Unknown input observer based scheme for detecting faults in a wind turbine converter

Abstract: In order to improve reliability of wind turbines, it is important to detect faults in the turbine as fast as possible to handle them in an optimal way. An important component in modern wind turbines is the converter, which for a wind turbine control point-of-view normally provides the torque acting on the wind turbine generator, as well as measurement of this torque. In this paper an unknown input observer is presented to estimate these faults in the converter and isolate them either to be an actuator fault or a sensor fault. The unknown input observer is used since the speed of wind acting on the wind turbine is assumed unknown, since measurement of it is influenced by the turbulence around the rotor plane. A detection scheme is formed based on these fault estimates. A detail simulation model is used to simulate a wind turbine in which both types of faults are present during the simulation. The detection scheme detects and isolates both faults with in 2 samples of its beginning. 1

Detection of Surface Defects on Compact Discs

Online detection of surface defects on optical discs is of high importance for the accommodation schemes handling these defects. These surface defects introduce defect components to the position measurements of focus and radial tracking positions. The respective controllers will accordingly try to suppress these defect components resulting in a wrong positioning of the optical disc drive. In this paper, two novel schemes for detecting these surface defects are introduced and compared. Both methods, which are an extended threshold scheme and a wavelet packet-based scheme, improve the detection compared with a standard threshold scheme. The extended threshold scheme detects the four tested defects with a maximal detection delay of 3 samples while the wavelet packet-based scheme has a maximal detection delay of 6 samples. Simulations of focus and radial positions in the presence of a surface defect are performed in order to inspect the importance and consequences of the size of the detection delay, from which it can be seen that focus and radial position errors increase significantly due to the defect as the detection delay increases

Fault tolerant control of wind turbines:a benchmark model

Abstract: The installed energy generation capacity of wind turbines is increasing dramatically on a global scale; this means that reliability of wind turbines is of higher importance. A part of this task is to improve fault detection and accommodation schemes of the wind turbine. This paper presents a benchmark model for simulation of fault detection and accommodation schemes. This benchmark model deals with the wind turbine on a system level containing sensors, actuators and systems faults in the pitch system, drive train, generator and converter system. 1