IEEE Power Electronics Magazine - December 2021 - 24

Introduction
Learning technology-related topics requires practicing the
acquired knowledge. In some situations, companies cannot
make their laboratories available to their employees for
technical training. Also, students interested in learning certain
disciplines cannot attend educational institutions to do
the practical work that corresponds with their fields of
study. Furthermore, companies or users can invest time in
training or learning remotely.
Therefore, creating tools that allow users to continue
learning or training at distance is necessary in order to
acquire or consolidate knowledge.
Research has been carried out on SPWM for several reasons:
it is a simple technique suitable for beginners. On the
other hand, more complex techniques such as space vector
modulation (SVM) require more computational capacity
than that provided by the Arduino UNO. While some
have worked on the control of inverter bridges by means of
SPWM for reducing the cost [1], work reported by others is
oriented toward the quality of the generated wave [2], [3].
From the point of view of training or learning, some remote
laboratories have been developed to carry out practices on
power electronics. As example, within the European project
EOLES, a remote laboratory including Arduino has been
developed to perform some experiments with diodes and
passive components [4], allowing students to compare real
versus ideal results.
Arduino has also been used in works related to power
electronics. In some of these works, Arduino is used as
an interface between some software that generates the
control signals and the hardware. Specifically, Arduino
is utilized as an interface between Simulink, and the
hardware, to generate different voltages at different frequencies
in [5]. The algorithm is rebuilt with Simulink
that generates the code that is uploaded to Arduino to
feed the switching signals to drive the power devices.
In other cases, the results of the simulations carried out
have been implemented on the Arduino. In [6], the authors
have developed algorithms using MATLAB-Simulink that
have been later loaded into Arduino which, after controlling
the feedback signals, generates the pulse-width modulation
(PWM) for motor control. Similarly, the authors
in [7] have developed a Newton-Raphson algorithm for
the elimination of harmonics in an inverter, using also
MATLAB-Simulink, for simulation and generation of
the code, and Arduino to generate the control signals to
drive de power devices.
The authors in [8] have used Arduino to control a single-phase
resonant inverter, generating a PWM signal that
varies the duty cycle. Arduino DUE has even been used to
implement a real-time space vector pulse-width modulation
(SVPWM), based on ARM cortex M3 processor's own
PWM signal [9]. Some of the mentioned works are focused
on the efficiency and/or functionality for which they have
been created, although they can involve high costs. Others
need additional tools that are not available remotely. In
24 IEEE POWER ELECTRONICS MAGAZINE z December 2021
most cases, there is an excessive complexity to be implemented
by users who are initially learning the concepts of
converter control.
The dimensions of Arduino UNO allow the implementation
of additional circuits as a shield, while other microcontrollers
are too small for this purpose. An Arduino
shield is a printed circuit board (PCB) with the same
dimensions as the Arduino itself, with pins located in
the same positions, therefore it can be mounted and connected
over the Arduino itself (Figure 8). The circuit built
on the PCB has to connect to the required pins. Moreover,
Arduino is widely available and cost-effective. For these
reasons it is desirable to create a model that is easy to
build, cost-effective, with low complexity and that can be
used for remote learning or training.
In this work, the control of a stand-alone single-phase
inverter bridge has been designed using SPWM, based on
the Arduino UNO. It is cost-effective and utilizes simple
algorithms for easy understanding of the concepts related
to its regulation. This function is supported by a custom
PCB Arduino shield on which circuitry has been implemented
to be able to manage the reference voltages for conducting
this control.
Developed Model
To simplify the model, instead of using traditional triangular
and sine signals, the pulse train generation was implemented
with Arduino. Initially, the setup defines the system
frequency (f, typically 50 or 60 Hz), the number of pulses to
be used (an odd number to obtain a better symmetry of the
generated wave), and the minimum shutdown time
(TOFF,MIN), which is dependent on the power device used.
The rest of the values to be used are automatically determined
in the setup process.
The duration of each half cycle (THALF-CYCLE) will be
divided into a number of sections equal to the number of
pulses, according to (1) and (2), where the runtime of the
program (TRUNTIME) has been considered.
T
HALF CYCLE = 2f * 1000 ns
-
1
pulses
TT T
1
HALF CYCLE /^h,i
i
- =+
=
SECTIONRUNTIME
(2)
In addition, each of these sections (TSECTION,i) will be composed
of a driving time (TON,i) and a shutdown time (TOFF,i),
according to (3), as shown in Figure 1.
TT T,, ,
SECTIONONOFFii i
=+
(3)
Since each half-cycle of the sine wave to be generated has a
duration of 180°, to relate the width of each pulse to the sine
function, the maximum possible driving time value (TON,MAX)
is multiplied by the sine of the corresponding angle at each
moment. Thus, by applying (3), (4), and (5), the parameters
used will be determined.
^h
(1)
IEEE Power Electronics Magazine - December 2021

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