IEEE EPEC 2011 October 2011 1

L.Luckose, N.J.Urlaub, N.J.Wiedeback, H.L.Hess,

B.K.Johnson

University of Idaho

Proton Exchange Membrane Fuel Cell (PEMFC) Modeling in PSCAD/

EMTDC

Paper Session: Microgrids October 4, 2011

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Background

• The US Navy Acoustic Research Detachment » Base on Lake Pend Oreille, Idaho

• Research vessel with electric propulsion » Diesel generator for transit to test area » Battery operation for test runs » Quiet operation is priority

• Batteries fully charged when leave dock » Need to recharge on the lake – time issues

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Operational Modes

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Limitations of Current System

• Diesel Generator » Limited power production » Sensitivity to harmonic current draw from

battery charger » Produces acoustic noise and exhaust that is

objectionable and interferes with testing

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Limitations with Batteries

• Recharge time of ~14 hours and runtime of ~3 hours

• Battery charging system » introduces harmonic distortion to generator » current-limited » requires a substantial amount of space

• The batteries take large amount of space » Currently lead acid batteries

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Why Consider a Fuel Cell?

• Sponsor considering adding fuel cell to the vessel » Navy research program into fuel cell » Use the vessel as a proof of concept » Possibly extend test duration before charging

• Earlier project looked at fuel cell alternatives » Proton Exchange Membrane Fuel Cell (PEMFC) » Best met sponsors requirements

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System Configuration

• Options explored included: » Replace diesel and all batteries » Replace only batteries » Replace diesel and retain all or some batteries

• Batteries combined with fuel cells gave better overall performance

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Fuel Cell Model Development

• Current propulsion system model developed in PSCAD/EMTDC

• Needed compatible fuel cell model • Detailed Matlab/Simulink model of PEMFC

developed by H. Nehrir and C. Wang » Experimentally verified

• This model was ported to PSCAD/EMTDC with some modification

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PEMFC Modeling • One-dimensional treatment of fuel cell • Ideal and uniform distribution of gases • Constant pressure in the fuel-cell gas flow

channels • The fuel cells operate at a temperature

under 100 0C » the reaction occurs in the liquid phase

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PEMFC Modeling • The fuel mix uses humidified air. • Thermodynamic properties evaluated

» at the average stack temperature » neglecting temperature variation across the

stack • Parameters for individual cells in stack

lumped together to represent entire fuel cell

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Overall PEMFC Model

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Module for Internal Potential, E

E = E00 + f1(I,T) + f2(I)

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Activation Loss Modules

Vact1 = η0 + f3(T) Vact2 = I (Ract0 + Ract1(I) + Ract2(I,T))

Convert to PSCAD equations

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Activation Loss Modules

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Double layer Charge Effect Module

» The gain G of the block transfer function is 1 and the time constant T is 40 seconds

» Represents “faster” response of fuel cell

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Calculation of Terminal Voltage

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Representation of Thermodynamic Behavior: Circuit Equivalent

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Inner Fuel Cell Loop

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Overall System: Fuel Cell Plus Battery Storage

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Unidirectional DC-DC Converter for Fuel Cell and Control

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Bi-directional DC-DC Converter for Battery Storage and Control

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Representation of Lead-Acid Batteries

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Load Current Demand-Mimics Test Ship Test Run

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Fuel Cell Output Voltage (blue) and Main DC Bus Voltage (green)

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Duty Ratio Variation for Fuel Cell

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Converter Switching Commands for Battery Storage Converter

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Fuel Cell Stack Temperature Variation

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Conclusions

• PSCAD/EMTDC of PEMFC based on verified

• Implemented in simulation model of electric research vessel

• Combined with battery energy storage to respond to fast load changes

• The test showed response to an operational load profile