08 rizzoni fc workshop osu gr

8/22/2019 08 Rizzoni FC Workshop OSU GR

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Modeling and Control of Fuel Cell

Systems for Automobile Applications

Fuel Cell Control Workshop Irvine, CA

April 3 & 4, 2003

Giorgio Rizzoni, Yann Guezennec, Gabriel Choi

Ohio State University

Center for Automotive Research

http://car.eng.ohio-state.edu


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Fuel Cell System Research Focus on Fuel Cell Systems for automotive applications, more

particularly PEM

Emphasis on complete systems rather than in-depth component

analysis - Treat the electro-chemistry as a black box

Phase 1 Focus on quasi-static modeling approach, i.e., steady-state characteristics + slow thermal dynamics (suitable for energy

analysis at the system level and vehicle level, system

optimization and supervisory control strategy

Phase 2 Low-frequency dynamics modeling approach, i.e.,

particularly the air supply dynamics under varying loads as seenin automotive powertrains

Phase 3 Model-based control system development, fuel cell

laboratory development for model validation and control

development


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Low-Frequency Dynamic System

Modeling Approach Analogous approach to mean-value models in IC engines

Focuses namely on modeling of dynamic effects with a time scale

commensurate with power demand changes in vehicles

System is modeled as an interconnected set of sub-systems, andtreated as unsteady control volumes (spatially lumped, as

appropriate)

Dynamic model is a superset of quasi-static model, where sub-

systems models are differential equations in time (mass, energy,

inertial dynamics, ), instead of strictly algebraic relationships Emphasis is still on model simplicity for computational efficiency

(low-order dynamic system), but capturing essential dynamics

Stack black-box model is separated into anode and cathode

Preliminary analysis shows that breathing (air/humidity),

thermal and rotational dynamics are dominant


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Fuel Cell System Model


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Some Results of Air Delivery Dynamic Model

Rotational

dynamicscoupled to

compressor

characteristics


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Some Dynamic Simulation Results

Evaporation

and mixing

dynamics

Manifold

dynamics


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Some Dynamic Simulation Results

Net effect on

FC stack

outputVoltage

Power


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Low-Frequency Dynamic System Control

Control objectives and controller structure must be more

precisely defined (possibly coupled with requirements

from vehicle supervisory control level

Possible actuators:

Compressor motor

Back-pressure air valve

Hydrogen flow control valve

Humidification pump/injectors Hydrogen recirculation pump motor

Coolant pump motor

Air recirculation pump motor (?)

Possible sensors:

Air pressure(s), flow rate,

temperature(s), humidity

Hydrogen pressure(s), flow rate,

temperature(s), humidity

Coolant flow rate, temperature(s)

Motor speed(s)


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Some Possible Fuel Cell System Control Objectives

Option 1 (simplest): Constant pressure operation, separate individual

controllers

Air side:

Current/power demand compressor motor control with feedback from mass air

flow meter

Pressure control downstream back-pressure valve with pressure signal feedback Humidity control water pump/injector control with humidity signal feedback

(problem with significant evaporation dynamics and humidity sensor dynamics)

Hydrogen side:

Pressure control hydrogen valve control with pressure difference signal between

anode and cathode to track cathode pressure

Recirculation of all excess hydrogen no control

Advantage: simple independent controllers (PI(D) controller)

Disadvantage: pressure and flow rate are strongly coupled, and independent

controllers may interfere with each other, poor dynamic response,

overshoot/undershoot


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Some Possible Fuel Cell System Control Objectives

Option n: Variable pressure operation to track best system efficiency, with

single MIMO controller

Advantage: May provide best dynamic response for given system as well as

best system efficiency operation across all possible operating conditions

Disadvantage: Complex controller design and implementation


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How much dynamic response is needed?

Strong link to vehicle implementation and supervisory

control strategy

Hybridization with ECMSSupervisory Control Strategy

can tolerate poor dynamic

response of fuel cell system

with no fuel economy

degradation


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OSU Fuel Cell Lab Plans


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Fuel Cell Laboratory Design

CharacteristicsFocus on Complete Automotive PEM Fuel Cell Powertrains

Capable of supporting 80 kW fuel cell stack nominally

Hydrogen supply from electrolyzer buffered to high pressure tank (300-350bar nominal)

Provision for evaluating fuel reformers Air delivery system capable of pressurized operation up to 3-3.5 bars

Easily reconfigurable air delivery system to evaluate differentcompressor/expander technology, system topology, etc.

Capable of operating as a stand-alone system or a hybrid powertrain withdifferent energy storage (battery, supercapacitor)

+/- 80 kW bi-directional load to simulate arbitrary driving cycles or othertransient operation

Extensively instrumented fuel cell stack, fuel cell system and completetraction chain

Rapid prototyping dSpace system for low-level fuel cell system and

supervisory energy management powertrain control


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Focus on System Efficiency, Dynamics, Control andDiagnostics of Complete Automotive Fuel Cell Systems

Support our efforts in (static and dynamic) modeling of fuel cell systems

Develop a systematic, model-based methodology for developingautomotive fuel cell control, both low-level control (ECU equiv.) andsupervisory (vehicle energy management) controller

Evaluate trade-off between system configuration, operating conditions,system efficiency, and dynamic response

Evaluate sensor and actuator set required to achieve suitable automotivecontrol

Develop a model-based diagnostic methodology for automotive fuel cellsystems

Ability to prototype complete fuel cell systems and control for use invehicle demonstration projects

Fuel Cell Laboratory


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Focus on air compressor/(expander), system efficiency, humidification

aspects, dynamic control over large turn down ratio, dynamic response,

heat/mass transfer aspects between intake and exhaust, different family ofcompressor/expanders

HIL stack simulation, power demand simulation (vehicle road load and

supervisory energy management)

System designed and sized to be directly usable for Phase 2 (complete fuel

cell system, including stack)

Implementation target: early summer 03

Fuel Cell LaboratoryPhase I: Air-Side System (in progress)


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Phase I Fuel Cell System Lab

Controlled/Monitored Values

Mass flow, Temperatures atmultiple points, Pressures at

multiple points, humidity

ValvesAir

Power inPump, valvesHumidifier

Torque, Speed, Power outSpeedExpander Drive

Torque, Speed, Power inSpeedCompressor Drive

MonitoredControlledAIR SIDE

Voltage, Current, Power OutVoltagePower supply

Mass flow air divertedDiverter ValveAir used

Stack temperaturePower inHeater

MonitoredControlledSIMULATED STACK

Physically implemented

HIL

Power output of fuel cell system,

system efficiency, vehicel speed,

drivability metrics, fuel

consumption, etc.

Power request to FC systemRoad load, supervisory control

MonitoredControlledSIMULATED VEHICLE

08 rizzoni fc workshop osu gr

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