This paper proposes a power-smoothing scheme for a variable-speed wind turbine generator (WTG) that can smooth out the WTG's fluctuating power caused by varying wind speeds, and thereby keep the system frequency within a narrow range. The proposed scheme employs an additional loop based on the system frequency deviation that operates in conjunction with the maximum power point tracking (MPPT) control loop. Unlike the conventional, fixed-gain scheme, its control gain is modified with the rotor speed. In the proposed scheme, the control gain is determined by considering the ratio of the output of the additional loop to that of the MPPT loop. To improve the contribution of the scheme toward maintaining the frequency while ensuring the stable operation of WTGs, in the low rotor speed region, the ratio is set to be proportional to the rotor speed; in the high rotor speed region, the ratio remains constant. The performance of the proposed scheme is investigated under varying wind conditions for the IEEE 14-bus system. The simulation results demonstrate that the scheme successfully operates regardless of the output power fluctuation of a WTG by adjusting the gain with the rotor speed, and thereby improves the frequency-regulating capability of a WTG.
Bibliographical noteFunding Information:
Manuscript received December 25, 2015; revised April 11, 2016, July 8, 2016, and October 5, 2016; accepted November 10, 2016. Date of publication December 12, 2016; date of current version June 17, 2017. This work was supported by the National Research Foundation of Korea grant funded by the Korea government (MSIP) under Grant 2010-0028509. The National Renewable Energy Laboratory’s contribution to this work was supported by the U.S. Department of Energy under Contract No. DE-AC36-08-GO28308 with NREL. Paper no. TSTE-01080-2015. (Corresponding author: Y. C. Kang.) Y. Kim is with the Green Energy Institute, Mokpo 58656, South Korea (e-mail: firstname.lastname@example.org).
© 2016 IEEE.
All Science Journal Classification (ASJC) codes
- Renewable Energy, Sustainability and the Environment