Research On Dynamic Modeling And Loading Strategy For Automotive Fuel Cell Loading Process

As a clean power source with high energy density,high efficiency and zero emission,proton exchange membrane fuel cell（PEMFC）is considered as one of the most promising technologies for future transportations.In recent years,great progress has been made for the commercialization of fuel cell vehicles.However,with the large-scale commercialization of heavy-duty fuel cell vehicles,the dynamic response capability of PEMFC remains the critical technological challenge in terms of load leveling with dynamic power demand for the fuel cell system.Therefore it is critical to improve the dynamic power response of the fuel cell system ensuring the stability and reliability of the power system.To the best of our knowledge,most studies on the loading characteristics of PEMFC mainly consider the stack average voltage ignoring the consistency of the stack cell voltages,which may lead to reliability and degradation issues due to the improper loading strategy.In this thesis,the dynamic characteristics of the PEMFC stack loading process are studied with the experiment of self-designed 60 k W fuel cell engine and a proposed multi-dimensional equivalent circuit model.Considering the dynamic behavior of cell voltage consistency,an efficient and reliable loading strategy of fuel cell system is designed and optimized.The specific research contents are as follows:Firstly,the structure of the self-designed 60 k W fuel cell engine,stack and auxiliary subsystem are introduced.The critical parameters evaluating the stack loading characteristic are proposed including the cell voltage undershoot value and cell voltage consistency.The effects of various operating conditions on the loading characteristics of fuel cell system are analyzed in the experimental study.Secondly,an equivalent circuit based dynamic model of fuel cell is established with multi-physical mechanism analysis and validated by the experimental results.For better understanding of the local performance uniformity of the fuel cell stack,the basic RLC equivalent circuit model is developed to a quasi-two-dimensional fuel cell stack model which considers the inconsistent distributions of gas pressure,flow rate and operating temperature inside the fuel cell stack.Thirdly,the loading strategy of the fuel cell system is studied based on the proposed dynamic equivalent circuit model.According to the key parameters of loading gradient and loading interval,multiple loading strategies are designed and optimized considering the dynamic characteristics of the fuel cell voltage inconsistency under various loading processes.