Design Of Air-cooled Fuel Cell/Lithium Battery Hybrid Power System

The proton exchange membrane fuel cell is a kind of green power generation device which directly converts hydrogen energy into electric energy.It has the advantages of cleanliness,high efficiency and high power density,and has wide application prospect in communication,aerospace and transportation.However,the proton exchange membrane fuel cell has a soft characteristic curve,slow power response and cannot recover braking energy and other shortcomings.In order to overcome these shortcomings,fuel cell-based hybrid system came into being.In order to study the effect of different topologies and energy management strategies on the performance of air-cooled fuel cell/lithium battery hybrid system,firstly,the topologies of fuel cell hybrid system at home and abroad are studied.By comparing several topologies of hybrid power control system,This article designs two types of air-cooled fuel cell/lithium battery hybrid system topology that meet the requirements of stability,high efficiency and ease of realization.Second,the energy management strategy plays an important role in coordinating the rational distribution of power between multiple power sources in a hybrid system.In this paper,two energy management strategies for air-cooled fuel cell/lithium battery hybrid system are studied in order to meet real-time power demand and improve fuel economy:The energy management strategy based on state machine control and Energy Management Strategy based on Equivalent Hydrogen Consumption.The energy management strategy based on state machine control(SMC)is to determine the operating status of the system according to the load power and the state of charge(SOC)of the lithium battery and then determine the reference power of each power source.Based on the equivalent hydrogen consumption minimization(ECMS)Energy management strategy is to coordinate the output relationship between the output power of the air-cooled fuel cell and the load demand power to realize the instantaneous optimization of the equivalent hydrogen consumption in the unit control cycle by solving the problem of instantaneous hydrogen consumption optimization.Then,based on the two topologies designed,this paper completes the design of air-cooled fuel cell/lithium battery hybrid system.In a hybrid system,DC/DC converter is an important device to achieve energy management.As the output characteristics of air-cooled fuel cell is"soft",this paper designs a unidirectional DC/DC converter to control the output power of air-cooled fuel cell for this output characteristic.At the same time,in order to realize the charge and discharge management of lithium battery,this paper designs bidirectional DC/DC converter according to the selected lithium battery parameters.Moreover,the hardware implementation of the two energy management strategies is completed for the two topologies,and the corresponding software design is completed.Finally,in order to verify the stability of the hybrid systems and the effectiveness of the energy management strategies,the air-cooled fuel cell/lithium battery hybrid system test platform is built on the basis of the hardware and software design.Experimental results show that the hybrid systems is stable and dynamic,and the two energy management strategies can effectively realize the power distribution between the two power sources.Through the comparison of experimental data,two kinds of energy management strategies under different topologies are compared and analyzed from the aspects of fuel economy and power source operating pressure and system efficiency,and so on.