Calculation Of Junction Temperature And Assessment Of Power Cycling Capabilities Of IGBT Modules For Wind Power Converter

Due to the intermittent characteristics of wind energy, wind power changes withhigh frequency, extensiveness and random, which always leads power converter tosuffer from sharp shock. Furthermore, the fault rate of power converter is high as thelow frequency operation for generator-side power converter of doubly fed windgenerator system. Junction temperature fluctuations caused by power cycling is one ofthe important factors that led IGBT module to fail. Therefore, the junction temperatureand the power cycling capability for wind power converter were investigated. Theresults have important academic significance and application value to improve theoperation safety and reliability of wind power converter.The main contents of this thesis are followings:①Based on the understanding of IGBT module package structure and heat transferprocesses, electro-thermal characteristics and failure mechanisms of IGBT module wasmastered, which lay the foundation for the further study of calculating the junctiontemperature and power cycling capability.②In order to accurately calculate the junction temperature of IGBT module fordoubly-fed wind power, a calculation model of IGBT module junction temperature wasstudied and proposed in a switching cycle loss analysis, the comparison of differentjunction temperature calculation was performed by using a practical IGBT converter.③In order to accurately analyze the variation of losses and junction temperatureof IGBT module for power converter of doubly fed wind generator system, combinedwith the operational characteristics of a wind turbine and the converter control strategy,the calculation model of IGBT module losses and junction temperature was presented,and the change rule of the IGBT module losses and junction temperature were analyzedunder different wind speed conditions.④In order to accurately assess the impact of the turbulent wind speed on thepower cycling capabilities of IGBT modules in generator-side power converter fordoubly fed wind turbine generator system, the assessment model to calculate mean timebetween failure(MTBF) of IGBT modules for generator-side power converter wasproposed, based on the information of junction temperature fluctuation extracted byusing the rain-flow algorithm. Then, effects of different turbulence wind on thecharacteristic of junction temperature fluctuations and power cycling capability was analyzed.The above achievement will provide some theoretical foundation and technicalsupport for the junction temperature accurately calculation of IGBT module and theassessment of reliability level of power converter.