Research On Control Strategy Of Three-level High-power Photovoltaic Grid-connected Inverter

Three level grid-on inverter can effectively improve the withstanding voltage of thesystem and reduce the switching loss, at the same time the output voltage has lowerharmonic distortion rate than two level grid-on system. Because of its superior performance,it gradually replaced the traditional two level inverter. So the research and analysis of highpower tri-level technology must be the needs of the development of technology, it also willbe the inevitable trend of future development.The first chapter briefly introduces the topic background and significance, as well asthe current control strategy in high-power photovoltaic grid-connected inverter; Chapter IIanalyzes the steady principle and dynamic inverter commutation process, according to thetopological structure of neutral point clamped three level inverter；Chapter III describes thekey technologies of high-power photovoltaic grid-connected inverter, including three-levelSVPWM control algorithm design, the neutral voltage balance control and virtual fluxorientation, focuses on the Setting of PI parameter and control strategy of Grid and LowVoltage Ride Through. Chapter IV, according to the actual application, use the DSPTMS320LF28335chip as the control system to design flow charts of Grid control system,and confirm devices selection, hardware circuits and cabinet structure; Chapter V showsthe experimental results, including the control panel of the prototype, signal acquisitionboard, driver board, switch device modules, and grid current waveforms; Meanwhile thewhole system is simulated and verified in the platform of Matlab/Simulink; The finalchapter summarizes past research work, and the after part of the in-depth development ofthe outlook.In the experimental research, this paper build an experimental platform of rated powerfor100kw grid inverter. In hardware, it makes some boards, such as control circuit, drivecircuit, power circuit and so on. The corresponding signals are debugged. In software, thewhole control strategy of three level inverter grid and low voltage ride through built onDSP platform, and a preliminary debugging is executed.