Fuel cell modeling and emulation for fault diagnosis and mitigation

The study focuses on modeling of a solid oxide (SOFC) and proton exchange membrane fuel cell (PEMFC) using electrical circuits, implementation of the model in a real-time controller for emulation, and design, building and testing of a power electronic converter to improve the tolerance of a proton exchange membrane fuel cell (PEMFC).; Single cell SOFC and PEMFC models using electrical components in Pspice and/or Matlab Simulink for real-time applications, and parameter estimation have been developed. The model is for a single cell, which can be extended to a fuel cell stack. The model also allows the study of the performance and reliability of the fuel cell under various flow rates and loading conditions. The model is lumped parameter with reduced complexity and computation time amenable to real-time applications. The output voltage of the cell is modeled based on four factors; the open circuit voltage (Nernst reversible voltage), activation loss, concentration loss, and ohmic drop. The mole flow rate conservation of the species is used to determine the open circuit voltage. The open circuit electrochemical reaction is represented using electrical circuits. The activation loss is modeled using the Butler-Volmer equation, which is reduced to an inverse of hyperbolic sine function. Finally, a simple mathematical expression is used to model the concentration and ohmic drops. The results of the model at different flow rates and operating temperature were comparable with experimental data for validation.; A fuel cell (FC) emulator based on the lumped dynamic SOFC model described above has been implemented. The fuel cell emulator is designed to include both the steady state and transient responses. A Matlab/Simulink environment is used to implement the FC model and then programmed into a dSPACE and/or DSP controller. The output of the controller is a reference to a linear power amplifier that drives a power converter or a load. A ds1104 R&D dSPACE controller of 16 bit analog-to-digital converter (ADC) for reading the measurement inputs from a sensors, an embedded slave DSP where the FC model and PWM controller are loaded, a 12 bit digital-to-analog converter (DAC) to interface the reference cell voltage of the FC model to the power amplifier, and a digital input/output port to send PWM control and receive digital inputs is used. An ezdsp R2812 DSP controller is inexpensive and a stand alone digital controller, which contains an ADC, a digital input/output, and TMS320R2812 floating point DSP. This is used to implement the FC model. Both implementation methods show very good results when compared with the experimental data.; The fuel cell performance can be reduced due to a number of reasons such as; drying and flooding of PEMFC membrane, carbon monoxide (CO) poisoning of platinum (Pt) catalyst, etc. CO poisoning of the PEMFC is a problem that drastically reduces the performance of the fuel cell. The CO from the input fuel is adsorbed on the Pt catalyst surface reducing the active area for hydrogen to be oxidized. A power converter circuit is developed to improve the performance of a fuel cell. The DC-DC power converter will draw a pulsating current at a wide range of frequencies, amplitudes and pulse widths, which mitigates the problem. Simulation of the power converter model has been done in Matlab/Simulink, and proper operation of the model is observed.