Design Of Single-phase Grid-Connected Micro-photovoltaic Inverter

The grid-connected micro-photovoltaic inverter is a device that converts the quasi-direct current of the photovoltaic module to the alternating current,which is the main component of the distributed photovoltaic grid-connected power generation system.A single phase grid-connected micro-photovoltaic inverter with pure sinusoidal waveform has been designed in this thesis.On the basis of optimizing the inverter topology and transformer,the output waveform of inverter has been improved and control strategy has been optimized.It is of great significance that the inverter minimization and application.A two-stage inverter topology consisting of the isolated push-pull step-up DC-DC and full-bridge DC-AC conversion circuit has been finished in this thesis.The push-pull step-up,full-bridge inversion circuit and grid-connected control strategies have been studied.PWM and SPWM waveforms are used to control the push-pull and the full-bridge respectively.Using voltage and current,a double closed-loop grid-connected control method has been designed.A scheme of single-phase grid-connected micro-photovoltaic inverter has been established.The model of the isolated push-pull step-up circuit and the full-bridge inversion circuit has been built,and simulated by MATLAB/Simulink.,and the feasibility of the scheme has been verified.An improved snubber circuit for full-bridge has been designed,specific parameters have been calculated,also simulated by Multisim,and the absorption ability has been validated.The hardware circuit of grid-connected inverter based on DSP has been designed,which mainly includes push-pull circuit and high-frequency transformer in isolated DC-DC circuit,full bridge and filter circuit in DC-AC circuit,control circuit and auxiliary circuit.The main control program of DC-DC circuit and DC-AC circuit,the program of PWM and SPWM,and the program of frequency and phase adjusted have been compiled.The prototype of grid-connected inverter has been achieved and the experiment has been carried out.The experimental waveform and data have been tested and analyzed.The expected effect of the inverter has been proved by analyzing waveforms and data.