Electrical Power Systems Quality, Second Edition
This book provides a non-mathematical guide to basic power-quality strategies and methods used to protect electronic systems.
TABLE OF CONTENTS Electrical Power Systems Quality, Second Edition
6.2: Principles for Controlling Harmonics
6.2 Principles for Controlling Harmonics
Harmonic distortion is present to some degree on all power systems. Fundamentally, one needs to control harmonics only when they become a problem. There are three common causes of harmonic problems:
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The source of harmonic currents is too great.
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The path in which the currents flow is too long (electrically), resulting in either high voltage distortion or telephone interference.
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The response of the system magnifies one or more harmonics to a greater degree than can be tolerated.
When a problem occurs, the basic options for controlling harmonics are:
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Reduce the harmonic currents produced by the load.
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Add filters to either siphon the harmonic currents off the system, block the currents from entering the system, or supply the harmonic currents locally.
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Modify the frequency response of the system by filters, inductors, or capacitors.
These options are described in Secs. 6.2.1 through 6.2.3.
6.2.1 Reducing harmonic currents in loads
There is often little that can be done with existing load equipment to significantly reduce the amount of harmonic current it is producing unless it is being misoperated. While an overexcited transformer can be brought back into normal operation by lowering the applied voltage to the correct range, arcing devices and most electronic power converters are locked into their designed characteristics.
PWM drives that charge the dc bus capacitor directly from the line without any intentional impedance are one exception to this. Adding a line reactor or transformer in series (as shown in Sec. 5.7.1) will significantly reduce...
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