| Proton Exchange Membrane Fuel Cell(PEMFC),as a renewable and pollution-free new energy power generation technology,has been widely studied and applied.PEMFC State of Health(SOH)detection is an important basis for battery fault diagnosis,including many undesirable conditions such as flooding of the electrodes of the stack,membrane dehydration,catalyst poisoning,and oxygen starvation.Electrochemical impedance spectroscopy(EIS)is an important indirect characterization scheme for the problems of water flooding and membrane dehydration during the operation of PEMFC.The offline EIS method requires expensive test equipment such as electronic loads,and a complete test takes a long time.In order to realize the PEMFC online EIS test with good accuracy conveniently at low cost,the thesis integrats the EIS method into the converter control loop of the PEMFC system to realize the EIS test in a wide frequency range,and designs a binary test signal group for excitation injection.The thesis will conduct research from four aspects: test signal design,incentive injection strategy,system model construction,experimental design and verification.The main research work and innovations are as follows:(1)The design method of the excitation signal for the EIS test of the stack is studied,and a test signal group is designed by using an excitation signal with rich frequency and good spectral line intensity—Pseudo-Random Binary Sequence(PRBS).It can be applied to fast and wide frequency EIS test.(2)According to the EIS test requirements of the PEMFC stack,a DC/DC converter with integrated EIS disturbance test is designed.By applying the test excitation signal to the loop control signal of the DC/DC converter,the DC voltage power achieves power transformation,also realizes the wideband EIS excitation and measurement of the stack.It lays a foundation for the design of EIS test methods combining different application topologies.(3)System modeling is carried out based on MATLAB/Simulink software,and the basic structure and test strategy of the experimental system are simulated.The EIS test strategy of the thesis is analyzed experimentally in the load fluctuation state,and it proves that the anti-interference is good;the simulation test is carried out for the dry and flooded state of the membrane;the experimental comparison between the design signal of the thesis and the multi-frequency sinusoidal signal excitation is considered;The influence of Boost converter input capacitance on EIS had been discussed;A port parameter identification strategy is proposed and verified.(4)Based on the NI fuel cell semi-physical real-time simulation platform and DSP controller,the hardware-in-the-loop simulation experiment and the controller program design is carried out,thus the EIS online test is realized,and the electrochemical impedance spectrum of the PEMFC stack model is obtained.Using software to identify the parameters of the experimental data confirms the feasibility of the online stack state detection and evaluation of this method,which is suitable for the application of embedded equipment and has certain engineering use value. |
