VOLTAGE SINGULARITY CLASSIFICATION FOR FUEL CELL DIAGNOSIS

Transcription

1 FRENCH INSTITUTE OF SCIENCE AND TECHNOLOGY FOR TRANSPORT, DEVELOPMENT AND NETWORKS VOLTAGE SINGULARITY CLASSIFICATION FOR FUEL CELL DIAGNOSIS Djedjiga BENOUIOUA IFSTTAR / COSYS / LTN FC LAB Belfort, FRANCE EFC 3 December -3, 3 djedjiga.benouioua@ifsttar.fr denis.candusso@ifsttar.fr fabien.harel@ifsttar.fr latifa.oukhellou@ifsttar.fr

2 Contents. Synopsis of the investigated PEM Fuel Cell. Experimental process 3. Development of a new non intrusive diagnosis tool based on Voltage Singularity Spectrum (VSS) 3.. VSS computation 3.. VSS classification 4. Conclusion & Future works

3 . Synopsis of the investigated PEM Fuel Cell F French ANR DIAPASON project aims: Ø Experimental characterization and faults study of a PEM Fuel Cell. Ø Development of non intrusive diagnosis tools. Table. Summary of the experimented PEMFC characteristics Number of cells Electrode active surface Size Gas distributor plates 8 cm mm x 6 mm x 86 mm Metallic plates Table. Summary of the nominal operating conditions Coolant flow: deionized water Anode stoichiometry (H) Cathode stoichiometry (air) Absolute pressure for H inlet Absolute pressure for air inlet Maximal anode - cathode pressure gap Temperature at cooling circuit outlet Anode relative humidity (8 C) Cathode relative humidity (8 C) Load current Current density l/min 5 kpa 5 kpa 3 kpa 8 C 5 % 5 % A.5 A.cm- The experimented 8 cell PEMFC Manufacturer : CEA LITEN Grenoble 3

4 . Experimental process F kw test bench of the FC test platform in FC LAB (UTBM Belfort-France) Acquired data: -Stack voltage -Cell voltages -Current -Power -Gas pressures -Gas flows -Temperatures -Hygrometry - -Impedance spectra (stack & cells) EIS Software Human Machine Interface Ancillaries 8 Cell PEMFC Materials Mates Electrochemical Impedance spectrometer (,Hz-kHz) Table 3. Operating parameters applied for the experimentation Parameter values Nominal Cathode Anode flow conditions flow failure failure Cathode stoichiometry Anode stoichiometry P (bar abs.).3.3 Pressure failure.3 4

5 3. Development of a new non intrusive diagnosis tool based on Voltage Singularity Spectrum (VSS) à Proposed method = pointwise singularity analysis of the PEMFC voltage signal To extract a latent information from the complex signal Analysis method: Continuous wavelets + multifractal formalism Analysis tool: Singularity spectrum (multifractal spectrum) Scanning wavelet ψ(x ) S(x) Scanned signal WS(u, s) = * x u S ( x ) ψ dx s s + An illustration of the continuous wavelet transorm 5

6 3. Development of a new non intrusive diagnosis tool based on Voltage Singularity Spectrum (VSS) F Pointwise regularity of a signal (or a function) is measured by Hölder exponent «h». Singularity hà (strong irregularity) F The whole of the singularities strengths of a complex signal is represented by the singularity spectrum. -4 Regularity hà (low irregularity ) h(x h(x )=. i)=.4 S(xii)=.6 ) xi xi xi x Example of an irregular signal Corresponding singularity spectrum 6

7 Monofractal Weierstrass function Multifractal WT WT WTMM WTMM Multifractional Brownian motion Partition function q q Scaling function Singularity spectrum 7

8 3. Development of a new non intrusive diagnosis tool based on Voltage Singularity Spectrum (VSS) 3.. VSS computation Scaling function VSS Map of the Wavelet transform 8

9 3. Development of a new non intrusive diagnosis tool based on Voltage Singularity Spectrum (VSS) 3.. VSS computation..8 D(h) Tension normalisée Normalized stack voltage h x Test duration = hour Acquisition frequency = Hz Signal duration / spectrum 4,5 min (3 points). VSS number / Test =..5 3 x.8 D(h) h 9

10 3. Development of a new non intrusive diagnosis tool based on Voltage Singularity Spectrum (VSS) 3.. VSS computation D(h) Stack voltage [V] VSS-Ref VSS-FSA=.3 VSS-FSC=.3 VSS-P=.3 bars Time [s] 5 3 Example of stack voltages for different operating conditions of the PEMFC...5 h Resulting average VSS on VSS / operating situation.

11 3. Development of a new non intrusive diagnosis tool based on Voltage Singularity Spectrum (VSS) 3.. VSS classification K-Nearest Neighbors (KNN) Support Vector Machines (SVM) 4 classes : C: «Ref» à Optimal operation of the FC. C: «DFSC» à Cathode flow failure. C3: «DFSA» à Anode flow failure. C4: «DP» à Gas pressure failure. Good rate of classification = 94 % K=, Euclidean distance 4 descriptors and 59 observations Computation time= 4 ms Ref 75 DFSC DFSA DP 5 Good rate of classification = 87 % Gaussian kernel 6 descriptors and 59 observations Computation time= 4 ms Ref 5 DFSC DFSA DP 5

12 Experimental step Characterization step Pattern recognition step

13 5. Conclusion & Future works F The singularity spectra reveal some latent and complex information contained in the raw FC voltage signals. F The singularity spectra results highlight the following cause-effect relationships: Ø A decrease of the cathode stoichiometry rate (FSC= à FSC=.3) induces a high irregularity of the FC voltage signal. Ø A decrease of the anode stoichiometry rate (FSA= à FSA=.3) affects slightly the regularity of the stack voltage signal. Ø A diminution of the inlet gas pressures (P= bars abs.à P=.3 bars abs) leads to a higher regularity of the voltage signal. F The results obtained through the singularity spectra classification are very promising and encouraging to develop a more complete diagnosis strategy based on singularity parameters in future works. F To consider other faults such as: ü monoxide Carbone poisoning at FC anode, ü temperature failure on the FC cooling circuit, ü and faults combination (by considering two or more failures simultaneously during the FC operation). 3

14 FRENCH INSTITUTE OF SCIENCE AND TECHNOLOGY FOR TRANSPORT, DEVELOPMENT AND NETWORKS VOLTAGE SINGULARITY CLASSIFICATION FOR FUEL CELL DIAGNOSIS Djedjiga BENOUIOUA - IFSTTAR / COSYS / LTN FC LAB Belfort, FRANCE Thank you for your attention EFC 3 December -3, 3 djedjiga.benouioua@ifsttar.fr denis.candusso@ifsttar.fr fabien.harel@ifsttar.fr latifa.oukhellou@ifsttar.fr 4

15 Typical curves of: singularity spectra (left side) and electrochemical impedance spectra, obtained at nominal operating conditions (Ref) and in poor operating conditions (fault modes) (right side). 5