31-10-2016, 09:28 AM
1462196806-Thesisdoc.pdf (Size: 1.85 MB / Downloads: 6)
Introduction
1.1Background
Solar power is a renewable source of energy, which has become increasingly popular in modern
times. It has obvious advantages over non‐renewable energy sources, such as coal, oil and
nuclear energy. It is non‐polluting, reliable and can produce energy anywhere that there is sun
shining, so its resources are not going to run out anytime soon. It even has advantages over other
renewable energy sources, including wind and water power. Solar power is generated using solar
panels, which do not require any major mechanical parts, such as wind turbines. These
mechanical parts can break down and cause maintenance issues and can also be quite noisy. Both
of these issues are virtually non‐existent with solar panels. Also, the solar cells, that connected
together make up the solar panel, can last up to several decades without replacement.
Conventionally, there are two ways in which electrical power is transmitted. Direct current (DC)
comes from a source of constant voltage and is suited to short-range or device level transmission.
Alternating current (AC) power consists of a sinusoidal voltage source in which a continuously
changing voltage (and current) can be used to employ magnetic components. Long distance
electrical transmission favors AC power, since the voltage can be boosted easily with the use of
transformers. By boosting the voltage, less current is needed to deliver a given amount of power
to a load, reducing the resistive loss through conductors. Dc power source like solar power,
battery and so on. Mostly in our home and different area we use ac power source, therefore we
need to have invert the dc source into ac form. For converting purpose we have to use inverter.
The adoption of AC power has created a trend where most devices adapt AC power from an
outlet into DC power for use by the device. However, AC power is not always available and the
need for mobility and simplicity has given batteries an advantage in portable power. Thus, for
portable AC power, inverters are needed. Inverters take a DC voltage from a battery or a solar
panel as input, and convert it into an AC voltage output.
There are three types of DC/AC inverters available on the market, which are classified by their
output type: square wave, modified-sine wave and pure sine wave. Off-the-shelf inverters are
generally either square wave or modified-sine wave. These types of inverters are less expensive
to make and the output, though delivering the same average voltage to a load, is not appropriate
Single phase solar power inverter and charge controller Design Page 2
to delicate electronic devices which rely on precise timing. Pure sine wave inverters offer more
accuracy and less unused harmonic energy delivered to a load, but they are more complex in
design and more expensive. Pure sine wave inverters will power devices with more accuracy, less
power loss, and less heat generation.
Pure sine wave inversion is accomplished 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, it can be
accomplished either before the AC stage by using a DC-DC boost converter, or after the AC
stage by using a boost transformer. The inverted signal itself is composed of a pulse-widthmodulated
(PWM) signal which encodes a sine wave. The duty cycle of the output is changed
such that the power transmitted is exactly that of a sine-wave. This output can be used as-is or,
alternatively, can be filtered easily into a pure sine wave. This report documents the design of a
true sine wave inverter, focusing on the inversion of a DC low-voltage source. The input voltage,
output voltage and frequency, and overall power handling, are dependent on the design of the
specific device or circuitry. A power inverter can be entirely electronic or may be a combination
of mechanical effects (such as a rotary apparatus) and electronic circuitry. Static inverters do not
use moving parts in the conversion process. A typical power inverter device or circuit will require
a relatively stable DC power source capable of supplying enough current for the intended overall
power handling of the inverter. Possible DC power sources include: rechargeable batteries, DC
power supplies operating off of the power company line, and solar cells. The inverter does not
produce any power, the power is provided by the DC source. The inverter translates the form of
the power from direct current to an alternating current waveform. The level of the needed input
voltage depends entirely on the design and purpose of the inverter. In many smaller consumer
and commercial inverters a 12V DC input is popular because of the wide availability of powerful
rechargeable 12V lead acid batteries which can be used as the DC power source.
A solar charge controller is a very important component of a solar panel power system and
should be used on systems over 15 Watts. A charge controller protects our rechargeable batteries
from overcharging as well as discharging at night. Charge controllers or voltage regulators
protect batteries from being overcharged, which can shorten their life as well as the life
expectancy of the equipment being powered. Electronic circuitry in the regulator measures
battery voltage, which raises as the battery state-of-charge (SOC) increases. At some voltage (which is different for different types of batteries at different temperatures), the regulator will
limit the charging of the battery.
1.2. Statement of Problem
Usually the power we use in different application area is in ac form but the power that generate
from solar panel is dc power which needs conversion. However the inverter that used convert ac
to dc power are not assemble in our country, they import from outside with high exchange
currency. In addition to the cost, the inverter is not available as we need and most of the inverters
that assembled from outside are high power rated inverter which requires much cost. But for our
country, especially for the rural area it is enough medium to get power inverter with moderate
cost. In addition to the inverters the charge controller that used to control the flow of current from
the solar panel to battery and from the battery to solar panel also import from outside by high cost
but we can make this charge controller by reducing its cost.
1.3. Objective
The objective of this project is to design single phase solar power inverter and charge controller.
1.3.1. Specific Objective
The specific objectives of this project are the following:
a. To design controlling signal for MOSFET gates
b. To develop circuit diagram of single phase inverter
c. To develop circuit diagram of charge controller
d. To simulate the designed circuit using multisim
e. To develop prototype of the system
1.5. Scope and limitation Of the Project
The scope of our project is designing the single phase pure sine inverter which has capability to
handle 250 watt for small loads especially for home appliances, in addition to the inverter we
design a charge controller system that controls the overcharging and over discharging of the
battery. We develop simulation system on multisim software and then constructing the prototype.
There are some limitations in both systems. The first limitation of this project work is the voltage
stability problem on the output of the inverter. The second limitation is on the charge controller
RYHUGLVFKDUJLQJFRQWUROOLQJSDUWLW¶VRSHUDWHVLIRQO\WKHEDWWHU\LQLWLDOO\YDOXHLVJUHDWHUWKDQ
volt.
1.6. Organizations of the Project
This project contains five chapters. The first chapter describes the introduction part of the project
with statement of the problem and its objectives. The second chapter describes about literatures
related to the single phase bridge pure sine wave inverter and charge controller. The third chapter
explains about system description and over all operation of the single phase solar power inverter
and charge controller. The fourth chapter describes the result and discussion of project prototype.
The fifth chapter deals about conclusion and recommendation.
Review of Literatures
2.1. Analysis of Single-Phase SPWM Inverter
This project deals with studying the basic theory of a Sinusoidal Pulse Width Modulated Inverter
(SPWM), its Simulink modeling, estimating various designing parameters and various
instabilities. The project is commenced by a basic understanding of the circuitry of the SPWM
Inverter, the components used in its design and the reason for choosing such components in this
circuitry. After this, it will be attempted to simulate a model circuit on any simulating software
e.g. MATLAB and analyze the output waveforms for various values of the elements used in the
circuit and hence study the system response and instabilities [1].
2.2. Microcontroller Based Photovoltaic MPPT Charge Controller
This paper describes a technique for extracting maximum power from a photovoltaic panel to
charge the battery. We make use of MPPT (Maximum Power Point Tracking) algorithms for
achieving maximum power point. The power from the solar panels is fed to charge controllers,
which is output to a battery where energy is stored. An inverter is present at the outlet of battery
to access stored power. A DC-to-DC converter is present inside the charge controller to match the
PV module voltage to battery voltage. A microcontroller is programmed to always output
maximum power. It performs this work by taking input voltage and current from solar panel,
output voltage and current from DC-to-DC converter, irradiance levels from light sensor and
temperature from temperature sensor. An additional feature here is to transmit the data from the
microcontroller to a remote location via RS485 interface so that this functionality aids in
remotely monitoring and logging the data [4].
2.3. Modeling and Simulation of Single Phase Inverter With PWM Using
Matlab/Simulink
This project is about modeling and simulation of single phase Pulse Width Modulation (PWM)
inverter. The model was implemented using MATLAB/Simulink with the SimPowerSystems
Block Set. The Insulated Gate Bipolar Transistor (IGBT) model was used as switching device.
This project is purposed to use MATLAB/Simulink software to design, analysis and evaluation of
power electronic converter and their controllers. Besides, it can show what differential in
simulation of this software with others. For modeling, Simulink provides a graphical user
interface (GUI) for building model as block diagram, using click-and-drag mouse operation.
Simulink includes a comprehensive block library of sink, sources, linear and nonlinear
components and connectors. it also can customize and create its own block. After a model is
defined, it can simulate, using a choice of integration methods, either from Simulink menus or by
HQWHULQJFRPPDQGLQ0$7/$%¶VFRPPDQGZLQGRZ,QDGGLWLRQWKHSDUDPHWHUFDQEHFKDQJHG
and immediately see what hDSSHQIRUµZKDWLI¶H[SORUDWLRQ,QLQYHUWHUIXOOEULGJHLQYHUWHUFLUFXLW
an AC output is synthesized from a DC input by closing and opening the switches in appropriate
sequence or switching scheme. For that, the Pulse Width Modulation technique is used in control
the closing and opening switches. The switching scheme applied is unipolar. The PWM signal is
used to control ON/OFF switching state of the IGBTs will functions in driver model that created
to control the switching scheme. Then, the simulation is made from the inverter model in
Simulink. The output voltage was obtained from Simulink and Pspice.
At the end of this project, the results from simulation were compared between Simulink and
Pspice [7].
2.4. Design of A Solar Charge Controller for A 100 WP Solar PV System
This paper presents a low cost Solar Charge Controller (SCC) using Atmel Corporation ATmega8
microcontroller to control and coordinate the functions properly. Details of design for the construction of
Solar Charge Controller using crystal oscillator, ceramic resistors, Light Emitting Diodes (LED) and
MOSFET are presented. The source code for the ATmega8 microcontroller is written in Arduino IDE to
obtain accurate and efficient automatic control action. Accordingly, battery can be disconnected from
solar cell when overcharging and reconnected while discharging. The loads can be disconnected according
to the over current and under flow current limit for both battery and PV. The proposed charge controller is
equipped with LEDs to display the battery charging /discharging status, charge level and short circuit
condition via microcontroller. The construction and operation of our proposed smart solar charge
controller indicates that it is cost effective and functions properly [11].
2.5. Low-Cost Off-Grid Solar Panel Inverter with Maximum Power-Point
Tracking
This project aims to design, build, and test a solar panel inverter. This inverter system could be
used as backup power during outages, battery charging, or for typical household applications.
The key features of the system are a true 60Hz, 120Vrms sinusoidal voltage output, a wide input
range, and maximum power-point tracking (MPPT), and a power output of up to 500W. The
overall goal is to design this system while minimizing component costs. Although systems with
similar features already exist, many are prohibitively expensive for those people who stand to
benefit the most. In addition, inverters in the lower price range typically lack the features
mentioned above
System Description and Overall Operation
3.1The main components of Solar power system
Solar electric systems are composed of four critical components; Solar Panels, Charge
Controllers, Batteries and Inverters. These components are necessary to have a Solar Electric
(PV) system that functions efficiently.
Solar Panels
Solar panels are the main components of the system. The solar panels charge the batteries.
Several solar panels wired together create what is called a solar array. The overall size of the
solar array will determine the amount of power or energy that will be produced from a solar
electric system. The location of a solar electric system plays a major role in the overall energy
output of a solar power system. Systems located closer to the equator will be the most efficient.
Charge Controllers
Although charge controllers come in many different sizes and types, they all perform a similar
function. Charge controllers prevent the solar panel or array from overcharging the battery(s).
Batteries
Batteries store energy for solar electric systems. Batteries play the role of storing the energy your
solar panels produce during the day. Batteries will provide you with the energy you need at night.
Components that are powered by solar electric systems receive their power from batteries rather
than directly from the output of a solar panel. A solar panel produces a high voltage that can
damage electronics if loads are powered directly.
Inverter
The last major component is the Inverter. The inverter converts the DC energy stored in your
batteries and turns it into the AC power you use in your home. Inverters are rated by wattage and
the quality of their output. You can use a 50 watt inverter that plugs into your car 12 volt outlet to
power a computer, or you could have a 4000 to 11,000 watt inverter system that powers your
Single phase solar power inverter and charge controller Design Page 10
home. These major components can be put together in many different ways. Minor components
like wire, disconnects, circuit breakers, and fuses are also needed for a complete system.
DC to AC inverting System
The inverter by itself has different components like the controlling components which contains
the pulse width modulation (reference sine wave and the carrier signal or triangular wave
generator), driver circuit, the filtering part and the step-up transformer. The H-Bridge circuit is
build from four high switching electronics devices like MOSFET, IGBT, SCR and BJT. These
switching devices make ON and OFF the incoming dc source and change into square wave. The
switch electronics device needs driver device which amplifies the controlling signal. The
controlling signal generates from the comparator by comparing the reference sine wave and
triangular wave and then generating fast square wave which is input for the driver. The output of the H-Bridge circuit is input to the filter to get pure sine wave, finally the output of the filter is
input to the transformer in order to step up the voltage as we want.
System component and Design analysis
3.2.1. Charger Controller Design and Analysis
This is one of our project works the design and application of the component is as follow.
This circuit regulates the charging of the battery in a solar system by monitoring battery voltage
and switching the solar or other power source off when the battery reaches a preset voltage. A
charge controller circuit can increase battery life by preventing over-charging which can cause
loss of electrolyte. The absence of a relay and its associated coil current makes this circuit
efficient for small systems as well as for systems using larger current components. In our project
work we make a simple zero drop or low drop solar charger controller system which can be
modified in many different ways. A zero drop solar charger is a device which ensures that the
voltage from the solar panel reaches the battery without undergoing any kind of drops either due
to resistance or semiconductor interference such as diodes etc in line.