Research On Coordinated Control Technology Of Photovoltaic Grid Connected Power Generation System Based On Distributed Energy Storage

Among the many effective forms of renewable energy generation technology,wind power generation technology and photovoltaic power generation technology are the most mature.Compared with wind power generation technology,photovoltaic power generation technology has been widely promoted by government departments and major enterprises due to its advantages of flexibility,simplicity and moderate investment.Therefore,photovoltaic poverty alleviation and other project policies are being promoted in full swing all over the country.However,in the process of grid connection of photovoltaic power generation,due to the random volatility,intermittence and uncertainty of photovoltaic renewable energy itself,there are some defects such as difficult grid connection,light abandonment and so on.In view of the problems of photovoltaic renewable energy generation,such as the difficulty of grid connection and light abandonment,domestic and foreign experts and scholars proposed to solve them by using the optical storage combined power generation technology.The energy storage system can realize the time-space translation of electric energy,with fast response speed and the feasibility of large-scale application.The application of energy storage technology can support the development of photovoltaic from many aspects,such as stabilizing the fluctuation of photovoltaic power,stabilizing its power output,helping to improve the reliability of photovoltaic grid connection,etc.However,in the research process of coordinated control technology of photovoltaic grid connected power generation system with distributed energy storage,due to the limitation of capacity and state of charge of the energy storage unit,the charging and discharging mode and capacity of the energy storage unit are different under different state of charge,while the energy storage device under different state of charge will be safe and reliable grid connected for photovoltaic grid connected power generation system Birth effect.Therefore,it is of great significance for improving the safety and reliability of grid connected photovoltaic power generation system to carry out energy storage unit echelon control strategy to achieve the echelon control of energy storage unit,so as to improve the service life of energy storage device.Based on the echelon control of the energy storage unit,this paper studies the echelon control strategy of the energy storage unit,and on the basis of the echelon control strategy of the energy storage unit,studies the grid connected coordinated control technology of the photovoltaic grid connected power generation system with distributed energy storage.The related work and conclusions are as follows:(1)Based on the power frequency control characteristics of VSG and the operation characteristics of storage battery,the research on the coordination control strategy between VSG and VSG is carried out with the state of charge of distributed energy storage device as an important index.A coordinated control strategy of distributed energy storage power frequency controller with variable droop coefficient is proposed by dividing the real-time state of chargeof battery as the control input of power frequency controller.Based on the MATLAB /Simulink simulation platform,the corresponding simulation model is built.Through the simulation analysis,it is verified that the proposed coordinated control strategy of power frequency controller with variable droop coefficient can effectively achieve the coordinated control of VSG control and energy storage device,and realize the distributed energy storage unit zone echelon control,so as to improve the service life of energy storage device.(2)Based on the research of the echelon control strategy of the energy storage unit based on the virtual synchronous generator,a strategy of the photovoltaic parallel control system based on the distributed energy storage unit is proposed.Firstly,the principle and mathematical model of photovoltaic power generation system and the control strategy of each unit of photovoltaic grid connected power generation system are proposed;secondly,the coordinated control strategy of photovoltaic grid connected power generation system based on distributed energy storage unit is constructed;finally,the photovoltaic grid connected system based on distributed energy storage unit is built based on MATLAB / Simulink 2016 b simulation platform,and the photovoltaic grid connected coordination based on distributed energy storage unit is carried out The simulation results show that the coordinated control strategy of photovoltaic grid connection based on distributed energy storage unit can effectively avoid over discharge and over charge of energy storage unit,which is conducive to the stable operation of the system under the premise of ensuring the service life of energy storage unit.Through the simulation analysis,the effectiveness of the proposed echelon control strategy based on virtual synchronous generator and photovoltaic grid connection coordination control strategy based on distributed energy storage unit is verified.(3)Based on the research of the echelon control strategy of the energy storage unit based on the virtual synchronous generator and the photovoltaic grid connection coordination control strategy based on the distributed energy storage unit,the echelon control strategy of the energy storage unit based on the virtual synchronous generator and the photovoltaic grid connection coordination control strategy based on the distributed energy storage are tested.State of charge(state of)is used in the verification of the echelon control strategy of energy storage unit based on virtual synchronous generator Charge,SOC)70-85% energy storage discharge,soc15-30% energy storage charge and soc60% energy storage charge are tested under three operating conditions,and the effectiveness of the coordinated control strategy is verified by experiments.In the process of experimental verification of two control strategies for grid connected coordinated control of photovoltaic grid connected power generation system based on distributed energy storage,soc70-85% energy storage discharge and photovoltaic load are used+ The load of soc15-30% energy storage charge is tested under two operating conditions,and the effectiveness of the coordinated control strategy is verified by experiments.The research of this paper can provide theoretical basis and practical basis for grid coordinated control technology of photovoltaic grid connected power generation system basedon distributed energy storage.