Research On Photovoltaic Power Generation Grid-connected System Based On Hybrid Energy Storage

In today's society,environmental pollution and energy shortages are increasingly serious.For this reason,people have begun to pay attention to the research and utilization of renewable energy such as solar energy.However,the volatility and intermittency of the output power will affect the power quality,and an auxiliary system is needed for this purpose.This thesis studies the grid-connection of photovoltaic system based on hybrid energy storage.In the thesis,current situation of photovoltaic power generation at home and abroad is introduced briefly,and research status of the core control technology of photovoltaic power generation and grid-connected systems is outlined.For the three-phase photovoltaic grid-connected power generation system with hybrid energy storage,power point tracking control method,hybrid energy storage to suppress power fluctuations to maintain bus voltage stability,grid-connected inverter control strategy,etc.,theoretical analysis and simulation research were achieved in output characteristics of photovoltaic arrays,the thesis's detailed work is as follows:Firstly,working principle of photovoltaic cells is analyzed and the mathematical model is deduced.A simulation model of photovoltaic array is established.For the maximum power tracking of photovoltaic arrays,a maximum power tracking method based on hysteresis loop control with variable step size disturbance is proposed.Simulation proved that it has a good optimization speed,and effectively solves the problem of output power oscillation of the traditional disturbance method.Secondly,Li-ion batteries and super capacitor are selected to design a new type of energy storage controller topology.Using low-pass filtering based on SOC state feedback strategy,the simulation verified that filtering algorithm can effectively suppress the PV output power fluctuation and achieve a reasonable average of the hybrid energy storage power.Finally,for the three-phase photovoltaic grid-connected power generation system with hybrid energy storage,the energy storage inverter model is introduced in the two-phase static coordinate system,three-phase static coordinate system and two-phase rotating coordinate system.For the model in the rotating coordinate system,double closed-loop control strategy of the power outer loop and the current inner loop is adopted.System model is built on the Matlab/Simulink platform and the simulation research and analysis is performed From the simulation results,it can be seen that the photovoltaic power generation system with mixed energy storage can meets the grid connection requirements.