An optimal control method for photovoltaic grid-connected interleaved flyback micro-inverters to achieve high efficiency in wide load range

For an interleaved flyback micro-inverter, the efficiency at heavy load is mainly determined by the conduction loss and switching loss of the semiconductor switches and magnetic components, whereas the efficiency at light load is primarily determined by the frequency-dependent losses such as the MOSFET driving loss, the turn-off loss and the transformer core loss. To shield one phase is an effective method to reduce the frequency-dependent loss and to minimize the overall loss during wide range. In this paper, both Boundary Conduction Mode (BCM) and Discontinuous Conduction Mode (DCM) control strategies are investigated for the flyback micro-inverters. Then 2Ф DCM and 1Ф DCM control methods are investigated and a hybrid control method is proposed to minimize the overall loss depending on different load current to achieve high efficiency in wide load range. The experimental results verified the benefits of the proposed hybrid control method.