A novel individual pitch control algorithm based on μ-synthesis for wind turbines

In this paper, we present a novel individual pitch control algorithm based on mu-synthesis for blade load reduction for wind turbines. Our algorithm is different from the conventional individual pitch control in the sense that the multi-blade coordinate transformation is not used at all. Instead, the wind turbine model coefficients that depend on the azimuth angle are regarded as structured uncertainties. The control objective is formulated with weighting functions on the disturbance input and performance output in the framework of the mu-synthesis approach. Our control algorithm can be added on to the collective pitch control as an on-off mechanism with minimal effect on it. Simulation results show that the proposed controller achieves very good robust stability and performance and can significantly reduce blade bending moments.