Study on quasi resonant grid-connected current compensation method with controllable switching period

In order to improve the performance-price ratio of the grid-connected photovoltaic power generation micro-inverter, with the grid-connected flyback inverter as the research object, an open-loop control strategy based on the critical continuous operation mode is studied in this paper. According to the current in the grid, the peak current in the primary and secondary inductors of the flyback inverter can be calculated, and the turn-on and turn-off time of switch can be calculated by the electromotive force formula of inductor, thus controlling the turn-on and turn-off of switch in the flyback inverter. As this open-loop control method does not need the feedback control of the actual grid current, the cost of the system can be reduced. In order to improve the efficiency of the flyback micro-inverter, a quasi resonant control method based on the equal average current is also presented in this paper. When the switch off, select the appropriate resonant valley point of the drain-source voltage to turn on the switch and follow the principle of equal average grid current, then new peak current in the primary and secondary side can be calculated, thus obtaining the turn-on and turn-off of switch. The method in this paper can effectively control the switching period and reduce the switching loss, and the experimental results show that the algorithm in this paper can realize the grid-connected power generation of the grid-connected flyback micro-inverter and have high reliability and low cost.