Simultaneous tuning of collective and individual pitch controllers for blade load reduction and power regulation in offshore wind turbines

Collective pitch control (CPC) and individual pitch control (IPC) are key strategies for power regulation and structural load mitigation in large offshore wind turbines operating in the nominal region. CPC and IPC operate in different frequency ranges, with CPC regulating power and IPC mitigating asymmetric blade loads. CPC tuning presents a significant trade-off, as improving power regulation often increases blade fatigue loads. IPC is typically implemented using the multiblade coordinate (MBC) transformation, which assumes decoupling between tilt and yaw control loops. However, practical implementations exhibit residual coupling effects. Advanced IPC schemes, such as azimuth offset compensation and static inverted decoupling, have been proposed to mitigate this interaction, but systematic comparative performance evaluations remain limited. This study proposes a multi-objective optimisation framework for the simultaneous tuning of CPC and IPC parameters to assess the trade-off between blade fatigue reduction and power regulation performance. Four gain-scheduled CPC-IPC configurations, including advanced IPC implementations, were implemented on a 15 MW wind turbine simulated using OpenFAST. Results show that simultaneous tuning of conventional CPC–IPC expands the achievable performance space, achieving average improvements of approximately 7–8% in blade fatigue loads and 23–24% in power regulation compared to the ROSCO–IPC baseline controller. Azimuth offset and static inverted decoupling IPC configurations exhibit comparable load–power performance, achieving reductions of approximately 17–19% in blade fatigue loads and 29–30% in power regulation relative to the ROSCO–IPC baseline, with only a moderate increase in pitch actuator activity of approximately 3–3.5%.