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