Dual-Input Grid-Connected Photovoltaic Inverter With Two Integrated DC–DC Converters and Reduced Conversion Stages

A dual-input dual-buck inverter (DI-DBI) with integrated boost converters (IBCs) is proposed for grid-connected applications. The proposed DI-DBI is composed of two buck-type inverter-legs and two IBCs. Two renewable dc sources, with independent maximum power point tracking, can be realized with the DI-DBI. The IBCs are used to provide a constant and stable dc-bus voltage for the inverter-legs, enabling the inverter to operate well, even when the dc source voltage varies widely and is lower than the peak amplitude of the grid voltage. Unlike a conventional two-stage dc-ac inverter, only a small ratio of the input power needs to be processed by the IBCs. The other part of the input power is directly fed to the grid through the inverter-legs; therefore, in comparison with a conventional dc-dc converter and inverter cascaded two-stage solution, the conversion stages of the DI-DBI, power rating, and losses of the IBCs are all reduced. The switching loss can be reduced as well because of the multivoltage-level characteristics of the proposed DI-DBI. As a result, a higher efficiency is achieved. Modulation and control strategies are proposed to realize independent regulation of the two dc inputs. Operation principles and characteristics of the proposed DI-DBI are analyzed in detail. Experimental results have been provided to verify the effectiveness and advantages of the proposed method.