Linearized dynamics and operating modes of a simple wind turbine model

Modal analysis and the future design of control strategies for a wind turbine rely heavily on the development of system descriptive dynamics models. Until now, wind turbine models have focused only on turbine simulations and not system characterization, which is necessary for the evaluation of operating modes, parameterization of stability, and controI designs. This paper presents an explicit, descriptive model of a rigid component, generic horizontal axis wind turbine, from which the system parameters and operating modes are extracted. A four degree-offreedom two-bladed turbine under free vibration is analyzed in parts and then as a complete system, presenting physical insight into the dynamic coupling behavior. A study perfonned at different rotor azimuth positions exposes the importance of Floquet analysis to better understand rotor-nacelle dynamic interactions. Mode shapes are identified and results are presented for modal frequencies at different rotor speeds.