Research On Control Strategy And Configuration Optimization Of Marine Hybrid Energy Storage Based On DC Grid

Due to the increasingly severe energy crisis and environmental pollution worldwide,as well as the implementation of mandatory regulations on energy conservation and emission reduction,the application of new energy sources such as solar energy,wind energy,lithium-ion batteries and supercapacitors in the field of ships has gradually become the focus of industry research.Among them,lithium-ion batteries have the advantages of high energy density and low self-discharge rate,but short cycle life and slow dynamic response;using the characteristics of high power density and extremely long cycle life of supercapacitors,they form a hybrid energy storage system with lithium-ion batteries,so that the energy storage system has the advantages of quick response and long power supply at the same time.This paper mainly focuses on the hybrid energy storage system in hybrid electric ships.Through theoretical analysis,mathematical modeling and simulation experiments,the energy management strategy of hybrid energy storage based on variable filter time constant and the lithium-ion battery under the multi-objective optimization mathematical model are deeply studied.The optimal allocation of energy storage capacity of battery and supercapacitor.The research results of this paper can provide theoretical basis and method support for the design of hybrid energy storage energy management strategy and the optimization of capacity allocation.The main research contents of the paper are as follows:First,the actual load power of the target ship under the typical working conditions of the target ship is analyzed,and the hybrid ship power system is refitted in the form of ship generator set+ hybrid energy storage system.The active topology structure of the hybrid energy storage system is selected,and the capacity allocation research based on equivalent calculation is carried out.Secondly,the basic principle of the DC network electric propulsion system for hybrid ships is analyzed.On the basis of the low-pass filtering algorithm and PI control,the coordination and cooperation control strategy based on variable filter time constant,the overcharge and overdischarge protection strategy and the maximum power limiting strategy,adjusting the output power of the energy storage element for many times,through the simulation test to compare and analyze the advantages and disadvantages of the DC bus voltage,the output power of the energy storage element and the SOC change trend under the coordination and protection control strategy of the hybrid energy storage.Verify the superiority of the coordination and protection control strategy.Based on the above-mentioned hybrid energy storage energy management strategy,the number and type of energy storage elements in series and parallel are used as decision variables to establish a quantitative multi-objective function of the total cost and total weight of the energy storage system taking into account the full-life cycle of the battery.According to the boundary constraints such as power and energy,charging and discharging,the multi-objective genetic algorithm NSGA-II is used to obtain the optimal solution of lithium-ion battery and supercapacitor capacity configuration.Finally,on the basis of the aforementioned research,the basic structure and composition of the hybrid energy storage system test platform are designed and improved,which provides a basis for subsequent experiments to verify the control strategy of hybrid energy storage.