Variable droop gain frequency supporting control with maximum rotor kinetic energy utilization for wind-storage system

• Published in: International journal of electrical power & energy systems Vol. 163; p. 110289
• Main Authors: Li, Wenbo, Li, Yujun, Li, Jiapeng, Zhang, Yang, Chang, Xiqiang, Sun, Zhongqing
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-12-2024; Elsevier
• Subjects: Droop control; Releasable kinetic energy; Short-term frequency support; Wind turbine generators; Releasable kinetic energy; Wind turbine generators; Droop control; Short-term frequency support
• ISSN: 0142-0615
• DOI: 10.1016/j.ijepes.2024.110289

To address the emerging frequency stability issue brought by the large replacement of synchronous generators with renewable generations, wind turbine generators are required to possess frequency-supporting capability. However, existing frequency-supporting control strategies lack the assessment of the frequency support capability of wind turbine generators, leading to degraded control performance under various situations. Aiming to solve this problem, this paper proposes a variable-droop-gain control for wind turbine generators with maximum rotor kinetic energy utilization. Firstly, an analytical relationship was established between droop gain, disturbance scale, and rotor speed. Subsequently, the released energy of the wind turbine generator is evaluated, which equals the difference in the rotor kinetic energy under the initial and the post-disturbance steady-state rotor speed. It was proved that the released kinetic energy cannot exceed a certain proportion of total rotor kinetic energy. Accordingly, a variable initial gain scheme is proposed, which determines the initial droop gain as per the disturbance scale for maximizing the kinetic energy release of wind turbines. Moreover, an additional real-time droop gain adjustment rule is added to prevent the over-deceleration of wind turbines. The simulation results show that the proposed scheme may provide the maximum KE release and effectively improve the system frequency nadir while ensuring the safe operation of wind turbine generators.
•A variable gain scheme for fully utilizing the releasable KE of WTG is proposed.•The KE released by WTGs cannot exceed a specific proportion of the total KE.•This derived proportion is determined by the limitation of the existence of EP.•The initial droop gain is tuned based on the disturbance scale and releasable KE.•An additional adjusting scheme is added to ensure the safe operation of WTGs.