Research On Energy Management Strategy For Marine Hybrid Power System

As China proposes the emission reduction target of "reaching the carbon peak in2030 and striving to achieve carbon neutrality by 2060",reducing the energy consumption and emissions of ships,and improving the level of energy conservation and emission reduction of ships,it is necessary for the shipping industry to achieve "carbon neutrality".through the road.It is difficult for traditional diesel ships to meet the requirements of zero or low emissions.With the rapid development of energy technologies such as clean energy,fuel cells,and composite energy storage,hybrid ships based on clean energy have become an important way for the shipping industry to achieve carbon neutrality.Therefore,it is of great significance to carry out research on the energy management strategy of ship hybrid power system to improve the economy of ships and the level of energy saving and emission reduction.In this research,a certain type of fuel cell ferry is taken as the research object.Aiming at the problems of insufficient dynamic response performance of its power system,rapid degradation of fuel cell performance and large voltage fluctuation of the ship’s busbar,a composite energy storage system is introduced to replace the single energy storage system of the parent ship and completed the overall design from the energy distribution among the energy storage devices to the energy management strategy of the hybrid power system.The main research work done in this paper is as follows:(1)Design and selection of hybrid power system.The power system of the parent ship only has the battery as the energy storage device,which is difficult to bear the high frequency fluctuation of the load and cannot respond to the dynamic changes of the system in time.The topology design of the composite energy storage system and the selection of the main energy storage equipment were carried out,and the configuration calculation and demonstration of the capacity were carried out.(2)Modeling and simulation of hybrid power system.A simulation model that can reflect the changes of ship state parameters and energy flow in real time and accurately is the basis for research on energy management strategies.Based on the idea of modular modeling,the simulation models of fuel cells,lithium iron phosphate batteries,supercapacitors and bidirectional DC/DC converters are built and verified in Matlab/Simulink.The results show the effectiveness of the built hybrid power system simulation model,which lays a good foundation for the following energy management strategy research.(3)Energy management strategy design based on wavelet packet decomposition.Aiming at the problem that the ship hybrid power system needs to formulate an energy management strategy to give full play to the working characteristics of each power source,an energy management strategy based on wavelet packet decomposition and limit protection is proposed to realize the optimal distribution of power among the power systems.Firstly,the wavelet packet decomposition algorithm is used to decompose the frequency band of the load power curve under the typical working conditions of the parent ship,and the power distribution of each frequency band is carried out in combination with the analysis of the amplitude-frequency characteristics,and then the work of the lithium battery and super capacitor is adjusted in real time according to the SOC limit.condition.The simulation results show that the formulated energy management strategy can realize the reasonable distribution of the load power,effectively suppress the power fluctuation of the fuel cell,and improve the stability and economy of the marine hybrid power system.(4)Energy management strategy optimization based on genetic algorithm.Aiming at the problems of the energy management strategy designed above,the output power peak value of lithium battery is too large,and the working characteristics of super capacitor are not fully utilized.A fuzzy controller is designed to redistribute the power of the composite energy storage system.The energy management strategy was optimized by using genetic algorithm(GA)with the performance as the optimization index.The simulation results show that the optimized energy management strategy can maximize the service life of lithium batteries,give full play to the high-power charging and discharging characteristics of supercapacitors,realize more reasonable power distribution of composite energy storage systems,and have better economic performance.performance and control effects.