Mass and Aerodynamic Imbalance Estimates of Wind Turbines

Jenny Niebsch,Thien T Nguyen,Ronny Ramlau

doi:10.3390/en3040696

Abstract

Due to its effect on the operation time of wind turbines, rotor imbalances of a wind turbine have to be detected early enough. We present a method that determines inhomogeneous mass distributions of the rotor as well as deviations in the pitch angles of the rotor blades from vibrational data only. To this end, a mathematical model connecting the load caused by the imbalances to the resulting vibrations was developed. After discretization, the resulting vibration equation was solved analytically. The inverse problem, i.e., the calculation of the mass and aerodynamic imbalance from vibrational data, was solved by using nonlinear regularization theory. Numerical simulations were performed using artificial vibration data.

Highlights

The efficient operation of wind parks calls for a long life time of each wind turbine
In this paper we developed an algorithm that can reconstruct both mass imbalances and aerodynamic imbalances arising from pitch angle errors in the rotor of a wind turbine
To this end we have developed a turbine model of a Vestas V80-2MW that provides us with the system mass and stiffness matrix

Summary

Introduction

The efficient operation of wind parks calls for a long life time of each wind turbine. The mass imbalance reconstruction from noisy vibration measurements was treated as an inverse problem with methods from the regularization theory [4]. Since aerodynamic imbalances cause vibrations in axial directions and torsional vibration around the tower axis, we had to expand our turbine model in these dimensions. Due to the BEM method, the direct problem of relating the imbalance cause (here the pitch angle deviation and a mass imbalance) to the vibrations of the turbine becomes non-linear. The mass and stiffness matrices are calculated by a model of the turbine that considers vibration in lateral and axial direction as well as torsional vibrations around the tower axis. Before we can think about reconstructing imbalances from vibration measurements we have to be able to handle the other direction, i.e., for a given imbalance cause we should compute the resulting vibrations of the wind turbine tower. The weak point of this method is the slowness in running time

Computational Results

Result

Summary