Analysis and emulation of pitch control forces in wind turbines

In this paper, a hardware in the loop (HIL) scheme using a polynomial approximation for the calculation of aerodynamic forces associated with wind turbine blades is presented. The proposed approach allows the real-time calculation of forces acting on a blade for use as input data for a force emulating system. The blade element momentum (BEM) theory was used to calculate the axial and tangential forces, but an iterative algorithm needs to be executed for each time of the system’s operation. In order to allow a real-time calculation, the BEM algorithm can be executed for a range of rotor angular speeds, wind velocities, and pitch angles covering the conditions under which the wind turbine will operate. The resulting power, torque, and forces are then approximated by polynomials and implemented in an HIL test facility. A comparison between the results obtained from the BEM algorithm and polynomials demonstrates the accuracy of the proposed approach. An experimental setup comprised of the software used for the force and pitch angle calculation and the hardware used for the force emulation and pitch angle control is presented. Experimental results obtained with the system running in real-time demonstrate the ability to apply effective moments without the need for an extensive test structure.