Research On Capacity Allocation And Power Control Strategy Of Photovoltaic And Energy Storage Hybrid System

In the development strategy of accelerating the construction of a clean,low-carbon,safe and efficient energy system for a new era,new energy generation is gradually becoming an important form of power generation in China.With the penetration rate of photovoltaic(PV)power in power grids increases continuously,the challenges in the safe and stable operation of power systems brought by PV generation,can’t be ignored and should be solved urgently.Energy storage technology can achieve the transfer of energy on the time axis,therefore photovoltaic and energy storage hybrid system(PV-ES hybrid system)can be formed by configuring energy storage system(ESS)in PV system.Not only can it smooth the fluctuations of grid-connected power,but also it can participate in the operation and control of grids.However,the cost of ESS is still relatively high,and the capacity allocation will affect the economy of PV-ES hybrid system.At the same time,the coordinated control between ESS and PV system also makes the active power control of PV-ES hybrid system more complicated.Based on the model of PV-ES hybrid system,this thesis analyzes and studies the energy storage allocation and active power control strategy of PV-ES hybrid system.The control strategies and output characteristics are analyzed,and the dynamic and static models are studied.According to the technical standard of PV system,the dynamic model of PV-ES hybrid system is improved,considering the impacts of control strategies.Based on the static characteristics of PV system and ESS,the static modeling methods for PV-ES hybrid system are proposed.The applicability of the model in different scenarios is discussed.By analysis and comparison with the simulated results,the validity of the model is proved.The cost and benefit of PV-ES hybrid system are analyzed.The comparative net income ratio evaluation index that reflects the economy is constructed by introducing the cost and benefit of PV system without ESS.And by analyzing the characteristics of PV power on long and short time scale,the probability index in power stability is defined in a statistic way.Aggregative index considering economy and power stability is constructed in a multiplication method,and the capacity optimization allocation model of PV-ES hybrid system is further proposed.A demonstration project is selected as the analysis example,and the results show that the model can provide an effective solution for the energy storage allocation of PV-ES hybrid system.On the basis of the energy storage allocation,this thesis studies the active power control strategy of PV-ES hybrid system.Based on the idea of system topology partition and multistrategy control,the charging and discharging strategies of ESS for different state of charge(SOC)and power fluctuations are improved,and a multi-strategy hierarchical power control of PV-ES hybrid system is proposed.Meanwhile the evaluation indexes of abandoned electricity of PV,frequency modulation,reactive power compensation,virtual inertia and life of energy storage battery are constructed.The IEEE 3-machine 9-bus power system simulation model with PV-ES hybrid system is built in Matlab/Simulink.The simulation results verify the availability of the proposed power control strategy,and the improvement effect of PV-ES hybrid system after adopting the multi-strategy hierarchical power control strategy is evaluated and discussed.