The Research And Design Of Grid-connected Microinverter Based On An Interleaved Flyback Structure

Into the new century, with the rapid population growth and urbanization, thedevelopment of new energy technology has becoming hot pressing issues for the energycrisis. Solar energy because of its mine, clean, safe, is considered to be the most ideal oneof the renewable energy. Photovoltaic (PV) grid inverter as interface device betweenphotovoltaic battery and network, is the key technology to grid-connected photovoltaicpower generation, the performance of the inverter directly determine photovoltaic system’sefficiency.PV grid-connected microinverter studied in this paper is to change the current fromdirect current(DC) to alternating current(AC) with a single solar panel module, eachcomponent can be separately transformed, so that it can scan each independent solar panelsof the peak power point in a relatively wide range, avoid local peak as the maximum powerpoint tracking (MPPT) point, and can improve MPPT efficiency. Thus the output power ofeach module is optimized, and make the overall output maximum.According to the features of the microinverter controller, a interleaved flyback with asimple and isolated structure is used, describing its working principle in detail. Bysimplifying the circuit model of flyback converter, this paper analyzes the converter’scontrol characteristics, makes the current get from MPPT control as the benchmark tocontrol the flyback transformer original side with the average current control method,realizing the half sinusoidal current output. For the interleaved flyback converter mayappears load imbalance, a load balance control loop is proposed. Establish a mathematicalmodel of the photovoltaic cell, and deduce the utilization relationship between inputdecoupling capacitor and the photovoltaic cell panel, by choosing the appropriate inputcapacitance, the efficiency of system is improved effectively. Validate its effectiveness inthe Matlab/Simulink simulation environment, and achieve a better output waveform..Finally, a digital control of200W prototype based on dsPIC is designed, thecorresponding circuit device is selected and program is designed. The experimental results show that grid-connected microinverter based on an interleaved flyback structure’sperformance meets the design requirements, which verify the topological structure and thecontrol method’s effective and the theoretical analysis’s correct. It provides the basis forPV inverter field and market.