Development Of A Interleaved Flyback Micro Inverter

The intensification of energy crisis and the increasingly prominent environmental problems make the development and utilization of new energy widely concerned by the society,especially speeding up the exploration of photovoltaic industry.In the photovoltaic grid system,micro inverter has become one of the hot topics in industrial and academic research because of its modular advantages.In this paper,the common micro inverter topology is analyzed and compared.Finally,a single stage interleaving flyback micro inverter is selected as the research object with simple structure and convenient control.Research status of key technologies of the flyback micro inverter are summaried.Considering the high cost and large volume of the existing micro inverter,this paper starts from the direction of low cost,small volume and high efficiency,and studies the topology and control method of interleaving flyback micro inverter.It is expected to contribute to the popularization of the micro inverter.First,the operation mode and operation principle of the flyback converter are emphatically analyzed.It is pointed out that the inductor discontinuous current mode is simple and easy to control and it is suitable for flyback micro inverter.In view of the leakage energy problem of flyback transformer,the RCD clamping circuit is deeply analyzed.According to the characteristics of interlaced flyback circuit,an improved clamping topology is proposed,which realizes the absorption of leakage energy and clamps the leakage inductance of switch tube.Simulation and experiment verify that it can reduce the volume and cost of the system while improving the conversion efficiency.Secondly,in view of the characteristics of flyback inverter,this paper analyzes the original primary peak current control strategy of the transformer and the traditional single frequency grid connected current control method.A dual frequency grid connected current control strategy is proposed,and the grid current expression and frequency switching point selection principle under the discontinuous current mode of inductor current are derived.The high frequency strategy is adopted to limit the primary side current of the transformer when the instantaneous output power is large,and the low frequency strategy is adopted to reduce the switching loss when the instantaneous output power is small.Simulation and experiment verify that the system can reduce the volume of the system effectively on the premise of ensuring the efficiency and stability of the system.Finally,the main circuit and control circuit of the interleaving flyback micro inverter system are analyzed and designed,especially the flyback transformer is designed in detail.An experimental prototype of 250 W photovoltaic grid connected flyback inverter withTMS320F2812 as the core controller is built,and the system experiment is carried out.The experimental results verify the feasibility of topology improvement,dual frequency control and system design.