National Conference on Recent Trends in Engineering & Technology
Simulation of Harmonics Producing Loads in Power
System Network
Ashok D. Pateliya Manish N. Sinha
P.G. Student of Electrical Department Assistant Professor in EE Department
B.V.M. Engineering College B.V.M. Engineering College
V.V.Nagar, Gujarat V.V.Nagar, Gujarat
ashokspce@yahoo.co.in manishsinha77@yahoo.co.in
Abstract:- The impact of harmonic distortion on the quality of
electrical power continues to be of critical concern for industrial
and commercial users. The basic objective of this paper is to show
how the waveforms of voltage or current is distorted and
harmonics are fed in to the system due to non-linear loads such as
Electric arc furnace, AC Drives, Fluorescent lamp, rectifier, cell
battery charger, photo copier, printers, etc. Electric arc furnace is
high rating, time varying non-linear load. Also the voltage and
current waveform distortions in an AC bridge due the
combination of converter, filter, and IGBT inverter are shown.
Keywords- Harmonics, Nonlinear load, TDD, THD, VHD.
I. INTRODUCTION Fig. 1 Distorted wave forms of fundamental and 3rd
It is well known that a nonlinear load draws a highly distorted harmonics.
current from the source, which consists of harmonics, Fig:-1 shows deviation from perfect sine wave due to 3rd
fundamental active and reactive current components. harmonics.
Harmonic can be defined as a sinusoidal component of The impact of harmonics and waveform distortion on the
periodic wave or quantity having frequency that is an integral quality of electrical power continues to be critical concern for
multiple of the fundamental frequency. If the source or/and the industrial and commercial users. Harmonic distortion is the
load is unbalanced, the source also contains negative sequence changes in the waveform of the supply voltage from the
currents. The harmonic currents in combination with line sinusoidal waveform. It is caused by the interaction of
impedance of the distribution network in turn causes distortion distorting customer loads with the impedance of the supply
in supply voltage. network. Much of the equipments used today generate
harmonics.
Further, the AC source because of its non ideal characteristics
also contributes to this distortion and thus aggravates the Its major adverse affects are increased losses, heating of the
problem. The amount of voltage distortion depends on a) induction motors, transformer, and capacitors, over loading of
system impedance b) load current. The value and wave shape neutral in the three wire systems, interference with protection,
of the distorted current drawn is decided by the characteristics control and communication circuits as well as costumer loads,
of end user equipment and the value of system impedance by etc. The harmonic current is measured by waveform
the utility. distortion, Total harmonic distortion (THD), RMS value,
The increase use of nonlinear load in industry is keeping Distortion Power, Crest factor, etc.
harmonics distortion in distribution system network on the
rise. the most use non linear load device is perhaps the static In the section II, we have presented total harmonics
power converter so widely used in industry application in the distortions. The different types of nonlinear load are discussed
steel, paper, and textile industry. Other application include in section III. The conclusion is shown in section IV.
multipurpose motor speed control, electrical transportation
system and electro domestic application.
13-14 May 2011 B.V.M. Engineering College, V.V.Nagar,Gujarat,India
National Conference on Recent Trends in Engineering & Technology
II. TOTAL HARMONIC DISTORTION: - (THD) B. AC Drives
The most commonly used harmonic index is In an AC drive, the converter stage consists of a three phase,
full wave diode Bridge, though SCRs (Silicon controlled
rectifiers) are sometimes used in place of diodes. A filter is
required to smooth out the ripple on the DC bus in order to run
the IGBT inverter. Therefore, a second or “filter” stage is
required. Primarily, this consists of a large capacitor bank.
This is defined as the ratio of the rms value of the harmonic Often an inductor or “link choke” may be added. The choke,
components to the rms value of fundamental component and when used, helps buffer the capacitor bank from the AC line
usually expressed in percent. Where F is either voltage, and serves to reduce harmonics. The inverter section uses
current,flux. This index is used to measure the deviation of a high-speed transistors as switches to apply a “Pulse Width
periodic waveform containing harmonics from a perfect sine Modulated” or PWM waveform to the motor. For an AC drive,
wave. The measures of individual harmonic distortion for the load is the Inverter section and has a three-phase diode
voltage and current at hth order are defined as Vh /V1and Ih /I1 bridge converter to get 6-voltage pulses for one complete three-
respectively. phase line cycle.
III. DIFFERENT TYPES OF NONLINEAR LOAD
A. Electrical arc furnace
ARC furnaces are used for melting and refining metals, and
highly efficient steel-making process achieved with electric
furnace led to their widespread development and together with
the large increase in their individual ratings enabled the
electric furnace to become one the most important non-linear
loads in the electric power network. So it is a time varying,
non-linear loads. As the popularity and use of the arc furnace
loads in the industry increase, so does the power-quality
problem as a result of this progress. Among the most common
adverse power quality effects introduced by electric arc
furnace are voltage and current harmonics, voltage and current
Fig-: 3 (a) three phase ac drive model
imbalance, low power factor, and voltage flicker.
The energy consumed in the each basket of the melting cycle Fig:-3(a) shows increase use of the power conditioners in
may be dividing into three main steeps 1. Drilling period 2. which parameter like voltage and frequency are varied to adapt
Melting period, 3.End of melting and rehearing. to specific industrial and commercial process has made power
converter the most widespread source of harmonics in
distribution system.
Fig: 3(b) shows the current distorted waveforms due to three
phases drive and power electronics components
Fig. 2 Active power consumed function of time in second
The fig:-2 show the active power consumed as function of
time for the above melting period given by [4]. This is due to
non-linear nature.
Fig.3 (b) Current distorted waveforms for three phase drive.
13-14 May 2011 B.V.M. Engineering College, V.V.Nagar,Gujarat,India
National Conference on Recent Trends in Engineering & Technology
C. Bridge Rectifire Model D. Fluorescent lamps:
This type of ac to dc converter is used in variable speed drive, The magnetic ballast in the fluorescent lamp produces
battery charging application and HVDC circuit. There are harmonics. The harmonics in the current waveform are caused
several harmonics source in the distribution system. These are by the nonlinearly of the lamp arc itself in series with the
loads with non linear characteristics. ballast. The typical waveforms reported by in an office
building are given in fig. 5 (a).
The single phase bridge rectifier model is developed in
MATLAB fig4 (a) shows the developed model.
,
Fig. 5 (a) Phase voltage and current for magnetic ballast
The magnetic core inductor or chokes contain inside the start
ballast function to limit the current to the tube. They use a
Fig 4 (a) single phase Bridge Rectifier model capacitor to increase efficiency of the ballast by increase its
The Rectifier Bridge produces the worst harmonics current power factor. Fig5 (b) shows the neutral current for system
and operates at a low power factor. In case of railroad with magnetic ballast and electronic ballast respectively.
application, it is common to see individual control in every
rectifier bridge.
The simulated result single phase bridge rectifier is shown
in fig. 4(b).
Fig. 5 (b) Neutral current for a three phase, four wire system
for magnetic ballast
Fig. 4 (b) Current distorted waveform for bridge rectifier.
Fig. 5(c) phase voltage and current of electronic ballast
13-14 May 2011 B.V.M. Engineering College, V.V.Nagar,Gujarat,India
National Conference on Recent Trends in Engineering & Technology
The electronic ballast operates at higher frequency, which
permits the use of smaller reactor and capacitor. The use of
higher frequency allows them to create more light for the same
power input.
Fig. 5(d) Neutral current for a three phase, four wire system
for electronic ballast
IV. CONCLUSION
Harmonic currents can have a significant impact on
electrical distribution systems and the facilities that they feed.
It is important to consider their impact when contemplating
additions or changes to a system. In addition, identifying the
size and location of non-linear loads should be an important
part of any maintenance, troubleshooting and repair program.
Harmonics are introduced in the system due to various
nonlinear loads.
REFERENCES
[1]IEEE Recommended Practices for Harmonic Control in Electric Power
Systems, IEEE Std.519-1992.
[2]Smith,C.W; Jr; Power systems and harmonic factors, POTENTIALS,
IEEE,Vol.20,Issue5, December 2001/JANUARY 2002
[3]J. Arillaga, et al, “Power System Harmonics” ISBN 0-471-90640-9.
[4]Enrique Acha, Manuel Madrigal,” Power systems Harmonics Computer
Modeling and Analysis”, ISBN 0-471-52175-2.
[5]Rockwell Automation Mequon, WI “ Straight Talk About PWM AC Drive
Harmonic Problems and Solutions”.
[6]Grasselli.U; Lamedica.R., Prudenzi.A, “Time-Varying Harmonics of
Single-Phase Non-Linear Appliances”, Power Engg. society winter meeting,
2002, IEEE ,Vol.2,27-31 Jan 2002page: 1066-1071.
[7]R.Lamedica, C.Sorbillo, A.Prudenzi, "The continuous harmonic
monitoring of single-phase electronic appliances: desktop PC and printers",
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13-14 May 2011 B.V.M. Engineering College, V.V.Nagar,Gujarat,India
