Assessment of Total Harmonic Distortion in Buck-Boost DC-AC
Converters using Triangular Wave and Saw-Tooth based Unipolar
Modulation Schemes
CANDIDUS .U. EYA1,8, AYODEJI OLALEKAN SALAU2,7, SEPIRIBO LUCKY BRAIDE3,
S. B. GOYAL4, VICTOR ADEWALE OWOEYE5, OLUWAFUNSO OLUWOLE OSALONI6
1Department of Electrical Engineering, University of Nigeria, Nsukka, NIGERIA
2,6Department of Electrical/Electronics and Computer Engineering, Afe Babalola University, Ado-Ekiti,
NIGERIA
3Department of Electrical and Electronics Engineering, Rivers State University, NIGERIA
4Faculty of Information Technology, City University, Petaling Jaya, 46100, MALAYSIA
5Department of Physical and Chemical Sciences, Elizade University, Ilara-Mokin, NIGERIA
7Saveetha School of Engineering, Saveetha Institute of Medical and Technical Sciences, India
8African Centre of Excellence, University of Nigeria, NIGERIA
Abstract: - This paper presents an assessment of the levels of total harmonic distortion (THD) in buck-boost DC-
AC converters using triangular wave and saw-tooth unipolar based-modulation schemes. This paper seeks to
identify a better technique for mitigating the total harmonic distortion on buck-boost DC-AC converters under
unipolar carrier-based modulation schemes. This was achieved by subjecting the buck-boost DC-AC converter
under triangular wave-based and saw-tooth based-unipolar modulation schemes. The voltage and current output of
the buck- boost DC-AC converter under each scheme was analysed using a power GUI Fast Fourier Transform
(FFT) analytical tool resident in the MATLAB Simulink environment unlike with the conventional scheme of
computing the percentage of THD. The test system was obtained by a combination of DC-DC buck-boost
converter, H-bridge based-insulated unipolar gate transistors, and a logic control unit. It was realized that THD of
0.2865%, peak output voltage of 294.1V and current of 9.805A were obtained by using the saw-tooth based-
unipolar modulation scheme, whereas a THD of 0.1479%, peak output voltage of 297.4V and current of 9.53A
were obtained by using the triangular wave based-bipolar modulation scheme on the same Buck-boost DC-AC
converter circuit. The results imply a high power factor utilization and low power loss in the triangular wave based-
unipolar modulation scheme compared to the saw-tooth based-unipolar modulation technique for improving the
performance characteristics of the buck-boost converter system. This study showed that power drives and heavy
load machines based-power electrical loads are required to use the saw-tooth based-unipolar modulation (STBUM)
scheme for high current and low THD%, whereas sensitive power electrical loads such as hospital equipment and
communication industries based-power electronic devices are required to use the triangular wave-based unipolar
modulation (TWBUM) scheme due to low current and THD%.
Key-words: Assessment, Fast Fourier Transform, total harmonic distortion, triangular wave, Saw-tooth wave,
unipolar modulation scheme.
Received: August 24, 2021. Revised: September 5, 2022. Accepted: October 11, 2022. Published: November 8, 2022.
1 Introduction
Apart from other sources of harmonics in power
electronics system based-applications, power
electronics devices on their own produce harmonics.
Excessive harmonics in the power system operations
affect the wave shapes of currents and voltages by
reducing their qualities, performances and market
values. By definition, harmonics are the soaring
frequency waveforms, superimposed upon the
fundamental frequency that is sufficient to disfigure
its waveform. They are high due to the introduction
of power electronics drives for AC-DC motors, DC
fans, pumps, and other related power electronic
devices, [1]. High presence of harmonics results in
malfunctioning of some load needs, overheating,
excess voltage, error in metering and control,
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Candidus U. Eya, Ayodeji Olalekan Salau,
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malfunctioning of relay, interference in
communication and control signals, [2]. There are
various means of mitigating total harmonic
distortions (THD) in power electronics systems. A
few of them are: wave-shaping regulation by
transformer connections, pulse-width modulation
techniques, wave-shaping control by multiple
commutations in each cycle, waveform regulation by
using delta-star transformer output, using filter, high
pulsed rectifier cascading , and so on. Under pulse-
width modulation, PWM, there are many sub-
divisions like carrier-based modulation schemes,
third harmonic- injection method, space vector
modulation, Random pulse width modulation
(RPWM) with their both merits and demerits. For
instance RPWM technique is mainly dependent on
randomizing the frequency of the carrier signal in
order to distribute the concentrated energy of the
harmonic frequency of the inverter output voltage in
a narrow high frequency band. The main advantage
of this technique is to reduce the energy of the
harmonics, which in turn will reduce the THD of the
inverter output voltage, [3]. However, this action will
also affect the energy of the fundamental frequency
component by minimizing the magnitude of the
amplitude which affects the quality of the waveform.
Authors in [4] worked on grid-connected
photovoltaic system with single stage buck-boost
Inverter for a very high gain of PV system using
single pulse width modulation. It was observed that
total harmonic voltage of their system obtained is
2.78%, at peak voltage of 321.1V. However,
naturally, due to the inherent performance
characteristic of having one pulse per half cycle, the
percentage of odd harmonics are still very high,
hence resulting in loss power factor utilization in the
system.
Single-stage single-phase transformer-less doubly
grounded grid-connected PV interface was carried in
[5] using modified pulse width modulation scheme.
They realized THD of 4.9% at 0.82A and a utility
peak operating voltage of 194V. Meanwhile, the
system suffers from the effects of current leakage to
ground and EMI to the surrounding. In [6] a novel
control scheme for buck-boost DC to AC converter
for variable frequency applications was carried out
dual slope delta modulation scheme. It is observed
that they accomplished total harmonic distortion of
3.95%, at fundamental voltage operating voltage of
317.8V. One demerit of this kind of modulation
scheme is increase in component count in logic
control circuitries.
Two-stage buck-boost multilevel inverter for
photovoltaic power generation. Scheme was
presented using high switching frequency modulation
(HSFM) based on sinusoidal pulse width modulation
technique, [7]. A 64.62% total harmonic distortion
was achieved at a fundamental operating voltage of
50V. However, the system has very poor power
factor utilization and high power losses as well as it
incorporates the conventional method of analysing
the parametric percentage of THD. Controlling of
boost direct current-alternating converter through
energy modelling utilizing non-linear control
approach was presented in [8]. The scheme involved
high cost and multifaceted implementation.
Comparative investigation of pulse-width modulation
techniques for five-phase voltage source inverter was
presented in [9] using Carrier based sinusoidal PWM
Fifth harmonic injection pulse width modulation,
offset addition pulse width modulation scheme,
traditional space vector pulse width modulation and
modified space vector pulse width modulation with
the THD of 1.6%, 1.8%, 1.8%. 0.3% and 3.2
respectively. However, the problem the investigation
had in the percentage of THD analysis is that they
were computed using conventional methods of
calculating % of THDs.
Simulation of a buck-boost converter for solar
panels using a PID controller was discussed in [10].
The dynamic time response of voltage was very poor.
Moreover, a simple boost controlled scheme was
proposed in [11]. It utilized two straight lines
equivalent or more than the maximum value three
phase modulating to regulate the shoot-through duty
ratio in a conventional SPWM. This scheme is very
simple and easy to implement, however, it has
tremendous high switching stress leading to
production % of THDs of 0.6%, 1.2%, 1.4%, and
3.5% under four prevailing case conditions between
voltage intervals of 170Vand 230V.
In this paper, the level of total harmonic
distortion in buck-boost DC-AC converter is
examined using power graphical user interface FFT
analytical tool with the aid of triangular wave-based
unipolar modulation (TWBUM) and saw-tooth
based-unipolar modulation (STBUM) schemes which
has not been undertaken before now. It is resident in
the MATLAB/Simulink environment. The research
will be of great importance in finding out which
scheme is better for buck-boost DC-AC converter
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operation to avoid working at low power factor.
Moreover, the assessment tool we employed in this
research is a very fast, less time-consuming, and
more accurate method of analysing total harmonic
distortion of any waveform unlike computational
conventional methods. This research work closes the
gap of using traditional methods of computing % of
THD in terms of complexity, inaccuracies and longer
time consumption as well as better identification of
carrier-based modulation schemes. This research
work is structured based on introduction,
methodology, simulation results and discussion as
well as the concluding part. The introduction aspect
has been carried out. Mathematical modelling of the
system, modelling of Fourier series, total harmonic
distortion analysis and buck-boost dc-ac converter
system are dealt with in methodology. The
performance characteristics and their descriptions of
the test systems are shown in simulation results and
discussion.
2 Methodology
The materials that are utilized are insulated gate
bipolar transistors, inductors, capacitors, battery,
voltmeters, ammeters, sensor and resistors. The
methods applied are triangular and saw-tooth based
unipolar modulation techniques available in the
Simulink environment. The tool used for the
examination of voltage and current level of THD is
power graphical user interface FFT analytical tool in
MATLAB Simulink Environment, 2014.
2.1 Mathematical Modelling of the System
2.1.1 Triangular wave- based and Saw-tooth
based Unipolar modulation Schemes
The triangular wave-based unipolar modulation
(TWBUM), saw-tooth based unipolar modulation
(STBUM), and 50Hz sine reference, signals are
modelled using MATLAB/ Simulink environment
with the expressions in Equations (1), (2), (3), and
(4) [12].
(1)
(2)
(3)
(4)
where , , and are the carrier frequency
of both and, amplitude of
, amplitude of , amplitude of
and the angle of the reference sine wave. The
Equations (1), (2), (3) and (4) represent triangular
wave carrier, saw-tooth carrier, reference sine wave
and inverted sine wave expressions. In order to fire
the power switches, S1, S2, S3 and S4 of DC-AC
buck-boost converter in Fig. 1 under TWBUM,
Equations (1) and (3); Equations (1) and (4) are
compared using two comparators for each set to
produce Equations (5), (6), (7) and (5). The
Equations (1), (2), (3), and (4) are used to generate
the triangular carrier wave, saw-tooth carrier wave,
modulating signal at 0o, while the modulating signal
operating at 1800 is used in generating waves forms
in Figs. 4 and 10 respectively.
(5)
(6)
(7)
(8)
, and are the switching signals for
triggering S1, S2, S3 and S4 power switches. The
Equations (5), (6), (7), and (8) are used in generating
the triggering signals in Fig. 5.
Under the STBUM scheme, Equations (2) and (3);
Equations (2) and (4) are compared using the same
two comparators for each set to generate Equations
(9), (10), (11), and (12).
(9)
(10)
(11)
(12)
, and are the switching signals
for triggering S1, S2, S3, and S4 power switches
under STBUM technique. The Equations (9), (10),
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(11), and (12) are used in generating the triggering
signals in Fig. 11.
2.1.2 Modelling of Fourier series
Fourier series of triangular wave and Saw-tooth can
be modelled using Equations (13) [12] and (14) [13].
(13)
(14)
where f- Frequency, k and n are integers.
2.1.3 Total Harmonic Distortion Analysis
(i) Formula for Computing THD
The current and voltage of total harmonic distortions
are computed traditionally using the expressions in
Equations (15) and (16) [2], [14].
(15)
(16)
and are amplitude harmonic
components of current, and voltage, .
The computation of THD of current and voltage
waveforms using Equations (15) and (16) is an
approximate method [6]. It is also a very
cumbersome, difficult and time-consuming process
[15] and because of that reason, we employed power
graphical user interface Fast Fourier Transform
(PGUIFFT). It does not require much expertise to
use. It is also faster and better than using Equations
(15) and (16).
(ii) Steps in using power graphical user interface
Fast Fourier Transform
Step 1: Build the proposed system in the Simulink
environment.
Step 2: Pick the PGUIFFT from the Simulink Library
browser.
Step 3: Double click on workspace block, single click
on the “parameters” inside the workspace. Then click
on “History” and change its “Format” with “Structure
with time” and then click “OK”.
Step 4: Run or simulate the proposed system.
Step 5: Double click on the PGUIFFT block, it will
display “simulation and configuration Option”.
Step 6: Single click on “FFT analysis”, it will
display four sub-sections: signal section, FFT
analysis section, available signal section, and FFT
setting section.
Step 7: Finally, click on the display button, the FFT
analysis section will show the total harmonic
distortion level of the output wave in percentage
value and in bar chart form.
2.1.4 Buck-Boost DC-AC Converter System
The circuit diagram of the Buck-boost DC-AC
converter used in this research is shown in Fig. 1
[16].
Fig. 1: Circuit diagram of boost DC-AC converter.
Fig. 1 displays the circuit diagram of the boost DC-
AC converter. The converter is made of a battery
source, DC-DC boost converter (power diode, D,
input inductor, L and capacitance C), inverter, and
low pass filter, single phase inverter, L-C filter, and
load. When the duty cycle of the DC-DC converter is
less than 50%, it blocks the output voltage but when
it is greater than 50%, it boosts the output voltage.
During the positive half cycle, Sw = ON and D =
OFF, the L1 momentary builds up the magnetic
energy, while the electrical energy stored in C1 feeds
the inverter. During the negative half cycle, Sw =
OFF and D = ON, the energy built in L1 discharges
to charge that capacitor and to feed the inverter. As
the inverter is fed, it converts the DC power to AC
power at the desired frequency [17].
The parameters of minimum inductance of inductor,
Lmin and minimum capacitance of Capacitor, Cmin of
the DC-to-DC converter, are obtained using
Equations (17) and (18).
(17)
(18)
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,, Vo, fc, and R are the minimum
capacitance, minimum inductance, output voltage,
carrier frequency, and output load resistance of the
DC-DC converter.
The MATLAB/Simulink models of the proposed
system are shown in Fig. 2 and Fig. 3.
Fig. 2: Simulink model of DC-AC converter under TWBUM.
Fig. 3: Simulink model of DC-AC Converter using STBUM.
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The results in Fig. 3 are similar to those in Fig. 2.
The only difference is that Fig. 3 possesses a saw-
tooth wave carrier, while Fig. 2 has a triangular wave
carrier.
3 Simulation Results and Discussion
This research work was modelled using 2014
MATLAB/ Simulink Environment. Fig. 4 shows the
triangular based-unipolar modulation scheme. It
consists of two reference sine waves at amplitudes of
0.8V, 50Hz, and at 180o out of phase and triangular
wave carrier with peak value of 1.0V and frequency
of 1k Hz.
Fig. 4: Triangular wave based unipolar modulation scheme.
The two reference sine waves are generated using
Equations (3) and (4) are derived from Equation (1).
It implies that their modulation index is 0.8. When
the two reference sine waves are compared with the
carrier wave according to Equations (5) and (7) and
inverted based on Equations (6) and (8), they produce
the firing signals shown in Fig. 5.
Fig. 5 contains 1V switching signals that are
responsible for setting the model shown in Fig. 3 into
an operational mode for producing waveforms in Fig.
6(b) and Fig. 7. It is made of S1, S2, S3 and S4-firing
signals which are the same thing with ,
and under TWBUM of Equations (5)-(8).
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
x 10-3
-1
-0.5
0
0.5
1
1.5
Time(seconds)
Signal Voltages(V)
Ref. sinewave at zero degree and 50Hz
Carrier wave at 1000Hz
Ref. sinewave at 180 degrees and 50Hz
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Fig. 5: Switching pulses of DC-AC converter using TWBUM.
Fig. 6: (a) DC voltage source, and (b) DC-DC Converter output voltage.
Fig. 6(a) shows that the source voltage of the modelled
power system is 120V DC. The DC-DC converter
output voltage is shown in Fig. 6(b). It transiently
fluctuates at a time interval of 0 ≤ t ≤ 0.96 seconds and
at 0.96 ≤ t ≤ 1.6 seconds, it stabilizes.
Fig. 7(a) shows the filter output voltage of the buck-
boost DC-AC converter. The transient stage of the
voltage occurred at a time interval of 0 ≤ t ≤ 0.96
seconds. During the period, the output fluctuates
between 450V and 295V. Beyond t = 0.96 seconds, the
output voltage of the DC-AC occurred 285.9V±0.5%.
The filtered output shown in Fig. 7(b), mimicked the
output voltage pattern but different in amplitudes.
The analysis of the inverter output voltage under
TWBUM is demonstrated in Fig. 8. In Fig. 8(a), a filter
output voltage is equally shown but this moment it is
from the pguifft system. The pguifft displayed the
magnitude of the voltage against the frequency in Fig.
8(b). It is observed that the magnitude of the inverter
output and the percentage of total harmonic distortions
at frequency of 50 Hz are 297.4V and 0.1471%. In
addition, the percentage of total harmonic distortion
seen in Fig. 8b is similar to the one seen in Fig. 2 of the
modelled Simulink block.
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02
0
1
Signal Vlotages(V)
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02
0
1
Signal Voltages(V)
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02
0
1
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02
0
1
Time(s)
S1 firing Signal
S2 firing Signal
S3 firing Signal
S4 firing Signal
00.2 0.4 0.6 0.8 11.2 1.4 1.6 1.8
0
50
100
150
Voltage(V)
(a) Time(s)
00.2 0.4 0.6 0.8 11.2 1.4 1.6
0
200
400
600
Voltage(V)
(b)Time(s)
Source Voltage
DC-DC Output Voltage
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Fig. 7: Filter Output Voltage and Current under TWBUM.
Fig. 8: Spectral analysis of Output Voltage of DC-AC converter under TWBUM.
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
-500
0
500
Voltage(V)
(a) Time(seconds)
00.2 0.4 0.6 0.8 11.2 1.4 1.6
-20
-10
0
10
20
Current(A)
(b)Time(seconds)
Filtered Inverter output voltage
Filtered Inverter outpu tCurrent
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Fig. 9: Spectral analysis of Output current of buck-boost DC-AC converter under TWBUM.
The spectral analysis of current output of the inverter
system is shown in Fig. 9. It is noticed that the THD of
current and its amplitude are 9.53A and 0.1479%.
Saw-tooth wave based unipolar modulation scheme is
represented in Fig. 10. It is detected that the saw-tooth
wave ramped up from zero volt to 1V and sharply
dropped down to -1.0V. The three waveforms are
formed from Equations (2)-(3). The comparison of the
two reference signals with the 1.0V saw-tooth carrier
wave using logic comparators generates the triggering
signals in Fig. 11.
Fig. 10: Saw-tooth wave based unipolar modulation scheme.
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
Time(seconds)
Signal Voltage(V)
Ref. sinewave at zero degree
Ref.sinewave at 180 degree
Sawtooth Carrier wave
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Fig. 11: Switching Pulses of DC-AC Converter under STBUM.
Fig. 12: Firing Signal of DC-DC Converter.
Fig. 11 is used for switching the H-bridge of buck-
boost DC-AC converter under STBUM. Fig. 12
represents the signal for triggering the DC-DC
converter. It has maximum voltage of 1.0V
Fig. 13(a) displayed that the source voltage of the
modelled DC-AC converter system has 120V DC. The
DC-DC converter output voltage is shown in Fig.
11(b). It transiently varies at a time interval of 0 ≤ t ≤
1.0 second and at 1.0 ≤ t ≤ 1.6 seconds, it stabilizes.
Fig. 13: (a) DC Voltage, and (b) DC-DC Converter Output Voltage.
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02
0
1
Signal voltages(V)
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02
0
1
2
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02
0
1
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02
0
1
2
Time(seconds)
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02
0
1
Time(seconds)
V
S1 Signal
S2 Signal
S3 Signal
S4 Signal
S5 Signal
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02
0
1
Signal voltages(V)
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02
0
1
2
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02
0
1
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02
0
1
2
Time(seconds)
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02
0
1
Time(seconds)
V
S1 Signal
S2 Signal
S3 Signal
S4 Signal
S5 Signal
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
0
100
Voltage(V)
(a) Time(seconds)
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
0
200
400
600
Voltage(V)
(b) Time(seconds)
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
-500
0
500
Voltage(V)
(c)Time(seconds)
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
-20
0
20
Current(A)
(d)Time(seconds)
Source Voltage
Voltage across the DC-DC Converter
Unfiltered inverter voltage
Unfiltered inverter
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Fig. 14: Filter Output Voltage and Current under STBUM.
Fig. 14(a) and Fig. 14(b) show the filtered output
voltage and current of the DC-AC converter under
STBUM.
The Spectral analysis of the output voltage and current
of buck-boost DC-AC Converter using STBUM are
displayed in Fig. 15 and Fig. 16. It is observed that Fig.
15(b) has peak voltage of 294.1V under stabilized state
and total harmonic distortion of 0.2865% at
fundamental frequency of 50Hz. It is also observed that
in Fig. 16(b), the total harmonic distortion and current
amplitude are 0.2865% and 9.805A.
Fig. 15: Spectral analysis of Output Voltage of DC-AC converter under STBUM.
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
-500
0
500
Voltage(V)
(a) Time(seconds)
00.2 0.4 0.6 0.8 11.2 1.4 1.6
-20
-10
0
10
20
Current(A)
(b)Time(seconds)
Filtered Inverter output voltage
Filtered Inverter outpu tCurrent
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Sepiribo Lucky Braide, S. B. Goyal,
Victor Adewale Owoeye, Oluwafunso Oluwole Osaloni
E-ISSN: 2224-350X
334
Volume 17, 2022
Fig. 16: Spectral analysis of output current of DC-AC converter under STBUM.
Table 1 shows the similarities and differences of
using STBUM and TWBUM to switch the buck-
boost inverter. It is observed that the saw-tooth
based-unipolar modulation scheme using the buck-
boost DC-AC converter has higher percentage THD
as well as lower output voltage but higher current
values than the triangular wave based-unipolar
modulation scheme. This implies a low power factor
utilization and higher power losses are experienced in
the STBUM than in the TWBUM. Then, from the
study, it was observed that in sensitive power
electrical loads such as hospital equipment and
communication industries loads, STBUM scheme is
preferred, while in power drives and heavy load
machines, the TWBUM is needed due to high current
control.
Table 1. Comparison of using STBUM and TWBUM buck-boost DC-AC converter.
Modulation
scheme used
Saw-tooth
based-
unipolar
modulation
(STBUM)
Triangular wave
based- bipolar
modulation
(TWBUM)
Type of
inverter
Buck-boost
DC-AC
converter
Buck-boost DC-
AC converter
DC-DC
converter
modulation
index
0.70
0.70
DC-AC
converter
modulation
index
0.8
0.8
Source voltage
120V
120V
DC-DC output
318V
300V
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2022.17.33
Candidus U. Eya, Ayodeji Olalekan Salau,
Sepiribo Lucky Braide, S. B. Goyal,
Victor Adewale Owoeye, Oluwafunso Oluwole Osaloni
E-ISSN: 2224-350X
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Volume 17, 2022
voltage
Inverter output
voltage
294.1V
297.4V
Inverter output
current
9.805A
9.530A
Percentage of
Total
Harmonic
Distortion
(THD)
0.2865%
0.1471%
In Table 2, the comparison of the present research
work with already published works is tabulated. It is
evident that the TWBUM technique outperformed
existing works in terms of percentage of total
harmonic distortion.
Table 2. Comparison of the proposed STBUM and TWBUM schemes with other existing modulation techniques.
4 Conclusion
This paper presented the assessment of total
harmonic distortion (THD) in buck-boost DC-AC
converter using triangular wave and saw-tooth based-
unipolar modulation schemes and PGUIFFT tool
resident in MATLAB software. In addition,
proposed methods were modelled and simulated in
MATLAB 2018 environment. The assessment results
show that the saw-tooth based- unipolar modulation
(STBUM) realized a THD of 0.2865%, peak output
voltage of 294.1V and current of 9.805A
respectively, while the triangular wave based-bipolar
modulation (TWBUM) produced a THD of 0.1479%,
peak output voltage of 297.4V and current of 9.530A.
Therefore, the TWBUM outperformed the STBUM.
Modulation
schemes
single
pulse
width
modul
ation
schem
e [4]
pulse
width
modula
tion
scheme
[5]
dual
slope
delta
modul
ation
schem
e [6]
High
switchin
g
frequenc
y
modulati
on
(HSFM)
based on
sinusoid
al pulse
width
modulati
on
techniqu
e [7]
Carrier
based
sinusoidal
PWM Fifth
harmonic
injection
pulse width
modulation
[10]
simple
boost
controll
ed
scheme
[11]
Saw-tooth
based-
unipolar
modulation
(STBUM)
Triangular
wave based-
bipolar
modulation
(TWBUM)
Inverter
output
voltage
321.1
V
194V
317.8
V
50V
(311-
345)V
(170-
230)V
294.1V
297.4V
Total
Harmonic
Distortion
(THD)
2.78%
4.9%
3.95%
64.62%
1.6%-3.2%
0.6% -
3.5%
0.2865%
0.1471%.
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2022.17.33
Candidus U. Eya, Ayodeji Olalekan Salau,
Sepiribo Lucky Braide, S. B. Goyal,
Victor Adewale Owoeye, Oluwafunso Oluwole Osaloni
E-ISSN: 2224-350X
336
Volume 17, 2022
This implies that overheating, high power losses, and
low power factor existence are prevalent in the
STBUM based system and vice versa. Then for this
reason, the STBUM scheme should be used in power
electronics buck-boost converter based drive systems
where high current and THD are considered less
importance; whereas the TWBUM scheme should be
used in sensitive power electronics buck-boost
converter based hospital and communication
industries where very low total harmonics distortion
is required.
Acknowledgement:
The authors acknowledge the support received from
the Africa Centre of Excellence for Sustainable
Power and Energy Development (ACE-SPED),
University of Nigeria, Nsukka that enabled the timely
completion of this research work. In addition, the
authors acknowledge the Laboratory of Industrial
Electronics, Power Devices and New Energy
Systems, University of Nigeria, Nsukka and the
laboratory Afe Babalola University that assisted us in
using their Computer systems to carry out the
MATLAB/Simulink simulation work.
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DOI: 10.37394/232016.2022.17.33
Candidus U. Eya, Ayodeji Olalekan Salau,
Sepiribo Lucky Braide, S. B. Goyal,
Victor Adewale Owoeye, Oluwafunso Oluwole Osaloni
E-ISSN: 2224-350X
337
Volume 17, 2022
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DOI: 10.37394/232016.2022.17.33
Candidus U. Eya, Ayodeji Olalekan Salau,
Sepiribo Lucky Braide, S. B. Goyal,
Victor Adewale Owoeye, Oluwafunso Oluwole Osaloni
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