Design Of Grid-connected Photovoltaic Inverter Based On DSP

The development of society is inseparable from energy.Facing the dual oppression of the exhaustion of fossil energy and the increasingly severe environmental problems,all countries in the world are adjusting and optimizing their energy structure,therefore,the photovoltaic industry has become a focus.This paper takes the single-phase grid-connected photovoltaic inverter system as the research object,aiming to maximize the utilization rate of light energy,reduce the energy loss caused in the conversion process,so as to improve the conversion efficiency.In this paper,the development status and application prospects of photovoltaic power generation at home and abroad are analyzed.The types,structures and standards of photovoltaic grid-connected power generation systems are reviewed.Firstly,the topologies of photovoltaic grid-connected inverter are compared and analyzed in detail,and the two-stage non-isolated topology is determined to be adopted.The control strategy of photovoltaic grid-connected inverter is analyzed and studied.The front stage is used to realize MPPT(Maximum Power Point Tracking)control,and the back stage is used to realize grid-connected control and to stabilize the voltage of the dc bus,the current inner loop and voltage outer loop were modeled and analyzed respectively to find out the optimal PI parameters.Secondly,solar cells are easy to be affected by environmental factors such as light and temperature,which results output power characteristics are non-linear under this two ever-changing factors.By analyzing solar photovoltaic cell model,this paper adopts the perturbation observation method based on variable step size to realize MPPT,on the basis of phase-locked voltage,active frequency offset method is adopted to detect isolated islands,the above two models were built in SIMULINK and analyzed with waveforms to judge their performance.In the whole modeling and simulation of the system,the double closed loop grid-connected control is verified.Finally,complete the hardware circuit with the main circuit and control circuit as the main body,the software with the main program and interrupt service program as the framework.On the basis of the above research,a 1KW prototype based on TMS320F28035 was designed,the grid-connected experiment was carried out on the equipment and relevant experimental data were obtained.From the output waveform,the grid-connected current and grid voltage were of the same frequency and phase,achieving the grid-connected power factor and verifying the feasibility and effectiveness of the system design.