Open Access

ARTICLE

Inertia Support Coordinated Control Strategy for Wind Power Connected to the Grid through MMC-HVDC Considering Secondary Frequency Drop

Yi Qi¹, Yuhao Xie^2,*, Zhibing Hu¹, Fan Ding¹, Junxian Ma³, Liang Zhao³, Shouqi Jiang²
1 Economic and Technological Research Institute, State Grid Ningxia Electric Power Co., Ltd., Yinchuan, 750000, China
2 School of Electrical Engineering, Northeast Electric Power University, Jilin City, 132012, China
3 State Grid Ningxia Electric Power Co., Ltd., Yinchuan, 750000, China
* Corresponding Author: Yuhao Xie. Email:

Energy Engineering https://doi.org/10.32604/ee.2025.073663

Received 23 September 2025; Accepted 20 November 2025; Published online 18 December 2025

Abstract

To address the challenges of low inertia support capability and poor frequency stability encountered in the process of power system electronification, this paper designs a coordinated inertia support control strategy for offshore wind power connected to the grid via Modular Multilevel Converter Based High Voltage Direct Current (MMC-HVDC), which enhances the system inertia level and accounts for secondary frequency drop. In terms of inertia support, building on the existing coupling relationship between grid frequency and DC voltage, the influence of wind turbine (WT) rotor speed is further integrated, leading to the proposal of a virtual inertia control method that synergistically leverages the frequency regulation capabilities of sub-module (SM) capacitors and WTs. Meanwhile, to mitigate the power impact on the system at the instant WTs exit inertia support control, an adaptive rotor speed recovery strategy based on a variable droop coefficient designed using a logistic function is proposed, along with an adaptive submodule switching control method that utilizes the MMC-HVDC capacitor energy margin to compensate for the power deficit caused by wind turbine rotor speed recovery. Compared with existing wind power recovery methods, the coordinated operation of these two strategies can prevent secondary frequency dips while shortening the rotor speed recovery time. Finally, the simulation verification was carried out based on the RTLAB OP5707XG-8 real-time digital simulation platform, where the installed capacity of the wind farm is 600 MW, and the results show that the original system experiences a secondary frequency dip of approximately 0.0013 p.u., whereas no secondary frequency dip occurs when the proposed method is applied, and the recovery time is shortened by about 5 s, demonstrating the effectiveness of the proposed coordinated control strategy.

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Keywords

Offshore wind farms connected to the grid through MMC-HVDC transmission; inertia support; secondary frequency drop; speed recovery; power impact; coordinated control

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