| With the sustained development and improvement of China’s rail transit construction,rail transit system has been widely used because of its large passenger capacity and independence from traffic conditions.Thus is has become an important component of urban public transportation in modern cities.As the source of traction force and electric braking force of the train,the reliability of the train traction inverter-motor system directly affects the operation performance of the train.Insulated Gate Bipolar Transistor(IGBT)power module,as the core component of traction inverter,is fully used in China’s train traction converter system.Due to the large power fluctuation,complex working conditions,variable and harsh working environment,the power modules of the train traction inverter are more prone to damage with the phenomenon of high junction temperature and violent fluctuations,which may lead to interruption of system operation and even train stoppage causing economic losses.During the normal operation process of the traction inverter,accurate online junction temperature extraction of power modules is the prerequisite to realize active thermal management and fast over-temperature protection.Therefore,as for the life prediction,reliability assessment,and health management of high-power converter equipment,it’s necessary to perform high accuracy,fast response,and non-intrusive online junction temperature extraction of power modules.This thesis takes the IGBT power modules in the three-phase two-level traction inverter as the research object.On-state voltage drop and off-collector voltage overshoot are the temperature sensitive electrical parameters(TSEP).The sampling circuits for two parameters are designed to realize the online junction temperature extraction of IGBT power modules.The main contents are as follows:First,four common methods of junction temperature extraction of IGBT power modules are analyzed in detail,focusing on the temperature sensitive electrical parameter method among them.The advantages and disadvantages of thermal sensitive electric parameters such as on-state voltage drop under low current,on-state voltage drop under high current,gate threshold voltage drop and turn-off voltage overshoot for online junction temperature extraction are compared and analyzed.As a static thermal sensitive electric parameter,the on-state voltage drop has the advantages of better generalization,more stability,higher accuracy,less influence of control strategy,and lower hardware invasiveness.As a dynamic thermal sensitive electric parameter,the turn-off collector voltage overshoot has the advantages of higher accuracy and lower hardware invasiveness.Furthermore,it also has the characteristics unaffected by aging,which means it’s not affected by bond wire breakage.Therefore,the on-state voltage drop and turn-off collector voltage overshoot are selected as the thermally sensitive electrical parameters to extract the junction temperature of power modules.Secondly,the equivalent physical model of the IGBT power module and the switching transient process are studied,and the mathematical expressions of the on-state voltage drop and turn-off collector voltage overshoot of the IGBT power module are deduced through their mathematical modeling.The relationship of these two thermally sensitive electrical parameters which collector current and temperature are analyzed.Selecting an IGBT power module of Infineon model FF100R12KS4,the on-state voltage drop,turn-off collector voltage overshoot,collector current,and junction temperature of the module can be obtained by building a double-pulse test experimental platform.The three-dimensional mapping representation models of collector current and junction temperature with the on-state voltage drop and turn-off collector voltage overshoot are constructed.Then,the design ideas and application drawbacks of traditional sampling circuits are analyzed,and the sampling circuits for the on-state voltage drop and turn-off collector voltage overshoot are designed.The experimental studies of on-state voltage drop method and turn-off collector voltage overshoot method are conducted.The experimental results of discrete points and online junction temperature extraction verify that the designed sampling circuits can effectively and accurately acquire the temperature sensitive electrical parameters,and the junction temperature can also be extracted online combined with the established mapping characterization model.Finally,an inverter experimental platform based on the selected IGBT module has been built,which mainly contains the main circuit of the two-level inverter,the electrical parameter sampling circuit,the IGBT driving circuit,the DSP controller,the auxiliary power supply,and the PC host computer.In order to test the function of the experimental platform and the effectiveness of the sampling circuit,a two-level inverter modulation algorithm based on the TI’s TMS320F28335 controller was written.And the on-state voltage drop method is selected for the online junction temperature extraction low power experiment of the IGBT module in the inverter to verify the effectiveness and availability of the proposed scheme under actual inverter operating conditions through experiment. |
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