Fault Diagnosis of a Direct Drive Wind Turbine Using a Bank of Goertzel Filters

Abstract

Direct Drive Wind Turbines (DDWTs) are used in newer wind farm installations. They are equipped with Permanent Magnet Synchronous Generators (PMSGs), which offer high efficiency for energy generation, but which are also prone to faults. They account for almost a quarter of the downtime of a DDWT. Machine Current Signature Analysis (MCSA) is often used to look for generator problems, as these impairments introduce supplementary harmonics into the generated currents. The Fast Fourier Transform (FFT) is utilized to compute the spectrum of the currents and to look for these additional harmonics. However, the FFT computes the whole spectrum, while the number of possible faults and the number of introduced harmonics is very low. The Goertzel Algorithm (GA), implemented as a filter - the Goertzel Filter (GF), is presented in this paper as a more efficient alternative to the FFT. The GF was tested in Matlab/Simulink and simulation results prove that it can return the squared magnitude of these harmonics. This information can be used to set thresholds for fault detection within a FDI algorithm.