc capacitors. In a conventional inverter, electrolytic capacitors with large capacitance have been used in order to reduce the large ripple voltage appeared on the capacitor. However, lifetime of the electrolytic capacitor is generally shortened by the large ripple current with twice the grid frequency. The authors have been studied an active power decoupling method that reduce the pulsating power flowing into the input dc bus line by transferring the ripple energy to a small film capacitor, and extension of the lifetime of the inverter can be enlarged. On the other hand, power loss caused by the power transfer of the pulsation power results in the decrease of overall conversion efficiency of the inverter system. In order to overcome this defect, a revised power decoupling circuit topology which realizes a minimum loss on the decoupling circuit is proposed. Simulation and experimental verifies the effectiveness of the proposed method.