Analysis of power allocation strategies in the smoothing of wind farm power fluctuations considering lifetime extension of BESS units

Abstract

The wind farm output power fluctuates because of the random intermittent speed of the wind. When the capacity of wind farms increases, the effect of wind power fluctuations on the power system stability becomes more considerable. Therefore, the fluctuations are mitigated by use of Battery Energy Storage System (BESS) units. The high cost of the BESS has always been one of the major challenges in the investment for the wind farms. Therefore, it is necessary to protect the lifetime of BESS units used in wind farms by using a proper power allocation for them. In this paper, a three-layer control method is proposed to reduce the required BESS in the wind farm, while satisfying the utility constraint and increasing the lifetime of the BESS units. Moreover, 9 power allocation strategies for charging/discharging process in the BESS units are investigated and the most appropriate strategy is introduced. The simulation results based on the output power data of a real 99 MW wind farm indicate that the proposed heuristic-based method is very successful in controlling the switching actions, because the maximum and the average achieved value of switching actions are equal to 2 and 1.14, respectively. In addition, the variance of the Number Of charging/discharging Cycles (NOC) of BESS units is 0.33 which reveals that the number of BESS units with switching actions higher than the average is very small. Moreover, the low average value of life-expended of all the BESS units represents the efficient performance of the proposed control method.