A Control Method of Charging Level for Battery Energy Storage System for Smoothing Output Fluctuation of Wind Power Generation -Development of State-of-Charge Feedback Control-

This paper proposes a new control method for maintaining a charging level for a battery energy storage system (BESS) coupled with a wind farm (WF) to stabilize WF output.Since output of wind power varies with wind speed, operation of a power system will be influenced if a large number of WFs are interconnected to the power system. The authors have made a research project to conduct demonstration tests of a BESS coupled with a WF to smooth out short-term fluctuations in WF output. In operating the BESS, it is essential to maintain a charging level of a battery within a proper range. This paper thus proposes a new control method called “State-Of-Charge Feedback Control (SOC-FB control)” to stabilize the charging level.In this paper, characteristics of the SOC-FB control are discussed through theoretical analyses with its transfer functions as well as through simulation studies. Analyses on the transfer functions show that the SOC-FB control is effective to stabilize the charging level of the battery. Sensitivity of the control parameters of the SOC-FB control is examined from the viewpoints of the performance of smoothing the output fluctuations and stabilizing the charging level. The performance of the BESS is also examined through simulations using actual WF output data. The results show that charging level is kept within its proper range without deteriorating the smoothing performance by adopting the SOC-FB control, while the charging level goes beyond its proper range without the SOC-FB control.These results clarified the effectiveness of the SOC-FB control to maintain the charging level of the battery. Results of the sensitivity of the control parameters are considered useful to select proper parameters for the control.