Solar microinverter toplogies for photovoltaic generation systems

摘要

Microinverter is an inverter to interface the output power of a single PV module to the AC Distribution grid. Microinverters can be classified based on the galvanic isolation. Isolated topologies such as flyback inverters are widely used to implement microinverters as they can provide high voltage gain required in grid-tied PV inverters. On the other hand, nonisolated topologies have high efficiency and easy ground fault current detection, but they lack the high voltage gain required. This thesis proposes a novel coupled inductor based two-stage non-isolated microinverter, which has high voltage gain and high efficiency. To compare the performance of proposed non-isolated topology with isolated microinverters two other novel isolated topologies are proposed namely Zeta microinverter and Cycloconverter-based microinverter. In Zeta microinverter by operating converter in Continues Conduction Mode (CCM) higher efficiency than flyback microinverter is achieved whereas in Cycloconverter-based microinverter direct high-frequency ac (HFAC) to lowfrequency ac (LFAC) conversion is used which reduces the number of power stages and limits the switching loss.