Offshore-Wind-Power Integrated System Sub/Super-Synchronous Oscillation Adaptive Mitigating Method and its HIL Tests

[Objective] This study addresses the emerging oscillation risks posed by power electronic converter-dominated control systems in large-scale integration of offshore wind power. Specifically， it aims to enhance the operational stability of AC transmission systems by focusing on sub/super-synchronous oscillation mitigation in offshore wind farms connected via AC transmission systems. To address the limitations of conventional mitigation measures， such as the necessity for extensive upgrades in wind turbine generator and insufficient parameter adaptability of system parameters， an adaptive oscillation mitigation strategy is proposed. [Methods] The proposed method adopts a “real-time measurement-identification-control” framework. The measured data provide observable input signals for identifying the system sub/super-synchronous oscillation modes， followed by the real-time oscillation characterization of oscillation dynamics. Based on this identification， the control parameters are dynamically tuned， and the control structures are modified to meet the specified objectives. To validate this method， a prototype controller was developed. An electromagnetic transient simulation model of the oscillations was developed in the Real-time Digital Simulator， and closed-loop testing was conducted by integrating it with the controller. [Results] Hardware-in-the-loop simulation results demonstrated that the proposed method accurately identifies oscillation frequency shifts， such as variations resulting from changes in turbine numbers， wind speeds， or AC line lengths， owing to system condition variations. The online-adjusted control parameters effectively mitigated oscillations， and the optimized damping control parameters achieved enhanced oscillation suppression. [Conclusions] Grid-side parallel VSC-based damping control provides a centralized and efficient solution for managing offshore wind farm oscillations， thereby obviating the need for the implementation of individual wind turbine generators. The prototype controller exhibited adaptive suppression capabilities for varying oscillation characteristics in hardware-in-the-loop simulations， thereby establishing a robust foundation for practical engineering applications. This approach demonstrates significant potential for addressing real-world oscillation challenges in high-penetration renewable energy grids.