A Magnetizing Current Controlled Dual-Input Flyback based Microinverter

This paper proposes a dual input flyback based microinverter (MI) in which two input photovoltaic (PV) panels are operated at their respective maximum power points under varying environmental conditions, e.g. insolation difference on the two panels. The power circuit of the proposed MI comprises of a high frequency DC-DC flyback conversion stage where the input and output of individual flyback stage are connected in series. Each flyback stage can independently regulate its associated PV input to enable maximum power extraction while generating a rectified sinusoidal voltage and current waveform at the output stage of it. This voltage and current are unfolded with a grid frequency unfolding stage, which interfaces with the single phase AC grid. A magnetizing current control scheme is implemented by using a single current sensor for each DC-DC stage. This control approach in CCM eliminates the right half plane zero in the current to duty transfer function of a flyback stage, resulting in increased bandwidth and improved dynamic response. No sensors are used to sense the output voltages of the DC-DC stages, rather they are estimated, thereby reducing the voltage sensing requirement of individual DC-DC stage. The topological configuration of the proposed MI achieves a high DC voltage gain with reduced transformer turns ratio and duty cycle as compared to a single-input single-output (SISO) MI. As compared to a SISO MI, the power harvesting becomes twice while the voltage gain requirement reduces to half. The leakage current issue of the proposed MI is mitigated by the inherent high frequency galvanic isolation stage of the power circuit. The working of the proposed MI along with its control strategy have been validated through a detailed simulation and experimental studies on a 200 W prototype. However, only experimental results are provided to adhere to the page limit of the initial submission.