Study On The Reliability Of IGBT Modules Based On Its Port Electrical Characteristics

Since the happening of industrial revolution,human's technology has been developed rapidly,which caused the increase of fossil fuel consumption as well as the issues about global environment.Therefore,during recent decades,in order to obtain clean resources and protect our environment,the renewable resource revolution has been evoked and obtained enough attentions in many of countries,especially for wind power generation.However,according to the relative statistic based on industry,power converter,as the key component of wind power generation system,is the one of most fragile parts,which was contributed by the failure of power devices in a large extent.Thus,it is necessary to research the strategies in improving the reliability of power device.It is revealed that power device failure is caused by continuous thermal stresses and electrical stresses which is induced by long-term power swing.Because stresses could induce internal mechanical strain and trigger the package relative failure.Currently,the methods of researching the reliability of power device could be classified into three categories: 1)building lifetime prediction model based on aging failure factors or physical characteristics,which could be used to evaluate power device's lifetime under certain operational conditions.2)the aging failure of power device is mainly contributed by temperature swing.Thus,during the operation process of converter,developing advanced control strategies to guarantee temperature swing is under safe area.This kind of thermal management method could extend the lifetime of power device.3)condition monitoring is another important method,which could indicate the healthy condition of power devices and send warning signals to protect converter from further failure.Based on above-mentioned three methods,this dissertation focuses on researching the reliability of IGBT modules based on its port electrical signals.The main contents are as follows:Obtaining accurate junction temperature is critical for building lifetime prediction model and researching thermal management strategies,as well as some condition monitoring methods.Therefore,based on current junction temperature measurement methods,this dissertation proposed degradation-independent temperature sensitive electrical parameters(TSEP),which could be used to evaluate junction temperature with more reliable and accurate than other TSEPs.Firstly,this dissertation analyzed therelationship between proposed TSEP and junction temperature.And then,a mathematical equation for this relationship has been reduced by using experimental data.The proposed method was compared with infrared thermometer in a developed single phase inverter,which verified the feasibility and accuracy of the proposed method.Finally,the merits and drawbacks of the proposed method were analyzed by comparing with other TSEPs.Various electrical parameters have been previously proposed for the condition monitoring of IGBT modules.However,it is a challenge that there parameters are both junction temperature and degradation level dependent and have low sensitivity with bond wires lift-off,making it complicated to use them in converter.In order to resolve this problem,this dissertation proposed junction temperature independent electrical parameters,which could be used to indicate the healthy condition of power devices no matter what the junction temperature is.Firstly,this dissertation proposed a method to measure the equivalent resistance of bond wires,which method is able to identify bond wires lift-off within a certain temperature swing.And then this dissertation also analyzed the relationship between the transfer characteristic of IGBT module and its bond wires,extracted transconductance and a cross point from transfer characteristic waveform as degradation indicators,this cross point is the common point of transfer characteristic waveform in different junction temperature.Also,a measurement circuit was developed to measure transfer characteristic waveform during the stop time of converter.The accuracy of the proposed circuit was verified by comparing the experimental results with the data coming from datasheet.Finally,the transfer characteristic of IGBT module was measured in different junction temperature and different bond wires lift-off number.The experimental results showed: the transconductance measured with proposed method could decrease with bond wired lift-off and the influences of temperature swing could be reduced by normalizing transconductance into one certain temperature point.The cross point of transfer characteristic waveform in different temperature is junction temperature independent and it could decrease with bond wires lift-off.