Mechanism Analysis and Suppression Strategy of Torsional Vibrations of DFIG Shaft System Considering Torque Control of Wind Turbine

doi:10.11930/j.issn.1004-9649.202102032

Abstract

Abstract: The shafting model of the doubly-fed induction generator (DFIG) can be equivalent to the wind turbine mass connected to the generator mass via the flexible shaft, and the shaft system has great flexibility and low damping and encounters torsional vibrations on site. Therefore, an electromechanical small-signal model of DFIG is proposed for analyzing the dynamic characteristics of the shaft system. In the model, the torque control of the wind turbine is embedded into the double-mass mathematical model of DFIG, and small signals are linearized. On this basis, this paper analyzes the torsional vibration mechanism and designs the suppression strategy. It is found that the essential reason for torsional vibrations of the shaft system is that the phase angle between the electromagnetic torque and the generator speed in the torsional vibration frequency band registers a lag of 90–270°, which is equivalent to reducing the damping of the generator mass or even make the damping negative. Thus, adjusting the torque control lag of the wind turbine or increasing the damping of the transmission chain can indirectly increase the generator mass damping for the suppression of torsional vibrations. In view of the actual mechanical shafting characteristics of DFIG, a model was built for the time-domain simulation analysis and suppression strategy validation of torsional vibrations, and the suppression effect was tested on a 2MW unit on site. The results reveal that the torsional vibration of the shaft system is effectively suppressed upon the adjustment of torque control.

Key words: doubly-fed induction generator (DFIG), torsional vibration of shaft system, damping, torque control of wind turbine

SUN Sujuan, HUO Qiantao, SUN Lixin, GUO Liang, WANG Rui, KONG Xiangmei. Mechanism Analysis and Suppression Strategy of Torsional Vibrations of DFIG Shaft System Considering Torque Control of Wind Turbine[J]. Electric Power, 2022, 55(5): 39-46.

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URL: https://www.electricpower.com.cn/EN/10.11930/j.issn.1004-9649.202102032

https://www.electricpower.com.cn/EN/Y2022/V55/I5/39

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