1. RELIABILITY EVALUATION OF GRID CONNECTED PV SYSTEM

2. INTRODUCTION
PV systems does not involve greenhouse gas emissions and no fossil fuel consumption.
Total capacity of grid connected PV system increased from 300mW in 2000 to 21GW in 2010
Annual growth rate increased from 60% in to % in 2011

3. FEATURES OF HIGHLY RELIABLE PV SYSTEM
Increase in renewable energy output
Guarantee higher return on investment
Curtail carbon emissions

4. RELIABILITY
measure of overall product health over the expected lifetime of the product
Concerned with probability and frequency of failures
Duration or probability of failures under stated condition
Expressed as probability over a given period of time

5. RELIABILITY EVALUATION STEPS
Reliability modelling of PV system components
Reliability evaluation of PV array
Discrete probability distribution of input power
PV reliability indices

7. RELIABILITY EVALUATION OF PV INVERTER
Thermal model of IGBT and diode
Failure rates of IGBT
Failure rates of diode
Failure rates of capacitor
Inverter reliability

9. THERMAL MODEL OF IGBT AND DIODE
Temperature rise in IGBT and diode
∆TIGBT-loss =11PIGBT-loss + 12PDiode-loss
∆TDiode-loss=21PIGBT-loss + 22PDiode- loss
Junction temperature of IGBT or diode
TJ = TC +∆T
Ta +a(PIGBT-loss + PDiode-loss + PAdd)+∆T

10. 1010
FAILURE RATE OF IGBT

11. FAILURE RATE OF IGBT Failure rate is related to Power loss
System power input levels
Temperature depends on
Power loss which in turn depends on system input power levels

12. FAILURE RATES OF DIODE

13. FAILURE RATES OF CAPACITOR

14. INVERTER RELIABILITY

15. INVERTER RELIABILITY Contd..

16. RELIABILITY EVALUATION OF PV ARRAY
Equivalent reliability parameters of PV string
State enumeration for reliability analysis of PV array

17. EQUIVALENT RELIABILITY PARAMETERS OF PV STRING
PV string has two repairable failure modes
Failure at a junction box
Short circuit of PV panel
Both result in outage of whole string
Two modes are characterised by an average failure rate and an average repair rate of PV panel

18. EQUIVALENT RELIABILITY PARAMETERS OF PV STRING

19. STATE ENUMERATION FOR RELIABILITY INDICES

20. DISCRETE PROBABLITY DISTRIBUTION OF INPUT POWER
Input power is metered every 1-15 minutes
It produces a chronological intermittent curve with large amount of data points
Input power measurement are aggregated into discrete probability distribution
K –mean clustering method is introduced

22. K-MEAN CLUSTERING METHOD

23. K-MEAN CLUSTERING METHOD Contd..

24. PV RELIABILITY INDICES
Evaluate system performance
Select best design option at planning stage
To reduce cost and increase benefit at operational stage
Two types: energy oriented and time oriented indices

25. ENERGY ORIENTED INDICES

26. EXPECTED OUTPUT ENERGY(EOE)

27. ENERGY AVAILABILITY

28. TIME ORIENTED INDICES

29. AVAILABLE , DERATED AND OUTAGE HOURS

30. CONCLUSION
Major contributions of proposed new analytical methods include
Input/power loss/temperature dependent failure rates for power electronic components
Evaluation of PV arrays considering power output-dependent failure rates
Application of clustering technique to the discrete probability distribution

31. REFERENCES
Peng Zhang,Yang Wang,IEEE transactions on sustainable energy,vol.3,no.3,july 2012
J L Sawin and E.Martinot,renewables global status report renewable energy policy network for 21st century,2010
A.Ristow,M.Begovoic, A.pregelji,”Development of a methodology for improving photovoltaic inverter reliability,IEEE trans.ind.electron,vol.55,no.7,jul 2008

32. REFERENCES PV Systems reliability,IEEE transactions,2008
Roy Billinton,Ronald.A.Allan,reliability evaluation engineering systems
William K Denson,Reliability assessment of critical electronic components, IT research institute
T K Vrana,A Johanasson,overview of power system reliability assessment technique,RECIFE,2011