Design Of Temperature Monitoring System Of Converter Valve Based On Fiber Bragg Grating

We are developing flexible DC transmission equipment with higher operating voltage,current and power density,which can be applied to major transmission channels and power grids with higher engineering reliability.High-voltage high-power insulated gate bipolar transistors(IGBTs)are the core devices for power conversion in flexible DC transmission networks,and their operating conditions affect the safety of the entire system.However,the actual operating life of existing IGBT modules is low and much lower than the design index.Previous research shows that the junction temperature of the device is the most critical factor for its operational reliability,but it is difficult to measure accurately inside the closed and complex IGBT module containing dozens of chips.The current domestic converter valve monitoring technology cannot realize the process data monitoring either.Therefore,real-time monitoring of the junction temperature of key components in the converter valve sub-module is essential.This paper investigates the key technologies for real-time temperature monitoring and reliability improvement of the converter valve sub-module of flexible DC power transmission.We analyze the thermal accumulation effect of IGBT chip,the causes of IGBT failure and the junction temperature monitoring technology of IGBT module.We propose a junction temperature monitoring scheme based on fiber Bragg grating(FBG)sensing of the converter valve sub-module,considering the operating environment of the converter valve and the package structure of IGBT module.We use finite element simulation software to investigate the internal chip of IGBT module and the substrate of heat sink.We design a FBG array sensor package structure suitable for high temperature monitoring and develop an IGBT module with internal optical sensor.We build an IGBT temperature monitoring and demodulation system in the laboratory and design an IGBT temperature monitoring software to verify the reliability of the sensor system.We simulate the load operation experiments and observed the junction temperature data under different conditions.We study the network technology of fiber grating sensor of converter valve and build a thermal management system of converter valve sub-module of flexible DC transmission to verify the reliability of the junction temperature monitoring system.The results show that the junction temperature online monitoring scheme can accurately obtain the dynamic junction temperature of the device,realize the safety monitoring and fault warning function in the flexible DC transmission system,and provide scientific basis for the maintenance and fault analysis of the converter valve.The paper presents the following main innovations:1.An IGBT module with built-in optical sensing is developed,which allows the first online real-time monitoring of the internal chip junction temperature of the IGBT during operation without compromising the module integrity and heat dissipation conditions.The femtosecond optical fiber grating array sensing has a shorter grid distance,can monitor more IGBT chip points,and has high junction temperature accuracy.2.An IGBT temperature monitoring and demodulation system is built,and a temperature monitoring software is designed according to the junction temperature monitoring position of the converter valve submodule.The software can monitor the junction temperature information of the upper and lower IGBT module chips,substrate and bus bar in partition.3.A thermal management system of the converter valve sub-module of flexible DC transmission is designed,and a sensor networking technology is studied to monitor the junction temperature change within100 °C of the converter valve sub-module.An independent sensor network is designed to facilitate submodule maintenance and installation,and a customized 200 GHz dense wavelength division multiplexer(DWDM)is used to solve the problem of insufficient spare fiber interface.