Design Of A Low-power Grid-connected Photovoltaic Inverter

As the reform of the national energy consumption structure and the urgent request of protecting the ecological balance in recent years, the penetration of renewable green energy represented by solar and wind is increasing year by year in the traditional distribution network.At the same time, Because of its wide use, the distributed photovoltaic(PV) grid technology has become a research hotspot. Low-power photovoltaic(PV) grid-connected inverter is an important part of distributed photovoltaic(PV) grid system, which can achieve the quality of output power improving, adjust the output power and output power factor.The working principle and control modes of Photovoltaic(PV) grid-connected inverter are analyzed in this thesis firstly; moreover, this thesis discusses several typical maximum power point tracking methods. At the last of this thesis, the quasi proportion resonant controller as inner control loop is adopted to realize zero steady-state error of current sine signal tracking and the strong anti-interference ability of the control system; joining the grid current dc component inhibition loop can improve the quality of grid current. In order to improve the PV grid-connected inverter’s performance, islanded detection loop is added.In the implementation of single-phase grid photovoltaic power generation system with grid synchronization technology, this thesis design a single-phase phase-locked loop based on cascaded delay signal cancellation(CDSC), and in the case of mutations of amplitude and frequency at the grid side, verifies the stability and superiority of the phase-locked loop algorithm in the thesis, which can basically guarantee the PV grid-connected inverter to achieve synchronization.Finally, this thesis builds simulation mode of control system using MATLAB/Simulink to verify its correctness and effectiveness, and also adopts TMS320F28335 chip of TI company as control core, designing the low-power single-stage PV grid-connected inverter control system’s hardware circuit, including the modulation signal circuit, phase lock circuit,signal sampling and regulate circuit and over-voltage and over-current protection circuit.Then, a single-phase PV grid-connected inverter is designed and verifies its performance by comparing the efforts of simulation and experiment.