A modified modulation control of a single-phase inverter with enhanced power decoupling for a photovoltaic AC module

A photovoltaic AC module system has been expected to be installed on the private residences. The AC module inverter needs an active power decoupling circuit in order to enlarge the lifetime and to decrease the volume of the inverter by eliminating a large electrolytic capacitor on the input DC-bus. This paper proposes novel flyback-type single-phase grid interactive inverters with two modulation methods, sequential magnetizing modulation (SMM) method and time-shared magnetizing modulation (TMM) method, and discuss those of the operation characteristics and the conversion efficiency. It is verified that the TMM method has advantage with respect to the conversion efficiency while the SMM method causes results in low conversion efficiency. However, current distortion of AC output remains on the TMM method due to the turn-on/off delay on the switching device. The influence of the turn-on/off delay upon the current waveform distortion is analyzed and a delay time compensation is proposed. Since the proposed compensation method achieves low distortion waveform and high conversion efficiency as well, it is concluded that the proposed inverter is one of the optimal method for the AC module systems.