Optimization of Battery Energy Storage System Capacity for Wind Farm with Considering Auxiliary Services Compensation  
[PERSON]  
1 School of Electrical Engineering, Zhengzhou University, Zhengzhou 450001, China;  
[EMAIL_ADDRESS] (X.J.); [EMAIL_ADDRESS] (Q.Z.)1 School of Electrical Engineering, Zhengzhou University, Zhengzhou 450001, China;  
[EMAIL_ADDRESS].  
time window, and not account for the influence of wind power integration on the system peaking and sparing demand. In reference [10], an optimization method of BESS capacity was proposed with taking hourly and inner-hour fluctuation of wind output. By providing some climbing ability, BESS can effectively reduce the addition peaking and sparing demand that is caused by wind power integration. A multi-objective optimization method for BESS configuration and capacity optimization is built in literature [11], and the uncertainty of wind output is added to the model in the form of probability. In [12], the benefit of electricity price on the difference between peak and valley in BESS is added to the optimization model based on the electricity market. In [13], when considering the duration time of BESS reserving the wind power uncertainty, the cost-benefit analysis model of BESS is established based on the optimal power flow. In [14], BESS is used to provide sparing reserve capacity for wind power integration, and it is of great significance to optimize the storage capacity with taking the sparing auxiliary service of BESS into account. All of these research focus on minimizing the cost of BESS investment based on the cost-benefit analysis. However, the above literatures have not analyzed the economy from the point view of wind-energy union system.  
Actually, the most direct benefit of wind-energy union system is the additional electricity of wind power integration though transferring the wind power during the hard peaking periods. What is more, BESS can also mitigate the peaking and sparing auxiliary services costs of systems that are caused by the fluctuation and uncertainty of wind power integration, which can be regarded as a certain degree of compensation to the wind energy union system. But, there is little literature to consider such auxiliary service compensation into the optimization storage capacity.  
Herein, from the point view of wind-energy storage, this paper puts forward a method to optimize the storage capacity with considering auxiliary service compensation. First of all, the fluctuation and uncertainty of the hourly wind output are analyzed. Based on description of BESS participating in the scheduling plan, the auxiliary service cost of BESS mitigation is quantified. Secondly, the equivalent life loss is introduced by considering the BESS irregular charge and discharge on the impact of cycle life. The BESS constraints adapting to the scheduling plan is put forward. Taking the wind power curtailment as one of decision variable, an optimal capacity model of BESS with considering BESS investment cost, wind curtailment saving, and auxiliary service compensation is built based on the cost benefit analysis. Finally, an example is given to validate the effectiveness of the proposed model, and the influence of the auxiliary services compensation, on-grid price of wind power, BESS investment cost, BESS cycle life, and BESS reserve level on the optimization result is analyzed. Results show that the auxiliary service compensation can effectively encourage the wind farm configuration BESS.  
The reminder of this paper is organized, as follows: Section 2 describes the optimization problem of BESS adapting to the scheduling with involved the auxiliary service compensation as one of the benefit of wind-energy union system. Section 3 provides the mathematical formulation of the optimization storage capacity problem. Section 4 presents the case results and Section 5 outlines the conclusions.