Double voltage step-up photovoltaic microinverter

In conventional photovoltaic microinverters configuration, a single PV module is connected to the grid through two converter stages: a step-up dc-dc stage and a step-down dc-ac stage. In the first stage, a high frequency transformer is generally used to achieve the high step-up voltage ratio conversion to a voltage above the grid peak value, reducing the converter efficiency while increasing its size. More recently single-stage step-up dc-ac configurations have been proposed to overcome these problems. However, they increase control complexity, and efficiency remains an issue due to the high step-up ratio required and being a single stage. Therefore, a two-stage configuration consisting of two consecutive step-up converters is proposed in this paper. With this scheme, it is possible to distribute the elevation effort to improve the global efficiency of the PV microinverter. The proposed topology merges a traditional boost dc-dc converter for the first stage, like in the conventional configuration, but operating with a below-grid-peak-voltage dc-link voltage. A step-up inverter is used for the second stage; it is composed of two boost converters connected in differential mode (dual boost inverter). Simulation results are provided to validate the proposed configuration.