Research And Development Of Marine Lithium Battery Management System

With the proposal of national energy strategy(2014-2020 Action Plans)and Energy Efficiency Design Index(EEDI),power supply composed of multi-energy sources has been increasingly applied to the marine electric power system.The lithium battery is an important part of the marine multi-energy electric power system,which safety and reliable operations,especially for the lithium Battery Management System(BMS),is the key to ensure the ship normal endurance.Besides,the special applications in ship,such as electrical equipment work in the high humidity,the high salinity,easy to mold and other harsh conditions for a long time,the large number of load,Wide range of voltage fluctuation and other uncertain sea condition of wind,waves and currents,put forward higher requirements for marine lithium battery management system.Therefore,based on multi-redundancy technology and battery equalization technology,this paper presents a battery energy management system to improve system reliability,extend the battery lifetime and ensure the new energy marine battery safe and reliable operation in a long time,according to the characteristics of ship special applications.Firstly,the paper analyses and compares the application status and main technical points of battery management system in the domain of car and ship.Considering the complexity of the operation condition of the ship and the regulations of punitive,this article puts forward two key technical problems for the Marine battery management system : BMS reliability and equilibrium problems.Secondly,a multi-redundancy marine-BMS which consists of the Master/Slave Hot-Standby Redundancy and Three Transmission Line Redundancies has been proposed.Then,the reliability analysis is established by using the theory of Markov process which results exhibits that the multi-redundancy marine-BMS can even work well in failure by choosing different redundancy modes,besides real-time monitoring the battery status in normal working mode.The reliability of multi-redundancy BMS is 89.67 %(non-redundant is 36.8%)after continuous operating 1000 h in the condition of unit failure rate λ= 0.0001.Then,the design of the Active equalization circuit with a concentrated transformer based on flyback converter is completed.Combined with the battery simulation model,the simulink model of the equalization control strategy is established by matlab.Simulation and results analysis are also carried out.Moreover,The Experimental data shows that the capacity declined rate of the battery pack is close to 31.5% after 1500 times of charge/discharge cycle,while thatof the non equalization device is 38.6%.That is,the equalization strategy can significantly improve battery lifetime.Finally,according to the multi-redundancy system architecture and function,this paper does research and development in detail on the function components and the key communication technology of electric ship’s lithium batteries battery management system,otherwise,the software flow of system redundancy switching is given.