Abstract:  Using battery energy storage system (BESS) to smooth wind power fluctuation can optimize wind power output characteristics and improve the stability of output power in wind farm. In order to extend the service life of BESS, it needs to control the state of charge (SOC) of BESS in a defined interval furthest, which can have enough capacity to charge and discharge at next moment and bring a better smoothing effect. Therefore, this paper proposes a new control strategy which consists of two control algorithms. The selection between these two algorithms is determined according to the value of wind power fluctuation during the operation of system. Two algorithms are switched with each other based on the actual operating conditions of wind farms. Simulation results show that, compared with the traditional low pass filtering, the new strategy not only has a good stabilizing effect but also can make the SOC of BESS in a reasonable range which can largely extend the service life of BESS and save the cost of energy storage investment.

Key words:  wind power generation, wind power fluctuation, battery energy storage system （BESS）, state of charge （SOC）