Modeling And Energy Management Of Fuel Cell Hybrid System

At present,traditional fossil energy is gradually drying up.Based on the needs of ecological protection and national security,it is urgent to develop renewable energy.Hydrogen energy is a new type of energy known for environmental protection、high efficiency and safety,which is clean and efficient.As a carrier to convert the chemical energy of hydrogen energy into electrical energy,fuel cell is one of the most common and efficient ways to use hydrogen energy.At present,fuel cell power generation technology has attracted great research enthusiasm in military,transportation,aerospace,distributed power generation,integrated energy system and other fields.This paper takes the fuel cell/lithium battery hybrid system as the research object.The main research contents and results are as follows:(1)According to the operating characteristics of fuel cell and lithium battery,the fuel cell/lithium battery hybrid system model is established.The model mainly includes fuel cell model,unidirectional boost DC/DC converter model and lithium battery model.On this basis,the hardware in the loop experimental platform of fuel cell hybrid power system is built based on rt-lab.Then,through the comparative analysis with the experimental data of the actual hardware system,the accuracy of the hardware in the loop experimental platform is verified,which can provide a platform basis for the verification of energy management methods in the following paper.(2)In order to reduce the total equivalent hydrogen consumption of fuel cell hybrid system,a dual-mode energy management method for fuel cell hybrid system is proposed.Firstly,the hydrogen consumption of fuel cell and the equivalent hydrogen consumption of lithium battery are analyzed;Then,according to the range of lithium battery SOC,two working modes of fuel cell hybrid system are divided,the corresponding objective function is established,and hysteresis control is adopted to avoid frequent transfer between states;By solving the optimal control laws of fuel cell power under different working modes,the optimal control of equivalent hydrogen consumption is realized.Finally,based on the hardware in the loop experimental platform,through comparative analysis,it is verified that the proposed method is superior to the traditional power following and state machine energy management methods in reducing the total equivalent hydrogen consumption and improving the efficiency of fuel cell system.(3)In order to optimize the equivalent hydrogen consumption of the system and the service performance of fuel cell,an adaptive Pontryagin minimum principle energy management method for fuel cell hybrid system is proposed.Firstly,considering that the output characteristics of the fuel cell are affected by the external characteristics such as temperature and humidity,the forgetting factor recursive least square algorithm is used to identify the parameters of the hydrogen consumption and efficiency model of the fuel cell system on-line;Then,the multi-objective optimization objective function considering the equivalent hydrogen consumption of the system and the performance degradation of fuel cell is established;The objective function is solved by the Pontryagin minimum principle method,and the optimal control law of fuel cell power is obtained.Finally,based on the hardware in the loop experimental platform,the advantages of the proposed energy management method in optimizing the system equivalent hydrogen consumption and delaying the performance degradation of fuel cell are verified by comparing with the traditional Pontryagin minimum principle method,the equivalent consumption minimization strategy and the dual-mode energy management method.