IGBT Temperature Monitoring System Based On Fiber Bragg Grating Sensor

Flexible DC transmission is a new generation of transmission technology following AC transmission and conventional DC transmission.At present,it is considered to be the most promising transmission method for realizing the integration of DC grid and new energy sources,and it is also a key technology for the construction of smart grids in the future.The converter valve is the core equipment of the flexible DC converter station.Once the converter valve fails,it will not only result in the suspension of HVDC transmission,but also cause serious safety accidents.There are many factors that cause the converter valve to fail,in which the chip junction temperature is too high or the junction temperature fluctuation is too large,which will affect the performance of the power electronic devices and reduce their reliability.Therefore,it is of great significance to strengthen the monitoring of the junction temperature of power electronic devices and further optimize the design,reliability analysis and life prediction.In order to effectively monitor the changes in junction temperature,it is necessary to find a long-term effective monitoring method to monitor the operating status of power electronic devices and take effective measures before they affect the normal operation of power transmission projects.The continuous development of fiber Bragg grating sensing technology and its extensive application in engineering practice provide a new idea for the junction temperature monitoring of insulated gate bipolar transistor(Insulate Gate Bipolar Transistor,IGBT).The application of fiber Bragg grating sensors in practical engineering can not only monitor the working state of the power electronic devices,provide alarm information,but also provide valuable data for the thermal analysis of IGBT chips.In this paper,the finite element analysis software ANSYS is used to simulate the heat transfer valve module,and the corresponding 3D model is established according to the actual module structure.The actual working environment of the chip is simulated by setting the environment conditions and the load of the chip.Observe the temperature distribution map and calibrate the highest temperature position to provide reference for IGBT online temperature monitoring system.In the flexible HVDC system,because IGBT chip is in a high temperature and complex environment,a fiber Bragg grating coated with high temperature resistant polyimide(Polyimide)is used in this paper to make a sensor suitable for the environment.The sensor is embedded inside the converter valve module and is tightly attached to the surface of the chip.In order to avoid the cross sensitivity of the sensor affected by the stress,the packaging method is improved to make the grating part only affected by the temperature.The demodulation system adopts a tunable scanning light source without mechanical components,and can realize multi-channel measurement.The demodulation accuracy is ±1?,which satisfies the requirement of IGBT junction temperature monitoring.After the sensor is embedded,the temperature fluctuation and temperature distribution of IGBT chip in different power conditions are monitored,the data collected and the survival rate and working state of the sensor are observed.By comparing the simulated heat distribution of IGBT module with the measured data of the junction temperature,it is concluded that the simulated temperature is high,but the temperature distribution is the same,and the highest temperature of the chip is located at the water outflow nozzle.The results show that the encapsulation method not only ensures the effectiveness of the IGBT chip,but also ensures the reliability of the sensor,meets the requirement of the IGBT junction temperature monitoring,and provides a new monitoring method for the chip junction temperature.