RELIABILITY EVALUATION OF GRID CONNECTE D PV SYSTEM

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 2004 to 80- 90% in 2011

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

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

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

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

THERMAL MODEL OF IGBT AND DIODE  Temperature rise in IGBT and diode ∆T IGBT-loss = 11 P IGBT-loss + 12 P Diode-loss loss ∆T Diode-loss= 21 P IGBT-loss + 22 P Diode  Junction temperature of IGBT or diode T J = T C + ∆T T a + a( P IGBT-loss + P Diode-loss + P Add )+∆T

FAILURE RATE OF IGBT

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

FAILURE RATES OF DIODE

FAILURE RATES OF CAPACITOR

INVERTER RELIABILITY

INVERTER RELIABILITY Contd..

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

EQUIVALENT RELIABILITY PARAMETERS OF PV STRING  PV string has two repairable failure modes a.

Failure at a junction box b.

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

EQUIVALENT RELIABILITY PARAMETERS OF PV STRING

STATE ENUMERATION FOR RELIABILITY INDICES

DISCRETE PROBABLITY DISTRIBUTION OF INPUT POWER  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

K-MEAN CLUSTERING METHOD

K-MEAN CLUSTERING METHOD Contd..

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

ENERGY ORIENTED INDICES

EXPECTED OUTPUT ENERGY(EOE)

ENERGY AVAILABILITY

TIME ORIENTED INDICES

AVAILABLE , DERATED AND OUTAGE HOURS

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

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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