Fault Detection And Degradation Evaluation Of Fuel Cell Based On Magnetic Field And Impedance Spectroscopy

Under the background of "carbon peaking and carbon neutralization",it is imperative to seek clean and efficient renewable energy.Proton exchange membrane fuel cell(PEMFC),as a conversion device that converts hydrogen energy into electric energy,has attracted extensive attention in many fields because of its high efficiency and cleanliness.Among them,the promotion and application of locomotives have become an important direction for the development of green and low-carbon rail transit.However,how to ensure the safe and reliable operation of the primary power source PEMFC is an urgent scientific problem to be solved in the popularization and application of hydrogen fuel cell locomotive.Stability and durability are the key problems to be solved.Among them,to ensure stability,it is necessary to quickly detect the faults caused by PEMFC in short-term operation.And to ensure durability,it is necessary to accurately evaluate the performance degradation caused by PEMFC in long-term operation.Therefore,appropriate fault detection and degradation evaluation methods are indispensable.The main research contents of this paper include :(1)This paper analyzes the existing PEMFC fault detection tools and degradation evaluation methods at home and abroad,selects the appropriate detection tools,and applies them to the real-time fault detection of PEMFC.The degradation evaluation method of PEMFC is explored and applied to the degradation evaluation of PEMFC under simplified locomotive conditions.(2)The structure and operation principle of PEMFC and the fuel cell test system used are introduced,including the PEMFC stack,fuel cell test bench,impedance spectrum analyzer and magnetic field measurement array,which provide experimental support for fault detection and degradation evaluation.(3)Aiming at the difficulty of on-line detection of PEMFC under dynamic conditions,taking 5k W PEMFC stack as the research object under simplified locomotive operating conditions,according to the experimental data of electrochemical impedance spectroscopy(EIS),voltage and stack humidity,and based on Biot-Savart law,explore the mapping relationship between EIS based off-line evaluation and magnetic field based non-invasive online evaluation of PEMFC stack health status,to realize magnetic field-based non-invasive online PEMFC fault detection.Experiments verify the effectiveness of on-line detection of PEMFC faults based on the magnetic field under dynamic conditions.(4)Aiming at the difficulty of degradation evaluation of PEMFC under dynamic conditions,taking a 5k W PEMFC stack as the research object,the cyclic degradation experiment under locomotive operating conditions is designed,and the degradation characteristics of the PEMFC stack are preliminarily evaluated according to the polarization curve;To further analyze the degradation characteristics of PEMFC stack,a third-order RQ equivalent circuit model is established based on EIS,and the degradation characteristics of different components in PEMFC stack are analyzed by using the parameters of the equivalent circuit model;To deeply analyze the aging characteristics of PEMFC stack,the distribution of relaxation time(DRT)method is used to explore the changing trend of different polarization processes in the degradation process.The effectiveness of the polarization curve,equivalent circuit model method and DRT method in evaluating PEMFC degradation is verified by experiments.