A Coupled Inductor Based Ćuk Microinverter for Grid Connected Photovoltaic Applications

A single phase single stage current source microin-verter scheme is proposed in this paper which can extract maximum power from a low voltage photovoltaic (PV) panel and can supply it to a single phase utility grid of (220 - 230) V at unity power factor (UPF). High voltage gain at the output stage is achieved by employing a Coupled inductor based Cuk topology at the input stage of the inverter. Energy trapped in the leakage inductance of the coupled inductor is utilized at the grid side by employing a coupling capacitor. Voltage spikes that appear across the power switch during the turn off process, are controlled by using a passive snubber. Discontinuous mode of conduction (DCM) of the magnetizing current is adopted to ensure simplicity in design of the controller. Soft turn on of the power switch is experienced by utilizing the phenomenon of resonance that occurs between the snubber capacitor and the magnetizing inductance during high frequency turn on period, thereby improving the overall system efficiency. The operating principle, followed by the current control strategy for the proposed microinverter is discussed in details. The viability and efficacy of the proposed scheme is verified by extensive simulation studies.