Study On Life Prediction And Environmental Factors Of IGBT For Wind Turbine Converter

The grid-connected ability of wind turbine is affected by control performance of converter.As the core component of converter,insulated gate bipolar transistor,also called IGBT,has the advantages of large current density,small conduction losses and high switching frequency.But it may be failure easily due to high voltage,high current,high frequency or bad environment.The materials of IGBT suffer from thermal stress because of power cycling,which leads to fatigue ageing.As a result,whole performances of wind turbine are influenced.At present,fatigue of IGBT has been studied at home and abroad.Based on characteristics of IGBT,this thesis focuses on analyzing power losses,junction temperature and establishing the device electro-thermal model,in order to achieve the purpose of predicting lifetime of IGBT in converter of wind turbine.Working principle,failure factors and failure model of IGBT are analyzed.It shows that fatigue caused by thermal stress is the main failure factor of IGBT in converter of wind turbine.This is the basis of analyzing lifetime of IGBT.Then waveforms of iC and vCE during working of IGBT are studied,and the current and voltage are function described in order to realize loss calculation of IGBT.The loss model of IGBT is established through real-time losses and average losses.In this way,the electro-thermal model is improved.Junction temperature of IGBT in different wind speed is also considered.Prediction analysis for IGBT lifetime is achieved through Rainflow Counting Algorithm and linear fatigue accumulation theory.Finally,according to the actual working situation in wind farm,environment influences on reliability of IGBT are analyzed.Some suggestions about improving efficiency and reliability of wind turbine are proposed.This thesis has studied on the power losses,electro-thermal model,lifetime prediction and the influence of the environment on reliability of IGBT.It has certain guiding significance for IGBT module cooling design,the temperature protection and real-time life prediction.