The Research Of A Photovoltaic Grid-connected System With H6 Bridge

Energy is the power source of human economic development.As the development of world economy,human demand for energy is increasing,while fossil resources are becoming depleted.For solar is clean,non-polluting,renewable and etc,it increasingly gets people’s attention.The application of photovoltaic technology has become an important area of research and development in all countries.Against this background,this paper has realized theoretical and experimental study of grid-connected PV systems controlled by TMS320F28035 which is produced by TI.1.A survey is made on the developments and trend of the PV power system home and abroad.The problem is analyzed in detail that single-phase full-bridge circuit and pulse width modulation generate common mode current.On this basis,H6 bridge structure is selected as the inverter main circuit.Finally,a single-phase non-isolated PV grid-connected topology and the system control program is determined.2.Through mathematical model analysis of photovoltaic cells,photovoltaic array simulation model under uniform illumination and part shadows is established.And this paper gives the principle analysis and simulation of conventional MPPT algorithm.3.In order to achieve grid-connected inverter output current with the same frequency and phase of grid voltage,a phase-locked loop structure based on second-order generalized integrator is used.Compared to the conventional phase-locked loop methods,this method has better filtering effect and dynamic response effect.And through Matlab simulation and experimental prototype,the correctness of PLL method is proved.4.Two-stage grid-connected inverter control strategy is selected as the program that the first stage is for maximum power point tracking,the last stage achieves bus voltage regulator and grid-connected control.The current track uses the method of grid current instantaneous feedback comparing with the triangular carrier.Controller is PI controller which is commonly used in practical application.After determining the control strategy,the mathematical model of the inverter,the theoretical principle and discrete mode of PI controller,PI parameter tuning methods are analyzed.In simulation PV system succeeds in grid-connected control.Based on the above analysis,a photovoltaic grid-connected system prototype is developed based on DSP control which successfully realizes the grid-connected control.And the waveform is good.