A Flyback DCM DC-AC Converter for PV Applications

An unfolding type Flyback converter is common for PV applications. This paper proposes another topology without centre tapping which improves the wave shape of the load voltage. By avoiding centre tapping of the Flyback transformer, a more symmetrical waveform without any dc component in the output is obtained. This further improves Transformer Utilization Factor (TUF) and the voltage stress across various components is also reduced. The presence of Flyback Transformer further avoids the problems of TCO corrosion in solar panel and the leakage current by providing double grounding on the PV panel side and ac neutral. Due to unfolding type inverter, switching losses are also reduced since only one switch is operated at high frequency during the entire operation. DCM operation is preferred due distortion of current waveform in CCM mode which in turn requires an additional inner current shaping loop and also voltage spikes in the transformer winding. Design and analysis of the proposed converter in DCM mode is discussed in detail. A simple closed loop control scheme without current loop for DCM operation is simulated and results are analysed.