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5/3/12 Dept of Electrical and

CONTROL TECHNIQUE FORCOMPENSATION OFNEUTRAL CURRENT

HARMONICSDone by,ANOOP K G7805

E6B

Guided by,Dr. BIJUNA KUNJUDept of Electrical and Electronics

11Dept of Electrical and

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INTRODUCTION

Linear and Non-linear loads

Unbalance Neutral current

Quality of power system

Harmonics in power system

Effect of Harmonics in power system

Control of Harmonics

Selective filtering of HarmonicsDept of Electrical and 22

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WHAT IS HARMONICS ?

Distortion of actual waveform

Due to superposition of higher frequencycomponents

Complex waveform

Analyzed using Fourier series

Causes power quality problems

Zero sequence component in the voltage

causes Dept of Electrical and 33

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How are Harmonics Formed?

44Dept of Electrical and

F(t)=

Fig1

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Supply

Voltage

NonlinearLoad

SupplyImpedance

Nonlinear Operating Conditions

SupplyCurrent

Vout

+

-

55Dept of Electrical and

Fig.2

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What Problems do Harmonics

Create ?

Excessive heating of the neutral

Degradation of cable dielectric and jacket

Core loss and copper loss in transformer

Pulsating torque in motors and generators

Reduces the trip point of circuit breakers

Interference with telephone signals

Inception of corona

Power quality reducesDept of Electrical and 66

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Active Filter for Three phase

Four wire System

Dept of Electrical and 1010

Fig. 3. Active filtering scheme for three phase four wiredistribution system

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Neutral CurrentReduction

Dept of Electrical and 1111

Fig. 4. Zero sequence equivalent

circuit

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Controller for Active

Filter

Dept of Electrical and 1212

In

vn

Powercalculator

Ia

Ire

Va

Vre

Harmoniccurrent

calculator

comparator

Ih

Pa

Pre

Phaseangle

detector

IN

Fig.5

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Simulation

Result

Dept of Electrical and 1313

Simulation result of the proposedactive filter circuit control

Fig.6

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Simulation Result

Dept of Electrical and 1414

Spectra of phase current before applyingactive filter

Spectra of phase current after applying

active filter

Fig.7

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CONCLUSION

Dept of Electrical and 1515

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REFERENCE G.Kamath, N.Mohan Hardware implementation of a novel reduced rating active filter for three

phase four wire load IEEE conference

M. Aredes , E.H Watanabe New control algorithms for series and shunt three phase four wireactive power filters IEEE transactions

T M Gruz, A survey of neutral currents in three phase computer

power IEEE transactions

T Key and J S Lai, Analysis of harmonic mitigation methods for

building wiring system

P P Khera, Application of Zigzag transformers for reducing harmonics

in the low voltage distribution system IEEE conference proceedings

P.Tai Cheng Design of neutral harmonic mitigator for three phase four wire distribution systemIEEE meeting Dept of Electrical and 1616

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REFERENCE H.Akagi and Y.Kanazawa Instantaneous reactive power compensators

comprising witching devices without energy storage components IEEE

transactions

Rajesh Gupta and Kamala Kant Mishra, Review of CFL and its harmonicimpact on electrical distribution system, Electrical India Magazine, CharyPublication (Mumbai), Feb. 2010.

http://en.wikipedia.org/wiki/Harmonics_(electrical_power)

http://en.wikipedia.org/wiki/Power_system_harmonics

Dept of Electrical and 1717

http://en.wikipedia.org/wiki/Harmonics_(electrical_power)http://en.wikipedia.org/wiki/Harmonics_(electrical_power)

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5/3/12 Dept of Electrical and

THANKS

Dept of Electrical and 1818