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
