Development Of Photovoltaic Power Generation System With A Battery Storage

Photovoltaic grid connected power generation system using inverter to generate the DC power of the photovoltaic cell components into alternating power,has become one of the main applications of solar renewable energy industry in recent years.However,due to the inevitable fluctuations in the intensity of the sun's light,the power of grid connected photovoltaic generated to the power grid will also fluctuate,which will have an impact on the stability of the power grid.In addition,when output power of the photovoltaic power generation system is low,not only the output current harmonic components will increase,but also the output power quality will decline,the electromagnetic environment will also deteriorate,and thus become a practical problem of photovoltaic power generation system.According to the output power fluctuation phenomenon of traditional photovoltaic power generation system,based on the analysis of the existing energy storage technology,a new type of photovoltaic power generation system is studied in this dissertation,in which the battery energy storage technology is used to smooth the power of the system.The main contents of this dissertation are as follows:In this dissertation,the structure of a new type of photovoltaic grid connected power generation system with the intermediate DC link connected to energy storage battery is designed.Based on the energy flow relationship between energy storage link,DC/DC link and DC/AC link,the four energy working states of the photovoltaic power generation system are analyzed.Furthermore,a new energy storage control strategy is proposed,which can reduce the THDI of grid connected current in the morning and evening,and also the power fluctuation can be more small.On this basis,the dissertation analyzes the relationship between the battery capacity and power fluctuation,and puts forward a reasonable method to determine the battery capacity.Then,the key design of three level three-phase inverter in PV system is introduced in detail.The inverter uses PLL soft lock control system which is based on dq rotation coordinate to realize synchronization,and the voltage and current double closed loop control is used to realize the fast and stable control of DC bus voltage and output voltage.The design process of parameters of phase locked loop and voltage and current control parameters are introduced in detail,and the results are verified by Matlab simulation.This dissertation introduces the analysis and design of Boost converter in the system.The Boost circuit uses the voltage outer loop and current inner loop control to achieve boost function,uses the disturbance observer method to achieve the maximum power tracking of photovoltaic cells(MPPT)function.The control parameters above are designed,and verified by the Matlab simulation.Finally,a 50 k W prototype is built,and a variety of tests are carried out.Among them,DC/AC,DC/DC link can work normally,the entire system can achieve a decline of daily output power fluctuation,output current harmonics can also meet the technical requirements of the standard.