Design and Implementation of a Demonstration
Laboratory Set for Power Quality Measurement
Nattapon Panmala1, Pakkawee Hayamin2,*, Pichet Sriyanyong3 and Natthawut Ritsiri4
Department of Teacher Training in Electrical Engineering, Faculty of Technical Education,
King Mongkut's University of Technology North Bangkok
1518 Pracharat 1 Rd., Bangsue, Bangkok, Thailand
1
nattapon.p@fte.kmutnb.ac.th,2,*pakkawee.h@fte.kmutnb.ac.th, 3pichet.s@fte.kmutnb.ac.th, 4natthawutrit.2545@gmail.com
Abstract— This paper presents the development of an
experimental setup for applying active filters in power systems.
With the increasing use of power electronic devices in industrial
plants, harmonic issues in electrical systems have become more
prevalent. Harmonics refer to sinusoidal currents or voltages
with frequencies that are multiples of the fundamental
frequency, often caused by nonlinear loads altering current and
voltage waveforms, leading to distortion at the Point of Common
Coupling (PCC). The setup for studying harmonics in power
systems involves the use of induction motors controlled by
Variable Frequency Drives (VFDs) to simulate nonlinear loads.
Parameters are measured using a power quality analyzer. The
experimental kit includes instructional materials receiving
satisfactory results from experts. The results from the setup
effectively showcase waveforms and parameters critical for
power quality analysis, providing valuable insights for
mitigating harmonic disturbances in power systems. The
summary of the expert evaluations indicated that the
preliminary testing of the instructional media demonstrated an
average score of 4.22 as a high level of appropriateness.
Keywords—Power System, Power Quality, Laboratory Set,
Teaching Package.
I.
INTRODUCTION
The current development of the industrial sector has led to
more efficient production processes. Most manufacturing
processes today rely on rotating machinery that requires
precise speed control and high power, which is facilitated by
electrical energy conversion systems. Presently, motor speed
controllers play a crucial role by replacing traditional
production systems that previously depended on speed
adjustments using direct current (DC) motors. These DC
motors required complex control equipment and intensive
maintenance. In contrast, alternating current (AC) motors,
combined with Variable Speed Drives (VSDs), now allow for
efficient speed control. In addition, the growing adoption of
electric vehicles (EVs) has directly impacted energy
consumption, particularly through high-power charging
systems that rely on AC-to-DC power conversion. As a result,
the presence of nonlinear electrical loads has significantly
increased [1].
Harmonics refer to the distortion of current and voltage
waveforms, typically caused by nonlinear loads. Power
electronic converters, primarily composed of semiconductor
devices, are responsible for converting electrical energy from
one form to another commonly referred to as converters.
These include AC-to-DC, DC-to-DC, and DC-to-AC
conversions, all of which contribute to nonlinear loads in the
power system. Examples of such equipment include
Switching Mode Power Supplies (SMPS), computer systems,
telecommunication devices, Variable Speed Drives (VSDs)
for motor control, and induction heating systems.
* Corresponding Author
979-8-3315-4276-4/25/$31.00 2025 IEEE
The converters used in industrial applications serve
various purposes, such as adjusting motor speed or voltage
frequency, providing continuous power delivery, and
switching power supplies, among others. However, these
devices inherently generate non-sinusoidal currents, causing
waveform distortion in the voltage at the Point of Common
Coupling (PCC).
Therefore, this paper presents a study on the flow of
harmonics in power systems. The parameters of the power
system, nonlinear loads, and their impacts at the Point of
Common Coupling (PCC) are modeled and measured.
Relevant standards for harmonic analysis are also presented in
this paper to provide a basis for comparison and to illustrate
the effects of harmonics on power systems. The instructional
course is designed to demonstrate the characteristics of
harmonics in power systems as well as power quality
measurement.
II.
HARMONICS IN POWER SYSTEM
According to IEEE 519-2019 [2], harmonics are defined
as the components of current and voltage waveforms that
deviate from a pure sinusoidal waveform at the fundamental
frequency. The combination of these harmonic components
results in waveform distortion in electrical systems. In
Thailand, the fundamental frequency of the power system is
50 Hz. For example, a harmonic component with a frequency
of 100 Hz is classified as the second harmonic order. As the
proportion of nonlinear loads in the power system increases,
the current and voltage waveforms exhibit greater distortion,
as illustrated in the Fig.1.
Fig. 1. Harmonics Distortion Waveform
When nonlinear loads are present in the system, they cause
distortion of the current waveform (non-sinusoidal current)
from the power source. This distorted current flows through
the impedance between the load and the power source. The
harmonic currents passing through the system impedance
result in voltage drops at each harmonic order, which can be
explained by Ohm's Law. The vector sum of the voltage drops
across the system impedance depends on the magnitude of the
system impedance, the level of current distortion, and the
harmonic order of the current, each of which varies according
to the harmonic frequency [2-4]. Fig. 2 illustrates the effects
of harmonic currents on the system impedance and the
resulting voltage drops at various points [5]. It can be observed
that the total harmonic distortion of voltage (%THDv)
calculated as the vector sum of each harmonic order decreases
at the power source. This behavior is primarily due to the
impedance that exists between the nonlinear load and the
source.
standards for efficient and safe operation of equipment. Poor
power quality can lead to equipment malfunction, reduced
lifespan of devices, energy losses, and even system failures.
Therefore, accurate measurement and monitoring are essential
to identify issues and maintain the stability and reliability of
the power system. The key principles of power quality
measurement include:
A. Measurement of Voltage and Current Waveforms
Voltage and current waveforms in a healthy power system
are expected to be purely sinusoidal at the fundamental
frequency (50 Hz in Thailand). Nonlinear loads, however,
introduce distortions that deviate from the ideal sinusoidal
waveform, generating harmonics and other anomalies. Power
quality analyzers measure these waveforms in real-time to
detect any deviations from the ideal condition.
Fig. 2. Harmonics Distortion Waveform
The equivalent circuit of a power system consists of the
impedances of the power source, transformer, and
transmission lines. The analysis and calculation of these
parameters can be performed using the following equations.
(
)
Vth = I h × ( Z th + Z sh )
Vsh = I h × ( Z sh )
V = I × Z +Z + Z
Lh
h
ch
th
sh
(1)
(2)
(3)
When
I h is harmonics order current,
VLh is load voltage,
Vth is voltage at transformer,
Vsh is source voltage,
Z ch is impedance of line,
Z th is impedance of transformer,
Z sh is impedance of source.
III.
POWER QUALITY MEASUREMENT
The Power Quality Analyzer (PQA) is an advanced
instrument designed for monitoring and recording
abnormalities in power supply systems. It enables users to
quickly identify the causes of power quality issues. This
device can also be used to assess various power supply
problems, including voltage sags, voltage flicker, harmonics,
and more. The key measurement capabilities of the PQA
include: Recording abnormal waveforms, Monitoring voltage
fluctuations, Observing supply voltage waveforms,
Measuring harmonic distortion, Measuring voltage flicker,
Measuring electric power parameters.
The PQA is capable of automatically detecting and
recording abnormal waveforms and power quality
disturbances. It automatically identifies and logs key power
quality issues that may affect system performance and
reliability. Power quality (PQ) measurement is the process of
evaluating various electrical parameters in a power system to
ensure that the power being delivered meets the required
B. Harmonic Analysis
Harmonics are voltage or current components at
frequencies that are integer multiples of the fundamental
frequency. These harmonics are typically caused by nonlinear
loads such as variable speed drives (VSDs), rectifiers, and
power electronic converters. Excessive harmonics can cause
overheating of equipment, increased losses, and interference
with communication systems. Harmonic analysis quantifies
the Total Harmonic Distortion (THD) and evaluates
individual harmonic orders to determine their impact on the
system.
C. Voltage Sag, Swell, and Interruption Monitoring
Voltage sags (dips), swells, and interruptions are common
power quality events that can disrupt sensitive equipment. PQ
analyzers continuously monitor voltage levels and record the
magnitude, duration, and frequency of such events. These
measurements are critical for troubleshooting issues related to
equipment shutdowns or malfunctions.
D. Power and Energy Measurement
PQ analyzers calculate various power quantities such as
active power (P), reactive power (Q), apparent power (S),
power factor (PF), and energy consumption. These
measurements help assess the efficiency of power usage and
identify opportunities for power factor correction or energysaving improvements.
E. Event Recording and Data Logging
Modern PQ analyzers automatically detect, classify, and
log power quality events. They capture waveforms and store
data for later analysis. This function is crucial for diagnosing
intermittent issues and providing evidence for maintenance
actions or compliance reporting.
IV. DEVELOPMENT OF AN EXPERIMENTAL SETUP FOR ACTIVE
FILTER APPLICATION IN POWER SYSTEMS
The design of the experimental setup began with a
comprehensive study of the impact of harmonics in power
systems, as well as an analysis of relevant standards and
guidelines. This included the development of simulation
circuits to assess the effects of harmonics and evaluate
compliance with applicable standards [6]. In applying an
active filter, the experimental system was specifically
designed to align with the chosen study methods. System
parameters were carefully determined and adjusted to suit the
conditions of the laboratory environment. Power quality
measurement required the use of high-precision instruments.
In this study, a Class A power quality analyzer was employed
to measure various parameters, including power, current and
voltage waveforms, as well as other related power quality
indicators particularly total harmonic distortion (THD).
The experimental equipment consisted of a three-phase power
control panel, an active power filter, an induction motor, a
voltage transformer, an eddy current brake system for the
induction motor, and a power quality analyzer. The complete
experimental circuit configuration is illustrated in Fig.3.
V. RESULT AND DISCUSSTION
Based on the outcomes of the experimental kit
development, the researcher designed three laboratory
worksheets:
•
Measurement of the power quality of a three-phase
induction motor driven directly under load conditions.
•
Measurement of the power quality of a three-phase
induction motor driven by a Variable Frequency
Drive (VFD) inverter under load conditions.
•
Measurement of the power quality of a three-phase
induction motor driven by a Variable Frequency
Drive (VFD) inverter under load conditions and
parallel running active power filter.
The developed materials include laboratory worksheets
and instructional videos to support the experimental activities.
These are presented in Fig. 4. The experiment clearly
demonstrated the differences in power system performance
resulting from the impact of harmonics. The tests were
conducted systematically, and the experimental results were
recorded for analysis.
Fig. 3. Experimental Setup for Power Quality Measurement.
The behavioral objectives of this study are as follows:
• To explain the operation of active filters when applied
to three-phase electrical loads.
• To differentiate between the power quality parameters
of three-phase loads before and after active filter
compensation.
• To identify the sources of harmonic distortion in threephase electrical load systems.
The experimental design incorporates an induction motor
coupled with a variable frequency drive (V/F control) system,
which serves as the primary source of harmonic distortion in
the circuit. The experimental setup focuses on the application
of an active filter to mitigate harmonic-related issues within
the power system.
Active filters are highly suitable for a variety of industrial
applications where numerous nonlinear loads are present.
Their primary function is to reduce harmonic currents in
power systems and improve the power factor, thereby
enhancing the overall quality of electrical power.
The measurement of parameters for study and analysis was
conducted using a power quality analyzer. Measurements
were taken under various experimental conditions to examine
the effects of harmonics on the power system.
Fig. 4. Laboratory Sheet for Power Quality Measuremnt.
In addition, the instructional video was utilized to enhance
understanding of data recording and the analysis of
measurement results obtained from the power quality
analyzer. The experimental results, both prior to and after the
activation of the active filter, clearly illustrate the differences
in the measured parameters. These findings are presented in
TABLE I., Fig. 5, and Fig 6.
TABLE I.
EXPERIMENTAL RESULT FOR LOAD 20 N-M
Parameter
Motor full
load (No VSD)
Not run active
filter
Run active
filter
n (min-1)
1445
1445
1445
I1 (A)
8.630
7.02
6.108
Pin (kW)
4.003
3.821
4.521
Pout (kW)
3.047
3.029
3.023
PF
1.015
0.74
0.95
η (% )
76.11
79.27
66.93
THD-U (%)
1.16
1.02
1.12
THD-I (%)
3.52
91.41
10.39
TABLE II.
Fig. 5. Harmonics Distortion Current Waveform.
LABORATORY COUSE EVALUATION RESULT
No.
Evaluation Item
Content
1
The content aligns with the
objectives of the course
2
Accuracy of the content
3
Appropriateness of the sequence
of each topic
4
Appropriateness of the content for
the student level
5
Clarity of the instructions in the
experiment, easy to understand
6
Clarity in specifying the tools and
equipment used in the experiment
7
Appropriateness of the sequence
of the experiment steps
8
Understanding in explaining the
sequence of the experiment steps
Format of the Experiment Sheet
9
Layout of elements, such as title,
name, logo, etc.
10
Accuracy of the language used
content amount in each sheet
11
Consistence between images and
descriptions
12
Motivation generated for learning
Overall Average
Score
S.D.
Criterion
4.66
0.58
High
4.00
4.33
0.00
0.58
High
High
4.33
0.58
High
3.66
0.58
High
4.66
0.58
High
4.66
0.58
High
3.66
0.58
High
4.66
0.58
High
3.66
0.58
High
4.00
0.00
High
4.33
4.22
0.58
0.48
High
High
VI. CONCLUSION
Fig. 6. Harmonics Current Waveform when Active Filter Running.
Based on the experimental results, the total power
performance of the system demonstrates that operating an
induction motor through a VFD yields the highest efficiency
among the three test conditions. However, the introduction of
the active filter, while effectively mitigating harmonic
distortion within the system, resulted in an increase in real
power consumption. Consequently, the overall efficiency of
the system decreased when compared to the other
configurations.
Initially, the VFD system exhibited a Total Harmonic
Distortion of Current (THD-I) of 91.41%, clearly indicating
significant waveform distortion due to non-linear loads. After
the implementation of the active filter, the power quality of
the system improved substantially. The power factor increased
from 0.74 to 0.95, and the THD-I was significantly reduced to
10.39%. These outcomes confirm the effectiveness of the
active filter in suppressing harmonic distortion and enhancing
power quality. Furthermore, the experiments revealed that
when the motor is operated via the VFD, the THD-I levels
increase in comparison to direct motor operation under load,
confirming that VFDs are a significant source of harmonic
generation in power systems.
Based on TABLE II, the evaluation of the quality of the
experimental set for the application of the active filter in
power systems was conducted by three experts. The
evaluation process involved reviewing, revising, and
assessing the quality of the experimental set. The results from
the expert assessments were averaged in order to ensure the
most accurate evaluation according to the established criteria.
The summary of the expert evaluations indicated that the
preliminary testing of the instructional media demonstrated a
high level of appropriateness, with an average score of 4.22.
The experts concluded that the learning kit effectively
enhances student engagement and enriches their learning
experiences.
The development of the harmonic experimental set in
power systems involved studying relevant power system
parameters. The experimental worksheet was designed using
an induction motor controlled by a variable frequency drive to
simulate a nonlinear electrical load. System parameters were
measured using a power quality analyzer, and the behavior of
the active filter was observed to address waveform distortion
issues. As a result of this development, an experimental
worksheet and instructional video were produced. The
instructional materials were evaluated by experts and received
a high rating. The experimental worksheet effectively
demonstrates the waveforms and essential parameters
required for analysis.
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