Study On Igbt Switch Trajectory Adjustment And Junction Temperature Control Based On Active Gate Drive Control

With the development of power electronics technology,power devices has been more widely used in electric vehicles and other new energy field,therefore,people are paying more attention to their reliability issues.Factors such as mechanical stress,electrical stress,and thermal stress affect the reliability of power devices.Under the impact of various stresses in actual working conditions,the IGBT inevitably suffers from aging fatigue during its use.When the fatigue damage accumulates to a certain degree,it will cause the device failure.Therefore,it is necessary to reduce the electrical stress and thermal stress impact of the device during use as much as possible to delay its aging rate and improve its service life.In this regard,this thesis proposes a switch trajectory adjustment and junction temperature control technology based on the active gate drive control.The main contents of the research are as follows:The gate driver is the important interface between the power circuit and the control circuit,which directly affects the switching behavior of the device.By analyzing how the gate drive current affects the switching trajectory of the power device,an active gate drive circuit is designed to regulate the gate current.The designed active gate drive circuit can be used in two aspects to improve the reliability of the device.On the one hand,it is used to adjust the switching trajectory,reduce the overshoot and oscillation of current and voltage,reducing the electrical stress on the device.On the other hand,by changing the switching trajectory to adjust the switching loss,it can be also used for junction temperature management,reducing thermal stress and delaying the aging of the device.The scheme of gate current classification adjustment and overall adjustment is proposed to realize the above application.The life of the device is closely related to the operating junction temperature,and the collection of junction temperature information is the basis of junction temperature management.Aiming at the inconvenience of the direct measurement of the junction temperature of the power module,the method of extracting the peak value of the parasitic inductance induced voltage at the turn-off time is used to indirectly obtain the junction temperature information.The algorithm for the calibration of the junction temperature curve is improved and verified by the double pulse experiment.Then,a temperature-dependent loss model related to the gate current is established,which is used to calculate the junction temperature under electro-thermal coupling simulation.By analyzing the ratio of the switching loss,the junction temperature adjustment capability of the gate control technology is estimated,which provides a reference for setting a given value of the junction temperature control.Based on the analysis of the Lesit life model,the influence of junction temperature swing and average junction temperature on the life is studied,and the life improvement factor and temperature change operation area that guide the formulation of the junction temperature control strategy are proposed to ensure that the junction temperature control plays a role in improving the life of power device.A conservative junction temperature control strategy that simultaneously reduces junction temperature fluctuations and average junction temperature is presented.Finally,a converter operating condition test platform was built in simulink,and a power circuit closed-loop control system was designed to reproduce the junction temperature condition for verifying the feasibility of the proposed gate current regulation to control the junction temperature.In order to reduce the fundamental frequency junction temperature fluctuations and increase the response speed of the junction temperature control,a method using load current feedback comparison to control the output loss and the junction temperature is proposed.In order to verify the life improvement effect of this method under complex working conditions,a model of electric vehicle motor drive system was established,and the junction temperature of the car converter before and after control under UDDS working conditions was simulated and compared.The rain flow counting method is used to calculate the thermal stress distribution of the working condition,and the effect of the proposed junction temperature control method to improve the life is evaluated by using the Miner linear cumulative damage theory.