Research On Grid-Connected Photovoltaic Micro-inverter Based On Interleaved Flyback Structure

Micro-inverter is the core component of rooftop grid-connected photovoltaic generation system,which has the advantages of small size,low cost,flexible installation location and convqenient disassembly.Micro-inverter grid-connected generation system can realize independent maximum power point tracking for each PV module,and its overall power generation efficiency is not affected by the module difference and partial shaded.Micro-inverter has become one of the research focus of the present solar power generation technology.Among Micro-inverters,the flyback photovoltaic gridconnected Micro-inverter can achieve simultaneous boost and isolation,and has simple structure and easy control,so it is widely used in small power applications.However,with the increasing of the output power level of PV modules on the market,the single ended flyback structure can not meet the demand.The multi module parallel technology is introduced into the interleaved flyback Micro-inverter,which can be adapt to the power level of the PV module in the current market,and reduce the current ripple effectively,and reduce the requirement of the system to the filter.Therefore,this paper focuses on the interleaved flyback Micro-inverter.The power decoupling technology and maximum power point tracking(MPPT)are researched on the basis of determining the grid current control strategy in DCM mode.specific research cotents are as follows:(1)Aiming at obtain the reference amplitude of grid-connected current and improve the tracking speed and stability of the system,this paper presents a variable step size MPPT control strategy based on current disturbance in the grid-connected generation system based on interleaved flyback Micro-inverter.The simulation results show that this method is simple and easy to achieve,through effective selection step to improve the tracking speed,and can solve the misjudgment caused by abrupt change of external environment and enhance the stability of the system.(2)In order to effectively suppress the secondary power disturbance and reduce the capacity of the decoupling capacitor,a novel power decoupling circuit is proposed for the interleaved flyback inverter.The working process and control method of the topology in the decoupling capacitor charging and discharging mode are analyzed in detail.The feasibility of the new decoupling circuit and the effect of suppress secondary power disturbance are verified by Matlab simulation software.(3)The hardware and software of the interleaved flyback Micro-inverter is designed.The design of hardware circuit mainly includes the selection of the main components,the design of flyback transformer and sampling circuit and driver circuit.This part of the software includes the introduction to the main characteristics of the TMS320F28035 chip and software design flow.On this basis,a prototype with rated power 250 W and output voltage of 220 V is built and tested,and the validity of the design is verified by experiments.