Evaluation of Total Harmonic Distortion tool for SOFC diagnostics

Transcription

1 Diagnosis-aided control for SOFC power systems FCH-JU GRANT AGREEMENT NUMBER: Project Mid-term Exploitation Workshop Evaluation of Total Harmonic Distortion tool for SOFC diagnostics Bertrand Morel André Chatroux CEA Grenoble Workshop on Monitoring, Diagnostics and Control for SOFC systems Improving SOFC-based CHP performance through innovative diagnosis and control Naples (I) December 16 th, 2015

2 Outline Introduc;on: What is Total Harmonic Distor;on (THD)? Applica;on of THD on small SOFC cell Transposi;on of THD to 25-cells stack Conclusions Mid-Term Workshop 2

3 ! Reasons for the use of THD Selection of the 3 most critical faults/failures made by all partners in project: o Fuel starvation o Air starvation o O/C & S/C ratio too low Cell voltage measurement is a good sensor but Are voltage probes necessary at every stages? è Total Harmonic Distortion Analysis could be a way to decrease the number of voltage probes Mid-Term Workshop 3

4 THD=Total Harmonic Distortion A small sinusoidal current signal is superimposed at an operating point è under ideal operating conditions (linear part of i-v curve) it leads to a sinusoidal voltage response transformed by a linear function (not distorted) è under critical conditions (like air or fuel starvation) the whole polarization curve shifts and there is an harmonic distortion of the cell voltage response. Mid-Term Workshop 4

5 THD=Total Harmonic Distortion THD = k = 2 Y 1 Y 2 k Then, THD is defined as the ratio of the Euclidean norm of the system response Y of all higher harmonic frequencies (k 2) to that of the fundamental frequency (k = 1). è THD = effective method to evaluate nonlinearity of a system: the harmonic content of a waveform is compared to its fundamental. References: Thomas, S., Lee, S.C., Sahu, A.K., Park, S., Interna;onal Journal of Hydrogen Mid-Term Energy Workshop 39, doi: /j.ijhydene Ramschak, E., Peinecke, V., Prenninger, P., Schaffer, T., Hacker, V., Journal of Power Sources 157, doi: /j.jpowsour

6 THD in the literature Ramschak, E., Peinecke, V., Prenninger, P., Schaffer, T., Hacker, V., Detec%on of fuel cell cri%cal status by stack voltage analysis. Journal of Power Sources 157, doi: /j.jpowsour Kiel, M., Bohlen, O., Sauer, D.U., Harmonic analysis for iden%fica%on of nonlineari%es in impedance spectroscopy. Electrochimica Acta 53, doi: /j.electacta Mao, Q., Krewer, U., Hanke-Rauschenbach, R., Total harmonic distor%on analysis for direct methanol fuel cell anode. Electrochemistry Communica;ons 12, doi: /j.elecom Mao, Q., Krewer, U., Sensing methanol concentra%on in direct methanol fuel cell with total harmonic distor%on: Theory and applica%on. Electrochimica Acta 68, doi: /j.electacta Mao, Q., Krewer, U., Total harmonic distor%on analysis of oxygen reduc%on reac%on in proton exchange membrane fuel cells. Electrochimica Acta 103, doi: /j.electacta Thomas, S., Lee, S.C., Sahu, A.K., Park, S., Online health monitoring of a fuel cell using total harmonic distor%on analysis. Interna;onal Journal of Hydrogen Energy 39, doi: /j.ijhydene Renner, K., Rechberger J., PEMFC Stack Monitoring with Advanced Total Harmonic Distor%on Analysis. A0801, Proceeding of EFCF 2015, Luzern. Mosbaek, R.R., DTU Ph.D. Thesis, October Solid Oxide Fuel Cell Stack Diagnos%cs. Chapter 6 Fuel starva;on detec;on with THD. Mid-Term Workshop è THD on SOFC cells and stack has not been largely studied and used 6

7 THD=Total Harmonic Distortion + DC load AC load SOFC cell/ stack Cell Voltage Measurements - i DC i AC U cell Autolab, electronic load, Autolab, Hioki, Alterna;ve Voltage Signal Windowing Fast Fourier Transform Detec;on of Fundamental Frequency THD calcula;on Mid-Term Workshop 7

8 THD on a SOFC single cell of 9 cm² I + V + Autolab PGSTAT302N = generator of sinusoidal current from 10 4 to 10-2 Hz è I DC + I AC è High sampling rate è High resolu;on = 30 µv I - V - Mid-Term Workshop 8

9 THD on a SOFC single cell Amplitude, frequency and FU tested for THD analysis SolidPower single cell with ac;ve surface area=9.08 cm² T=800 C, AU=20% and i DC =0.5 A/cm² è Frequency range tested: >10-2 Hz è 4 amplitudes tested: 1, 5, 10 and 20% of i DC è 5 FU tested: 60, 70, 80, 85 and 90% by varying i DC i DC =0.5 A/cm² 1% è +/ A/cm² 5% è +/ A/cm² 10% è +/ A/cm² 20% è +/- 0.1 A/cm² FU=60% FU=70% FU=80% FU=85% FU=90% Mid-Term Workshop 9

10 THD on a SOFC single cell T=800C, AU=20% EIS performed between 10 4 and 0.01 Hz FU=60% FU=70% FU=80% FU=85% i DC =0.5 A/cm² +/-5% è +/ i DC =0.584 A/cm² +/-5% è +/ i DC =0.667 A/cm² +/-5% è +/ i DC =0.708 A/cm² +/-5% è +/ i DC =0.750 A/cm² +/-1% è +/ A/cm² Mid-Term Workshop 10

11 THD on a SOFC single FU=60% T=800 C, i DC =0.5 A/cm² i(dc)=0.5 A/cm² è FU=60% +/- i AC =1%, 5%, 10%, 20% i DC è No effect of amplitude Mid-Term Workshop 11

12 THD on a SOFC single FU=60% T=800 C, i DC =0.5 A/cm² i DC =0.5 A/cm² è FU=60% +/- i AC =1%, 5%, 10%, 20% i DC è THD analysis impacted by noise when a small amplitude (1%) is used è %THD increases at low frequency (0.01 Hz) and when AC amplitude is increased Mid-Term Workshop 12

13 THD on a SOFC single FU=70% T=800 C, i DC =0.584 A/cm² i(dc)=0.584 A/cm² è FU=70% +/- i AC =1%, 5%, 10%, 20% i DC è Distorsion of EIS diagram only with an AC amplitude of 20% Mid-Term Workshop 13

14 THD on a SOFC single FU=70% T=800 C, i DC =0.584 A/cm² i(dc)=0.584 A/cm² è FU=70% +/- i AC =1%, 5%, 10%, 20% i DC è Idem, THD analysis impacted by noise when a small amplitude (1%) is used è %THD increases significantly at low frequency (0.01 Hz) and when AC amplitude is increased Mid-Term Workshop 14

15 THD on a SOFC single FU=80% T=800 C, i DC =0.667 A/cm² i DC =0.667 A/cm² è FU=80% +/- i AC =1%, 5%, 10%, 20% i DC è Distorsion of EIS diagram starts with an AC amplitude of 5% Mid-Term Workshop 15

16 THD on a SOFC single FU=80% T=800 C, i DC =0.667 A/cm² i DC =0.667 A/cm² è FU=80% +/- i AC =1%, 5%, 10%, 20% i DC è Idem, THD analysis impacted by noise when a small amplitude (1%) is used è %THD increases significantly at low frequency (0.01 Hz) and when AC amplitude is increased è %THD increases also at 0.1 Hz è An addi;onal phenomena is imposed at low frequency by a 20% AC amplitude that could be reoxida;on of Ni Mid-Term Workshop 16

17 THD on a SOFC single FU=85% T=800 C, i DC =0.708 A/cm² i DC =0.708 A/cm² è FU=85% +/- i AC =1%, 5%, 10% i DC è Distorsion of EIS diagram starts with an AC amplitude of 5% Mid-Term Workshop 17

18 THD on a SOFC single FU=85% T=800 C, i DC =0.708 A/cm² i DC =0.708 A/cm² è FU=85% +/- i AC =1%, 5%, 10% i DC è Idem, THD analysis impacted by noise when a small amplitude (1%) is used è %THD increases significantly at low frequency (0.01 Hz) and when AC amplitude is increased è %THD increases also at 0.1 Hz è An addi;onal phenomena is imposed at low frequency by a 10% AC amplitude that could be reoxida;on of Ni Mid-Term Workshop 18

19 THD on a SOFC single FU=90% T=800 C, i DC =0.75 A/cm² i DC =0.75 A/cm² è FU=90% +/- i AC =1%, 5% i DC è Huge distorsion of EIS diagram at AC amplitude of 5% Mid-Term Workshop 19

20 THD on a SOFC single FU=90% T=800 C, i DC =0.75 A/cm² i DC =0.75 A/cm² è FU=90% +/- i AC =1%, 5% i DC è Idem, THD analysis impacted by noise when a small amplitude (1%) is used è %THD increases significantly at low frequency (0.01 Hz) and when AC amplitude is increased è An addi;onal phenomena is imposed at low frequency by a 5% AC amplitude that could be reoxida;on of Ni Mid-Term Workshop 20

21 THD results - Summary : effect of amplitude, frequency and FU on THD analysis FU=60, 70, 80, 85 et 90% i AC =5% i DC FU=60, 70, 80, 85% i AC =10% i DC è Usefull range of frequency to be studied: 1->0.01 Hz è With a 5% AC amplitude it s possible to detect FU>80% between 0.01 Hz and 0.1 Hz. A reoxida;on phenomena seems to be detected with THD analysis at FU=90%. è With a 10% AC amplitude it s easier to detect FU>80% between 0.01 Hz and 0.1 Hz. Mid-Term Workshop 21

22 ! THD on a 25-cells stack 25-cells stack Autolab PGSTAT302N = generator of sinusoidal current from 104 to 10-2 Hz è IDC + IAC Hioki = portable data logger è Simultaneous acquisi;on of 25 cell voltage measurements è High sampling rate = 20 ms è High resolu;on = 50 µv + - Mid-Term Workshop 22

23 THD on a faulty 25-cells stack THD -i DC =40 ma/cm² -i AC =4 ma/cm² (10% of i DC ) -fq=0.1, and 0.01 Hz è With i-v curves, it s easy to make a diagnos;c! è Is THD abble to detect cell 21? Mid-Term Workshop 23

24 THD on a faulty 25-cells stack THD -i DC =40 ma/cm² -i AC =4 ma/cm² (10% of i DC ) -fq=0.1, and 0.01 Hz è THD value is high for the cell 21 and also for the cell 15 è This value is increasing when frequency is decreased 0.01 Hz, difference of THD value between a good cell and a bad cell is a 10 factor Mid-Term Workshop 24

25 THD on a faulty 25-cells i=40 ma/cm² è Ra;o between Standard Devia;on and Mean value indicates that a higher sensibility is obtained with THD than with cell voltage measurement by a factor 28 Mid-Term Workshop 25

26 Conclusions and perspectives è THD analysis is adapted for fuel/air starva;on detec;on at single cell level Usefull range of frequency to be studied: 1->0.01 Hz è Transposi;on of THDA has been done on a 25-cells stack è It appears that detec;on of fault like high FU will be more accurate with mean value of THD than mean value of cell voltage measurements. è Decreasing the number of cell voltage probes seems to be realis;c è This work on THD has to be con;nued with other stacks and by simula;ng faults Mid-Term Workshop 26