Power Quality

• Determines fitness of electrical power to consumer devices

• Complexity in transferring the electric energy from point of generation to consumer premises

• Factors such changing demand, varying weather, various non linear devices, switch, and circuit breaker operation etc

• Fluctuation in frequency, amplitude and phase of voltage signal

• May lead to failure of sophisticated devices/equipment

Common Source of Disturbances

• Switched mode power supply• Television, Computer• Mobile Charger• Fluorescent lamp with electronic balast• Energy Saving Bulbs • Welding Equipment• Light Dimmers• Variable Speed Drives• Variable Frequency Drives• Power Converters• Thyristor control for heating and ovens• Static VAR Compensator

Power System DisturbancesVarious disturbances as per IEEE standards encountered in power system

1. Voltage Sag

2. Voltage Swell

Cont…..3. Voltage Interruption

4. Voltage Fluctuation(Flicker)

Cont…5. Harmonics

Cont….6. Notch

7. Noise

Cont….8. Transientsa) Impulsive

b) Oscillatory

Short Time Fourier Transform - 1970

Hilbert Huang Transform - 1998

Gabor Transform - 1946

Methods Available For Signal Analysis

Q1 Q2 Q3

Q4

Discrete Wavelet Transform – 1980s

Wavelet Packet Transform

Kalman Filter

Wigner Ville Distribution - 1980

S-Transform - 1996

Empirical Wavelet Transform - 2013

INTRODUCTION TO S-TRANSFORM(1996)

)2||(*)).((),( 22

22 ffj efethfS

Cont…

WHY S-TRANSFORM

Better time-frequency distribution of signal and better frequency detection From its time-frequency matrix instantaneous variation of every frequency

component of signal can be detected

Instantaneous Phase of every sinusoid can detected using time-frequency matrix

FFT is used in finding time-frequency matrix making it fast

S-Transform

Short Time Fourier Transform

Discrete Wavelet Transform

Wigner-Ville Distribution

SimulationVoltage sag

Cont…..Voltage swell

Cont..

Interrupt

Cont….Transient

Cont…Harmonics

Cont…Flicker

Limitation

Cont..

Cont…

Empirical Wavelet Transform(2013)

FFT• FFT of signal

Maxima

• Detecting maxima in FT of signal using thresolding and frequency distancing

Boundaries• Boundaries for wavelet filters

iFFT• iFFT{(Wavelet filter in frequency )*FFT}

Individual F component

• Desired frequency component of signal

Cont..

Future Work

• Further reading on Empirical Wavelet Transform

• Develop code of Empirical Wavelet Transform

• Compare the results with S-Transform results

References

Caramia,P., Carpinelli, G., Verde, P. “Power quality indices in liberalized markets,” John Wiley & Sons Publication, 2009, 1st edn.

IEEE Recommended Practice and Requirements for Harmonic Control in Electric Power Systems, IEEE Standard 519-1992, Apr. 1993

IEEE Recommended Practice for Monitoring Electric Power Quality, IEEE Std. 1159-2009 M. Bollen and I. Yu-Huaa Gu, Signal Processing of Power Quality Disturbances, New Jersey, Wiley,

2006. Estimation of time-varying power quality indices with an adaptive window-based fast generalised S-

transform by M. Biswal and P.K. Das Yong-June Shin, Member, IEEE, Edward J. Powers, Life Fellow, IEEE, Mack Grady, Fellow, IEEE, andAri

Arapostathis, Senior Member, IEEE ”Power Quality Indices for Transient Disturbances”

THANK YOU