Design And Construction Of A Transformerless Power Inverter

ABSTRACT

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, industries and in homes in the absence of power supply from the power grid. In order words the device serves as a substitute for national grid which almost monopolises the power supply to people.

This work is aimed at building a transformerless inverter that converts direct current (DC) into an alternating current (AC) suitable for injecting into an electrical power grid without using transformer that can be used to power appliances both in homes and industries. It is designed in such a way that it will take high voltage DC from battery and inverts it to an output of 230v, 50Hz AC. It makes no noise during operation and no hazardous carbon monoxide is generated in the surrounding.

CHAPTER ONE

1.0                                          INTRODUCTION

1.1                            BACKGROUND OF THE STUDY

Electricity supply is one the economic infrastructural facilities that are indispensable to a nation’s economic development. The efficiency of the supply of electricity will not only influence returns on investment on existing enterprises, it also plays a major role in the creation of an economic environment which influences decisions on potential investment.

The electricity which is the main source of power for our domestic consumption, industrial development, learning centres and medical centre should really be rehabilitated into enhancement of productivity.

However power failure has resulted in people buying 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 construction of inverter and other standby system that can deliver maximum output power to the load. As society grows from simple to complex, mankind began to spread all over the earth and so it becomes necessary  to enjoy power using inverter.

A power inverter converts DC power, 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.

In this work, we are building a transformerless inverter. As the name suggests, the inverter is not equipped with a standard step-up transformer like traditional inverter for converting low voltage AC to high voltage AC.

Transformer-less inverters utilizes high voltage DC as input which is converted to high voltage AC output by oscillators and H-bridge drivers, since there is no transformer great efficiency more than 97% is achievable, the only loss is from the MOSFETs of H-bridge. The high voltage DC source can be solar panels or battery.

1.2                                                  PROBLEM STATEMENT

Traditionally, dc to ac power inversion is always achieved by using a step up transformer and this makes the whole system bulky, cost effective, heavy and inefficient due to iron core losses. The invention of transformerless power inverter came to solve this problem. Transformer-less inverter are relatively inexpensive due to absence of bulky iron core transformer which is the most expensive part of the inverter and now, there are no losses related to transformer so more efficiency. Now the inverter gets lighter and makes it portable which makes less challenging to install.

1.3                                           AIM OF THE PROJECT

The aim of this work is to converts direct current (DC) into an alternating current (AC) suitable for injecting into an electrical power grid without using transformer.

1.4                                              PURPOSE OF THE PROJECT

The main purpose of carrying out this work is to reduce cost, size, and weight, but also increases the whole system efficiency of an inverter.

1.5                                              ADVANTAGES OF PROJECT

Transformerless inverters are being widely used in grid-connected photovoltaic (PV) generation systems. Transformer elimination, in grid-connected PV systems, has many advantages. This not only reduces cost, size, and weight, but also increases the whole system efficiency.

1.6                                          APPLICATION OF THE PROJECT

Transformerless inverters are used between local electrical power generators for solar panel, wind turbine, hydro-electric, and the grid.

1.7                                           LIMITATION OF THE PROJECT

1. Power inverter don’t offer isolation from the HV line and present more of a safety issue.
2. Square wave is not suitable many medical and sensitive electronics equipments.

• Need huge battery bank / long solar panel array to meet the voltage needs.

1. Need separate battery source for oscillator.
2. Battery discharge rate affects output AC voltage (240V to 210V).

1.8                                         METHODOLOGY

To achieve the aim and objectives of this work, the following are the steps involved:

1. Study of the previous work on the project so as to improve it efficiency.
2. Draw a block diagram.

• Test for continuity of components and devices,

1. Design and calculation for the device was carried out.
2. Studying of various component used in circuit.
3. Construction of the circuit was carried out.

• Finally, the whole device was cased and final test was carried out.

1.9                                        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 transformerless 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 transformerless 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.

SYSTEM CIRCUIT DIAGRAM

The circuit diagram of the device is as below: