Research On Power Conversion Technology Of Seafloor Observatory Junction Box

The seafloor observatory network is called the third largest platform of the earth observation system.It has the characteristics of long-term,continuous and real-time observation in severe weather.The seafloor observatory network is mainly composed of shore base station,junction box,scientific instrument,and photoelectric composite cable.The junction box is the basis for power conversion and distribution and data transmission and communication,and an important part of the seafloor observatory network platform.The high-medium voltage DC converter converts thousands of volts of high-voltage direct current transmitted by the submarine cable into several hundred volts of medium-voltage direct current required by the secondary junction box,which is the core component of the main junction box.This paper mainly studies the high-medium voltage DC conversion technology of the seafloor observatory network junction box power supply.Taking into account the special environment of the seafloor observatory network,the high-medium voltage DC converter of the junction box has the characteristics of high input and output voltage,wide input voltage range,large output power,high reliability and small size.LLC resonant converter is based on soft switching technology.The switch tube works in ZVS in the full load range without voltage and current cross-operation,and the turn-on loss is zero;the output rectifier diode works in ZCS without reverse recovery loss.At the same time,the magnetizing inductance of the transformer participates in resonance.It has the advantages of low switching loss,small device stress,wide voltage input range,large power density and high conversion efficiency,etc.Therefore,LLC resonant converter is suitable for the design of the power supply of the s seafloor observatory network junction box.The common schemes of high-medium voltage DC converter in the junction box of seafloor observatory network include single module DC converter or multi module combined DC converter.The traditional single module DC converter has simple structure and high reliability,but its disadvantage lies in low transmission voltage level.The single module DC converter designed in this paper selects LLC resonance as the basic topology,and uses four silicon carbide power tubes in series to achieve the purpose of high voltage input application.Firstly,the research status of submarine observation network and junction box power supply module is introduced.Secondly,the basic characteristics and working principle of LLC resonant converter are analyzed,Thirdly,the half bridge LLC resonant main circuit,drive circuit and auxiliary circuit based on four MOSFET transistors in series are designed.Finally,the simulation circuit of 3KVDC / 400 VDC converter is built.The test results show that the silicon carbide power tube Q1Q2 or Q3Q4 is turned on and off synchronously and the voltage is the same.The circuit works in soft switching to achieve 3kVDC/400 VDC conversion,and the efficiency is more than 90%.