Time-varying sliding mode ADRC-based inertia control for offshore wind farm

• A nonlinear feedback controller incorporating the time-varying sliding mode approach is proposed. • Simplifies the tuning process of ADRC and enhances the system’s dynamic regulation capability and robustness. • Enhanced the disturbance rejection capability by accelerating the frequency stabilization and active power recovery for the duration of the transient event. Offshore wind farms typically lack the natural inertia required to maintain grid frequency stability during disturbances. To overcome this, this paper presents a virtual inertia control strategy based on Improved Time-Varying Sliding Mode Active Disturbance Rejection Control (TVSM-ADRC). The core contribution of this work is the integration of a time-varying sliding mode approach directly into the nonlinear feedback controller of the ADRC. Unlike standard hybrid methods, this design explicitly optimizes the ADRC tuning process, resulting in faster dynamic regulation and stronger immunity to external disturbances. The strategy utilizes an Extended State Observer to estimate system perturbations in real-time, allowing the virtual inertia controller to precisely modulate the kinetic energy of wind turbines. Experimental results on a Real-Time Digital Simulator (RTDS) confirm that the proposed method effectively regulates active power output and provides robust frequency support during transient grid faults.