pemfc stack monitoring

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AVL List GmbH

Richard Schauperl

PEMFC STACK MONITORING with Advanced Total Harmonic Distortion Analysis

Richard Schauperl,| PTE/DRF | 27th April 2016 | 2Public

BACKGROUND FUEL CELL STACK MONITORING

STATE OF THE ART

• Measuring of individual single cell voltages or cell voltage pairs and analysis in terms of voltage drifts (CVM*)

• Large stack monitoring costs high instrumentation effort and elaborated wiring concepts for reliable operation (EMC**)

• Determination of failure causes or lifetime estimations are not possible

REQUIREMENT

• Real time indication of critical fuel cell conditions, i.e. online monitoring

• Detection of cell voltage drops and its reasons set counteractions

• HW instrumentation for comprehensive diagnostics on stack level and also for serial application


AVL’S APPROACH FOR STACK MONITORING

THDATM (Total Harmonic Distortion Analysis) for stack monitoring

• Measure no longer voltage drifts, but instead analyses effects which results from voltage drifts.

• In parallel the approach provides additional information towards causes of voltage drops which can’t be provided by CVM.

• Signals are analyzed in real time, to provide online failure identification during stack operation.

• Dynamic failure mode detection allows immediate avoidance of potentially irreversible failures and serious lifetime consequences for fuel cell stacks.

• These effects are detectable in the entire stack sum signal i.e. the cabling of individual cells is not necessary.


AVL PEMFC STACK MONITORING

current superimposition

voltage measurement

THDATM (Total Harmonic Distortion Analysis) for stack monitoring

signal analysis on stack level

diagnostic algorithms on stack level

dryout low media liquid wateron stack level

FC Stack

• Under „normal“ operating conditions, the frequency spectrum of the superimposed current signal is identical with the spectrum of the responding voltage signal

• Under “critical” operating conditions a fuel cell distorts a superimposed signal harmonically and generates measurable spectral components.

• Additional spectral components (i.e. harmonics) are formed at particular frequencies during “critical” operating conditions.


PRINCIPLE OF FC-MONITORING WITH AVL-THDA

*patented, registered trademark

“THDA™” – Total Harmonic Distortion Analysis*

6AVL THDA

MATRIX EXAMPLE FOR CLASSIFICATION (SIMPLIFIED)

* criteria are… • derived from FC voltage & current at four different frequencies, analysed in time or frequency domain• total 12-15 different criteria implemented in detection algorithms

criterion #1 criterion #2 criterion #3 criterion #4 criterion #12low media supply + + +++ o o

liquid water droplets o + +++ ++ + o

membrane dry out o o o o +++

…

sensitivity of effects to criteria: o = none, + = sensible, ++ = moderate influence, +++ = high influence

effe

ct

criteria: measured physical parametere.g. thd@f1, imaginary@f1, phase@f3, real@f5 etc.

membrane issue#12 (only)

water issue(#3 & #2 & #4) and not #1

low media(#1 & #2 & #3) and not #4 rule

METHODOLOGY

• Different operating conditions typical changes of electr. characteristics (collection of several criteria*)

• Interpretation of changes in criteria and correlation to operating conditions description with mathematical formulas


THDA INSTRUMENTATION PRINCIPLEDEMONSTRATION & TESTING PHASE

HARDWARE PRINCIPLE

1. Superimposition of a small alternating current signal burst* during operation2. (Spectral-)Analysis of signal response = voltage (thd measurement,

impedance spectroscopy, statistical parameters, …) 3. Results via CAN or RS232 interface to FC controller or GUI

* iAC = typ. 1A (1mV/cell, sinusoidal, low frequency)

output data

1

23


AVL THDA HW/SW

HW and GUI,available as serial devicefor laboratory purpose, or product demonstrationall signal processing integratedplug and play device

For serial application and integration into complete Fuel Cell systems THDA requires no additional hardware. The THDA algorithms can run

in the fuel cell system controller.


OPTION: ONLINE FAST EIS-MEASUREMENT

On-line measurement of electrical impedance spectroscopy

simultaneously scan at five frequencies (1-1000 Hz) every 0.5 sec. up to 500V max stack voltage, max 2A current superimposition changes in EIS correlates with harmonic distortion

Niquist Plot under Stable Conditonsair lambda = 2.1;frequencies=6/14/26/96/1000Hz, P=500W

AVL List GmbH, July 2010-0.03

-0.025

-0.02

-0.015

-0.01

-0.005

00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

real [Ohm]

imag

inar

y* [O

hm]

Z1Z2Z3Z4Z5


ON-LINE MONITORING EXAMPLE

450A Dry + Flood + Low Media detection

• Dry out leads to alower conductivity ofthe membrane

• Low media signal isindicating this effect


ON-LINE MONITORING EXAMPLE

450A Dry + Flood + Low Media detection


SPECIAL APPLICATION MULTIDIMENSIONAL THDA

2x sensor plates

current superimposition

New approach in Austrian funded A3 FALCON project2-dimensional distribution of failure modes for 1 cell

voltage, current, temperaturemeasurement for each segment

signal analysis for each segment

diagnostic algorithms for each segment

dryout low media liquid waterfor each segment

FC Stack


100 CHANNEL MEASUREMENTAIR STARVATION

• Reduce Air Lambda stepwise 2.0, 1.7, 1.6, 1.49 (causes drop out)• Voltage loss ~ 0.32V


SUMMARY THDA is intended to monitor fuel cell stacks in real product applications

like FCEV, Range Extender, CHP, mCHP, APU,…

THDA gives online info on state of dry out, low media, liquid water

THDA offers fast EIS

The laboratory THDA device is a commercial laboratory instrumentation product.

AVL THDA was validated by 7 major automotive OEMs and >10 fuel cell system integrators from other industries.

Outlook: in final product application THDA requires no additional hardware.THDA algorithm runs in fuel cell system controller, only a license agreement with AVL requiredFuture developments shall increase the set of detectable failure modes, with special focus on separation of anode and cathode effects. Also the application for SOFC, SOEC and PEM electrolyzer stacks is investigated in current research projects.

[email protected]

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pemfc stack monitoring

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