This project is titled the design and construction of a DC to AC inverter system. It is designed to meet up with the power demand in the offices and in homes in the absence of power supply from the national supply authority, NEPA. In order words the device / item serves as a substitute for NEPA which almost monopolises the power supply to people.
It is designed in such a way that it will take up 12v DC from battery and inverts it to an output of 240v, 50Hz AC. It makes no noise during operation and no hazardous carbon monoxide is generated in the surrounding.   
This is a feature that makes it safe to use any where when compared to generator. Also, the circuit is capable of charging the battery (i.e 12v source) when the power from the supply authority is on. This greatly reduces the cost of operation of the system.
This work is aimed at designing a modified sine wave inverter of power rating of 5kva that can be used to power appliances both in homes and industries.

 

TABLE OF CONTENTS
TITLE PAGE
APPROVAL PAGE
DEDICATION
ACKNOWLEDGEMENT
ABSTRACT
TABLE OF CONTENT
CHAPTER ONE
1.0     INTRODUCTION
1.1     OBJECTIVE OF THE PROJECT
1.2     SIGNIFICANCE OF THE PROJECT
1.3    APPLICATION OF THE PROJECT
1.4     SCOPE OF THE PROJECT
1.5     LIMITATION OF THE PROJECT
1.6     PURPOSE OF THE PROJECT
1.7     PROJECT ORGANISATION

CHAPTER TWO
2.0     LITERATURE REVIEW
2.1     REVIEW OF HISTORY OF AN INVERTER
2.2   REVIEW OF HOW TO CHOOSING THE RIGHT INVERTER
2.3      REVIEW OF THE DIFFERENCE BETWEEN SINE WAVE AND MODIFIED SINE WAVE   INVERTER.
2.4     REVIEW OF INVERTER CAPACITY
2.5     SAFETY OF INVERTER
2.6     INVERTER RATING
2.7     WHY CHOOSE A MODIFIED SINE WAVE INVERTER?
2.8     TYPES OF INVERTER

CHAPTER THREE
3.0     CONSTRUCTION
3.1     BASIC DESIGNS OF AN INVERTER
3.2      BLOCK DIAGRAM OF THE SYSTEM
3.3     SYSTEM OPERATION
3.4     CIRCUIT DIAGRAM
3.5     CIRCUIT DESCRIPTION
3.6     DESCRIPTION OF COMPONENTS USED
3.7      HOW TO CHOOSE A RIGHT INVERTER AND BATTERY
3.8      HOW TO CHOOSE THE BEST INVERTER BATTERY
CHAPTER FOUR
RESULT ANALYSIS
4.0     CONSTRUCTION PROCEDURE AND TESTING
4.1     CASING AND PACKAGING
4.2     ASSEMBLING OF SECTIONS
4.3     TESTING OF SYSTEM OPERATION
4.4      COST ANALYSIS    
CHAPTER FIVE     
5.0     CONCLUSION
5.1     RECOMMENDATION
5.2     REFERENCES

CHAPTER ONE
1.0                                                        INTRODUCTION
A power inverter converts DC power (also known as direct current), to standard AC power (alternating current). Inverters are used to operate electrical equipment from the power produced by a car or boat battery or renewable energy sources, like solar panels or wind turbines. DC power is what batteries store, while AC power is what most electrical appliances need to run so an inverter is necessary to convert the power into a usable form. For example, when a cell phone is plugged into a car cigarette lighter to recharge, it supplies DC power; this must be converted to the required AC power by a power inverter to charge the phone [1].
In modified sine wave, The waveform in commercially available modified-sine-wave inverters is a square wave with a pause before the polarity transition, which only needs to cycle through a three-position switch that outputs forward, off, and reverse output at the pre-determined frequency. The peak voltage to RMS voltage does not maintain the same relationship as for a sine wave. The DC bus voltage may be actively regulated or the "on" and "off" times can be modified to maintain the same RMS value output up to the DC bus voltage to compensate for DC bus voltage variation.
The ratio of on to off time can be adjusted to vary the RMS voltage while maintaining a constant frequency with a technique called PWM. Harmonic spectrum in the output depends on the width of the pulses and the modulation frequency. When operating induction motors, voltage harmonics is not of great concern, however harmonic distortion in the current waveform introduces additional heating, and can produce pulsating torques [1].
Most AC motors will run on MSW inverters with an efficiency reduction of about 20% due to the harmonic contents.

1.1 OBJECTIVE OF THE PROJECT

The objective of this project is to design and construct a modified sine wave inverter which can be powered from the source of 12V battery to produce an output of 240vac. This inverter is capable of operating a wide variety of loads; electronic and household items including but not limited to TV, VCR, and satellite receiver, computers, and printers which also give an output load of 4kva to load.

1.2                                           PURPOSE OF THE PROJECT
The purpose of this work is to design an electronic device or circuit that changes direct current (DC) to alternating current (AC). The input voltage (12vdc), output voltage (240vac) and frequency (50hz), and overall power handling depend on the design of the specific device. The inverter does not produce any power; the power is provided by the DC source.
A typical power inverter device or circuit requires a relatively stable DC power source capable of supplying enough current for the intended power demands of the system. The input voltage depends on the design and purpose of the inverter.
The waveform of this work is modified sine wave. The modified sine wave output of such an inverter is the sum of two square waves one of which is phase shifted 90 degrees relative to the other. The result is three level waveform with equal intervals of zero volts; peak positive volts; zero volts; peak negative volts and then zero volts. This sequence is repeated. The resultant wave very roughly resembles the shape of a sine wave [7, 8].

1.3                                       SIGNIFICANCE OF THE PROJECT
In the recent years,  power  inverter has become a major power source due to its environmental and economic benefits and proven reliability. Since the solar power system does not have moving parts, virtually it does not require any kind of maintenance once installed.
Power inverter is produced by connecting the device on the 12VDC battery as the input to produce 240VAC as the required output. It can also be connected to solar panel.
Second, the whole energy conversion process is environmentally friendly. It produces no noise, harmful emissions or polluting gases. The burning of natural resources for energy can create smoke, cause acid rain and pollute water and air. Carbon dioxide, CO2, a leading greenhouse gas, is also produced in the case of burning fuels. Power inverter uses only the power of the battery as its fuel. It creates no harmful by-product and contributes actively to the reduction of global warming [4].

1.4                                              SCOPE OF THE PROJECT
A power inverter is a power conversion device. It converts fixed direct current (DC) voltage to frequency sinusoidal alternating current (AC) voltage output.
Power inverters are used to power and control the speed, torque, acceleration, deceleration, and direction of the motor. The use of inverter has become prevalent in wide range of industrial applications; from motion control applications to ventilation systems, waste water processing facilities to machining areas, and many others. Though power inverters offer lower operating costs and higher efficiency, they are not without their problems [2].

1.5                                       LIMITATION OF THE PROJECT

i. Input voltage:  A typical power inverter device or circuit requires a relatively stable DC power source capable of supplying enough current for the intended power demands of the system. The input voltage depends on the design and purpose of the inverter. The input voltage of this work is 12 VDC, for smaller consumer and commercial inverters that typically run from a rechargeable 12 V lead acid battery [2].

ii. Waveforms: An inverter can produce a square wave, modified sine wave, pulsed sine wave, pulse width modulated wave (PWM) or sine wave depending on circuit design. The output waveform of this particular inverter is modified sine wave [3].

iii. Output frequency: The AC output frequency of a power inverter device is usually the same as standard power line frequency, 50 or 60 hertz. The output frequency of the work is 50hertz.

iv. Output voltage: The AC output voltage of a power inverter is often regulated to be the same as the grid line voltage, typically 240 VAC ( for Nigeria consumers) at the distribution level, even when there are changes in the load that the inverter is driving. This allows the inverter to power numerous devices designed for standard line power. Therefore, the output voltage of this work is 240vac [3].

v. Output power: A power inverter will often have an overall power rating expressed in watts or kilowatts. This describes the power that will be available to the device the inverter is driving and, indirectly, the power that will be needed from the DC source. The output power of this work is 5000 watts.

1.6                                           PROBLEM OF THE PROJECT

• Expensive when compared to traditional generators
• There are no large capacity inverters in the markets compared to conventional generator.
• The output supply depends wholly on the input source, which means that the inverter will stop working whenever the battery which is the input goes low.

1.7                                       APPLICATION OF THE PROJECT
The applications and uses of a power inverter which are as follows:
DC power source utilization
Inverter designed to provide 240 VAC from the 12 VDC source provided in an automobile. The unit shown provides more than 20 amperes of alternating current, or enough to power more than 5KW load.
An inverter converts the DC electricity from sources such as batteries, solar panels, or fuel cells to AC electricity. The electricity can be at any required voltage; in particular it can operate AC equipment designed for mains operation, or rectified to produce DC at any desired voltage [6].
Uninterruptible power supplies
An uninterruptible power supply (UPS) uses batteries and an inverter to supply AC power when main power is not available. When main power is restored, a rectifier supplies DC power to recharge the batteries.
Induction heating
Modified Sine wave Inverters convert low frequency main AC power to higher frequency for use in induction heating. To do this, AC power is first rectified to provide DC power. The inverter then changes the DC power to high frequency AC power[4].
HVDC power transmission
With HVDC power transmission, AC power is rectified and high voltage DC power is transmitted to another location. At the receiving location, an inverter in a static inverter plant converts the power back to AC. The inverter must be synchronized with grid frequency and phase and minimize harmonic generation.
Variable-frequency drives
A variable-frequency drive controls the operating speed of an AC motor by controlling the frequency and voltage of the power supplied to the motor. An inverter provides the controlled power. In most cases, the variable-frequency drive includes a rectifier so that DC power for the inverter can be provided from main AC power. Since an inverter is the key component, variable-frequency drives are sometimes called inverter drives or just inverters.
VFDs that operate directly from an AC source without first converting it to DC are called cyclo-converters. They are now commonly used on large ships to drive the propulsion motors.
Electric vehicle drives
Adjustable speed motor control inverters are currently used to power the traction motors in some electric and diesel-electric rail vehicles as well as some battery electric vehicles and hybrid electric highway vehicles.
Air conditioning
An inverter air conditioner uses a variable-frequency drive to control the speed of the motor and thus the compressor.
Electroshock weapons
Electroshock weapons and tasters have a DC/AC inverter to generate several tens of thousands of V AC out of a small 12 V DC battery. First the 12VDC is converted to 400–2000V AC with a compact high frequency transformer, which is then rectified and temporarily stored in a high voltage capacitor until a pre-set threshold voltage is reached. When the threshold (set by way of an air gap or TRIAC) is reached, the capacitor dumps its entire load into a pulse transformer which then steps it up to its final output voltage of 20–60 kV. A variant of the principle is also used in electronic flash and bug zappers, though they rely on a capacitor-based voltage multiplier to achieve their high voltage [5].

1.8                                        PROJECT WORK ORGANISATION
The various stages involved in the development of this project have been properly put into five chapters to enhance comprehensive and concise reading. In this project thesis, the project is organized sequentially as follows:
Chapter one of this work is on the introduction to a power inverter. In this chapter, the background, significance, objective limitation and problem of a power inverter were discussed.
Chapter two is on literature review of a power inverter. In this chapter, all the literature pertaining to this work was reviewed.
Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.
Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.
Chapter five is on conclusion, recommendation and references.

REFERENCES
[1]       The Authoritative Dictionary of IEEE Standards Terms, Seventh Edition, IEEE Press, 2000,ISBN 0-7381-2601-2, page 588
[2].     James, Hahn. "Modifi ed Sine-Wave Inverter Enhanced". Power Electronics.
[3].     Barnes, Malcolm (2003). Practical variable speed drives and power electronics. Oxford: Newnes. p. 97. ISBN 0080473911.
[4].     Rodriguez, Jose; et al. (August 2002). "Multilevel Inverters: A Survey of Topologies, Controls, and Applications". IEEE Transactions on Industrial Electronics (IEEE) 49 (4): 724–738.
[5].     Owen, Edward L. (January–February 1996). "Origins of the Inverter". IEEE Industry Applications Magazine: History Department (IEEE) 2 (1): 64–66.
[6].     Dr. Ulrich Nicolai, Dr. Tobias Reimann, Prof. Jürgen Petzoldt, Josef Lutz: Application Manual IGBT and MOSFET Power Modules, 1. Edition, ISLE Verlag, 1998, ISBN 3-932633-24-5.
[7]                  https://www.energysage.com/solar/101/microinverters-power-optimizers-advantages-disadvantages/

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