Study On Optimal Scheduling Strategy Of Battery Energy Storage System And Its Energy Management Method

In recent years,battery energy storage systems(BESS)have obtained rapid development and become an indispensable part in power system.BESS plays important roles in promoting renewable energy consumption,peak shaving,and voltage regulation.In this paper,the dispatching strategy and energy management method of BESS in power system are investigated.The major contributions of this paper can be summarized as following:(1)In a distribution network that integrates BESS,different application scenarios of BESS are investigated including promoting local consumption of distributed generation,improving voltage distribution,and participating peak load shifting.Furthermore,considering the constraints of distributed PV operation,line capacity,peak load shifting,main transformer capacity,load power factor and so on,a dispatching model for BESS integrated distribution network based on mixed integer programming is established,where the objective function is formulated by minimizing the power exchange cost between distribution network and transmission network and the penalty cost of node voltage deviation.In order to solve the problem that power flow calculation is difficult to consider in mixed integer programming mathematics,this model presents a simplified flow consideration method that can set uni/bi-directional power flow,and linearize the nonlinear terms in objective function and constraint conditions by using large M method.The proposed model is simulated and verified in modified IEEE 33 bus system.The influence of bidirectional power flow on BESS's regulating function is discussed,the improvement effect of BESS on various indexes of distribution network is analyzed,and the validity of the proposed model is verified.(2)In the terms of BESS's energy management method at the station level,basic topological structures of BESS are introduced and major factors that affect the battery cycle life are analyzed.Through the measured data of the relationship between Depth of Discharge(DOD)and battery cycle life of lithium iron phosphate battery,the functional relationship between battery cycle life and DOD is obtained by fitting.To solve the problem that BESS has inconsistent life attenuation due to different of operation conditions of each battery pack when BESS tracks the dispatching instruction of power system,an energy management strategy considering SOH of battery packs is proposed.In the proposed method,the SOH of each battery pack is taken into account in the energy management strategy of BESS.Meanwhile,two strategies,constant parameter strategy and variable parameter strategy,are summarized in this paper according to the designed charge-discharge sequencing rule for battery pack.Specifically,the constant parameter strategy optimizes the SOC working interval for the batteries with low SOH.In addition,the variable reference value strategy can optimize the charge and discharge amount of low SOH battery so that the total charge and discharge amount of low SOH battery in a scheduling cycle is less than that of high SOH battery.Both strategies can restrict DOD for batteries with low SOH,so that the SOC of each battery pack convergences to the optimized reference value.In this way,the battery life attenuation for batteries with lower SOH is delayed to some extent and the overall service life of BESS can be extended.The proposed method is simulated through a BESS real-time scheduling instruction from a PV/BESS station in Qinghai province.And the SOC and changes of charge and discharge amount of each battery pack under different scenarios were analyzed in detail,which verified the effectiveness of the energy management method proposed in this paper.The effectiveness of the proposed energy management method is verified.