Multi-Objective Optimal Control of Wind Turbines for Speed Regulation and Load Reduction

This paper presents a multi-objective control method for regulating speed and reducing structural loads on large wind turbines. Structural loads become more pronounced as the turbine size increases resulting in the need to develop control algorithms to minimize the load in addition to the mainstream objectives of regulating speed and maximizing power extraction in the turbines. To realize the two competing objectives of controlling speed/power and structural load minimization, two control loops are employed. The first loop, collective pitch controller (CPC), is designed to regulate rotor rotation speed by reducing aerodynamic power coefficient in high speed regime. Then a multi-input multi-output (MIMO) controller based on Stochastic Proportional-Integral-Observer is used in the second control loop to fulfill the objective of load reduction of rotor blades. The performance of the proposed control algorithm is evaluated against Proportional-Integral controller (PI-Controller). The results demonstrate that the proposed control method can achieve the objective of reducing structural load without much influence on the speed regulation objective.