Research On Efficiency Optimization Method Of Two Stage Inverter

Efficiency index has attracted increasingly attention in the field of modern power electronic equipment all around the world.Two-stage single phase inverter is widely used in communication,new energy power generation technology and transport field,and so on.But its efficiency is relatively low.So this thesis proposed an on-line efficiency optimization method of two-stage inverter.Efficiency optimization method of two-stage inverter can be divided into two methods in the industry: on line type and off line type.Off line methods include optimization of existing topological parameters or proposed new topology and optimization of control strategy.The key lies in the two methods was using the technology of soft switching or reducing the switching loss.On-line methods included on-line switching topologies and on-line switching control strategies,and so on.This thesis proposed an on-line efficiency optimization method of two-stage inverter which belongs to on-line methods.It used DSP program to change the value of bus voltage within limits.The system automatically searched to the point of maximum efficiency.Firstly,the general impact factors of efficiency of two-stage inverter was simply summarized in this thesis.The relationship of bus voltage and power loss of each device was deduced in detail in this thesis.Then the pure digital and ordinary two stage inverter was detailed designed.Both of the two stages used the average current method.Former stage Boost used three loop control strategy.Backward stage full bridge inverter used double loop SPWM control strategy.The controller parameters of the inverter were detailed designed by Saber,bode diagram and experimental method.On-line efficiency optimization method of two-stage inverter--Maximum Efficiency Point Tracking method(MEPT)which based on perturbation and observation method and main circuit parameters were detailed designed in this thesis.Finally,this method was applied to photovoltaic grid-connected systems.The topological structure,overall controlling design and system startup sequence were proposed.Power loss analysis of the devices were mainly discussed.Ordinary two-stage inverter and photovoltaic grid-connected inverter platform were built.The experiment results verified the feasibility and validity of proposed on-line efficiency optimization method.