Research On Grid Connected Control Technology Of Photovoltaic Power Generation

Nowadays,people pay more and more attention to environmental protection.Clean energy is required to occupy a certain proportion in the power supply of power grid.As an important part of clean energy,solar energy,with its unique advantages,has attracted much attention in the field of new energy power generation.With the development of photovoltaic power generation technology,the cost of photovoltaic modules is becoming lower and lower,which provides more convenient conditions for the popularization of photovoltaic power generation.In order to make more convenient and full use of solar energy,efficient grid-connected control of photovoltaic power generation has become a hot topic in the field of photovoltaic power generation.In this thesis,single-phase photovoltaic grid-connected system as the main research object,focusing on the maximum power point tracking and inverter grid-connected control of photovoltaic power generation,the two key technologies are analyzed in depth.First of all,photovoltaic cell MPPT unit control is discussed.Starting from the basic principle of photovoltaic cells,the characteristics of photovoltaic cells under different light intensities and temperatures are studied.The maximum power point tracking(MPPT)method is analyzed theoretically.The common MPPT methods are compared.An improved MPPT method based on Boost circuit is proposed.The validity and optimal step size of the strategy are obtained by simulation.Secondly,the control technology of PV grid connected inverter unit is studied.This thesis introduces the structure and working principle of grid-connected inverter,analyzes the dual-closed-loop grid-connected control structure of single-phase photovoltaic power generation system,designs the current inner loop and voltage outer loop of voltage-current double-closed-loop SPWM control strategy,and presents a quasi-PR control current inner loop compound based on voltage outer loop compensation to overcome the shortcomings of the inner loop PI control.The simulation results show that the control method can improve the dynamic response of PV grid connected inverter.Finally,a simulation experiment of photovoltaic grid connected control is carried out.Taking the 3kW photovoltaic system as the research object,the hardware circuit,MPPT controller and inverter controller software program of the grid-connected system are designed.The simulation results show that the grid-connected control method designed in this paper can realize the unity power factor grid-connected of the inverter current.The grid-connected technology of low-power photovoltaic power generation studied in this thesis has fast dynamic response and high power factor,which provides a useful reference for engineering practice.