PV Power Fluctuation Mitigation And BESS Capacity Optimization In Power Grids With High PV Power Penetration

At present,with the rapid global development,addressing the problem of energy crisis and global warming are imminent.China plays an important role in the world,and actively promotes the global energy revolution,such as solar energy,with the aim of promoting the sustainable development of the global economy and energy.Solar energy as a green energy source that can be directly obtained from nature.The use of solar energy for power generation,which has the advantages of being environmentally friendly,short construction cycle,noise-free and pollution-free in the operation process,and has become a global solution to the energy crisis.However,as photovoltaic power generation is affected by environmental temperature,solar radiation,weather and other factors,the outout power has greater uncertainty and volatility.With the increasing penetration of photovoltaic power generation,large-scale photovoltaic grid connection will cause a series of problems with the power quality and scheduling of the power grid.However,battery energy storage system(BESS)has the advantages of fast regulation speed and high energy density.Therefore,the current photovoltaic power station installs BESS to build a photovoltaic storage system,so as to solve the problem of PV power fluctuations.However,due to the high cost of BESS,it is impossible to configure unlimited BESS capacity to completely eliminate the power fluctuation.Based on this,this paper mainly studies the smoothing strategy of photovoltaic power fluctuations,capacity optimization configuration,charging and discharging control strategy and real-time operation issues for BESS in a high penetration photovoltaic power grid.The specific research contents of this article are as follows:For the problem of BESS capacity configuration in the high penetration photovoltaic power grid,lithium-ion battery is used as the energy storage medium,and on this basis,the optimal BESS capacity configuration method is studied.First of all,a power fluctuation optimization model that can follow the change of photovoltaic output is proposed.The PV reference output power obtained after the optimization,which provides a basis for the BESS capacity optimization.Then,in order to avoid the BESS working in the over-limit state for a long time,which will cause the BESS operating cost increasing,the charging and discharging control strategy of the BESS is designed.And the charging and discharging power is adjusted according to the state of charging(SOC)and the ramp-rate,so as to reduce the BESS operating cost.Finally,considering the impact of the smoothing effect on the BESS capacity optimization,an optimization model with the minimum construction cost and operating cost of the BESS is established.And the BESS optimal capacity configuration can be obtained.For the real-time control of BESS,this paper proposes a real-time control strategy of BESS based on model predictive control(MPC).The prediction accuracy of the PV output power will affect the real-time power fluctuation smoothing.The model predictive control method has a good robustness.The MPC method can effectively smooth the PV power fluctuation in the future optimization time period under the condition of limited prediction accuracy of the PV output power.Based on this,an optimization model with BESS charge and discharge power,PV power ramp-rate and BESS capacity deviation is constructed in the future optimization time period.The optimal control sequence of the BESS can be obtained.The first result of the optimal control sequence is applied to the BESS,the operating state of the system is updated and feedback correction is performed.Then through the rolling optimization,the optimal control of the BESS in the entire research time domain is realized.The examples verify that the proposed method can effectively smooth the fluctuation of the PV power output.