Estimação e análise estatística de distorções harmônicas em usinas eólicas a velocidade variável

Abstract

The harmonic distortions generated by wind turbines have not been reported as it should by the technical literature, despite the obligation of these studies by standards for interconnecting wind farms to the electrical grid. As a consequence, great part of the softwareused for studies involving harmonic penetration on electrical systems doesnt include mathematical models for simulating wind generators connected to the grid. The most common method for harmonic content estimation of voltage and current signals is the FFT algorithm (fast Fourier transform). This algorithm has the disadvantage ofnot describing the harmonic content as a function of time. Representing the harmonics along the time has a fundamental importance for studying the distortions emitted by wind turbines, once they are dependent on the operational conditions, which has a time varying behavior. System identification techniques for harmonic estimation have been successfullyapplied in many areas, such as electrical power systems and acoustics. Apart from estimating harmonics along the time, these techniques are more appropriate for estimating time varying harmonics. Furthermore, they are able to filter measurement noise. In this work, the author aims to describe the harmonic injections of a variable speed wind turbine that applies the DFIG (doubly fed induction generator) topology as a function of operational conditions. This aim will be reached by the application of system identification techniques for tracking harmonics along the time. The studies are made on a simulation environment, using ADTDraw® for time domain models implementations, and MATLAB® for frequency domain simulations and for implementing the estimators. Finally, this work represents the harmonic distortion generated in a wind farm using a stochastic approach.