Study On The Photovoltaic Maximum Power Point Tracking And Grid-connected Inverter Control

In order to improve the utilization of DC electric energy of photovoltaic output, and ensure the power quality of grid-connected PV system, this paper researched on the two-phase grid-connected inverter(GCI) and its network structure. It respectively studied the output,harmonic wave of GCI, the maximum power point tracking(MPPT) control method of photovoltaic(PV) cell.By analyzing the characteristics of PV array output, aiming at the issue that the photovoltaic incremental conductance(INC)of Maximum Power Point Tracking controls occurs oscillations caused by excessive step and the causes the system to misjudge the MPP due to sudden large irradiance changes. An improved INC method is proposed,which add power forecasting module to prevent misjudgment.The new method can improve the MPPT response speed and accuracy at steady state at the same time,when the irradiance occurs a substantial change. Simulation results show that the proposed algorithm can quickly track the maximum power point of photovoltaic cells in sudden large irradiance changes and has good dynamic and static performance.Grid-connected PV system is letting the inverting control system to track the amplitude of fundamental and the phase of grid voltage, in order to output the satisfactory electric power and unity power factor parallel in grid. However, the grid has harmonic, while high frequency inverter switching elements will produce harmonic and reactive component. Therefore, space vector pulse width modulation(SVPWM) has been used to control the inverter in this thesis,and combined the repetitive control with PI control to achieve the grid-connected power control. Repeated control and PI control uses synchronous rotating frame on the grid-connected voltage?current analysis, achieved the reactive power and active independently controlled with the use of decouple control. Repeated control and PI control eliminate the periodic harmonic and realize rapid tracking for grid voltage, so improve the quality of power. To validate the effectiveness of this control method, simulation has been and the feasibility of the method had been proved.