seminar on power factor improvement on power electronics
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Seminar OnSeminar On
POWER FACTOR IMPROVEMENT
IN
POWER ELECTRONICS
Presented By
Subhankar Dam
M.Tech (Power Electronics & Drives)
Jalpaiguri Govt Engg. College
What is Power Factor
Ratio of delivered power to the product of RMS voltage and RMS current
The cosine that represents the phase angle between the current and voltage waveforms.
power factor = cos ø
Causes of Low Power Factor
ac motors and transformers.Arc lamp & electric discharge.Magnetizing component of inductive
reactance increases during low load periods. Improper maintenance of motors.Arc furnacesHarmonics
Advantages of High Power Factor
Decreasing utility bill.Branch capacity of the system increases.Penalty can be avoidedSaving in Hardware Cost.
Methods of controlling power factor
Extinction angle controlSymmetric angle controlPulse width modulationSingle phase Sinusoidal PWM
Extinction angle control
Waveform
Symmetric angle control
Waveform
Pulse width modulation
Single phase Sinusoidal PWM
Harmonics
It is a steady state periodic phenomenon that produces continuous distortion in voltage and current waveform.
It is normally caused by saturable devices, power electronics devices and non linear consumer loads.
Effects of Harmonics
Increases the amount of Current on the neutral conductor
Creates Interference on Communication Circuit.
Excessive heating in induction motorCrawling in induction motors.Affect the operation of control &
regulating ckt.
Effect of harmonics on waveform
Spectrum of a Typical Distorted Voltage Waveform
0 0.005 0.01 0.015 0.02-1.5
-1
-0.5
0
0.5
1
1.5
Time(s)
Vol
tage
(pu)(a) Distorted Waveform
Fundamental
1 2 3 4 5 6 7 8 9 10 11 12 13 14 150
0.2
0.4
0.6
0.8
1
Harmonics Number
Har
mon
ics
Mag
nitu
des
(pu)
(b) Spectrum of (a)
THD= 4383%
Total Harmonic Distortion
Total Harmonic Distortion (THD) is a measure of harmonic voltage/current. The THD in a voltage waveform is defined as
Total harmonic distortion (THD)Ratio of the RMS value of all the nonfundamental frequency terms to the RMS value of the fundamental
A view to different power factors for different loads (A case study)
Harmonic Reduction
Low pass L-C filter ckt on ac sideActive shaping of input line current
Low pass L-C filter ckt on ac side
Design consideration.
Active shaping of input line current
Line waveform & (iL & Vs)
Single Pulse Width Modulation.
For 3rd Harmonic p=120◦
For 5th Harmonic p=72◦
Harmonic Reduction in Voltage Controlled inverters
Multiple commutation in each half cycle
Harmonic Reduction using multiple commutation
Order of typical harmonics generated by non-linear loads (A case study)
Harmonic Voltage Limit as per IEEE-519(utilities’ responsibility)
Bus Voltage Maximum Individual Harmonic Component (%)
Maximum THD (%)
69 kV and below
115 kV to 161 kV
Above 161 kV
3.0%
1.5%
1.0%
5.0%
2.5%
1.5%
Harmonic Current Limit as per IEEE-519(customers’ responsibility)
SCR =Isc/IL
h<11 11<h<17 17<h<23 23<h<35 35<h TDD
<20
4.0 2.0 1.5 0.6 0.3 5.0
20 -50 7.0 3.5 2.5 1.0 0.5 8.0
50 -100 10.0 4.5 4.0 1.5 0.7 12.0
100 -1000 12.0 5.5 5.0 2.0 1.0 15.0
>1000 15.0 7.0 6.0 2.5 1.4 20.0
Values shown are in % of “average maximum load current”SCR = short circuit ratio (short circuit current at point of commoncoupling divided by customer average maximum load current)TDD = Total Demand Distortion (uses maximum load current asthe base, rather than the fundamental current)
CONCLUSION
Links & References
Power Electronics (M.H.Rashid)
Power Electronics (Khanchandani & Singh)
http://ieeexplore.ieee.org
www.books.google.com
www.en.wikipedia.org
Thank You
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