Application Of FBG Sensors In The Flexible DC System

Optical fiber grating as a typical passive optical device,due to its advantages of small size,light weight and anti-electromagnetic interference,etc.At present,it has been widely used in the fields of aerospace,civil engineering,power systems,medicine,etc.This article describes in detail the development history of fiber gratings,sensing principle,multiplexing technology and demodulation technology commonly used at home and abroad.Focused on the analysis of scanning semiconductor laser demodulation technology and volume grating demodulation technology.In recent years,flexible DC transmission(HVDC)as a new generation transmission technology is widely used in the new energy grid connected and DC transmission network.The converter valve is the core equipment of the flexible DC transmission system.There are many factors causing the valve failure.The most important thing is that the operating temperature of the converter valve is too high,which leads to the outage of the flexible DC transmission system and even the major safety accidents.Therefore,the real-time monitoring of the temperature of the converter valve is very important,because the module is in a strong magnetic field environment,which puts forward higher requirements for the sensor and the system.Traditional electromagnetic sensors can no longer meet their needs.Therefore,a new method of on-line monitoring of converter modules based on FBG temperature sensors is presented in this paper.A demodulation system based on FBGA demodulation module is designed in this paper,which includes wavelength demodulation hardware module and host computer software module.The hardware equipment includes the core module FBGA demodulator and its peripheral devices,such as broadband light source,ring-shaped device,coupler and other devices,and build the performance of the demodulation system verification equipment.The upper computer software based on LabVIEW is designed and the functions of data acquisition,data processing,data storage and user interface design are analyzed and designed for customer requirements.By monitoring the maximum temperature of the radiator and the temperature of the outlet,the working state of the converter module is known.First,through the engineering experiment,the temperature distribution of the radiator is verified,and the maximum temperature value is found out,which lays the foundation for the placement of the sensor.Secondly,a specific scheme for embedding the FBG sensor on the radiator surface and outlet nut is designed.By using the parameter method,the temperature value of the electrical parameters is retrieved.The temperature of the chip is calculated to be up to 102?,which provides reference for the real-time temperature monitoring of the following fiber Bragg grating.Finally,according to the requirements of the project,different power is applied to the chip,and the temperature of the radiator shell and the temperature of the outlet are analyzed.It is known that the difference between the temperature and the temperature of the heat sink is between 0.6~1.2? and temperature.Because of the temperature of the radiator shell and the water temperature of the outlet,the difference between the temperature and the temperature is small in the acceptable range.Comparing the difficulty of the implementation of the two schemes,the nut grooves can protect the integrity of the commutation valve module more and reduce the effect on the performance of the valve.Therefore,monitoring the outlet water temperature is more valuable.Based on the demonstration project of the Xiamen Heron Island + 320 KV flexible DC transmission station,a temperature on-line monitoring system based on Fiber Bragg grating sensor is designed to monitor the temperature state of the converter valve module in real time.At present,the system has been used in engineering,and the accuracy of long-term operation can reach ±1?.The system will provide the most direct monitoring measures for the engineering application,to a great extent,to improve the reliability of the converter valve,and make great progress in monitoring the safe operation of the flexible DC transmission system engineering.