1.0 Introduction
Pure sine wave inverter is a power electronic device or circuitry that changes direct current (DC) to alternating current (AC). The resulting AC frequency obtained depends on the particular device employed. Pure sine wave inverters are primarily used in electrical power applications where high currents and voltages are present; circuits that perform the same function for electronic signals, which usually have very low currents and voltages, are called oscillators. Circuits that perform the opposite function, converting AC to DC, are called rectifiers (Wikipedia, 2021).
As a prelude to other parts of this study, this chapter will discuss the background upon which this study was initiated, the statement of problems that led to this study, the Aim and Objectives of the study. Others are Significance of the study, Scope of work, Limitations of the Study and Definition of technical terms.
1.2 Background of Study
Pure sine wave inverters are the most affluent in terms of efftciency and accurate timing output. They use batteries to generate power and it’s important to have a means of recharging (Cunningham, 1999). Various methods can be adopted such as solar panels, wind turbine etc. Pure sine wave inversion is obtained by taking a DC voltage source and switching it across a load using an H-bridge. If this voltage needs to be boosted from the DC source in the inverter, it can be accomplished either before the AC stage by using a DC-DC boost converter, or after AC stage by using a Boost transformer (Crowley and Leung, 2001). The inverted signal is composed of a pulse width-modulated signal which encodes a sine wave. The duty cycle of the output is changed such that power transmitted is exactly that of a sine wave. This output can be used as it is or, alternatively, can be ftltered easily into a pure sine wave (Nuzhat et al., 2010).
Electricity is one of the greatest inventions man has ever made, due to its very important role in socio-economic and technological development (Owen and Edward, 1996). Electricity Can be transmitted in two different ways namely: alternating currents (AC) or Direct current (DC). Alternating current is the form obtained from power outlets in homes and offtces. It consists of a sinusoidal voltage source in which a continuous change in the direction of flow of voltage (and current) can be used to employ magnetic components (Cooks et al., 2001). Direct current is electricity flowing in a constant direction, and/or possessing a voltage with constant polarity and is appropriate for short-range transmission. Direct current is the form stored up in batteries. It uses is limited and it depends on AC power (Owen and Edward, 1996).
A common difference between AC and DC involves the amount of energy that each can carry. Direct current has a voltage level and cannot travel very far until it losses energy. Ac is safer to transmit over long distance (Nergaard et al., 2001). DC is preferred over AC because of its portability hence the introduction of the inverter that are mobile AC source from a portable DC battery. An inverter is an electrical device that converts DC to AC; the converted AC can be at any required voltage frequency with the use of appropriate transformers, switching and control circuits. There are three types of DC-AC inverters, the square wave, the modifted sine wave and pure sine wave.
This work is the design of a pure sine wave inverter, focusing on the inversion of a DC voltage source (Gurdjian and Maxwell, 2000). Therefore, in Nigeria where the research was carried out, the activities that was conducted is to know the design process and construction of 1000W pure sine Wave Inverter using Microprocessor.
1.3 Aim and Objectives of Study
The main aim of this project is to design and construct a pure sine wave single phase 1000w inverter. In achieving this aim, the following specific objectives were laid out as follows:
- To build an inverter with output power which is rated 1000w which can be powered from a 12v input source.
- To produce an inverter with a waveform like that of the mains / utility voltage. In a sine wave, the voltage rises and falls smoothly with a smoothly changing phase angle and also changes its polarity instantly when it crosses 0 Volts
- To use a microcontroller as the main circuit control component hence reducing system complexity.
- To ensure that provision is made for backup supply to consumer equipment.
1.4 Significance of Study
The following are the relevance of the research work:
- The study will facilitate output voltage wave form, which is pure sine wave with very low harmonic distortion and clean power like utility-supplied electricity.
- Provision of inductive loads like microwave ovens and motors run faster, quieter and cooler.
- Reduces audible and electrical noise in fans, fluorescent lights, audio amplifiers, TV, Game consoles, Fax, and answering machines.
- Prevents crashes in computers, weird print out, and glitches and noise in monitors.
- Provision of reliably powers, which will normally not work with modified sine wave inverters.
Besides, the study will serve as reference material for subsequent researcher in the field or related topics.
1.5 Scope of Study
The study focuses on the design process and construction of 1000W pure sine Wave Inverter using Microprocessor.
1.6 Limitations of the Study
During the course of this study, many things militated against its completion, some of which are:
- Time Constraint: The time frame given to accomplish this project was very short due to school academic calendar and it was carried out under pressure which made the researcher not to implement some necessary features.
- Establishment Policies: Establishment policies posed a serious limitation as most staffs are not ready to release information needed for this project work.
- Research material: availability of research material is a major setback to the scope of the study.
- Frequent power failure: This made the researcher append more money on fuel to ensure sustainable power.
- Financial Constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials.
1.7 Definition of Terms
Utility-Scale PV Plant: It is a installation that is ground-mounted. The plant owner sells energy directly to the electric utility. The interconnection occurs on medium or high voltage level
Utility-Scale Inverter: Inverter which is used in an Utility-scale installation
Maximum Input Voltage (VDCMAX): allowed maximum voltage at the inverter input
Minimum Input Voltage (VDCMIN): minimum input voltage for the inverter to energize the utility grid, independent of mode of operation
Start-Up Input Voltage (VDCSTART): input voltage at which the inverter starts energizing the utility grid rated input voltage (Vdc,r) input voltage specified by the manufacturer, to which other data sheet information refers
Maximum MPP Voltage (VMPPMAX): maximum voltage at which the inverter can deliver its rated power
Minimum MPP Voltage (VMPPMIN): minimum voltage at which the inverter can deliver its rated power
Maximum Input Current (IDCMAX): maximum current at which the inverter can operate. If the inverter has multiple MPP inputs, Idcmax is related to each single input
Maximum Grid Voltage (VACMAX): maximum voltage at which the inverter can energize the grid.
Rated Power (PAC,R): the active power the inverter can deliver in continuous operation
Rated Frequency (FR): utility grid frequency at which the inverter performs as specified
Maximum Frequency (FMAX): maximum frequency at which the inverter can energize the grid.
Minimum Frequency (FMIN): minimum frequency at which the inverter can energize the grid.
Night-Time Power Loss: power loss of the inverter, which is supplied from the public grid, when no solar generator power is present.
Inverter: electric energy converter that changes direct electric current to single-phase or poly-phase alternating current.
Inverter Back-feed Current: the maximum current that can be impressed onto the PV array and its wiring from the inverter, under normal or single fault conditions.
