Design And Energy Management Of Fuel Cell Hybrid Power System For Tram

With the rapid development of global economy and the sharp increase in demand for traditional energy,the problems such as energy shortage,environmental pollution and the greenhouse effect become more and more serious.The development and utilization of new energy sources have become an inevitable trend of energy research all over the world.Because of the abundant source,high power density,high efficiency and environment-protection,hydrogen fuel cell,is gradually becoming a hot research issue.At present,high power fuel cell technology has made breakthrough progress.Fuel cell hybrid locomotive has become a new type of rail transit with great potential and has received wide attention for its good performance and environmentally friendliness.In this paper,the hybrid power system of fuel cell hybrid electric locomotive is researched.According to the indicators and operational requirements of the locomotive,a fuel cell and battery hybrid system has been designed and an energy management strategy based on finite state machine theory has been proposed.The simulation analysis and experimental verification are carried out to demonstrate.On the basis of comprehensively comparing the advantages and disadvantages of different typical hybrid power system topologies,the structure in which fuel cell connects to bus through an unidirectional DCDC converter and battery hybrid power system directly connect to bus is adopted(FC+B).Considering the dynamic characteristics and economy of locomotive operation,the proton exchange membrane fuel cell(PEMFC)is used as the main power supply and the lithium ion battery(Li-Ion)is the auxiliary power supply.According to the established locomotive dynamics model,the traction powers of the locomotive in three running states,namely maximum speed,maximum acceleration and maximum climbing are calculated.According to the maximum traction power,the output powers of the fuel cell and the battery are determined and parameter matching of hybrid fuel cell system is accomplished.Based on the performance parameters of each module of the system,the simulation model of fuel cell,battery,DC/DC converter and the whole system is established in Matlab/Simulink software to provide a platform for the following simulation analysis and energy management strategy research.An energy management strategy based on finite state machine theory is proposed,which divides the working mode of the system into 3 levels according to the high,medium and low SOC of the battery.Then according to the numerical relationship of the demand power,fuel cell output power and battery output power,10 sub patterns are obtained to hierarchical management and control.The proposed energy management strategy is analyzed on the established simulation model.Three different working conditions,the high SOC mode,the medium SOC mode,and the low SOC mode,are simulated respectively.To further verify the effectiveness of the energy management strategy,this paper develops a scaled-down hybrid fuel cell power ratio experimental platform,on whih the experiment is carried out.After the comparison between experimental results and simulation results,it is shown that the proposed finite state machine energy management strategy in this paper can effectively adjust the battery SOC to reach gradually a reasonable range,which can effectively reduce the dynamic load of the fuel cell and achieve high fuel economy of the whole vehicle.