A Research On AC Impedance Measurement Technology Of Fuel Cell Based On DC/DC Current Perturbation

Proton Exchange Membrane Fuel Cell(PEMFC)has been widely used because of its advantages of cleanness,high efficiency and high energy density.However,service life of PEMFC and sudden failures have greatly restricted the commercialization process of fuel cells.At present,conventional fuel cell fault diagnosis methods are difficult to be applied to fuel cell system in order to realize real-time monitoring.Integrating AC impedance measurement technology into power converter of fuel cell system can realize on-line fault diagnosis,which is a promising method In this thesis,the online AC impedance measurement system of fuel cell based on DC/DC current disturbance was studied.The specific research contents are as follows.In this thesis,the technical requirements of fuel cell AC impedance technology were analyzed in details.The advantages and disadvantages of power level AC impedance measurement technology and signal level AC impedance measurement technology were compared.The technical solution of online AC impedance measurement system was proposed considering the limitations of applying AC impedance measurement method into the fuel cell system,Based on the requirements,this thesis completed the design of high bandwidth,fast response DC/DC converter,and the simulation results show that the dynamic disturbance performance and the steady-state performance are excellent.In addition,this thesis completed the design of high synchronization disturbance signal acquisition module,and its function and gain were verified by simulation.Finally,the real-time calculation module of AC impedance was designed,and the online measurement of impedance was realized by using the fast Fourier transform technology.The design of on-line AC impedance measurement system is completed.In the end,the online AC impedance measurement system was set up.Through the experiments,this thesis analyzed the static and dynamic characteristics of the DC/DC converter,the signal gain and synchronization of acquisition module,and the accuracy of on-line AC impedance measurement system.The evaluation on the functionality and accuracy at the module and the system level were completed.The system designed in this thesis was used to measure the fuel cell membrane moisture content online with high accuracy,and the research will provide great value to the potential applications.