Seminar On Power Factor Improvement On Power Electronics

Seminar 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 furnaces  Harmonics

Advantages of High Power Factor

 Decreasing utility bill.  Branch capacity of the system increases.  Penalty can be avoided  Saving in Hardware Cost.

Methods of controlling power factor  Extinction angle control  Symmetric angle control  Pulse width modulation  Single 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 motor  Crawling in induction motors.  Affect the operation of control & regulating ckt.

Effect of harmonics on waveform

Spectrum of a Typical Distorted Voltage Waveform (a )

(b )

D is t o r t e d W a v e fo r m

S p e c tru m

o f (a )

1 .5

1

THD= 4383%

1

0 .8 H a rm o n ic s M a g n itu d e s (p u )

V o lta g e (p u )

0 .5

0 F u n d a m e n ta l

-0 .5

0 .4

0 .2

-1

-1 .5 0

0 .6

0 .0 0 5

0 .0 1 T im e (s )

0 .0 1 5

0 .0 2

0

1

2

3

4

5 6 7 8 9 1 01 11 21 31 41 5 H a r m o n ic s N u m b e r

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 side  Active 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)

Harmonic Reduction in Voltage Controlled inverters 

Single Pulse Width Modulation.

For 3rd Harmonic p=120◦ For 5th Harmonic p=72◦

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 3.0%

5.0%

115 kV to 161 kV 1.5%

2.5%

Above 161 kV

1.5%

1.0%

Harmonic Current Limit as per IEEE-519 (customers’ responsibility) SCR =Isc/IL

h<11

11
17
23
35
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 common coupling divided by customer average maximum load current) TDD = Total Demand Distortion (uses maximum load current as the 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