A Single-Phase Grid-Connected Inverter with a Power Decoupling Function

This paper presents a single-phase grid connected inverter with a power decoupling circuit. In the single-phase grid connected inverter, it is well known that a power pulsation with twice the grid frequency is contained in the input power. In a conventional inverter, electrolytic capacitors with large capacitance have been used in order to smooth the DC voltage. However, lifetime of those capacitors is shortened by the power pulsation with twice grid frequency. The authors have been studied a active power decoupling method that reduce the pulsating power on the input DC bus line, this enables to transfer the ripple energy appeared on the input DC capacitors into the energy in a small film capacitor on the additional circuit. Hence, extension of the lifetime of the inverter can be expected because the small film capacitor substitutes for the large electrolytic capacitors. Finally, simulation and experimental results are discussed.