Novel Control Scheme for an Interleaved Flyback Converter Based Solar PV Microinverter to Achieve High Efficiency

Abstract

The paper proposes an optimal control strategy for the interleaved flyback based microinverter to improve its efficiency over the entire operating range. This control scheme is based on the choice of an appropriate operating mode [1-converter discontinuous conduction mode (DCM), 1-converter boundary conduction mode (BCM), 2-converter DCM, and 2-converter BCM] at various instantaneous power magnitudes. The proposed control method reduces the fixed losses associated with the gate driver and the transformer at the low power level. It also reduces the switching losses that may result due to the extremely high-frequency operation of the BCM at the low power level. Additionally, it also reduces the conduction losses through low current peak due to BCM and equal current sharing between the two converters at the high power level. Switching losses, due to the low-frequency operation of the BCM at a high power level, are also reduced. Operating mode selection of the interleaved inverter at a particular power level is based on the information of optimal efficiency. Detailed calculations of peak current references have been carried out for the various operating modes of the interleaved flyback based microinverter. Simulation and experimental results have validated that the proposed control method results in better efficiency compared with the conventional (DCM, hybrid DCM/BCM, hybrid 1-converter/2-converter) control methods with the output current total harmonic distortion remaining within the specified limits.