Design And Implementation Of Internal Resistance Test Device For Proton Exchange Membrane Fuel Cell

Proton exchange membrane fuel cell(PEMFC) which is clean, green and high energy efficient is the focus of current research in the field of new energy. Every piece of fuel cell can be understood as a variable voltage source having a very small internal resistance. Its internal resistance reflects the fuel cell operating status and the important parameters of the power generation efficiency. In order to assess the single cell performance and timely find the abnormal single cells, we must detect the internal resistance of single cells. Compared with other fuel cell impedance testing method, the EIS (electrochemical impedance spectroscopy) testing method is now highly respected, because of its excellent performance of accuracy testing and the ability of drawing frequency impedance spectrum. This article research and design a high-precision fuel cell internal resistance test device basing on EIS. The main contents are as follows:Firstly the working principles and the equivalent circuit model of fuel cells were explained, and then this thesis compared several test methods of internal resistance and developed the general design of internal resistance test device of fuel cell basing on the EIS method.Secondly, five most important parts of the internal resistance test device were described. They are preamplifier, high-end tracking filter, low-noise linear power, phase-amplitude detection circuit and MCU hardware circuit. In these five parts, preamplifier and high-end tracking filter could achieve the function of collecting and filtering weak AV signal; Linear power has applied negative feedback to achieve low noise output and improve the accuracy of the signal collecting; through the CPLD and RMS detection Phase-amplitude detection circuit, we can detect the phase and amplitude of the two AC signals; AD acquisition and process control of internal resistance test can be completed by MCU Controller.Thirdly, the software design of fuel cell internal resistance test device was completed. According to the working principles of test device, the software design can be divided into CPLD software design and microcontroller software design. In the software design, the author not only divided system software to some functional subprograms but also drew the corresponding flow chart of software including CPLD phase test module, CPLD and MCU communication module, MCU test procedures and RMS amplitude detection module. At the same times the author made the detail application layer protocols of SCI and CAN communication.At last, the thesis did some experiments about the preamplifier and high-end tracking filter and tested the equivalent model of fuel cell internal resistance in a lab environment. These experiments have verified the stability and accuracy of the test device. In the ending of this thesis we tests two kinds of fuel cells, the results show that measured data of the resistance test device is accurate and reliable.