Research On Key Technologies Of Constant Current Transmission Cabled Seafloor Observatory Network

Cabled seafloor observatory networks(CSONs)which can realize long-time,continuous,real-time and in-situ seafloor observation with advantages of strong power supply,ultra high data communication bandwidth and high-precision time synchronization,are becoming one of the important means for deep sea scientific research and marine defense security.Constant current transmission cabled seafloor observatory networks(CC-CSONs)with advantages of powerful resistant ability to short circuit fault,high reliability and good robustness have wide application prospects in areas such as seismic and tsunami monitoring,marine military observation,reutilization of transoceanic communication cable and so on.However,domestic technology of CC-CSONs is poor,almost in blank.In this dissertation,key technologies such as constant current transmission mechanism,constant current constant voltage power transformation,load self-adaptive energy management,underwater cooling and high-precision time synchronous are researched.This dissertation first studies the stability of single-node constant-current transmission,and analyzes the unstable characteristics and stabilization solution of traditional DC/DC converter that applied in constant current power supply junction box.The theoretical research and scheme design of constant current branch unit are carried out,and the function is verified by software simulation.The topologies of CC-CSONs are studied,and the characteristics of resistance to transmission cable short circuit fault of different topologies constant current transmission system are simulated,and the reliability and robustness of the different topological structures are obtained.Considering the system volume,power conversion efficiency,reliability,voltage and power level,this dissertation presents a constant current constant voltage power conversion system with push-pull topology and input series output parallel multi-modules stack structure.A power balancer for power compensation is designed and analyzed for the stability characteristics of constant current transmissions ystem,and the control strategy of the power balancer based on common duty ratio is studied.A compensating controller with performance of high gain in low frequency band,enough phase margin in middle frequency band,and suppress the high frequency interference effectively in high frequency band.Aiming at the shortcomings of low energy utilization rate and excessive temperature rise of the power balancer,this paper design a load self-adaptive energy management system and a heat dissipation system of the power balancer based on load self-adaptive energy management.The system can adjust the input power of the constant current constant voltage power conversion system according to detecting the load power consumption,and improve the energy utilization efficiency.The heat dissipation system with elastic adjustment mechanism can adapt to the deep sea application environment.The effectiveness of the load self-adaptive energy management system and the power balancer cooling system are verified by software simulation.The time synchronization technology of network time protocol(NTP)and precision time protocol(PTP)are analyzed and studied,and the high-precision time synchronization system of CC-CSONs is constructed by combining NTP,PTP and pulse per second(PPS).The experimental platform is built in the laboratory environment,and the synchronous precision of PTP and PPS signals in different background traffics and different clock modes are studied experimentally.The experimental results show that the lighter the background traffic,the better synchronization accuracy of the PTP and PPS signals;the synchronization accuracy under transparent clock mode is slightly better than under boundary clock mode.However,when the number of nodes is not much and the topology is not complicated,the clock mode has little effect on synchronization accuracy.According to the mentioned theories and technologies,1 A/400 V junction box prototype of CC-CSONs is developed.The feasibility of the key technologies such as constant current constant voltage power transformation technology,load self-adaptive energy management technology,heat dissipation technology and high precision time synchronization technology are verified in the laboratory environment.Finally,the integration test and laboratory pool experiment of the prototype system are carried out to verify the feasibility and reliability of the system function.The successful development of the prototype of CC-CSONs and the pool test fully illustrate the key technologies,such as constant current constant voltage power transformation,load self-adaptive energy management,underwater heat dissipation,high precision time synchronization,have strong availability and reliability.These researches provide theoretical foundation and technical support for future research and construction of long-term practical multi-nodes CC-CSONs.