The Design And Implementation Of Harmonic Test System Of Grid-connected Wind Turbine

Based on the rapid consumption of fossil energy worldwide and the promotion of public environmental awareness,traditional fossil energy is gradually replaced by renewable energy.Wind resources are abundant and non-polluting,which are cost-effective renewable energy sources.Therefore,the application prospects of wind power generation are very wide.However,due to the randomness and instability of wind energy itself,wind turbines generate harmonics in the process of outputting electrical energy.Power quality is affected by the existence of harmonics seriously,so it is very necessary to accurately measure the harmonic current of grid-connected wind turbines.On the basis of extensive reading of relevant domestic and foreign results,this thesis has studied harmonic test systems for grid-connected wind turbines in accordance with the International Electrotechnical Commission Standard IEC 61400-21 and IEC 61000-4-7.This thesis analyzes the related concepts,implementation methods and performance indexes of harmonic test of grid wind generator set based on discrete Fourier transform algorithm.In order to overcome the limitation of Fourier transform in studying nonlinear signals,a new harmonic measurement algorithm based on EEMD and HT is proposed.On the basis of studying the harmonic test algorithm,this thesis realizes the simulation analysis of IEC harmonic measurement,EMD,EEMD and HT transformation in MATLAB,and analyzes the feasibility of the algorithm based on EEMD and HT transformation,which provides a theoretical basis for developing the harmonic test system of grid-connected wind turbine.The harmonic test system of grid-connected wind generator set is developed using LabVIEW as a platform.The harmonic test system mainly includes hardware and software.The hardware part which used to achieve signal acquisition includes three parts: sensor,acquisition card and industrial computer;Software functions include signal acquisition,harmonic measurement and power measuring three modules.The software design firstly drives the data acquisition card,and then processes the sampling signal provided by the acquisition card to realize the real-time acquisition of current and voltage signals and harmonic measurement,and generate a test report ultimately.