Design And Construction A 1KVA Pure Sine Wave Inverter

CHAPTER ONE

INTRODUCTION

• Background of study

Power electronic systems are used widely to convert electric energy from one form to other using electronic devices. Four basic power electronics functions are AC to DC conversion, DC to AC conversion, DC to DC conversion and AC to AC conversion. These basic functions are used to build power supplies, DC transmission systems, electric drives and others [1].

Mobility and versatility have become a must for the fast-paced society today. People can no longer afford to be tied down to a fixed power source location when using their equipment. Overcoming the obstacle of fixed power has led to the invention of a DC/AC power inverter [2].

Companies, Industries, Organizations, Homes among the others are posed with a major problem of power shortage especially here in Nigeria. Although in developing countries, shortage of power is a problem commercially and domestically. New offices have tremendous load on already existing power generation sources. When added to rapidly increasing private and domestic demand, the situation, especially in certain urban areas becomes devastating. Simply stated, our ability to consume power is growing faster than our ability to supply power. Under such conditions, failure will occur unpredictably and without any warning due to stresses on the inadequate sources of power. Hence, there is need for the alternative source of power which could fill in the gap and cover the lapses of shortage in power supply. Overcoming this obstacle led to the invention of DC/AC power inverters. At the early stage, sun was the source of energy for generating power. Due to the inadequacy of the power generated through this source, there was a need to find other ways to improve the power supply when the generating station could not meet the demand of the people. As the technology advances, the hydroelectric generation was developed, gas firing generating station, and wired tubing methods of generating power supply were developed. In spite of all these developments, there was still failure in electrical power generation as a result of obsolete equipment at the generating stations. There was still need to find alternative for solving the problem. As a result of this, some options like alternators, inverters and others were developed [3].

Power inverter is an electronic device that has the ability to convert the direct current (DC) from the battery or solar cells (panels) into an alternating current (AC) which is the conventional form that powers many electrical appliances. It maintains a continuous supply of electric power to the connected loads or equipment when the utility power is not available. Inverters are generally used in a host of applications that include variable speed drive, uninterruptible power supplies, flexible AC transmission systems, (FACTS), high voltage DC transmission systems (HVDC), active filters among the others [4].

An inverter is a device which maintains a continuous supply of electric power to connected equipment or load by supplying power from a separate source, like battery, when utility power is not available. It is inserted between the source of power (typically commercially utility power) and the load it is protecting. For alternative energy systems, inverters are the essential step between a battery’s DC power and the AC power needed by standard household electrical systems. In a grid connected home, an inverter/charger connected to a battery bank can provide an uninterruptible source of backup power in the event of power failures, or can be used to sell extra alternative energy power back to the utility company. Batteries produce power in direct current (DC) form, which can run at very low voltages but cannot be used to run most modern household appliances. Utility companies and generators produce sine wave alternating current (AC) power, which is used by most commonly available appliances today. Inverters take the DC power supplied by a storage battery bank and electronically convert it to AC power. An inverter is a device that takes a direct current input and produces a sinusoidal alternating current output.  An inverter needs to be designed to handle the requirements of an energy hungry household yet remain efficient during periods of low demand. The efficiency of inverter is highly dependent on the switching device, topology and switching frequency of the inverter [1].

Alternating current (AC) power is used as a power source as well for transmission purpose because it can be generated and also converted from one voltage to another. Transmission of AC power over long distance is still used until now, however it results in relatively high transmission loses. The types of loses are transient stability problem, and operational requirements such as dynamic damping of electrical system may also arise along the transmission line. Direct Current (DC) transmission is an alternative which overcomes most of this problem. Besides that, it is more economically feasible only when the transmission distance exceeds 500 to 600 km, underwater cables for the case in a small distance transmission. At the receiving end HVDC is converted back to HVAC or LVAC. The design of an inverter is referring to the requirement of point distribution and economical aspect [5]. Power inverters come in all shapes and sizes, from low power functions such as powering a car radio to that of backing up a building in case of power outage. Inverters may come in different varieties, differing in price, power, efficiency and purpose. Power inverters are used today for many tasks like powering appliances in a car such as cell phones, radios and televisions. They also come in handy for consumers who own camping vehicles, boats and at the construction sites where an electric grid may not be as accessible to hook into [7]. Inverters, besides coming in a wide variety of power capacities, are distinguished primarily by the shape of the alternating current wave they produce. The three major waveforms are square-wave, modified sine wave and pure sine-wave. Square wave inverters are largely obsolete, as the waveform shape is not well suited for running most modern appliances, and prices have come down considerably for the superior modified sine wave and pure sine wave types [3].

This project report documents the design and construction of a 1kVA pure sine wave inverter, focusing on the conversion of a 12V DC voltage source to a 220V AC output [4].  The various applications of the inverter are: Wind/solar electrical systems, Back-up for power cells, Generator support systems, Remote homes, Telecommunications, Computers, Tools, Security applications, Mobile power, Boats and yachts, Airplane, Monitoring equipment, Emergency power and lighting etc.

1.2 Problem Statement:

Constant power supply increases industrial commercial productivity of any nation. But owing to several issues associated with power generation, transmission, and distribution industry, constant power supply is rarely achieved even at small scale. Hence in other to extend power supply duration to consumers so as to increase productivity, the idea of power storage was borne which invariably gave rise to inverter design and construction. Inverter being an electrical electronics device that converts stored direct current electrical energy in batteries back to alternating current, and voltage readily stepped in to solve this problem.

1.3 Aim and Objectives of the project:

The aim of this work is  Design and Construction a 1kVA Pure Sine Wave Inverter.

The objectives of the project are:

1. To design a 1 kVA inverter using proteus.
2. To construct and assemble the inverter.
3. To package and test the inverter.

• Motivation:

Rapid industrialization in the developed countries gave rise to global warming, a situation which is considered a big threat to human existence in the nearby future. The quest by engineers, and researchers to develop alternating source energy and related technology caught my attention, this move me to learn inverter design and construction.

1.5 Significance of the project:

With the help of inverter homes, industries, and offices get to enjoy extended power supply duration, depending on the installed capacity. It helps to increase their saving from fuel and diesel purchase. Being a clean energy conversion scheme, it is environmentally friendly, and contributes to greenhouse gas effect reduction. Offers low maintenance cost and it is highly durable.

1.6 Scope of the project:

This paper covers the history of inverter, highlights on the different types of inverters based on various classifications, with focus on the design, construction and analysis of 1kVA pure sine wave inverter.

1.7 Limitation of the project:

In spite of the base of construction of an inverter and its noiseless and pollution free nature unlike other alternative sources of generating electricity, there is a need for charging and recharging the battery from time to time.

The pure sine wave inverter is more expensive than the modified sine wave power inverters and physically larger than the modified sine wave counterparts.

CHAPTER FIVE

      CONCLUSION AND RECOMMENDATIONS

• CONCLUSION

The construction of this project 1kVA, 220Volts inverter at a 50Hz frequency was a gradual process from gathering of materials to testing of components. It is to be noted that the efficiency of this project depends on the power rating of the battery connected to the input and on the total power of the load connected to its output terminals. Thus, the inverter could deliver constant power for a calculated number of hours.

In view of the inconsistence and unreliable public power supply and high cost of electric power generators coupled with the high cost of maintenance, the inverter is found to offer a better constant additional power supply for a sustainable duration. It is noiseless, harmless, and cost effective. It is also a preferred power backup to a computer and other appliances because it switches automatically to the battery when the AC mains is not available. Thus, reduce system breakdown, prevent hard disk damages and data loss. In addition, the life span of the computers and other devices connected to either a standby or a continuous inverter is prolonged. The objective of the circuit was to invert power from low voltage DC sources to boost into AC power similar to one available in our wall sockets for any load.

Some of the important conclusions that can be drawn from this work are;

• Output waveform frequency was found to be satisfactory at 50Hz equivalent of standard Nigeria power system.
• Sine pulse width modulation circuit is much simplified by the use of SG3524IC.
• In addition, with the high programming flexibility, the design of the switching pulses can be altered without further changes on the hardware.

5.2 RECOMMENDATION

Although the objectives of this project have been achieved, the inverter cannot be used to power any device of higher power rating. In addition, when the inverter is operating on mains supply, any fluctuation of the AC input gets to the inverter output. Therefore, for improvement on this project, further research can include: Increasing the power rating of the inverter by increasing the number of the power switching devices and the current rating of the transformer. In addition, Also, hardware designed that isolates the load from the supply in case of over voltages, under voltages and phase outs would be of great importance if this project is to be commercially produced in large scale.