CHAPTER ONE

INTRODUCTION
1.1 Background of Study

A 5kVA inverter system is a critical component in a photovoltaic solar power system. It converts the
direct current (DC) output of a photovoltaic solar panel into a utility frequency alternating current
(AC) that can be fed into a commercial electrical grid or used by a local, off-grid electrical network
[1]. The system is designed to provide a clean sinusoidal 50 or 60 Hz AC current that can be applied
directly to the commercial electrical grid or to a local, off-grid electrical network [1].

Electricity is the main source of power for domestic consumption, industrial development, and
medical centers.However, power failure has resulted in people buying fuel generators for their own
daily activity. Other businesses are also not functioning due to absence of constant power supply.
These are the reasons that necessitate the designing and the construction of a solar powered inverter
and other standby system that can deliver maximum output power to the load[2]. As society grows
from simple to complex, the need for power grew with this complexity and so it becomes necessary
to generate another type of power using inverter[2].

It should really be rehabilitated for enhancement of productivity.The importance of inverters cannot

be exaggerated. Given the increasing reliance on electronic devices and the generation of renewable
energy systems, inverters can be incorporated into the Power needing infrastructure to help provide
Power seamlessly when needed. Inverters act as the bridge between power sources and the devices
that require AC power. They are instrumental in ensuring that electricity generated from sources
such as solar panels, wind turbines, and batteries are efficiently utilized for household and industrial
applications. In addition to supporting green energy initiatives, inverters are also essential for
ensuring uninterrupted power supply in critical areas, such as hospitals, data centers, and emergency
services.
The scope of the project is to design and construct an inverter with an output power rating of 5kVA,
a maximum output current of 22.72A, and an output voltage of 220V AC from a 24V DC input [2].
The project is designed for single-phase domestic loads and is realized using simple and relatively
cheap components available in the local markets [2].

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1.2 Problem Statement

Nigeria is a country that has been buoyant in the production of crude oil and carbon by-products.
However, despite this, the country remains underdeveloped, and one of the reasons for this is the
lack of electricity. The country is unable to provide constant electricity, which has led to problems
for citizens, especially business owners. In addition, the use of carbon by-products has left the
country dirty and polluted. Therefore, there is a need for the construction of a 5kVA inverter system,
which would provide less pollution and noise, and help to address the country's energy needs in a
more sustainable way.

1.3 Aim and Objective of the work

The aim of this project is to design and construct a 5 KVA inverter.

The specific objective of the project includes:

a. To design a circuit that will convert dc to ac in most domestic homes.

b. To design a source of electricity that has no green house effect, there by reducing global
warming which has become a threat to human survival.
c. To identify, calculate the component values, and select the necessary components, such as for
the design of a 5kVA power inverter that is suitable for the Nigerian environment.
d. Create a schematic diagram of the power inverter circuit using computer-aided design software.
e. To test the power inverter, connect it to a 24v D.C source, such as a battery, and measure its
output voltage and current with an oscilloscope to ensure that it is working properly.
f. To evaluate the inverter's performance by measuring key parameters such as efficiency,
harmonic distortion, and other relevant metrics to ensure that it meets Nigerian electrical
standards and is suitable for local use.
The success of this study will be beneficial to the society at large. Mass production of inverters will
lead to improve standard of living of the populace and the nation will move forward in its pursuit of
technological development. The study will also serve as a means of impacting practical knowledge
and skills to students, lecturers and others who may wish to acquaint themselves with the principles
of operation of an inverter.
1.4 Significance of the project
Inverters have become very important in modern technology because of the need to produce
continuous supply of electric power to critical loads such as computers, surgical equipment, air

3
condition, refrigerator, telecommunication and broadcast equipment, public address systems,
rechargeable lambs etc. is a major segment of an uninterrupted power supply unit(UPS).
Efficiency and reliability in power conversion are paramount, and this project offers the opportunity
to improve both. Achieving a high efficiency rating in an inverter can reduce energy wastage and
operational costs, making it not only an environmentally friendly solution but also a cost-effective
one.
The inverter is in high demand because of the advantage it offers against other alternative ways of
power generation, such as generators [3].
1.5 Scope and limitation of the project
The scope of this project is to design and construct an inverter with an output power rating of 5KVA,
from a 12V dc input. The design and construction of a 5KVA inverter is justified by the fact that it
converts 12V dc from a battery to 220V ac, 5KVA output which can be used to power essential
circuits such as computers, electric bulb, refrigerator, air conditions etc.

Despite the benefit of constructing an inverter and its pollution and noise free nature unlike other
alternative sources of power generation, there is need to charge the battery so as to supply power in a
cloudy day or in the night.

1.6 Project Outline

This Project is written in five chapters.

Chapter one contains introduction which dives into the background of the work, problem statement,
aim and objectives of the project.

The second chapter discussed the theory of the inverter system, it features a review of current
literature on inverter system, a summary of the review and literature gaps.

The third chapter is the method used to execute the project also mentions the design analysis of the
work, circuit diagram explanation and preliminary design assumption. It discusses the design and the
construction process, principle operation of an inverter, design principle of transformer.

The chapter four explains the different tests taking before the project commence and after the
completion of the project with result analysis.

The last chapter is the conclusion, recommendation and references of the project.

4
 CHAPTER TWO

LITERATURE REVIEW
2.1 Theory of the Inverter System:

2.1.1 Introduction

An inverter is a device that converts direct current (DC) to alternating current (AC) [4]. It serves the
opposite purpose of a rectifier, which transforms alternating current to direct current. The oscillator,
amplifier, switching, and transformer stages of the inverter system all work together to provide the
appropriate alternating current output. These inverter system stages are designed to create output
with the desired frequency, phase, and voltage that is compatible with that required in domestic
appliances and industries [4].

2.1.2 History of Power Inverter

The power inverter was invented in the late 1800s as a result of significant research into current
electricity[5]. Early inverters were electromechanical devices that looked like generators and
operated via a rotating-coil mechanism. David Prince coined the name "inverter" when he published
an essay on inverters in the GE Review in 1925[5].

Inverters were developed throughout the middle of the twentieth century, and we would not have
them now without Tesla's work and inventions1. Inverters switched from mechanical vibrations to
solid-state transistors (which control the flow of signals through a circuit) in the 1960s to oscillate
DC and generate square wave AC[6].

Vanner Inc introduced a 1000 watt inverter for use in ambulances in 1979[6]. The company's
technology was celebrated for its incredible 87% efficiency and a rising product range that
influenced the future[6]. Having already merged with Weldon, it purchased the rights to the pure sine
wave inverter in 1994[6].

Power inverters as we know them today first appeared on the market about 1995[6]. Statpower Tech
Corp of Canada, along with Vanner-Weldon, developed the pure sine wave inverter/charger on the
back of its high-frequency modern sine wave inverters[6]. Using high-frequency switching
techniques, it was able to deliver more output with less distortion in both charger and inverter
modes[6].

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2.1.3 Classification of Inverters

a. Mode of Operation:

I. Stand-alone inverters: These supply stable voltage and frequency to the load[7].

II. Grid-connected inverters: These are the most commonly used option.

III. Bimodal inverters: These are usually more expensive and are used less often[7].

b. Type of Output:

I. Sine wave inverters: These are used for general applications[8].

II. Modified square wave inverters: These are used for resistive, capacitive, and inductive loads[8].

III. Square wave inverters: These are used for some resistive loads[8].

c. Source of Inverter:

I. Pure sine wave inverters

II. Modified square wave inverters

III. Square wave inverters

d. Input Base Classification:

I. Voltage Fed Inverters: These are constant input voltage inverters[9].

II. Current-fed inverters: These have constant input current[9].

III. Variable DC-link inverters: Their input voltage is controllable by adjusting the values of
inductor and capacitor used for DC link[9].

e. Output Base Classification:

I. Square Wave inverter: The square wave inverter converts DC input into square wave AC
output[9].

II. Quasi Square Wave inverter: Quasi square wave came as modification of square wave
inverter[9].

III. Sine Wave Inverter[9].

6
f. Communication Base Classification:

I. Serial Communication (e.g., RS-232, RS-485): This is reliable and easy to implement but can be
slow and limited in terms of data transfer rates[10].

II. Parallel Communication (e.g., Centronics, SCSI): This offers high speed and throughput but
requires a large number of cables and pins, and can be difficult to synchronize[10].

III. Ethernet Communication (e.g., Ethernet, Modbus TCP): This also offers high speed and
throughput, and long-distance capability. However, it requires additional equipment such as
switches and routers, and can be susceptible to network congestion and packet loss[10].

IV. Bluetooth Communication (e.g., Bluetooth Classic, Bluetooth Low Energy): This has low power
consumption and is easy to use and implement. However, it has a limited range and data transfer
rates, and can be susceptible to interference from other wireless devices[10].

V. Zigbee Communication (e.g., Zigbee, Thread): This also has low power consumption, offers
mesh networking, and is secure. However, it has limited bandwidth, range, and the number of
devices that can be connected to a single network[10].

VI. Wi-Fi Communication (e.g., Wi-Fi, Modbus TCP/IP): This offers high speed and throughput,
wide range, and is easy to use. However, it requires additional equipment such as routers and
access points, and can be susceptible to interference from other wireless devices[10].

g. Bridge Model Base Classification:

I. Half Bridge Inverter: This type of inverter uses two switches, and it is commonly used in low
power applications[11].
II. Full Bridge Inverter: Also known as an H-bridge inverter, this type uses four switches. It is
capable of providing higher power output compared to a half-bridge inverter[11].
III. Three Phase Bridge Inverter: This type of inverter is used in high power applications. It uses six
switches and can provide three-phase AC output[11].

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2.1.4 Diagram of an Inverter

Figure 2.1 Diagram of an Inverter[12].

Fig 2.1 shows a typical inverter, and it’s various components. These components work hand in hand
to aid proper function of the inverter. The functions of these components are as follows:

a. Battery(s):

The battery is a crucial component of an inverter. It provides the initial electrical energy in the form
of direct current (DC) which the inverter then converts into alternating current (AC) for use in
appliances[12]. The DC is drawn from the batteries and converted to AC Sby the inverter for use in
appliances[12]. Conversely, the batteries are charged by being plugged into a power source.

There are several battery chemistries used in inverter batteries, including lead-acid, lithium-ion, and
nickel-cadmium[12]. Lead-acid batteries are the most common type of inverter batteries and are
available in two variants: flooded lead-acid batteries and sealed lead-acid batteries[13]. The capacity
of a battery is the amount of wattage in run time that is to be expected from a battery. It is calculated
in Ah (Ampere hours). For instance, purchasing a battery that provides a run time of 3hrs and
assuming the standard battery voltage is 12V will require a battery with a capacity of (400 * 3) / 12 =
100 Ah[13]. Most inverter batteries are rated at 12 volts, but some larger systems may use 24-volt
batteries[13]. Another important thing to consider is the depth of discharge, which is the capacity to
which the lead-acid battery is discharged before it is charged again. The recommended depth of
discharge for lead-acid batteries is often 50%[13]. Except for locally made and non-branded
inverters, all inverters have battery protection technologies which protect the batteries from damage,
overheating, overcharging, deep discharge, and misplacement of the battery terminals. They also
have displays, LED lights, and alarms that show and inform the user of the state of the battery[13].
b. Oscillator:
The oscillator is a crucial component of an inverter. It generates a periodic signal, often a sine wave
or a square wave, which is used to switch the inverter’s output between positive and negative

8
states[14]. This switching action is what converts the DC input from the battery into AC
output[14].There are several types of oscillators that can be used in inverters, including relaxation
oscillators, ring oscillators, and crystal oscillators. The choice of oscillator depends on the specific
requirements of the inverter, such as the desired frequency and stability of the output[14]. An
oscillator circuit typically consists of an amplifier and a feedback loop. The amplifier provides gain,
while the feedback loop determines the frequency of the oscillation[14]. In many inverter designs,
the amplifier is implemented using a CMOS unbuffered inverter, which has high input impedance,
high gain, and high bandwidth[14]. The feedback loop often includes passive components such as
resistors and capacitors, which determine the frequency of the oscillation[14]. The performance of
the oscillator is critical to the overall performance of the inverter. A stable and accurate oscillator can
produce a high-quality AC output with low distortion[14]. On the other hand, an unstable or
inaccurate oscillator can result in a poor-quality output with high distortion[14]. In some inverter
designs, the oscillator is controlled by a microcontroller or DSP processor. These processors generate
the required pulses with the desired frequency[15]. This allows for precise control of the inverter’s
output[15].
c. Current Driver:
The current driver is a crucial component of an inverter. It amplifies the AC from the oscillator to
increase its power. This is necessary because the oscillator usually generates signals with low
power[16]. The current driver circuit typically consists of a network of power transistors[16]. These
transistors are responsible for turning the DC into three phases for the motor. This network of power
transistors in a small inverter drive is often one ‘Intelligent Power Module’ (known as an IPM) and
includes its own protection and basic control circuits[16]. The performance of the current driver is
critical to the overall performance of the inverter. A stable and accurate current driver can produce a
high-quality AC output with low distortion. On the other hand, an unstable or inaccurate current
driver can result in a poor-quality output with high distortion[16]. In some inverter designs, the
current driver is controlled by a microcontroller or DSP processor. These processors generate the
required pulses with the desired frequency. This allows for precise control of the inverter’s output.
d. Step-up Transformer:
A step-up transformer is a type of transformer that increases the voltage from its primary (input) side
to its secondary (output) side. It’s called a “step-up” because it elevates the voltage level.
In the context of an inverter, the step-up transformer comes into play after the DC power has been
converted into AC. Here’s the basic process:
I. DC to AC Conversion: The inverter first converts the low-voltage DC power into AC power.
This is typically done using electronic switches that rapidly turn the DC power on and off,
creating a square wave or sine wave pattern that mimics AC power[17].
II. Voltage Elevation: The AC power is then fed into the step-up transformer. Because the
transformer is designed with more turns of wire on the secondary coil than on the primary coil, it
increases (or “steps up”) the voltage of the AC power[18].
III. Power Output: The high-voltage AC power from the secondary side of the transformer can then
be used to power AC devices or fed into the electrical grid.

9
e. Control Unit:
This is the brain of the inverter. It manages and regulates the operation of all other components to
ensure efficient performance and safety. It controls the switching of signals according to the
requirement. The control unit of an inverter is responsible for controlling the frequency of power
supplied to an AC motor to control the rotation speed of the motor[19]. Without an inverter, the AC
motor would operate at full speed as soon as the power supply was turned ON[19]. The use of an
inverter to adjust the speed and acceleration of an AC motor increases the range of applications of
the motor compared with a motor that operates at a constant speed[19].
f. Output:
This is where the converted AC power is delivered to external devices or systems[20].
g. AC Power Supply:
This represents an alternative source of power, indicating that this inverter can also be powered by an
external AC source[21].
2.2 Review of Related Literatures:

“Design and Construction of 5KVA Solar Power Inverter System”[22]: This paper presents the
design and construction of a 5kVA solar power inverter system. The solar panels were installed free
from trees/building shade aligned to receive maximum sun rays at 450 North-East. The panels were
then connected to the charge controller and the circuit was wired to the battery. It was observed that
7.8% of the total output power was lost during the testing and measurements which resulted from
components used. The output voltage (VOUT) for both expected and achieved values of the solar
cell is 100V, the output current (IOUTPUT) for the inverter is 10A for expected value and 9.7A for
the achieved value[22].

“Design and Construction of 5KVA Inverter”[23]: This document discusses the use of inverters as an
alternative for un-interruptible power supply due to their greater environmental compatibility. The
major challenge remains local production of sufficiently high powered inverters for big loads and
longer periods of time. In this study, effort is made to produce a robust KVA inverter. The
construction is divided into four units consisting of oscillator unit, MOSFET assembly unit,
Transformer unit and battery charger monitor unit. Each constructed unit was independently tested
for proper functionality before the composite coupling[23].

“Multilevel Inverters for High-Power Applications”[24]: This study, published in 2023, reviews and
compares different topologies of Multilevel Inverters (MLIs) used in high-power applications. The
authors found that MLIs present better control and a good range of system parameters than two-level
inverters. They suggest that MLIs are more suitable for high-power applications[24]. The paper aims
to review and compare the different topologies of MLI used in high-power applications. Single and

10
multisource MLI’s working principal and switching states for each topology are demonstrated and
compared. A Simulink model system integrated using detailed circuit simulations in developed in
MATLAB Simulink program[24].

“Comparative Review of Three Different Power Inverters for DC–AC Applications”[25]: This paper,
published in 2023, presents a comparative review of three different widely used power inverters: the
conventional six-switch inverter, the reduced switch count four-switch inverter, and the eight-switch
inverter. The authors discuss each inverter with respect to cost, complexity, losses, common mode
voltage, and control techniques[25]. The paper is intended to serve as a guide regarding selecting the
appropriate inverter for each specific application[25].

“A Comparative Review on Single Phase Transformerless Inverter Topologies for Grid-Connected

Photovoltaic Systems”[26]: This review provides a concise summary of the control methods for
single- and three-phase inverters. It also reviews and compares various controllers applied to grid-
tied inverters[26].

“A General Review of Multilevel Inverters Based on Main Submodules”[27]: This review provides a
comparative study between different topologies of multilevel inverters. The MLIs are categorized
and investigated from different perspectives such as the number of components, the ability to create
inherent negative voltage, working in regeneration mode and using single dc source[27].

“Best Solar Inverters 2023”[28]: This review provides a guide to the best grid-tie solar inverters. The
hype around home batteries is also growing, but battery systems still require a solar inverter to
enable charging from solar[28].

“The Best Power Inverters of 2024”[29]: This review provides a guide to the best power inverters of
2024. The best power inverters should have high wattage, plenty of outlets, resistance to overloads,
short circuits, and high temperatures to keep your devices safe[29].

2.3 Summary of the Reviewed Literatures:

[27], The authors present the background and motivation for studying multilevel inverters (MLIs),
which are DC-to-AC converters that offer more output levels and lower harmonic distortion than
traditional two-level inverters.

[26],The authors review and compare five types of MLI topologies based on the number and
configuration of voltage sources, switches, capacitors, and diodes. They discuss the advantages and
disadvantages of each topology in terms of complexity, cost, efficiency, and performance.

11
 [24],The authors develop a MATLAB-Simulink model to simulate the behavior of different MLI
topologies under varying speed and torque conditions. They measure the total harmonic distortion
(THD) of the output voltage and current waveforms and compare the results among the topologies.

The authors conclude that MLIs are more suitable for high-power applications than two-level
inverters, and that cascade-five-level and NPC-five-level MLIs have shown the lowest current
harmonics. They also suggest some possible improvements and extensions for future research.

2.4 Literature Gap:

a. Advanced Control Techniques: While the literature discusses various control methods for single-
and three-phase inverters, there is a lack of research on advanced control techniques that can improve
the efficiency and reliability of power inverters.

b. Integration with Renewable Energy Sources: As the world moves towards renewable energy, there
is a need for research on how power inverters can be better integrated with renewable energy sources
like solar and wind.

c. Inverter Design for Specific Applications: Most of the literature focuses on general-purpose
inverters. There is a gap in the research on inverters designed for specific applications, such as
electric vehicles or industrial machinery.

d. Efficiency Improvement: While the efficiency of power inverters has improved over the years,
there is still room for research on how to further improve this aspect, especially for high-power
applications.

e. Cost Reduction: The cost of power inverters is a significant barrier to their widespread adoption.
Research on how to reduce the cost of these devices, either through improved manufacturing
techniques or innovative design, is needed.

f. Reliability and Durability: Power inverters are often used in harsh environments and under
demanding conditions. Research on how to improve their reliability and durability is another
potential gap in the literature.

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 CHAPTER THREE

METHODOLOGY AND SYSTEM DESIGN

3.1 Methodology
By convention, the electronic circuit that serves to convert from DC to AC is the power inverter. It is
utilized to convert a steady Direct current (DC) input into a particular voltage and frequency
Alternating current (AC) output as well as with a DC regulated voltage. In this project a battery of
48V as input DC voltage source would be used and hence from which a 220Vrms, 50Hz pure sine
wave would be produced. The output can be used by any electronic load connected to it similar to
what is found in a Kenyan wall socket.
3.2 Design Objectives
The main objective is to convert Direct Current (DC) power, typically from a battery or solar panel,
into Alternating Current (AC) power that can be used by household appliances and other electrical
equipment and it should be able to handle a load of up to 5kVA.The inverter should convert the DC
power to AC power efficiently, with minimal power loss during the conversion process, safe to use
equipped with features like over-voltage, under-voltage and overload protection.

3.3 Design Specification

The First step in this project is to determine the exact requirements of the individual parts of the
system, this in general enables the system designer to have a concrete idea on what the system is
required to achieve at the end putting into consideration also, a standard of measurement of how
much of the specified qualities of the system is to be achieved at the end of the system design. As
applied to this project, the design specifications will be analyzed under the following headings -
functional, power and physical structure specification.

3.3.1 Functional Specification

Considering the computing requirements of the system, the central component of the design
hardware is chosen to be a microcontroller with high enough internal flash memory to contain the
program code. For this project, the dsPIC30F2010 microcontroller was chosen due to its faster
processor which uses a 16-bit for signal processing, and the ease to be interfaced with other
components such as NTC 10K heat sensor and CT5A/5mA current sensor, low power consumption,
and easily availability of development tools and libraries.

13
The display unit chosen for the project is a 16x2 LCD, the choice is made due to its portability and
low power consumption. It has backlight and potentiometer adjustable contrast for visibility
adjustment. It can display 16 characters per line and there are two of such lines. Each of the character
is created by 7 by 5-pixel matrix.

The conditions to be monitored by this system are the heat / temperature, current overloading and
battery voltage, which are sensed by NTC 10k sensor, CT 5A/5mA sensor and by the use of potential
divider circuit with comparator respectively. These are in general low cost and low power
consumption sensors which are easily interfaced with the microcontroller. More on these sensors will
be discussed in the proceeding chapter when we discuss the circuit design.

3.3.2 Power Specification

The design and functionality of this project requires the use of both an AC and DC supplies. The
sensors and the microcontroller require a 48v supply while the relays used in switching the AC
appliances requires a 12 DC power supply. The battery bank was designed to be charged with power
from the mains power supply or a standby power generator. This relay automatically changes over to
the mains when there is supply and back to the inverter when there is power outage.
3.3.3 Circuit Design
This shows the individual components used in designing and construction of the inverter.

Figure 3.1: Circuit diagram of the Inverter System

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3.4 Analysis of the System
This section provides a detailed analysis of the circuit diagram and explains the concept behind each
section of the entire circuit diagram. The system operates in two modes, inverting mode and
charging mode. At inverting mode, the system converts the D.C source to A.C signal to power A.C
loads while in the charging mode; the system uses the Mains A.C signal as a source to charge the
battery. This it accomplishes by the use of a rectification technique to convert the A.C signal to
suitable D.C signal for charging of the battery.

This inverter circuit is grouped into two parts

a. The Control Stage and

b. The Power Stage.

3.4.1 Control Stage

The control stage comprises of the following: Oscillator, Indicator, Sensors and Changeover Section.

3.4.1.1 Indicator Section

This consists of a liquid crystal display (LCD) and a buzzer. The LCD shows the inverter's
operational state. It displays information such as the ON state, battery voltage, mains state, and so
on. The buzzer can also indicate the ON-State and issues such as overloading or overheating.
The indicator circuit interfaces the LCD with the microcontroller (dsPIC30F2010).

Pin Description of the LCD:

a. VSS, VDD and VEE

Pin 1 (VSS) is a ground pin and it is certainly needed that this pin should be grounded for LCD to
work properly. VEE and VDD are given +5V normally. However, VEE may have a potentiometer
voltage divider network to get the contrast adjusted. But VDD is always at +5V.

b. RS, R/W and E

RS is used to make the selection between data and command register. For RS=0, command register is
selected and for RS=1 data register is selected.

R/W gives you the choice between writing and reading. If set (R/W=1) reading is enabled. R/W=0
when writing.
Enable pins is used by the LCD to latch information presented to its data pins. When data is supplied
to data pins, a high to low pulse must be applied to this pin in-order for the LCD to latch in the data

15
present at the data pins. D0-D7 The 8-bit data pins, D0-D7, are used to send information to the LCD
or read the contents of LCD's internal register.
In the interfacing of the LCD to the dsPIC30F2010, the data pin D4- D7 were used to send
information to the LCD from the controller. These data pins are connected to the RB3, RB3, RB5,
RB6 of the controller respectively. The RS and E pin are connected to the RB0 and RB1 pin of the
controller respectively.

Figure 3.2: Image of Interfacing LCD to the micro-controller

3.4.1.2 Oscillator Section

This part contains the microcontroller unit that produces the signal (frequency) for the switching
section. In this project, the operating frequency is 50 hertz, and the microcontroller IC is the
dsPIC30F2010.
This microcontroller was chosen because it has a quicker processing speed, employs 16 bits for
signal processing, and is a low-cost processor that is widely available. Additional characteristics of
the dsPIC30F2010 include: It has modified Harvard architecture, uses C-Compiler optimized
instructions, it has three external interrupt sources, and it has two information sources, an improved
flash program, and high current source/sink I/O pins (25mA / 25mA).

16
 Figure 3.3: Pin Layout of dsPIC30F2010 Microcontroller

Table 3.1: Table showing the pin description of dsPIC30F2010 controller

S/N PIN NAME + DESCRIPTION Port

1 MCLR Master Clear (Reset) input or programming
voltage input.
2 EMUD3/AN0/VREF+/CN2/RB0 B
3 EMUC3/AN1/VREF-/CN3/RB1 B
4 AN2/SS1/CN4/RB2 B
5 AN3/INDX/CN6/RB3 B
6 AN4/QEA/IC7/CN6/RB4 B
7 AN5/QEB/IC8/CN7/RB5 B
8 Vss Ground reference for analogue module
9 OSC1/CLKI Oscillator Input
10 OSC2/CLKO/RC15 Oscillator
11 EMUD1/SOSCI/T2CK/U1ATX/CN1/ C
RC13
12 EMUC1/SOSCO/T1CK/U1ARX/CN0/ C
RC14
13 RC2/CCP1/VDD1A C
14 EMUD2/OSC2/IC2/INT2/RD1 D
15 EMUC2/OC1/IC1/INT1/RD0 D
16 FLTA/INT0/SCK1/OCFA/RE8 E

17
17 PGD/EMUD/U1TX/SDO1/SCL/RF3 F
18 PGC/EMUC/U1RX/SDI1/SDA/RF2 F
19 Vss Ground
20 VDD Positive Power Supply for analogue module
21 PWM3H/RE5 E
22 PWM3L/RE4 E
23 PWM2H/RE3 E
24 PWM2L/RE2 E
25 PWM1H/RE1 E
26 PWM1L/RE0 E
27 AVSS Analogue Ground
28 AVDD Analogue Power Supply

3.4.1.3 Sensor Section

The sensors used for this project are heat/temperature sensor and A.C sensor. The NTC 10K
thermistor, a type of heat sensor, was used in this project to detect overheating. These are resistors
with a negative temperature coefficient, which indicates that resistance reduces as temperature
increases. They can measure temperatures from -550C to 2000C. To connect this sensor to the
controller, a potential divider circuit is utilized to measure the voltage drop in the NTC. This dip is
then used by the controller to assess temperature variations.

Figure 3.4: NTC used as Temperature Sensor

CT 5A/5mA (current transformer) is a sensor that measure alternating current (AC). They are
particularly useful for measuring whole building electricity consumption or generation. It is a device
that detects and converts current to an easily measured output voltage which is proportional to the
current through the path. CT was used in this work to check for current over-loading in the inverter.
The two terminals of the CT are used to connect to ground and to the microcontroller. The line to
measure for the current is allowed to pass through the hollow of the CT.

18
 Figure 3.5: Current transformer used as current sensor

3.4.1.4 Battery Sense

The battery is sensed by using a voltage divider of 100k to 12k, hence reducing the value of voltage
reaching the controller pin by some factor. This circuit could be able to measure up to 500V. This is
required to be able to cut off the output when the voltage is less than the acceptable voltage of 45V
and to cut off charging when the voltage is above the acceptable 55V. The schematic is shown in fig
3.2.

Figure 3.6: Battery sensing circuit

For example, if the voltage input is 52v, then the voltage appearing in the microcontroller will be:

R1
V R2 = x V¿ (1)
R 1+ R 2

12 k
V R 2= x 52 v
100 k +12 k

19
 12
x 52=0.107 x 52=5.57 V
112

In mains mode the inverter is expected to charge the batteries; in this mode, the low side MOSFETs
are switched to ensure charging. Power from the mains is stepped down by series of resistors and
then rectified to DC, the output is connected to pin 2 of ADC module of the dsPIC30F2010
microcontroller. The output voltage sense is achieved by using series of resistors to lower the output
voltage to a safe working voltage for the microcontroller pin 3 after passing through a rectification
diode.

3.4.2 Change-Over Section

The relay circuit is controlled by dsPIC30F2010. Whenever there is mains, the microcontroller sends
signal to the relay circuit to switch mains into the inverter circuit for charging, and also to supply the
load. Figure 3.3 shows the relay circuit for the power inverter.

Figure 3.7: Changeover section

3.4.3 Power Stage

The power stage consists of the driver section, switching section, transformer section, filter section
and the power supply section.
3.4.3.1 Driver Section
For the MOSFET switch to be turned on the voltage at the gate terminal must be 10V higher than the
drain terminal voltage. The drain of the high side device is connected to 48V DC power which is to
be inverted into the 220V AC power. This is a problem because the 48V is the highest voltage in the
system therefore, to drive MOSFETs in the H-Bridge, MOSFET driver IC is used with a bootstrap
capacitor specifically designed for driving a half-bridge. For this design the TLP250 MOSFET driver
was chosen, it is rated at 600V, with a gate driving current of 2A and a gate driving voltage of 10-
20V. The turn on and turn off times are 120ns. The MOSFET driver operates from a signal input

20
given from the microcontroller and takes its power from the battery voltage supply that the system
uses. The driver is capable of operating both the high side and low side MOSFET, but in order to get
the extra 10V for the high side device, an external bootstrap capacitor is charged through a diode
from the 18V power supply when the device is off. Because the power for the driver is supplied from
the low voltage source, the power consumed to drive the gate is small. When the driver is given the
signal to turn on the high side device, the gate of the MOSFET has an extra boost in charge from the
bootstrap capacitor, surpassing the needed 10V to activate the device and turning the switch on.

Figure 3.8: The Driver Section

3.4.3.2 Switching Section

This is where actual power conversion occurs. The switching topology used for this project is the H-
Bridge/Full Bridge Switch. The power transistors form the H-Bridge circuit. Other example of
switching circuit is the push-pull.

H-Bridge is rather simple circuit, containing four switching element, with the load at the center, in an
H-like configuration. The switching elements are usually bi-polar or FET transistors, but for this
project, the switching element is MOSFET (IRF4110). MOSFET was used because of its fast
switching response and because of its ability to handle higher voltages.

The top end of the bridge is connected to a power supply (battery) and the bottom-end is grounded.
In general, all four switching elements can be turned on and off independently, though there are
some obvious restrictions. The load in this aspect is the step-up transformer.

21
 Figure 3.9: The Switch Section

Table 3.2: Truth Table for H-Bridge Switching

S/N Q1 Q2 Q3 Q4 RESULT
1. ON OFF OFF ON +VE
2. OFF ON ON OFF -VE
3. ON ON OFF OFF ZERO
4. OFF OFF ON ON ZERO

The number of MOSFET in each side of the H-bridge required for the inverter is calculated by
computing the maximum current Imax required which is given by

max power rating of inverter

I = (2)
input voltage

And then dividing the maximum current of the inverter by maximum current capacity of each
MOSFET.

max power rating 5000

I = = =104.167 A
input voltage 48

22
 104.167
Number of MOSFET = =0.58
180

wℎere 180 is tℎe maximum drain current I D of MOSFET IR 4110, gotten ¿ tℎe datasℎeet

Number of MOSFET = approximately 1 for each sides of the H-Bridge.

3.4.3.3 Transformer Unit

In the design of the 5KVA inverter transformer, the size of the lamination was obtained from the
following formulas listed from equations 3 to equation 7 so that it can provide enough magnetic flux
for stepping 48V AC to 220V AC at the required power rating.

The following calculations were made in designing the transformer, for a 5KVA:

Core Area (CA )=1.152 x √ ( output voltage x output current ) − −−−(3)

Calculating turns per volt (TPV)

1
TPV = −4
− −−− −−(4)
(4.44 x 10 x CA x flux density x AC frequency)

(secondary volts x secondary current)

primary winding current= − −− −(5)
primary volts x efficiency ( 0.8 )

Number of turns=TPV x primary volts −− −(6)

secondary number of turns=( TPV x secondary voltage ) − −−(7)

Actual calculated values:

core area=1.152 x √ 5000=1.152 x 70.71=81.5 cm

2

1
turns per volt= =0.425
( 4.44 x 10 x 81.5 x 1.3 x 50 )
−4

(5000)
primary winding current= =130 A
(48 x 0.8)

primary copper wire tℎickness =10 SWG

Number of turns for primary winding=48 x 0.51=20.4 turns

23
 (5000)
secondary winding current= =28.4 A
220 x 0.8

secondary number of turns=0.51 x 220=93.5 turns

primary copper wire tℎickness =17 SWG

3.4.3.4 Filter Section

The final component necessary to output a pure sine wave signal is an output filter. For this work, an
L-C low pass filter was used. It filters out all the excess noise above the critical frequency. The goal
for this is to bring the critical frequency as close as possible to the desired 50Hz, removing other
harmonics that crops up with the system.
Since the secondary side of the transformer has an inductance, we calculated for the shunt capacitor
as there is no need for an additional inductor for filtration. The filter network is applied just after the
transformer stage of the inverter as shown below;

1
F c= −− −−(8)
2 π √ LC

Where

F c – cut-off frequency

L – Secondary winding inductance

C – Shunt capacitor

Since the secondary side of the transformer has an inductance all that was needed was just a shunt
capacitor.

From the earlier calculations Transformer core area, a = 0.000815m2.

From the core used B = 1.3T.

So tℎat flux linkage ɸ=B x a ɸ=1.3 x0.000 815=0.000 10595

Φ
Tℎe secondary windinginductance L= −− −−(9)
¿

0.000 10595 −8
L= =5.69 x 10 H
93.5 x 19.9

Hence the minimum capacitor value needed for the low pass filter is given by;

24
 1
C= 2 2
−−−(10)
4π xf L

1
C= 2 2 −7
=25.5 F
4 π x 50 x 3.97 x 10

3.4.3.5 Power Supply Unit

This is a 12v switch mode DC power supply circuit. This circuit uses a ferrite core transformer to
step down the 48v from the switching section to 12v supply. This 12v supply is being tapped by the
control stage to extend power to the control part of the transformer.

3.4.3.6 Battery Charging unit

When the inverter senses mains supply, the changeover section switches the inverter mode of
operation. Here, the inverter operates in the charging mode; in the switching section, the MOSFETs
switches only on one side of the H-Bridge. The transformer functions as a step-down transformer to
reduce the 220v to 48v signal. Then the MOSFETs switch this signal only in one direction, thus,
converting the AC signal to a DC signal.

3.4.4 System Flowchart

25
 Figure 3.10: flow diagram of the inverter

Description of the above flow chart:

Step 1: The start icon indicates the beginning of the flow.

Step 2: Initialize ADC and LCD Libraries: This imports the libraries to be used for the program, port
declaration and clearing.

Step 3: IS MAINS ON? : A decision is made here, if YES, the charging algorithm is implemented to
charge the battery. When the battery is greater than 55V, the charging stops, but if the battery is less
than 55V, the battery charging continues. If MAINS ON IS NO, then PWM is initialized. This
initialization occurs only if battery voltage is greater than 42V; otherwise the battery charging
algorithm is implemented. After initializing PWM, the system checks the output voltage if it is
greater than 220V. If greater than 220V, the duty cycle of the PWM is reduced, if lesser than 220V,
the duty cycles of the PWM is increased.

26
 Figure 3.11: Flow Chart of current sensor

Flow Chart Explanation:

Step 1: This begins the flow.
Step 2: The I/O port where the sensor will be connected is declared and cleared. The PIC time is
adjusted.
Step 3: The controller collects readings from the sensor through the port in form of voltage Vin.
Step 4: The Vin is converted from analog to digital value.
Step 5: A current-voltage relationship is implemented in order to calculate the current value.
Step 6: Is Current > 15A?; if YES, the inverter is circuit breaker is activated to shut-down the
inverter. if NO, the process jumps back to step 1.

27
 CHAPTER FOUR

SYSTEM IMPLEMENTATION AND RESULT ANALYSIS

4.1 System Implementation

The third chapter explained that the inverter is separated into two parts: the control stage and the
power stage. These components were developed and tested independently, and once all of them had
produced the expected results, they were combined to form the inverter system.

The system was implemented using the following tools:

a. Soldering iron
b. Soldering lead
c. Multi-meter
d. PCB
e. Cutter
f. Pliers.

4.1.1 Implementing the Control Stage

As explained in chapter three, the control stage consists of four sections: oscillating, signaling,
switching, and sensing. The connection of these sections to the microcontroller was addressed in
Chapter three. In order to implement these sections, the various interface devices were tested to
ensure they were in good working order.

The LCD was tested by giving power to its anode and cathode pins. When this connection was made,
the LCD's backlight lit up. In addition, a variable resistor was connected to the VSS pin to control
the backlight's contrast. After establishing the LCD's viability, it was connected to the
microcontroller. The same procedure was carried out the buzzer, but this time electricity was
supplied to the buzzer's positive and negative terminals to see if it beeped. The various sensors used
were also tested.
The CT current sensor and the NTC heat sensor were employed to measure AC current overload and
temperature, respectively. Before connecting these devices to the microcontroller, the CT was tested
to measure the current in an AC line. This was accomplished by attaching an AC line to the CT's
sensing terminal and reading the output with a digital meter. After confirming that the CT was in
good working order, it was connected to the microcontroller.

28
The NTC heat sensor, which is a variable resistor, was tested by simply measuring the resistance
value of the NTC with a meter. It read a good value, indicating that it is in good operating order.

The relay, which is a crucial component of the switching section, was also tested prior to connecting
with the controller. A multi-meter was used to carry out the test, which includes measuring the
resistance value of the relay's pins. For a 12v relay utilized in this project, the coil resistance value
stated by the manufacturer should be around 320 ohms. When the test was completed, the coil
resistance measured 280 ohms. This is a high value, indicating that the relay coil is good. The relay's
other terminals were also tested (COM, NO, and NC). The test was carried out by measuring the
resistance between the COM, NO, and NC terminals. For a NO terminal, the resistance value should
read high indicating an open circuit while for NC terminal, the resistance value should read
approximately zero; indicating a closed circuit. Following confirmation, it was connected to the
controller.

All of the control sections of the inverter were implemented on a separate PCB from the power part.
This control portion requires a voltage source of 12v and 5v for the relay and LCD, respectively.
Hence, a supply of 12V was tapped from the power part of the inverter to the controller part.
LM324N voltage regulator was used to supply a stable 5v to the LCD. The circuit of the control part
was implemented such that it was placed at the front end of the inverter system. This is because it
comprises of the LCD. The LCD shows the status of the inverter, hence more reasonable to be placed
at the front.

29
 Figure 4.1: Image of the Control Part of the Inverter

4.1.2 Implementation of the Power Stage

From chapter three, the sections of this power stage include the driving section, the switching
section, transforming section, filtering section and power supply section. The interfacing of these

30
sections to the controller has been discussed in chapter three. A test for the workability of the
components used in these sections was carried out.

For the switching section, a test of the MOSFET working condition was carried out. A test for the
MOSFET pins was done by the use of multi-meter to test for the Gate, Source and Drain pin. This
was done by setting the multi-meter to the diode mode. Firstly, the internal capacitance in the
MOSFET is discharged by touching the gate and drain pins of the MOSFET with a conductor
material. Then the meter black probe is connected to the source and the red probe to the drain of the
device. An open circuit indication on the meter confirms that the MOSFET is in good working
condition. To compensate for the heat generated by MOSFETs when in operation, a heat sink was
attached to all MOSFETs. In the configuration of the H-Bridge circuit, two MOSFETs were used at
each side of the h-bridge instead of one MOSFET as seen from the calculation in chapter three. The
reason is to increase the current handling capacity of the MOSFETs in case of current surge. In the
H-bridge circuit connection, the drain of all the MOSFETs were linked to another, hence, in the
implementation, the body of the MOSFET to the drain was used to join all the drains of the
MOSFETs through the heat sink (heat sink being an aluminum is a good conductor).

The iron-core transformer being a low frequency transformer is always large in size and very heavy.
These necessitated that the transformer be positioned at the center of the inverter circuit. This was
done to prevent a case whereby the mass of the inverter system is being shifted to just one end of the
body. By so doing, being at the center will make the weight of the inverter system to be balanced.
The iron cores of the transformer were tightened firmly with a screw and nut. This is to ensure close-
packing of these cores in order to reduce excess noise that results from vibration of these cores if
loosely packed.

The driving section and the switching section were implemented on same PCB; separated from the
other sections. It is in this board that DC supply battery goes to for inversion. It is positioned at the
back of the inverter, very close to the fan. The essence of the fan is to reduce the heat temperature of
the MOSFETs.

31
 Figure 4.2: Image Showing the Power Stage Input

The power supply section of 12v switch mode was implemented using a ferrite core transformer and
rectification circuit. This section was implemented on a separate PCB placed in between the control
stage and switching/driving section. It is from this section that the control stage taps a 12v supply.

32
 Figure 4.3: Image of the 12v Power Supply Unit

4.2 Testing of the System

After the sections of the systems were integrated into a whole, few tests were carried out before the
packaging of the system. The tests were majorly on the control stage and the power stage of the
inverter.

In the control stage, emphasis was placed on the LCD display. When the inverter was operated in the
inverting mode, the LCD display was able to display that it is in the inverting mode, it was able to
tell the present voltage value of the battery. In the case of charging mode, the LCD display was able
to tell the difference.

33
 Figure 4.4: LCD Display of the Inverter

In the power stage, a test was carried out on the switching section using multi-meter. A test of DC
voltage reading showed the voltage of the battery. Then a test of the voltage reading at the secondary
side of the transformer showed an AC reading of 220v.

4.3 Load Testing of the System

The 48V battery of 200Ah was used to power electrical loads. These loads include a television,
ceiling fan, light bulbs, Music player, refrigerator and laptops. The combined wattage of these loads
is about 1600 watts. There was no long delay for the refrigerator to start producing ice, the light
bulbs were very bright and there were no fuzzy images on the television screen. This confirms that
the output signal produced had minimum distortion.

An analysis of different load characteristics applied to the inverter was carried out. This analysis
involved an evaluation of loads and power consumption. It was carried out with the battery fully
charged. Four cases will be examined and a load-time graph will be plotted to see how long the
battery lasts before discharging all its power.

CASE 1: Inverter system behavior at maximum load (i.e 4000 watt)

load power , P L=4000 W

battery current rating , I B=220 Aℎ

battery voltage ,V B=48 V

battery power∈ watt − ℎour , P B=I B V B =220 Aℎ x 48 V =10560 wℎ

34
 PB
duration of battery , BL = −−− − ( 11)
PL

10560
¿ =2.6 ℎours=2 ℎr 60 minutes
4000

CASE 2: Inverter system behavior at a load of 2000 watt

load power , P L=2000 W

battery current rating , I B=220 Aℎ

battery voltage ,V B=48 V

battery power∈ watt − ℎour , P B=I B V B =220 Aℎ x 48 V =10560 wℎ

PB
duration of battery , BL =
PL

10560
¿ =5.3 ℎours=5 ℎr 30 minutes
2000

CASE 3: Inverter system behavior at a load of 1000 watt

load power , P L=1000 W

battery current rating , I B=220 Aℎ

battery voltage ,V B=48 V

battery power∈ watt − ℎour , P B=I B V B =220 Aℎ x 48 V =10560 wℎ

PB
duration of battery , BL =
PL

10560
¿ =10.6 ℎours=10 ℎr 60 minutes
1000

CASE 4: Inverter system behavior at a load of 750 watt

load power , P L=750 W

battery current rating , I B=220 Aℎ

battery voltage ,V B=48 V

35
 battery power∈ watt − ℎour , P B=I B V B =220 Aℎ x 48 V =10560 wℎ

PB
duration of battery , BL =
PL

10560
¿ =14.1 ℎours =14 ℎr 10 minutes
750

CASE 5: Inverter system behavior at a load of 500watt

load power , P L=500 W

battery current rating , I B=220 Aℎ

battery voltage ,V B=48 V

battery power∈ watt − ℎour , P B=I B V B =220 Aℎ x 48 V =10560 wℎ

PB
duration of battery , BL =
PL

10560
¿ =21.1 ℎours =21 ℎr 1minutes
500

Table 4 shows the evaluation of the different battery duration at different loads

Table 4.1: Load-Time relationship of the battery duration

Load (KW) Time (Hr)

4 2.6
2 5.3
1.0 10.6
0.75 14.1
0.5 21.1

36
 Figure 4.5. Graph Showing Battery Variation with Load.

4.4 Packaging

The constructed project was packaged to create a visually appealing device. Several aspects were
considered for packaging, including the longevity of the material utilized (wood, plastic, or metal).
Metal sheet was chosen for this project. This is to ensure that heat is easily dissipated into the
surroundings.

To avoid short-circuiting, all conducting components were appropriately insulated from the case, and
suitable connections were earthed.

The package's portability was considered in order to restrict the amount of space it will take up and
to reduce the strain associated with device relocation.

The ventilation of the package was also studied; this is to aid in the temperature regulation of the
gadget, as the majority of the components in the construction generate heat.

37
Figure 4.6: Packaged Inverter

38
4.5 Bill of Engineering Measurement and Evaluation (BEME)

Table 4.1 Bill of Engineering Measurement and Evaluation (BEME)

S/N ITEMS QUANTITY UNIT PRICE AMOUNT

Microcontroller
1 DSPIC30F2010 1 ₦10000 ₦10000

2 Resistors 80 ₦20 ₦1,600

3 LM324N 1 ₦1000 ₦1000

4 TLP250 5 ₦350 ₦1,750

5 Buzzer 1 ₦1,000 ₦1,000

6 LCD 1 ₦7,000 ₦7,000

7 Capacitors 50 ₦50 ₦2,500

8 Heat Sink 3 ₦4,000 ₦12,000

9 MOSFETS 20 ₦300 ₦6,000

10 Keyboard 1 ₦5,000 ₦5,000

11 Relay 1 ₦1,000 ₦1,000

39
12 Temperature sensor 1 ₦3,000 ₦3,000

13 LM393P 1 ₦1,400 ₦1,400

14 Transformer 1 ₦100,000 ₦100,000

15 IN4007 Diode 6 ₦50 ₦300

16 IN4148 Diode 7 ₦50 ₦350

17 Copper coil 4rolls ₦30,000 ₦120,000

18 Lamination paper 1 ₦5,000 ₦5,000

19 Inverter casing 1 ₦75,000 ₦75,000

20 BC337 Transistor 10 ₦150 ₦1,500

21 LEDs 6 ₦50 ₦300

22 Fan 3 ₦4,000 ₦12,000

TOTAL 367,700

40
 CHAPTER FIVE

CONCLUSION AND RECOMMENDATION

5.1 Conclusion
This project demonstrated the feasibility of designing and building an inverter system capable of
converting a 48V DC battery power to a 220V AC output voltage. The project consisted of several
steps, including design, implementation, and testing, which were all completed in a systematic
manner to ensure that the system satisfied the design parameters. The final system was successfully
built and tested, and it met the design specifications. The project also provided significant insights
into the complexities of developing an inverter system, as well as the different factors to consider
during the design and implementation stages.
5.2. Recommendation
Based on the project results, it is advised that more work be done to improve the efficiency of the
inverter system. This could include using more efficient components, such as high-frequency
MOSFETs, or adding additional circuitry to reduce switching losses. Furthermore, it may be
advantageous to test the system under more intense load levels to confirm its robustness and
reliability. Finally, future research could investigate the use of alternate battery chemistry or energy
storage technologies to improve the overall performance and usefulness of the system.

Also, this inverter is a general-purpose inverter. It would be advisable for more research to be carried
out on inverters designed for specific applications, such as electric vehicles or industrial machinery.

41
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Inverter Topologies for Grid-Connected Photovoltaic Systems,” Energies, p. 16, 1363.
[27] Ali Abdel-Aziz, Mohamed A. Elgenedy, and Barry Williams, “A Comparative Review of Three
Different Power Inverters for DC–AC Applications,” Energies,P. 16, 1363.
[28] Short Publishing Works, “Inverter battery capacity: What you need to know,” Inverter Guides, 4
April 2023.[Online]. Available:https://shorturl.at/gDSZ1[Accessed 9 November 2023].
[29] David Beren, “The Best Power Inverters of 2024,” Life Wire Tech for Humans, 7 February
2024.[Online]. Available:https://shorturl.at/sINY1[Accessed 8 February 2024].

43
 APPENDIX
Code for the Microcontroller
#include <p30f2010.h>
#include <libpic30.h>
#include "DataEEPROM.h"

_FOSC(CSW_ON_FSCM_OFF & XT_PLL16);

_FWDT(WDT_OFF);
_FBORPOR(MCLR_EN & PBOR_ON & BORV_42 & RST_PWMPIN &
PWMxH_ACT_HI & PWMxL_ACT_HI);
_FGS (CODE_PROT_ON);

#define faultin LATEbits.LATE8

#define buzzer LATEbits.LATE4
#define change LATDbits.LATD1

#define stbyinv 1
#define upsmode 2
#define invmode 3
#define modekey 4
#define upkey 5
#define downkey 6
#define stbyups 7
#define fanheat 640

///////////////////////////////////////////////////////////////////////////////////////////
const signed int
sine_table[91]={0,174,348,523,697,871,1045,1218,1391,1564,1736,1908,2079,2249,2419,2
588,2756,2923,3090,

3255,3420,3583,3746,3907,4067,4226,4383,4539,4694,4848,5000,5150,5299,5446,

5591,5735,5877,6018,6156,6293,6427,6560,6691,6819,6946,7071,7193,7313,7431,7547,76
60,7771,

7880,7986,8090,8191,8290,8386,8480,8571,8660,8746,8829,8910,8987,9063,9135,9205,92
71,9335,

9396,9455,9510,9563,9612,9659,9702,9743,9781,9616,9848,9876,9902,9925,9945,9961,99
75,9986,
9993,10000,10000};

signed int factory[16]={0,0,100,350,220,80,265,180,270,100,142,108,100,115,5000};

signed int setting[16];
char arr[4];

44
struct
{
unsigned int frstdisp:1;
unsigned int setup:1;
unsigned int gravity:1;
unsigned int onflag:1;
unsigned int vcorrect:1;
unsigned int chrcorrect:1;
unsigned int chon:1;
unsigned int swon:1;
unsigned int nofeed:1;
unsigned int shorttrip:1;
unsigned int zincfail:1;
unsigned int mainsok:1;
unsigned int lbwarn:1;
unsigned int olwarn:1;
unsigned int olcut:1;
unsigned int lbcut:1;
unsigned int fault:1;
unsigned int hiload:1;
unsigned int msgrtn:1;
unsigned int chrmsgrtn:1;
unsigned int firston:1;
}flags;

int chshoot;
int chshootdly=0;
int flicker=0;
int *adjust;
int *ptr;
int adj;
int *value;
int chadj;
int champs1;
signed int duty_cycle_1;
signed int p=0,flag=1,rising=1;

signed int pr=0,kflag=1,rising1=1;

int amplitude=0;

int pb,qb,cth,ctl;
////////////////////////////////
unsigned int setdly;
unsigned int menudelay;
unsigned int lcdtmr;
unsigned int counter;
unsigned int resumedelay;

45
unsigned int buzzcount;
unsigned int buzzdelay;
unsigned int buzzoftme;
unsigned int buzzontme;
unsigned int peakfail;
unsigned int oldelay;
unsigned int tripdly;
unsigned int round;
unsigned int chrdly;
unsigned int slowdly;
unsigned int fbdly;
unsigned int ctfaildly;
unsigned int deadshortdly;
unsigned int lbdly;
unsigned int acdly;
unsigned int keydly;
unsigned int msgrtndly;
unsigned int gravitydly;
unsigned int fltdly;
unsigned int blinkdly;
unsigned int startdly;
////////////////////////////////
unsigned long endtimer;
unsigned long controlavg;
unsigned long mainsavg;
unsigned long outavg;
unsigned long wattsavg;
unsigned long batavg;
unsigned long keyavg;
unsigned long heatavg;
unsigned int modeavg;
/////////////////////////////////
unsigned int indummy;
unsigned int outdummy;
unsigned int ctdummy;
unsigned int keys;
unsigned int ntcvalue;
unsigned int batts;
unsigned int batrecharge;
//////////////////////////////////
unsigned int loaddisp;
unsigned int acoutdisp;
unsigned int mainsdisp;
unsigned int battdisp;
unsigned int battvolts;
unsigned int batrestart;

46
unsigned int loadpercent;
unsigned int champs;
unsigned int chdisp;
unsigned int mainsvolt;
unsigned int acout;
unsigned int keyvalue;
unsigned int key;
unsigned int heat;
unsigned int post;
unsigned int err;
unsigned int cherr;
unsigned int prect;

///////////////////////////////////
signed int upspeak;
signed int acpeak;
signed int ctpeak;
signed int batclb;
signed int mainsclb;
unsigned int chrclb;
unsigned int loadclb;
unsigned int pdctemp;
////////////////////////////////////
unsigned int deadshort;
unsigned int controlvolt;
unsigned int setvout;
unsigned int setchramp;
unsigned int setoverload;
unsigned int setupshi;
unsigned int setupslo;
unsigned int setinvhi;
unsigned int setinvlo;
unsigned int setbatful;
unsigned int setbatwrn;
unsigned int setbatlo;
unsigned int setbatres;
unsigned int defaults;
/////////////////////////////////////

unsigned int x,y,u;

unsigned long Ax,bx;
unsigned int aclo;
unsigned int achi;
unsigned int zinc;
/////////////////////////////////////
void InitADC1();
extern void Eeprom_WriteWord(unsigned short pushAddressOffset, unsigned short value);

47
extern unsigned short Eeprom_ReadWord(unsigned short pushAddressOffset);
void delay_ms(unsigned int gs);
void delay_us(unsigned int gs);

///////////////////////////////////////////////
const char str0[17]= "CALIBRATION MENU";
const char str20[17]="BATTERY V: V";
const char str21[17]="INVERTER MODE ON";
const char str22[17]=" U.P.S MODE ON ";
const char str23[17]=" SBY SWITCH OFF ";
const char str24[17]=" SBY SWITCH ON ";
const char str25[17]="MAINS VOLT: V";
const char str26[17]="INVERTER V: V";
const char str27[17]="TOTAL LOAD: %";
//////////////////////////////////////////
//const char str28[17]=" TRIP:C-T FAULT ";
const char str29[17]="TRIP:LOW-BATTERY";
const char str30[17]=" TRIP:OVERLOAD ";
const char str31[17]="SHORT CKT FAULT";
const char str32[17]="WARN:LOW-BATTERY";
const char str33[17]=" WARN:OVERLOAD ";
const char str34[17]=" TRIP:F-B FAULT ";
const char str35[17]="TRIP:SYNC FAULT ";
const char str36[17]="AC CHARGR: A";
const char str38[17]=" DSP SINEWAVE ";

#include "lcdsoft.h"
#include "functions.h"
void clear_flag();
void trip(int s);
int getvalue(int ch);
void chargeron();
void chroff();
void invon();
void invoff();
void stabilise();
void Modulate();
void find_key();
int findpeak(int ct);
void mains_stat_check();
void find_mainsvolt();
void find_batvolt();
void find_champs();
void find_upsvolt();
void find_load();
void overload_check();
void lobat_check();

48
void chr_stabilize();
////////////////////////////////////
void feed_buzz(int a,int b,int c)
{
buzzdelay=0;
buzzoftme=b;
buzzontme=a;
buzzcount=c;
}
//////////////////////////////////////////////////////
void __attribute__((__interrupt__,no_auto_psv)) _FLTAInterrupt(void)
{

_FLTAIF = 0;
}
//////////////////////////////////////////////////////////
void __attribute__((__interrupt__, __auto_psv__)) _T1Interrupt(void)
{
_T1IF = 0; // Clear interrupt flag
if(PORTEbits.RE8==0)
{
fltdly++;
if(fltdly>3000)
{
flags.olcut=1;
__asm__ volatile ("reset");
}
}
counter++;
acpeak=getvalue(0); //4.4 us
indummy=acpeak;
acpeak=indummy-508;
if(acpeak<0)
{
acpeak=508-indummy;
if(!flags.onflag)
{
rising=0;
flag=0;
}
}

mainsavg+=acpeak;

if(flags.setup)
{

49
OVDCON= 0X0000;
change=0;
buzzer=0;
}

if(!flags.setup)
{
if((indummy<600)&&(indummy>400)&&(flags.swon))
{
if(peakfail<150)
{
peakfail++;
}
if(peakfail==149)
{
if(flags.vcorrect)
{
invon(150);
}
}
}
else
{
peakfail=0;
}

if(flags.onflag)
{
Modulate(); //4.4 us
upspeak=getvalue(1); //4.4 us
outdummy=upspeak;
upspeak=outdummy-508;
if(upspeak<0)
upspeak=508-outdummy;
outavg+=upspeak;
if(upspeak<150)
{
fbdly++;
if(fbdly>30000)
{
flags.fault=1;
trip(5);
}
}
else
fbdly=0;
}

50
 else
{
rising=1;
flag=1;
loadpercent=0;
acout=0;
}

ctpeak=getvalue(2);

if(flags.onflag)
{
if((ctpeak>750)||(ctpeak<250))
{
deadshortdly++;
if(deadshortdly>1500)
{
deadshort=1;
OVDCON= 0X0000;
trip(1);
}
}
}

else
{

if(flags.chon==1)
{
if((ctpeak<508)||(ctpeak>512))
ctfaildly=0;
else
{
ctfaildly++;
if(ctfaildly>10000)
{
chroff();
}
}
}

if(ctpeak>506)
{

51
 pb=ctpeak-506;
if(cth<pb)
cth=pb;
}
if(ctpeak<506)
{
qb=506-ctpeak;
if(ctl<qb)
ctl=qb;
}
wattsavg+=cth+ctl;
ctl=cth=0;
heat=getvalue(3);
}

batavg+=getvalue(5);

lcdtmr++;
if(counter==359)////////////////////// 20 milli sec
{
mainsvolt=__builtin_divud(mainsavg,288)+mainsclb; //2.2 microseconds
mainsavg=0;
if(mainsvolt<90)
{
mainsvolt=0;
mainsdisp=0;
}
else
{
if((indummy>180)&&(indummy<900))
{
if(mainsdisp==0)
{
mainsdisp=mainsvolt-80;

}
if(mainsdisp<mainsvolt-2)
{
mainsdisp++;
}
if(mainsdisp>mainsvolt+2)
{
mainsdisp--;
}
}
}

52
find_batvolt();

keyavg+=getvalue(4);
keydly++;
if(keydly==10)
find_key();

if(!flags.setup)
{
mains_stat_check();
if(flags.onflag==1)
{
acout=__builtin_divud(outavg,285);
outavg=0;
if(acoutdisp<acout-2)
acoutdisp++;
if(acoutdisp>acout+2)
acoutdisp--;

find_load();
overload_check();
lobat_check();
}
}

wattsavg=0;

if(buzzcount>0)
{
buzzdelay++;
if(buzzdelay<=buzzontme)
buzzer=1;
else
{
buzzer=0;
if(buzzdelay>=buzzoftme)
{
buzzdelay=0;
buzzcount--;
fltdly=0;
}
}
}
else
{

53
 FLTACON=0x0001;
IEC2bits.FLTAIE = 1;
if(round>0)
{
if((!flags.onflag)&&(flags.swon)&&(round<4))
{
if(mainsvolt<110)
{
clear_flag();
invon(0);
}
}
}
if(round==4)
change=0;
}

if(!flags.setup)
{

if((resumedelay==200)||(flags.mainsok==1))
{
LCD_DB6=1;
if(flags.swon==1)
{
blinkdly++;
if(blinkdly<30)
LCD_DB7=1;
else
LCD_DB7=0;
if(blinkdly>60)
blinkdly=0;
}
else
LCD_DB7=0;
}
else
{
LCD_DB6=0;
if(flags.onflag==1)
LCD_DB7=1;
else
LCD_DB7=0;
}
}

counter=0;

54
if((key==modekey)&&(flags.setup==0))
{
menudelay++;
if(menudelay>124)
flags.setup=1;
}
else
menudelay=0;

if(flags.setup==1)
{
setdly++;
if(setdly>3000)
__asm__ volatile ("reset");
}
}
cherr=mainsvolt;
}

//////////////////////////////////////
void init_PWM()
{
PTCON= 0XE003;
PTMR = 0x0000;
PTPER = PDC1=PDC2= 1230;
SEVTCMP = 0x0000;
PWMCON1 = 0x0033;
PWMCON2 = 0x0000;
DTCON1= 0X0059;
FLTACON = 0x0000;
OVDCON= 0X0000;
PTCONbits.PTEN = 1;
IEC2bits.PWMIE = 0; // disable PWM interrupts

T1CON = 0XE000;
TMR1 = 0;
PR1 = 1355;
_T1IF = 0;
_T1IE = 1;
}
/////////////////////////////////////////////////
void memread()
{
int x;
for(x=0;x<15;x++)

55
{
setting[x]=Eeprom_ReadWord(x);
}
}
//////////////////////////////////////////////////////////
void memwrite()
{

int x;
for(x=0;x<15;x++)
{
if(flags.setup==0)
Eeprom_WriteWord(x,factory[x]);
else
Eeprom_WriteWord(x,setting[x]);
}
}
//////////////////////////////////////////////
void modedisp()
{
if(flags.msgrtn)
return;
if((key==upsmode)||(key==stbyups))
{
printmes(str22,100); //"\fU.P.S MODE ON";
if(key==upsmode)
{
aclo=setupslo;
achi=setupshi;
}
}

if((key==invmode)||(key==stbyinv))
printmes(str21,100); //"\fINVERTER MODE ON";
}
//////////////////////////////////////////////////////
void swdisp()
{
if(flags.msgrtn)
return;

if((key==stbyinv)||(key==stbyups)) //"\fSBY SWITCH OFF";

{
printmes(str23,100);
aclo=setinvlo;
achi=setinvhi;
}

56
if((key==upsmode)||(key==invmode))
printmes(str24,100); //"\fSBY SWITCH ON";
}

// MAIN ROUTINE
//
**************************************************************************
***/
int main()
{
TRISF=0X0000;
TRISE=0X010F;
TRISD=0X0000;
TRISC=0X0000;
TRISB=0XFFFF;
OVDCON=0X0000;
PWMCON1 = 0x0000;
PTCONbits.PTEN = 0;
buzzer=0;
lcd_init();
InitADC1();
init_PWM();
keyvalue=getvalue(4);
if(((keyvalue>660)&&(keyvalue<680))||((keyvalue>560)&&(keyvalue<575)))
{
flags.swon=1;
flags.firston=1;
}

prect=getvalue(2);

flags.frstdisp=0;

defaults=Eeprom_ReadWord(14);
if(defaults!=50)
{
memwrite();
}
memread();
batclb=setting[0];
mainsclb=setting[1];
chrclb=setting[2];
loadclb=700-setting[3];
setvout=setting[4];

57
setchramp=setting[5];
chshoot=setchramp;
setchramp+=30;
setupshi=setting[6];
setupslo=setting[7];
setinvhi=setting[8];
setinvlo=setting[9];
setbatful=setting[10];
setbatwrn=setting[11];
setbatlo=setting[12];
setbatres=setting[13];
defaults=setting[14];
battdisp=90;
aclo=setinvlo;
achi=setinvhi;
batrestart=setbatful-13;
menudelay=0;
while(1)
{
//lcd_init();
//
//while(1)
//{

//lcd_init();
//printmes(str36,3); //"AC CHARGR:";

//flags.msgrtn=0;
////printmes(str20,1); //"\fBATTERY V:";
//

//printmes(str25,2); //"\fMAINS VOLT:";

//printmes(str27,4); //"\fTOTAL LOAD:";

//
////printmes(str23,0);
////
//printmes(str24,100); //"\fSBY SWITCH ON";
////
////
////
//printmes(str26,0); //"\fINVERTER V:";
////
////printmes(str27,4); //"\fTOTAL LOAD:";
//

58
//
//
//
//
//}
//

while(PORTEbits.RE8==0)
{
flags.msgrtn=0;
printmes(str31,100); // SHORT CKT FAULT
if(flags.swon==0)
__asm__ volatile ("reset");
}

while(flags.nofeed==1)
{
flags.msgrtn=0;
printmes(str34,100); // NO FEED BACK
if(flags.swon==0)
__asm__ volatile ("reset");
}

//while(flags.ctfail==1)
//{
// flags.msgrtn=0;
//printmes(str28,100); // TRIP:C-T FAULT
//if(flags.swon==0)
//__asm__ volatile ("reset");
//}

while(flags.zincfail==1)
{
flags.msgrtn=0;
printmes(str35,100); // TRIP:SYNC FAULT!
if(flags.swon==0)
__asm__ volatile ("reset");
flags.fault=1;
}

while(flags.lbcut==1)
{
flags.msgrtn=0;
printmes(str29,100); //" TRIP:LOW-BATTERY ";
if((flags.swon==0)||(resumedelay>175))
__asm__ volatile ("reset");

59
}

while(flags.olcut==1)
{
flags.msgrtn=0;
printmes(str30,100); //" TRIP:OVER-LOAD ";
if((flags.swon==0)||(resumedelay>175))
__asm__ volatile ("reset");
}

while(flags.olwarn)
{
flags.msgrtn=0;
printmes(str33,100); //" WARN:OVER-LOAD ";
if(flags.swon==0)
__asm__ volatile ("reset");
}

while(flags.lbwarn==1)
{
flags.msgrtn=0;
printmes(str32,100); //"WARN:LOW-BATTERY";
if(flags.swon==0)
__asm__ volatile ("reset");

printmes(str20,1); // 0/0/"\fBATTERY V:";

if(flags.chon==1)
{
if(champs==0)
goto outmes;

printmes(str36,3); //"AC CHARGR:";

}
outmes:

if((key==upsmode)||(key==invmode))
{
if(flags.onflag==1)
{
printmes(str27,4); //"\fTOTAL LOAD:";
}
modedisp();

swdisp();

60
printmes(str25,2); //"\fMAINS VOLT:";

if(flags.onflag==1)
{
printmes(str26,0); //"\fINVERTER V:";
}

else
{
modedisp();
swdisp();
printmes(str25,2); //"\fMAINS VOLT:";
}

//printmes(str38,100); //"\fTITLE NAME

if(menudelay>=125)
{
flags.setup=1;
menudelay=0;
lcd_putc('\f');
printmes(str0,100); //"\fCALIBRATION MENU";
while(key==modekey);
while(1)
{
if(key==modekey)
{
setchramp=setting[5]/10;
loadclb=setting[3];
functions();
memwrite();
flags.setup=0;
__asm__ volatile ("reset");
}
}

}//main

61