| In the development and utilization of renewable energy,photovoltaic power generation has randomness.It causes dynamic disturbance to the stable operation of power grid,and its large number of access leads to the frequent occurrence of light discarding phenomenon.Residential photovoltaic energy storage system has a certain absorption capacity.It is conducive to supporting the stable operation of power grid and reducing the phenomenon of light discarding,and has a good development prospect.This subject is based on the mode of spontaneous self-used,the remaining electricity is used for energy storage,the surplus electricity is connected to the grid,and the lack of electricity is provided by the grid.This project carries out multi-modal analysis on the residential single-phase photovoltaic power generation system with energy storage under the conditions of actual working conditions,and carries out in-depth research on the single-phase five level converter,so as to achieve the goal of improving the quality of residential waveform and power supply capacity.Firstly,this thesis analyzes the research background and significance of residential single-phase photovoltaic power system,as well as the research hotspots of topology and energy coordinated control of residential photovoltaic energy storage system.Then,summarizes the research status of topology,modulation strategy and capacitor voltage balance of multilevel converter,and puts forward the main research content of this topic according to the existing research hotspots.Secondly,the working principle and mathematical model of Photovoltaic cell and battery cell in the system are analyzed,and the corresponding simulation model is built in MATLAB/Simulink.The photovoltaic output characteristics and battery charging and discharging characteristics were simulated and studied.Based on the characteristics of photovoltaic and battery,the constant voltage control strategy and maximum power point tracking control strategy of photovoltaic cell were studied respectively,and the two-segment charging control strategy of battery unit,DC side constant voltage control strategy and discharge control strategy were studied.The simulation model is built in MATLAB/Simulink to verify the effectiveness of each control strategy.This paper focuses on the topology and working principle of the five-level bi-directional converter in the bi-directional DC/AC cell with energy regulation.The modulation principles of six carrier PWM modulation strategies are studied in detail,and the simulation is carried out in MATLAB/Simulink one by one to verify the rationality and correctness of each modulation strategy;theoretical analysis and deduction are made for the two times power frequency fluctuation and neutral point potential imbalance on the DC side of the converter;the instantaneous value control strategy and vector control strategy of the system are compared and analyzed.The simulation model is built in MATLAB/Simulink.The simulation results verify that the five-level bidirectional converter can meet the grid connection requirements in the grid connected state and meet the load supply demand in the off-grid state.Finally,the multi-modal control strategy is deeply studied under the four dynamic energy supply and demand balance relationships of photovoltaic,battery energy storage,load power consumption and grid regulation balance.According to the multi-modal energy balance condition of each unit,five working modes are designed,the energy dynamic flow relationship of the system in each mode is analyzed,the switching principle of each mode is determined,the switching flow chart of the system in multi-modal is designed,and the simulation models corresponding to the dynamic switching of five working modes are built in MATLAB/Simulink,the simulation results show that the judgment of the multimodal control strategy is reasonable,the energy balance of the system is stable,and the units operate stably and reliably. |
PDF Full Text Request