SINGLE SOURCED DOUBLE STAGE

MULTILEVEL INVERTER FOR

GRID-CONNECTED SOLAR PV
SYSTEM

A PROJECT REPORT

Submitted by

DEEPAK S 621721105006
DOSITH D 621721105009
LOGESHWARAN M 621721105014

in partial fulfillment for the award of the degree

of

BACHELOR OF ENGINEERING

in

ELECTRICAL AND ELECTRONICS ENGINEERING

MUTHAYAMAL COLLEGE OF ENGINEERING, RASIPURAM

ANNA UNIVERSITY :: CHENNAI 600 025

MAY 2025
 ANNA UNIVERSITY :: CHENNAI 600 025
BONAFIDE CERTIFICATE

Certified that this project report “SINGLE SOURCED DOUBLE STAGE

MULTILEVEL INVERTER FOR GRID-CONNECTED SOLAR PV

SYSTEM” is the bonafide work of “DEEPAK S, DOSITH D,

LOGESHWARAN M” who carried out the project work under my supervision.

SIGNATURE SIGNATURE
Dr.C.NAGARAJAN,M.E.,Ph.D., Mr.G.NEELAKRISHNAN,M.E.,Ph.D.,
HEAD OF THE DEPARTMENT SUPERVISOR
Professor Assistant Professor
Department of EEE, Department of EEE,
Muthayammal College of Muthayammal College of
Engineering, Engineering,
Rasipuram –637408 Rasipuram –637408

Submitted for the project viva-voice examination held on …………………

INTERNAL EXAMINER EXTERNAL EXAMINER

 DECLARATION

We affirm that the project work titled “SINGLE SOURCED DOUBLE

STAGE MULTILEVEL INVERTER FOR GRID-CONNECTED SOLAR
PV SYSTEM”, being submitted in partial fulfillment for the award of the
Bachelor of Engineering, is our original work. It has not formed part of any
other project work submitted for the award of any degree or diploma, either in
this or any other university.

………………..…………………………..

………………..…………………………..

………………..…………………………..

Signature of the candidates

DEEPAK S 621721105006
DOSITH D 621721105009
LOGESHWARAN M 621721105014

I certify that the declaration made above by the candidates is true.

Signature of the Guide,

Mr.D.KALIDASS, M.E.Ph.D.,
ASSISTANT PROFESSOR /EEE
 ACKNOWLEDGEMENT

We express our gratitude to our management for providing this golden

opportunity to prove ourselves and being major source of inspiration to carry out
this work.

We wish to divulge our heartfelt thanks to our honorable Chairman

Shri.R.KANDASAMY, and Secretary, Dr.K.GUNESKARAN,M.E.,Ph.D.,FIE

Muthayammal College of Engineering, Rasipuram,for providing all the facilities to

develop our Project successfully.

Our personal gratitude goes to Dr.P.VENUGOPAL,M.E.,Ph.D.,Principal,

Muthayammal College of Engineering, for having given the opportunity to bring
out this project successfully.

Perhaps, Our deepest thanks to Dr.C.NAGARAJAN,M.Tech.,Ph.D., Head

of the Department, Department of Electronics and Communication Engineering,
Muthayammal College of Engineering, for her stimulating comments, which
helped us in bringing things in our way.

Our special thanks to Mr.G.NEELAKRISHNAN,M.E.,Ph.D., project

coordinator who has motivated us in the completion of this project.

Our special thanks to Mr.D.KALIDASS ,M.E.,Ph.D., our project guide,

who has constantly motivated and inspired us in rending the completion of the
project.

We also express our gratefulness to our parents, our faculty members and
friends for affectionate blessing and loving cooperation at all stages of this
academic venture.
 TABLE OF CONTENT
CHAPTER NO TITLE PAGE NO
ABSTRACT 1
1 INTRODUCTION 2
2 LITERATURE REVIEW 4
2.1 Grid Integration of a Reduced Switching
Loss Single-Source Boost Multilevel Inverter 4
with Independent Control of Power Transfer
and DC-Link Voltage
2.2 Fault Tolerant Backstepping Control for
Double-Stage Grid-Connected Photovoltaic 4
Systems Using Cascaded H-Bridge
Multilevel Inverters
2.3 Next Generation of Smart Solar Modular 5
Multilevel Converters for Photovoltaic Farms
3 EXISTING SYSTEM 6
3.1 Block Diagram of Existing System. 6
3.2 Solar Energy Generation and DC-Link 6
3.3 Inverter Topology and AC Grid Integration 7
3.4 Battery Management 7
3.5 Limitations of the Existing System 7
4 PROPOSED SYSTEM 8
4.1 Block Diagram of Proposed System. 8
4.2 System Description 9
4.3 Key Features 10
4.4 Components Required. 10
5 HARDWARE DESCRIPTION 11
5.1. Photovolatic Array 11
5.1.1. Working 11
5.1.2. Features of Photovoltaic (PV) 12
5.1.3. Applications of a Photovoltaic (PV) 13
5.1.4. Benefits of a Photovoltaic (PV) 14
5.2. MPPT 15
5.3. Battery 16
5.4. Inverter 19
5.5. Controller 20
5.6. Memory Organization 21
5.7. Key Peripherals and Modules 22
5.8. Special Function Registers (SFRs) 23
5.9. Power Management Features 23
5.10. Programming and Tools 23
5.11. PWM 23
6 SOFTWARE DESCRPITION 31
6.1 Introduction 31

6.2 Flow Diagram of software logic 32

6.3. LOOP( ) FUNCTION 33

6.4. Program 33
7 CONCLUSION 37
8 FUTURE SCOPE 39
REFERENCES 41
 ABSTRACT
The growing emphasis on renewable energy has led to an increased
adoption of solar photovoltaic (PV) systems for grid-connected applications.
Efficient power conversion and high-quality grid integration are critical
challenges in this domain. This project proposes a Single-Sourced Double Stage
Multilevel Inverter (SSDSMI) for grid-connected solar PV systems, designed to
enhance energy conversion efficiency, reduce harmonic distortion, and ensure
reliable operation.
The system consists of two stages: a DC-DC boost converter and a
multilevel inverter. The boost converter elevates the variable DC output from the
PV panels to a stable level, while the multilevel inverter converts it into an AC
output suitable for grid synchronization. Unlike traditional multilevel inverters
that require multiple DC sources, the proposed design uses a single DC source,
simplifying the architecture and reducing cost.
The multilevel inverter topology enables multiple output voltage levels,
resulting in reduced Total Harmonic Distortion (THD) and improved power
quality. Advanced modulation strategies and Maximum Power Point Tracking
(MPPT) algorithms are incorporated to optimize energy extraction and system
performance. Simulation results confirm the system's ability to maintain high
efficiency and meet grid standards.
This SSDSMI approach offers a reliable and scalable solution for efficient
solar energy conversion and grid integration, making it ideal for residential,
commercial, and small-scale utility applications.

1
 CHAPTER 1
INTRODUCTION
The demand for renewable energy sources has increased significantly due
to the rapid depletion of fossil fuels, rising energy costs, and growing
environmental concerns. Among various renewable options, solar photovoltaic
(PV) systems have gained prominence due to their sustainability, ease of
deployment, and scalability. However, integrating solar energy into the power
grid presents technical challenges, particularly in terms of efficient power
conversion, grid compatibility, and power quality. The inverter plays a vital role
in this process, converting the DC output of solar panels into AC power that can
be supplied to the grid. To address these challenges, this project proposes a
Single-Sourced Double Stage Multilevel Inverter (SSDSMI) specifically
designed for grid-connected solar PV systems.
Conventional inverter topologies such as single-stage or two-level
inverters, while simple, suffer from significant limitations including high Total
Harmonic Distortion (THD), poor power quality, and limited voltage control.
Multilevel inverters (MLIs), by contrast, are known for producing near-sinusoidal
waveforms, which reduces the stress on electrical components and improves
system efficiency. However, traditional MLI configurations often require
multiple isolated DC sources, making them complex and costly to implement in
solar PV applications where a single power source (PV panel string) is common.
The proposed SSDSMI system overcomes this drawback by using a single
DC input source, derived from the solar PV array, and employing a two-stage
conversion process. The first stage is a DC-DC boost converter, which raises the
voltage level to match the input requirement of the multilevel inverter and
facilitates the implementation of Maximum Power Point Tracking (MPPT) for
optimized energy harvesting. The second stage is a multilevel inverter, which
converts the boosted DC voltage into an AC waveform with multiple voltage
levels. This approach not only enhances power quality but also reduces the
filtering requirements due to lower harmonic content.
Advanced switching and modulation techniques such as Sinusoidal Pulse
Width Modulation (SPWM) are used to control the inverter, enabling precise
control of output voltage and frequency. The system is designed to maintain
synchronization with the utility grid, ensuring stable and reliable operation under
various load conditions. Compliance with grid standards such as IEEE 519

2
ensures that the output remains within acceptable harmonic limits, promoting safe
and efficient grid integration.
By reducing the number of required DC sources and maintaining high
conversion efficiency, the SSDSMI architecture presents a cost-effective,
compact, and scalable solution for grid-connected solar PV applications. It is
particularly suitable for residential and commercial rooftop installations, where
simplicity and efficiency are crucial. The proposed design is validated through
simulations using tools such as MATLAB/Simulink, where system performance
is analyzed under different environmental and load conditions.
This multilevel output significantly improves power quality by reducing
Total Harmonic Distortion (THD) and minimizing the need for bulky output
filters. Additionally, it enhances system efficiency due to lower switching losses
and reduced electromagnetic interference. The inverter is controlled using
advanced techniques, such as PWM or multilevel modulation schemes, while
the DC-DC stage often incorporates Maximum Power Point Tracking (MPPT)
algorithms to ensure optimal energy extraction from the PV source.
The first stage, the DC-DC converter, boosts this voltage to a higher,
regulated DC level suitable for inversion. In the second stage, the multilevel
inverter (such as a Cascaded H-Bridge, Neutral Point Clamped, or Flying
Capacitor topology) converts the high DC voltage into an AC output with
multiple voltage levels, resulting in a waveform that closely approximates a sine
wave.
In conclusion, the Single-Sourced Double Stage Multilevel Inverter
addresses key limitations of existing inverter systems and provides a practical
solution for improving solar PV integration with the electrical grid. The
architecture supports enhanced energy efficiency, better power quality, and
reduced system complexity, paving the way for more reliable and sustainable
solar power solutions.

3
 CHAPTER 2
LITERATURE SURVEY
2.1 Title: Grid Integration of a Reduced Switching Loss Single-Source Boost
Multilevel Inverter with Independent Control of Power Transfer and DC-
Link Voltage
Authors: A. Priyadarshi, P. K. Kar, and S. B. Karanki
Year: 2021
This paper presents a novel grid-tied single-source multilevel inverter
(MLI) designed to reduce switching losses while providing independent control
over power transfer and DC-link voltage. The proposed topology incorporates a
diode-capacitor ladder network to generate multiple inherently balanced voltage
levels, effectively addressing the common challenge in MLIs that require multiple
separate DC sources. A key feature of this design is the achievement of zero-
voltage-switching (ZVS) for the primary high-frequency switch, which
significantly mitigates switching losses. The high-frequency operation also
contributes to a reduction in component size, leading to a more compact and cost-
effective converter.
The authors developed an experimental setup to implement closed-loop
control of the hardware prototype and evaluated its performance under various
real-time conditions. The experimental results demonstrated the converter's
ability to maintain stable grid integration with reduced total harmonic distortion
(THD) and improved efficiency. This study highlights the potential of the
proposed MLI topology to enhance the performance of grid-connected solar PV
systems by offering a simplified structure with lower switching losses and
effective power management capabilities.
2.2 Title: Fault Tolerant Backstepping Control for Double-Stage Grid-
Connected Photovoltaic Systems Using Cascaded H-Bridge Multilevel
Inverters
Authors: [Authors not specified in the provided information]
Year: 2021
This research introduces a fault-tolerant control strategy for double-stage
grid-connected photovoltaic (PV) systems utilizing cascaded H-bridge multilevel
inverters (CHB-MLIs). The proposed backstepping control approach aims to

4
enhance the reliability and performance of PV systems by effectively managing
faults that may occur within the inverter stages. The study emphasizes the
importance of maintaining system stability and power quality, even in the
presence of component failures, which is critical for the seamless integration of
renewable energy sources into the power grid.
Through detailed simulations and analytical evaluations, the authors
demonstrate that the backstepping control method provides robust fault detection
and compensation capabilities. The control strategy ensures continuous operation
and minimizes the impact of faults on the overall system performance.
This work contributes to the advancement of fault-tolerant mechanisms in
multilevel inverters, offering a viable solution for improving the dependability of
grid-connected solar PV applications.
2.3 Title: Next Generation of Smart Solar Modular Multilevel Converters
for Photovoltaic Farms
Author: Saad Mekhilef
Year: 2023
In this distinguished lecture, Professor Saad Mekhilef discusses the
evolution and future prospects of modular multilevel converters (MMCs) in the
context of large-scale photovoltaic (PV) farms. The presentation highlights the
unique features of MMCs, such as high modularity, scalability, flexibility, and
efficiency, which make them promising candidates to replace traditional
centralized solar inverters. The lecture emphasizes the potential of MMCs to
enhance internal power flow, fault tolerance, and operational flexibility, thereby
contributing to the development of resilient and efficient grid services.
Professor Mekhilef elaborates on how these advanced converter
technologies can be integrated into next-generation solar inverters to deliver
improved performance and reliability. The discussion includes insights into the
design considerations, control strategies, and practical implementation aspects of
MMCs in photovoltaic applications. This lecture serves as a valuable resource for
researchers and practitioners aiming to advance the integration of smart converter
technologies in renewable energy systems.

5
 CHAPTER 3
EXISTING SYSTEM
3.1 BLOCK DIAGRAM OF EXISTING SYSTEM

In traditional solar PV systems, energy conversion and grid integration are

achieved through a sequence of power electronic stages. The typical architecture
consists of solar photovoltaic panels, battery energy storage, MPPT controllers,
DC-DC boost converters, and DC-AC inverters for grid synchronization. These
systems are designed to supply power directly to the load, store excess energy in
batteries, or inject the surplus power into the utility grid. While this setup has
served as a reliable foundation for solar energy systems, it faces several
limitations, particularly in terms of efficiency, modularity, and waveform quality.
3.2 Solar Energy Generation and DC-Link
The existing system begins with the solar PV array, which generates direct
current (DC) power depending on solar irradiance and temperature. The DC
output from the PV array is variable and nonlinear in nature, requiring regulation.
This is achieved using a DC-DC boost converter combined with MPPT
(Maximum Power Point Tracking) algorithms such as Perturb and Observe
(P&O) or Incremental Conductance (INC). These ensure the PV panel operates
at its maximum power point, thus maximizing energy harvesting.
The boost converter increases the voltage level to meet the requirements of
the inverter input. This regulated high-voltage DC becomes the main input to the
inverter stage. Some systems also integrate charge controllers to divert part of
this energy to battery storage systems, which are particularly critical in off-grid
or hybrid applications.

6
3.3 Inverter Topology and AC Grid Integration
The next stage is the DC-AC conversion, typically accomplished using
two-level Voltage Source Inverters (VSIs) or three-level Neutral Point Clamped
(NPC) inverters. These inverters switch the high-voltage DC into pulse-width
modulated (PWM) waveforms, which approximate sinusoidal AC. However,
conventional two-level inverters are known to produce high Total Harmonic
Distortion (THD), and they require complex low-pass filters to smoothen the
waveform before supplying it to the grid.
In grid-connected setups, synchronization with the utility grid involves
Phase-Locked Loops (PLLs) and anti-islanding protection mechanisms. While
these ensure stable grid operation, the system's reliance on multiple conversion
stages leads to increased switching losses, control complexity, and reduced
efficiency.
3.4 Battery Management
In hybrid systems, battery energy storage plays an essential role in
improving system resilience. During periods of high solar generation and low
load demand, excess energy is stored in the battery bank. Conversely, when solar
generation is low (e.g., during cloudy weather or nighttime), the stored energy is
released to meet the load demand or support the grid.
Battery systems are typically managed using bidirectional DC-DC
converters, which regulate charging and discharging currents, ensuring battery
safety, longevity, and efficiency. Battery Management Systems (BMS) monitor
temperature, voltage, current, and State of Charge (SoC), adding another layer of
control complexity to the system.
3.5 Limitations of the Existing System
While the existing system is functional and widely adopted, it suffers from
multiple inherent drawbacks:
High Component Count: Use of separate MPPT controllers, converters, inverters,
and battery interfaces increases the hardware footprint and cost.
Low Efficiency: Multiple power conversion stages result in significant
cumulative energy loss.

7
 CHAPTER 4
PROPOSED SYSTEM
4.1 BLOCK DIAGRAM OF PROPOSED SYSTEM

The proposed system is designed to offer a reliable, efficient, and compact

solution for integrating solar power into the electrical grid using a double-stage
multilevel inverter architecture, powered solely by a single solar source. It aims
to simplify the overall structure of conventional solar systems while improving
performance in terms of power quality, stability, and energy management.
In this system, solar energy is the primary source, and it forms the
backbone of the complete setup. The entire design is organized into stages that
handle energy extraction, storage, conversion, and delivery. These stages are
managed in a synchronized manner to ensure stable energy flow and
compatibility with the grid and connected loads. The system is scalable,
environmentally friendly, and ideal for both residential and commercial use
where direct grid connection is required.
This setup significantly reduces the complexity of using multiple DC
sources, enhances efficiency by utilizing multilevel inverter architecture, and
ensures better quality AC output suitable for direct grid integration.

The proposed system is a power conversion architecture designed to

integrate solar photovoltaic (PV) energy into the electrical grid with high
efficiency and superior power quality. It consists of a single DC source, a

8
double-stage power conversion, and a multilevel inverter for AC output. This
setup is aimed at improving energy extraction, minimizing power loss, and
ensuring grid compatibility.

4.2 System Description

The proposed system begins with a solar photovoltaic (PV) module, which serves
as the single energy input to the system. The energy produced by this module is
processed and conditioned through different stages of the setup, allowing smooth
flow and usage of the solar power. The core strength of this system lies in its two-
stage energy conversion structure, which maintains system simplicity without
compromising output quality.
A battery backup system is integrated to support the solar module. This
addition helps in maintaining continuous power availability during periods when
sunlight is insufficient or during fluctuations in grid supply. The battery not only
provides backup but also stores excess energy generated during peak solar
conditions, making the system efficient in energy usage and minimizing wastage.
The inverter section is designed to convert the DC energy from the solar
and battery setup into AC energy. What makes this inverter unique is its
multilevel structure, which enhances the quality of the AC signal by providing
multiple stepped voltage levels, thereby reducing distortion and improving
compatibility with sensitive grid equipment. A controller unit is included to
manage various operations in the system. It ensures coordination among solar
energy input, battery operations, inverter control, and grid communication. It also
oversees timing, switching, and proper functioning of the system under varying
load and supply conditions. The controller plays a central role in supervising
system health, energy flow, and safety.
waveforms, which reduces the stress on electrical components and
improves system efficiency. However, traditional MLI configurations often
require multiple isolated DC sources, making them complex and costly to
implement in solar PV applications where a single power source (PV panel string)
is common.
The grid interface enables the system to directly feed AC power into the
utility grid. It ensures that the output of the inverter matches the grid’s
requirements in terms of voltage, frequency, and phase. This connection allows

9
the generated solar energy to be either used locally or exported to the grid when
excess power is available.
Additionally, the system can supply power to a connected load
independently. This dual capability (grid and load) increases the flexibility of the
system, allowing it to operate efficiently in different environments and
conditions. The system can support grid-connected homes, small businesses, or
standalone installations in areas with limited power access.
4.3 Key Features
Single Power Source: Entire system driven by a single solar PV module.
Double Stage Conversion: Clean separation of energy conditioning and
conversion for better reliability.
Multilevel Inverter: Produces high-quality AC output suitable for grid
connection.
Battery Integration: Provides backup and supports peak demands.
Grid & Load Compatibility: Can feed power to the grid or supply it to standalone
loads.
Smart Controller: Oversees system operation and maintains synchronization.
Compact & Scalable: Easily adaptable to various power ranges and applications.
4.4 COMPONENTS REQUIRED
● Solar
● MPPT
● Battery
● Controller
● Current Measurement
● Switching Devices
● H Bridge
● Grid

10
 CHAPTER 5
HARDWARE DESCRIPTION
5.1. PHOTOVOLTAIC (PV) ARRAY
A Photovoltaic (PV) Array is a collection of interconnected solar panels designed
to capture sunlight and convert it into electrical energy. The term "photovoltaic"
comes from the process by which these panels generate electricity. When exposed
to sunlight, photovoltaic cells within each solar panel produce an electric current
through the photovoltaic effect. This effect involves the absorption of photons
from sunlight, causing the release of electrons and the generation of an electric
voltage. PV Arrays are a key component in solar energy systems, providing a
sustainable and renewable source of power.
5.1.1. Working:
The working principle of a PV Array is rooted in the behavior of semiconductors,
usually made of silicon, within the photovoltaic cells. When sunlight strikes these
cells, it excites electrons, creating an electric current. The interconnected cells in
a solar panel generate direct current (DC) electricity. In grid-tied systems,
inverters convert the DC electricity into alternating current (AC), which is
suitable for powering homes, businesses, or feeding into the electrical grid. The
overall efficiency of a PV Array depends on factors such as sunlight intensity,
angle of incidence, and the quality of the photovoltaic cells.
PV Arrays consist of multiple solar panels arranged in a specific configuration to
maximize sunlight absorption and energy production. They can be installed on
rooftops, ground-mounted structures, or integrated into building materials. The
modular nature of PV Arrays allows for scalability, making it possible to
customize installations based on energy requirements.

11
 The working process of a PV Array exemplifies the direct conversion of solar
energy into electricity, offering a clean and sustainable power generation
solution. Advances in PV technology continue to improve efficiency, durability,
and cost-effectiveness, further enhancing the appeal and widespread adoption of
photovoltaic systems worldwide.
5.1.2. Features of Photovoltaic (PV) Arrays:
Modularity: PV Arrays are modular systems, comprising interconnected solar
panels. This modularity allows for flexibility and scalability in design, facilitating
adjustments based on energy needs and available space.
Renewable Energy Source: One of the primary features of PV Arrays is their
reliance on sunlight as a renewable energy source. This makes them
environmentally friendly, contributing to a reduction in dependence on non-
renewable fossil fuels and decreasing greenhouse gas emissions.
Sustainability: PV Arrays promote sustainable energy practices by converting
sunlight into electricity without depleting finite resources. Their use aligns with
the principles of sustainable development and minimizes the environmental
impact associated with conventional energy generation.
Versatility in Installation: PV Arrays can be installed in various locations,
including rooftops, ground-mounted structures, and integrated into building
materials. This adaptability makes them suitable for a wide range of applications
in both urban and rural settings.
Low Operating Costs: Once installed, PV Arrays have relatively low operating
and maintenance costs. They require minimal upkeep, with routine cleaning being
the primary maintenance task. This cost-effectiveness contributes to their
attractiveness as a long-term energy solution.
Silent Operation: PV Arrays operate silently, without generating noise during
the electricity generation process. This characteristic makes them particularly
suitable for residential and urban environments where noise pollution is a
concern.
Reduced Transmission Losses: By generating electricity at or near the point of
use, PV Arrays help reduce transmission losses associated with centralized power
generation. This decentralized approach enhances the overall efficiency of the
electricity supply chain.

12
Off-Grid Capability: PV Arrays can be utilized in off-grid systems, providing a
reliable source of electricity in remote or isolated areas where conventional power
infrastructure may be unavailable or impractical.
Long Lifespan: High-quality PV panels exhibit a long lifespan, typically ranging
from 25 to 30 years or more. This longevity contributes to the overall economic
viability and sustainability of PV Array installations.
Technology Advancements: Ongoing research and technological advancements
continue to improve the efficiency and cost-effectiveness of PV Arrays.
Innovations in materials and design enhance their performance, making solar
energy an increasingly competitive and viable energy solution.
5.1.3. Applications of a Photovoltaic (PV) Array:
Residential Solar Power: PV Arrays are commonly used on residential rooftops
to generate clean and renewable energy for homes, reducing reliance on grid
power.
Commercial and Industrial Buildings: Businesses and industrial facilities
utilize PV Arrays to offset energy costs and demonstrate corporate environmental
responsibility.
Utility-Scale Solar Farms: Large-scale PV Arrays are deployed in solar farms
to contribute significant amounts of electricity to the grid, supporting utility-scale
power generation.
Off-Grid Power Systems: In remote areas or locations without access to a
reliable grid, PV Arrays can be part of off-grid systems, providing a self-
sufficient power source.
Solar Street Lighting: PV Arrays are employed in solar-powered street lighting
systems, harnessing sunlight during the day to illuminate streets and public spaces
at night.
Agricultural Applications: PV Arrays are integrated into agricultural
infrastructure to power irrigation systems, pumps, and other equipment,
promoting sustainable farming practices.
Educational and Research Facilities: PV Arrays are often used in educational
institutions and research facilities to study solar energy and showcase sustainable
practices.

13
Mobile and Marine Applications: Portable PV Arrays are used to charge
batteries for recreational vehicles, boats, and mobile electronic devices, offering
clean energy on the go.
5.1.4. Benefits of a Photovoltaic (PV) Array:
Renewable Energy Source: PV Arrays harness sunlight, a virtually limitless and
renewable energy source, reducing dependence on finite fossil fuels and
contributing to a more sustainable energy mix.
Environmental Impact: Utilizing solar energy through PV Arrays produces
electricity with minimal environmental impact, significantly lowering
greenhouse gas emissions and mitigating climate change.
Energy Independence: PV Arrays provide an independent and decentralized
source of power, reducing reliance on centralized power grids and enhancing
energy security for homes, businesses, and communities.
Reduced Electricity Bills: Homes and businesses with PV Arrays can generate
their own electricity, leading to reduced reliance on grid power and lower
electricity bills over the long term.
Grid Support: Grid-tied PV Arrays can feed excess electricity back into the grid,
supporting overall grid stability and reducing the strain on traditional power
infrastructure during peak demand periods.
Low Operating Costs: Once installed, PV Arrays have minimal operating costs
as they require little maintenance and have no fuel or ongoing fuel costs
associated with their operation.
Sustainable Development: Integrating PV Arrays aligns with sustainable
development goals by promoting clean energy practices, reducing air pollution,
and minimizing the environmental impact of electricity generation.
Job Creation: The growing solar industry, including the production, installation,
and maintenance of PV Arrays, contributes to job creation and economic growth
in various regions.
Technological Advancements: Ongoing advancements in PV technology
continually improve efficiency, making solar energy more accessible and cost-
effective, further enhancing the benefits of PV Arrays.

14
Community Resilience: PV Arrays contribute to community resilience by
providing a reliable and continuous source of electricity, especially in areas prone
to power outages or with limited access to traditional power infrastructure.
5.2. MPPT
MPPT stands for Maximum Power Point Tracking, a technique to
regulate the charge of your battery bank. The function of an MPPT charge
controller is analogous to the transmission in a car. When the transmission is in
the wrong gear, the wheels do not receive maximum power. That’s because the
engine is running either slower or faster than its ideal speed range. The purpose
of the transmission is to couple the engine to the wheels, in a way that lets the
engine run in a favorable speed range in spite of varying acceleration and terrain.
Let’s compare a PV module to a car engine. Its voltage is analogous to
engine speed. Its ideal voltage is that at which it can put out maximum power.
This is called its maximum power point. (It’s also called peak power voltage,
abbreviated Vpp). Vpp varies with sunlight intensity and with solar cell
temperature. The voltage of the battery is analogous to the speed of the car’s
wheels. It varies with battery state of charge, and with the loads on the system
(any appliances and lights that may be on). For a 12V system, it varies from about
11 to 14.5V.
Maximum Power Point Tracking (MPPT) is a critical technology used
in solar energy systems to optimize the efficiency of photovoltaic (PV) panels.
Its primary function is to ensure that the solar panels operate at their maximum
power output under varying environmental conditions, such as changes in
sunlight intensity and temperature.
MPPT works by continuously adjusting the operating point of the solar
panels to maintain maximum power output. This is achieved by tracking the
maximum power point (MPP) of the solar panel's voltage-current (V-I) curve,
which represents the combination of voltage and current that yields the highest
power output.
The process involves varying the electrical load applied to the solar panels
and monitoring the resulting power output. By iteratively adjusting the load, the
MPPT controller can determine the optimal operating point where the panels
produce the most power.

15
 MPPT controllers utilize different algorithms to track the MPP efficiently.
Perturb and Observe (P&O) and Incremental Conductance are two common
algorithms used for this purpose. P&O adjusts the operating point by perturbing
the voltage or current and observing the change in power output, while
Incremental Conductance uses the derivative of the power-voltage (P-V) curve to
determine the direction of adjustment.
In operation, as environmental conditions change, such as cloud cover or
shading, the MPPT controller continuously adjusts the electrical load to ensure
that the solar panels operate at their maximum power point. This optimization
maximizes the energy harvested from the solar panels, resulting in increased
system efficiency and higher energy yield.
Overall, MPPT technology plays a crucial role in enhancing the
performance of solar energy systems by dynamically optimizing the power output
of photovoltaic panels, thereby improving energy efficiency and maximizing the
utilization of renewable solar energy resources.
5.3. BATTERY
The lead-acid battery is one of the oldest types of rechargeable batteries,
invented in 1859 by French physicist Gaston Planté. It remains widely used due
to its low cost, high surge current capability, and reliability in various
applications. Unlike modern lithium-ion batteries, lead-acid batteries have a
lower energy density but are still preferred for applications requiring high power
output, such as automobiles, backup power systems, and industrial machinery.
These batteries store energy in the potential difference between metallic lead
(negative electrode) and lead dioxide (positive electrode), with sulfuric acid
acting as the electrolyte.
Despite their low cost and high power delivery, lead-acid batteries come
with certain drawbacks, including a shorter cycle lifespan (typically under 500
deep cycles) and longer charging times. Additionally, lead-acid batteries are
prone to sulfation, a process where lead sulfate crystals build up on the plates
during discharge, reducing battery efficiency and lifespan. However, proper
charging techniques and regular maintenance can help prolong their usability.
Sealed versions, such as Absorbed Glass Mat (AGM) and Gel batteries, reduce
maintenance needs by eliminating the need for electrolyte refilling.
A typical 6V lead-acid battery with a 4.7Ah capacity is commonly used in
backup power supplies, electric vehicles, and portable lighting systems. The

16
battery specifications include a nominal voltage of 6V, a capacity of 4000mAh
(or 4Ah, depending on the model), and a black, rectangular casing made of
durable materials. It generally weighs 0.66 kg and has dimensions of 108 mm
(width) × 71 mm (depth) × 48 mm (height). Most lead-acid batteries come with
a two-year warranty, depending on the brand and usage conditions.
When two 6V lead-acid batteries are connected in series, the voltage
doubles while the capacity remains the same. This means the total voltage
becomes 12V, but the capacity remains at 4.7Ah. This configuration is ideal for
applications requiring higher voltage, such as solar power storage, UPS systems,
and electric mobility solutions. However, when connecting batteries in series, it
is crucial to ensure that both batteries have a similar charge level to prevent
imbalance and premature degradation.
The charging process for a 12V lead-acid system typically follows a
three-stage method: bulk charging, where the battery receives a high current;
absorption charging, where the voltage remains constant while the current
gradually decreases; and float charging, where the battery is maintained at a full
charge with a minimal current to prevent overcharging. Using a regulated charger
designed for lead-acid batteries is essential to prevent overcharging and sulfation,
which can significantly shorten the battery's lifespan.
The lifespan of a lead-acid battery depends on temperature, discharge
depth, and maintenance. Under optimal conditions (25°C), a well-maintained
lead-acid battery can last up to 7 years. However, for every 8°C rise in
temperature, the lifespan reduces by half. For example, if regularly used at 33°C,
a battery’s lifespan may drop from 7 years to just 3.5 years. Additionally,
discharging the battery below 45% capacity frequently can further shorten its life.
Lead-acid 6V batteries are widely used in lighting systems for
construction sites, electric vehicles such as golf carts, and RVs and trailer homes.
They are also a preferred choice for backup power in UPS systems, providing
stored energy during power outages. Their ability to sustain high energy outputs
makes them ideal for camping light sources, medical equipment, and emergency
power applications.
These batteries are available in spring-top and screw-top terminal
configurations, designed for different applications. Spring-top terminals are used
in portable devices like lanterns, while screw-top terminals are preferred in
electric vehicles and industrial machines that require firm electrical connections.

17
Popular brands producing 6V lead-acid batteries include Fusion, Stryka, Mallory,
Panasonic, Powersonic, and MI Battery Experts, offering different sizes for
various needs.
Proper maintenance is crucial to extending the battery lifespan. Flooded
lead-acid batteries require regular distilled water top-ups, whereas sealed lead-
acid (SLA) and AGM batteries are maintenance-free but still require proper
ventilation to prevent overheating. A Battery Management System (BMS) or
voltage regulators help in monitoring charge levels and preventing deep
discharges, thereby improving battery efficiency and longevity.
In conclusion, lead-acid batteries remain a reliable and cost-effective
energy storage solution for various applications, despite competition from newer
lithium-based technologies. Their ability to deliver high surge currents, sustain
deep discharges, and provide stable voltage makes them indispensable in
automotive, industrial, and backup power systems. With proper usage,
temperature control, and maintenance, they can provide years of reliable service,
ensuring uninterrupted power in critical applications.

Power supply RECHARGEABLE BATTERIES

Batteries included YES
Battery (type) OTHER
Battery (capacity mAh) 4000
Battery technology LEAD ACID
Materials OTHER
Colour Black
Product width (mm) 108
Product depth (mm) 71
Product height (mm) 48
Net weight kg 0,66

18
5.4. INVERTER
An inverter is one of the most frequently used electronic
circuits in most of the applications. It’s a circuit that converts fixed DC supply to
alternating AC supply to feed AC loads. Widely used in commercial, aviation,
residential and industrial applications. It could be regarded as the backbone for
most of the applications. It is frequently used as an interfacing unit between DC
supply and load. In many cases, it acts as an interfacing unit between AC supply
and load also. For example, in the speed control of induction motor, the supply is
AC, but AC supply is converted to DC by a rectifier circuit and again DC is
converted to AC by inverter and fed to the induction motor. It helps to improve
power quality by overcoming the harmonic content.
The inverter is an electronic circuit that converts fixed DC
supply to variable AC supply. The inverter is used to run the AC loads through a
battery or control AC loads via AC-DC conversion. Inverters are also available
as single-phase inverter and three-phase inverters. Of course, in three-phase
inverter more switching operations are required. Let see the circuit diagram and
working principle of single-phase and three-phase inverters.
A single-phase inverter or also called as half-bridge
inverters, converters DC supply to single-phase AC supply. For this purpose, two
switching devices are used to convert DC to AC. Diodes, capacitors help the
circuit to operate smoothly.
As the name implies, half-bridge inverter, the output varies
from +Vs/2 to -Vs/2. As shown in the circuit, two switching devices are
connected in one common branch or also called a leg. This switching may be
SCR, MOSFET, or IGBT. Generally, we use MOSFET more commonly for high-
19
frequency applications. One more advantage with MOSFET is it has low
switching losses but high conduction losses.
As shown in the circuit, we have two switching devices S1 and S2. To obtain
one cycle of Alternating voltage, each device is triggered at one time. The other
being off at the same moment. For example, to obtain the positive cycle of
Alternating supply, device S1 is turned on, while S2 is kept off. Similarly to
obtain a negative cycle of alternating supply, device S2 is turned on while S1 is
kept off. The output wave is shown as below.
Firstly, the devices need to be numbered for the correct operation. Note
that, we have six devices, two devices on one leg. This circuit is also called as
three leg operation. There is a logic behind the numbering of the devices. The
devices are numbered as per the sequence of triggering. This means that as shown
in the circuit, the switch S2 is triggered after S1, and similarly for the rest of the
devices. The output required is three-phase voltage, which means that three-phase
sequences, separated by 120 degrees each are required. For each phase sequence,
one pair of switching devices are operated. This means that to obtain the R phase,
S1-S2 is turned on. To obtain Y phase S3-S4 are turned on and to obtain B phase
S5-S6 are turned on. The output waveform is shown below.
5.5. CONTROLLER
The PIC16F887 microcontroller is a high-performance 8-bit device developed
by Microchip Technology. It belongs to the popular PIC16 series and is widely
used in embedded systems, automation, consumer electronics, industrial control,
and academic projects. Its balance of memory, peripherals, and low power
consumption makes it ideal for both beginner and advanced-level applications.
The PIC16F887 features a Reduced Instruction Set Computer (RISC)
architecture, providing a rich set of instructions with fast execution. It includes
analog and digital peripherals such as ADC, timers, PWM modules, USART,
SPI, and I2C, enabling users to develop a wide range of real-time applications.
5.5.1. Pin Configuration and Block Overview
PIC16F887 is available in 40-pin DIP, 44-pin TQFP, and QFN packages. The
40-pin DIP version is the most commonly used in educational and prototyping
applications.
Pin Features:

20
I/O Pins: 35 general-purpose digital I/O lines across Ports A, B, C, D, and E.
Analog Inputs: 14 channels available for analog input (used with ADC).
Power Pins: Vdd and Vss for power and ground.
Oscillator Pins: OSC1/OSC2 for external crystal connection.
Programming Pins: MCLR (reset), PGC, PGD used for in-circuit
programming/debugging.

5.5.2. Harvard Architecture

The PIC16F887 follows a Harvard architecture, meaning it has separate
memory and data buses. This allows simultaneous access to program
instructions and data, speeding up processing.
5.5.3. CPU
8-bit processor
Executes most instructions in a single cycle (4 clock cycles)
Supports 35 single-word instructions
5.5.4. Clock System
Operates up to 20 MHz
Supports internal and external oscillator options
Can run on internal RC oscillator if crystal isn’t used
5.6. Memory Organization
PIC16F887 includes three types of memory:
5.6.1 Flash Program Memory
14 KB of non-volatile memory for storing program code
Retains data after power off
Can be reprogrammed many times
5.6.2 SRAM (Data Memory)
368 bytes used for temporary data storage during execution

21
Organized in banks for register access
5.6.3 EEPROM
256 bytes of Electrically Erasable Programmable Read-Only Memory
Used for storing permanent data like configuration settings
Can be read/written during run-time

5.7. Key Peripherals and Modules

5.7.1. Timers
Timer0: 8-bit timer, widely used for time delay generation and counters
Timer1: 16-bit timer, supports asynchronous operation
Timer2: 8-bit timer with a postscaler, used with PWM generation
5.7.2 ADC – Analog to Digital Converter
10-bit resolution
Up to 14 input channels
Converts analog voltage into digital values
Important for interfacing with sensors (temperature, light, etc.)
5.7.3 PWM (Pulse Width Modulation)
Two CCP (Capture/Compare/PWM) modules: CCP1 and CCP2
Used for motor control, signal generation, inverter control
Adjustable duty cycle and frequency
5.7.4 USART (Universal Synchronous/Asynchronous
Receiver/Transmitter)
Supports serial communication
Can be used with RS232 or Bluetooth for PC/remote control interfacing
5.7.5 SPI and I2C
SPI: High-speed synchronous communication
22
I2C: Two-wire protocol for connecting EEPROMs, RTC, displays, etc.
Used for master-slave communication in embedded networks
5.7.6 Interrupts
PIC16F887 supports multiple interrupt sources
External interrupts, timer interrupts, ADC interrupts, etc.
Prioritizes events for efficient real-time operation

5.8. Special Function Registers (SFRs)

SFRs control the behavior of the microcontroller. Each peripheral has
associated registers. For example:
PORTx, TRISx – Control input/output settings
ADCON0, ADCON1 – Configure ADC
TMRx, PRx – Configure timers
TXSTA, RCSTA – Configure USART
PIR1, PIE1 – Interrupt control
Understanding and using these registers is essential for low-level control and
embedded application development.
5.9. Power Management Features
Sleep Mode: Puts CPU in low-power state to conserve energy
Watchdog Timer (WDT): Resets microcontroller if it hangs or crashes
Brown-out Reset: Protects device during voltage drops
These features are especially useful in battery-powered and solar-based systems.
5.10. Programming and Tools
MPLAB X IDE: Official development environment by Microchip
XC8 Compiler: C compiler used for programming PIC devices
PICkit 3/4 or ICD: Used for uploading code and debugging

23
Code is written in embedded C and compiled into HEX files that are loaded into
the microcontroller.

5.11. PWM
Pulse Width Modulation (PWM) is a powerful technique used in electronic
control systems to generate a simulated analog signal using digital pulses. It
works by varying the width of a series of digital pulses to control the average
voltage supplied to a load. In inverter systems, PWM is essential for generating
AC waveforms from a DC source.

5.11.1 Working Principle

PWM involves two signals:
A reference sine wave (low frequency, e.g., 50 Hz)
A carrier triangle wave (high frequency, e.g., 10 kHz)
These two signals are compared using a comparator:
When the sine wave > triangle wave → Output HIGH
When sine wave < triangle wave → Output LOW

This comparison generates PWM pulses that replicate the sine wave's amplitude
in digital form. The average voltage of these pulses follows the shape of the sine
wave.
5.11.2 PWM Signal Parameters
Duty Cycle: The percentage of time the signal stays HIGH in one cycle.
Frequency: How many PWM cycles occur per second.
Amplitude: Typically fixed, controlled by supply voltage.
By adjusting the duty cycle dynamically, the output power delivered to a load
can be precisely controlled.

24
5.11.3 Applications in Inverter Systems
Generates sinusoidal AC waveforms from a DC source
Reduces harmonic distortion (THD)
Controls motor speed in drives
Manages voltage and frequency in grid-tied systems
Used in MPPT controllers, battery charging, and solar inverters

5.11.4 PWM in Microcontrollers (e.g., PIC16F887)

Microcontrollers like the PIC16F887 have built-in CCP
(Capture/Compare/PWM) modules that:
Generate PWM signals with configurable duty cycle
Are controlled using Timer2 and CCP registers
Provide up to 10-bit resolution in PWM mode
Example registers:
CCP1CON, PR2, T2CON, CCPR1L
5.11.5 PWM Signal Filtering
At the inverter output, a low-pass LC filter is used to convert the PWM
waveform into a smooth sinusoidal signal, removing high-frequency
components and making it suitable for appliances and grid use.
5.12. SWITCHING DEVICES
Switching devices are electronic components that control current flow in
circuits by acting like electronic switches. In inverter systems, these switches
rapidly turn ON/OFF to convert DC into AC power using PWM logic.
5.12.1. Types of Switching Devices
MOSFET (Metal-Oxide-Semiconductor FET)
Used in low to medium voltage systems
High-speed switching
Easy to drive with logic-level signals

25
IGBT (Insulated Gate Bipolar Transistor)
Combines the ease of control of MOSFET and high power of BJT
Used in medium to high voltage applications
Preferred in multilevel inverters and industrial drives
SCR / Thyristors
High current handling
Require special triggering to turn OFF
Common in industrial and phase-control systems

5.12.2. Switching Mechanism in Inverters

Each switch (MOSFET or IGBT) is controlled by PWM pulses sent from a
microcontroller or a PWM generator. When the pulse is HIGH:
The gate of the switch is activated
Current flows from source to drain (MOSFET) or collector to emitter (IGBT)
Load receives power in that switching interval
Switches alternate to create positive and negative half-cycles of the output AC
signal.

5.12.3. Gate Driving Circuitry

Switches require gate drivers to interface with microcontrollers. A typical driver
(e.g., IR2110) performs:
Signal level shifting (5V to 12V)
Isolation using optocouplers
High-speed switching capability

26
 5.12.4. Switching Losses and Efficiency
Every switching action introduces losses:
Conduction losses (when switch is ON)
Switching losses (during transition)
To improve efficiency:
Soft-switching techniques like Zero Voltage Switching (ZVS)
Snubber circuits
Proper heat sinks
5.12.5. Protection Mechanisms
Overcurrent protection
Dead-time insertion between switches
Short-circuit and reverse polarity protection
5.13. GRID
Grid-connected inverters are essential in renewable energy systems,
especially solar PV setups. These systems do not operate in isolation but feed
power into the electric utility grid. Unlike standalone inverters used in off-grid
systems, grid-tied inverters are designed to synchronize with the utility voltage
and frequency and transfer surplus energy back to the grid.

5.13.1 Key Features of Grid-Connected Inverter Output

A grid-tied inverter must ensure that:
The output AC waveform is sinusoidal
The voltage and frequency of the inverter match the grid
The phase angle is synchronized to allow proper energy flow
Power factor correction is performed if needed
Safety and anti-islanding protection is built-in
The inverter converts DC power from the solar panel (via MPPT and controller)
into AC and pushes it into the grid when conditions are favorable.

27
  5.13.2. Synchronization with the Utility Grid
Synchronization is a critical function of a grid-tied inverter. It ensures that the
inverter operates in-phase with the grid voltage to allow seamless power
injection. The inverter uses phase-locked loops (PLLs) or zero-crossing detection
to achieve this.
Steps in Synchronization:
Grid Voltage Detection: The inverter senses the grid’s voltage and frequency.
Phase Matching: The internal inverter oscillator adjusts to align with the grid's
phase.
Waveform Shaping: PWM is used to shape the inverter output waveform to
match the grid sine wave.
Safe Connection: Once matched, the inverter’s relay or solid-state switch
connects the output to the grid.
🔸 5.13.3. Power Flow Mechanism
When solar generation > load demand, the surplus energy is exported to the
grid.
When load demand > solar generation, the deficit is drawn from the grid.
A net metering system keeps track of energy imported and exported.
The inverter must always generate slightly higher voltage than the grid at the
point of connection to push power into the grid (as current flows from higher to
lower potential).
🔸 5.13.4. Inverter Output Waveform Quality
The quality of the AC output is vital for grid compatibility. The inverter must
produce:
A stable 230V RMS (single-phase) or 400V (three-phase)
50Hz frequency (or 60Hz in some regions)
Low Total Harmonic Distortion (THD), usually <5%
This is achieved using:
Sinusoidal PWM (SPWM) for smooth waveform synthesis

28
 Output LC filters to remove switching harmonics
Advanced DSP or microcontroller algorithms to regulate waveform quality
🔸 5.13.5. Safety Features and Grid Compliance
A grid-connected inverter includes several safety mechanisms to comply with
utility regulations:
Anti-islanding protection: Prevents inverter from continuing to power the grid
during an outage.
Over/under voltage and frequency protection: Disconnects the inverter if grid
conditions are unstable.
Ground fault detection
Reverse current protection
These features are often monitored using microcontrollers or digital signal
processors (DSPs).
🔸 5.13.6. Output Connection Configuration
There are generally two types of output connection for a grid-tied inverter:
Single-phase output (230V) for residential or small commercial setups
Three-phase output (400V) for larger commercial or industrial installations
The output is usually connected through a grid-interactive distribution panel,
often including:
A circuit breaker or fuse
A manual disconnect switch
Energy meters (for billing or net metering)
🔸 5.13.7 Inverter Grid Interface in Solar PV Systems – Flow Summary
plaintext

The inverter grid interface is the critical link between the solar PV system
and the utility grid. The process begins with the solar PV array generating DC
power from sunlight. This DC power is fed into a DC-DC converter, which
boosts the voltage and ensures maximum power output through MPPT
(Maximum Power Point Tracking).

29
 The boosted DC power is then delivered to the multilevel inverter, which
converts it into AC power suitable for the grid.

To ensure proper integration, the inverter synchronizes its output with the
grid’s voltage and frequency using a Phase-Locked Loop (PLL). The AC output
is then routed through a protection panel, which includes a circuit breaker or
fuse, a manual disconnect switch, and energy meters for tracking power usage
or enabling net metering.

[ Solar Panel ]
↓
[ MPPT Controller ]
↓
[ Battery (optional) ]
↓
[ DC-AC Inverter ]
↓
[ Filter + Synchronization ]
↓
[ Grid-Tied Output (230V / 400V, 50Hz) ]
↓
[ Utility Grid or Load ]
The inverter ensures that the output is phase-aligned, voltage-regulated, and
grid-compliant to allow stable operation with the utility.
🔸 5.13.8. Inverter Efficiency and Grid Utilization
Grid-tied inverters generally operate with efficiencies ranging from 95% to
99%, depending on load and input voltage. High-quality power conversion
ensures:
Minimal heat loss
Stable operation of household appliances
Reduced electricity bills via energy export credits

30
 CHAPTER 6
SOFTWARE DESCRIPTION
6.1 Introduction

In modern embedded systems, the ability to generate analog-like signals using

digital microcontrollers is crucial for a wide range of applications such as motor
control, LED brightness modulation, audio signal synthesis, and inverter
systems. One common technique to achieve this is Pulse Width Modulation
(PWM), where a digital signal is rapidly switched on and off to emulate varying
voltage levels.

This project focuses on the development of a software-based multilevel PWM

waveform generator using a microcontroller. Instead of using a single PWM
output, the system employs four discrete digital outputs to represent multiple
voltage levels. By adjusting the combination of active output lines, the circuit
simulates a stepped sine wave, improving the quality of the waveform and
reducing harmonic distortion.

The waveform generation is handled via a Timer0-based interrupt routine,

allowing the processor to operate efficiently while maintaining precise timing.
A predefined sine wave approximation array is used to control the output
pattern dynamically, enabling the system to replicate a smooth periodic
waveform.

This software demonstrates how low-cost microcontrollers can be used to create

high-performance signal generation systems by combining bit-level hardware
control, interrupt-driven programming, and digital waveform synthesis
techniques.

31
6.2 FLOW DIAGRAM OF SOFTWARE LOGIC

Start

Initialize Output Ports (PORTB as Output)

Initialize Timer0:

- Set Prescaler (1:256)

- Enable Timer0 Interrupt

- Enable Global Interrupts

Main Loop:

Wait (idle; all logic handled in ISR)

[Timer0 Overflow Interrupt Triggered]

Check Current Value from pwm_values[i]

Set Output Levels Based on Value:

- < 50 → Level1 = 1, Level2 = 0, Level3 = 0, Level4 = 0

- 50–99 → Level1 = 1, Level2 = 1, Level3 = 0, Level4 = 0

- 100–149 → Level1 = 1, Level2 = 1, Level3 = 1, Level4 = 0

- ≥ 150 → Level1 = 1, Level2 = 1, Level3 = 1, Level4 = 1

32
Increment Index (i = i + 1)

If i ≥ 50 → Reset i = 0

Clear Timer0 Interrupt Flag

Return from Interrupt

(Back to Main Loop)

6.3. LOOP( ) FUNCTION

Keeps the Microcontroller Running:

The infinite while(1) loop ensures that the program continues executing and
does not exit, which is standard in embedded systems.

Delegates Work to Interrupts:

All time-critical tasks (i.e., updating output pins based on the PWM sine table)
are handled in the interrupt function, triggered by Timer0 overflow. The main
loop does not interfere or delay these tasks.

Idle Mode Placeholder:

This loop can later be extended to:

 Monitor inputs
 Add communication (UART, I2C)
 Change waveform dynamically
 Enter low-power sleep modes between interrupts

6.4. PROGRAM
sbit Level1 at PORTB.B0;
sbit Level2 at PORTB.B1;
sbit Level3 at PORTB.B2;
sbit Level4 at PORTB.B3;

33
unsigned int pwm_values[50] = {
0, 10, 20, 30, 40, 50, 60, 70, 80, 90,
100,110,120,130,140,150,160,170,180,190,
200,210,220,230,240,250,240,230,220,210,
200,190,180,170,160,150,140,130,120,110,
100,90,80,70,60,50,40,30,20,10
}; // Sine wave approximation

unsigned int i = 0;

void setupPWM() {
TRISB = 0x00; // Set PORTB as output
PORTB = 0x00;

TMR0 = 0;
OPTION_REG = 0b00000111; // Prescaler 1:256
INTCON.TMR0IE = 1; // Enable TMR0 interrupt
INTCON.GIE = 1; // Enable global interrupts
}

void interrupt() {
if (INTCON.TMR0IF) {
// Generate PWM levels manually for multilevel output
if (pwm_values[i] < 50) {
Level1 = 1; Level2 = 0; Level3 = 0; Level4 = 0;
} else if (pwm_values[i] < 100) {
Level1 = 1; Level2 = 1; Level3 = 0; Level4 = 0;
} else if (pwm_values[i] < 150) {
Level1 = 1; Level2 = 1; Level3 = 1; Level4 = 0;

34
 } else {
Level1 = 1; Level2 = 1; Level3 = 1; Level4 = 1;
}

i++;
if (i >= 50) i = 0;

TMR0 = 0;
INTCON.TMR0IF = 0;
}
}

void main() {
setupPWM();
while (1) {
// Loop does nothing; PWM handled in interrupt
}
}

6.5. KEY FEATURES

1. Multilevel PWM Output

 Generates stepped analog-like signals using four digital outputs.

 Simulates voltage levels with combinations of binary outputs (e.g., 0001,
0011, 0111, 1111).

2. Sine Wave Approximation

 Uses a lookup table with 50 precomputed values to represent one cycle of

a sine wave.
 Smooth waveform transition with minimal computation overhead.

3. Timer0-Based Interrupt Control

 Uses Timer0 interrupt to trigger waveform updates at regular intervals.

 Ensures precise timing and consistent waveform generation.

35
4. Efficient Interrupt-Driven Design

 Main loop remains idle, maximizing CPU availability for other tasks or
power saving.
 Interrupts handle time-critical PWM updates without delay.

5. Direct Port and Bit-Level Control

 Uses sbit directives to control individual PORTB pins for fast and fine-
grained output control.
 Minimal use of high-level libraries ensures efficient and compact code.

6. Low Resource Usage

 Designed to run on low-cost 8-bit microcontrollers (e.g., PIC16 series).

 No floating-point operations or complex math at runtime.

7. Software-Based DAC Concept

 Simulates Digital-to-Analog Conversion (DAC) using discrete binary

levels via software logic.

8. Flexible and Scalable Design

 Easy to modify lookup table for different waveforms (triangle, sawtooth,

etc.).
 Number of output levels can be scaled up with additional digital pins.

9. Real-Time Behavior

 Deterministic output based on hardware timer ensures real-time system

performance.
 Suitable for real-time control and signal generation tasks.

10. Educational and Practical Value

 Excellent demonstration of embedded systems principles: timers,

interrupts, bit manipulation, waveform generation.
 Useful for learning PWM, DAC simulation, and real-time embedded
programming.

36
 CHAPTER 7
CONCLUSION
The project titled “Single-Sourced Double Stage Multilevel Inverter for
Grid-Connected Solar PV Systems” successfully demonstrates a smart,
sustainable approach to efficient solar energy utilization. This work focused on
integrating renewable solar power with modern inverter technologies to ensure
reliable, grid-compatible energy conversion. The system utilized a double-stage
inverter topology, starting with MPPT-based DC regulation and followed by a
multilevel inverter output stage designed for optimal grid connection.
Through the design and development of this system, various challenges
associated with traditional single-stage inverters—such as increased harmonic
distortion, lower voltage levels, and inefficient switching—were addressed. The
double-stage approach allowed for better power conditioning and voltage level
management before interfacing with the grid. Additionally, the multilevel
inverter configuration significantly improved output waveform quality by
reducing Total Harmonic Distortion (THD), which is critical in grid-tied
applications.
The use of MPPT (Maximum Power Point Tracking) algorithms ensured
that the solar panels operated at their highest efficiency, adjusting dynamically
to changing environmental conditions. The inclusion of a battery energy storage
system also allowed for load balancing, making the system more resilient and
responsive during fluctuating solar availability.
From the control side, the use of a PIC16F887 microcontroller enabled
precise generation of PWM signals, switch timing, synchronization with the
grid, and overall system control. This controller was selected for its balance of
simplicity, cost-effectiveness, and functionality, supporting real-time switching
operations and communication with power management circuits.Furthermore,
the H-Bridge topology, supported by effective PWM techniques, provided a
robust and scalable inverter structure.
In conclusion, this project offers a technically sound and environmentally
responsible solution to modern energy challenges. Future work can include
implementing real-time IoT-based monitoring, adaptive machine learning for
power optimization, and scalability for three-phase or industrial loads. This
project not only meets current energy demands but also paves the way for a
smarter, greener electrical infrastructure.

37
PHOTOGRAPHY

38
FUTURE SCOPE
The successful implementation of a Single-Sourced Double Stage
Multilevel Inverter in a grid-connected solar PV system opens multiple
pathways for further research and development. As the global demand for
renewable energy increases, particularly in the context of smart and sustainable
energy systems, there are significant opportunities to enhance this project in
terms of efficiency, scalability, smart control, and integration.
One of the most promising directions is the integration of IoT (Internet of
Things) and cloud-based monitoring. By incorporating wireless modules and
sensors, real-time data such as solar irradiance, battery health, inverter
efficiency, and grid parameters can be collected and visualized on mobile apps
or dashboards. This allows for remote diagnostics, predictive maintenance, and
adaptive control, ensuring the system operates optimally under various
conditions.
Another major enhancement involves the use of Artificial Intelligence
(AI) and Machine Learning (ML) algorithms. AI-based predictive models can
be trained to optimize power flow, battery usage, and inverter switching in real-
time. These intelligent control strategies can improve system performance in
dynamic environments by forecasting load demands, weather changes, and solar
availability. Machine learning can also support fault detection and self-
correction in the inverter system, making it more resilient and self-sustaining.
From a hardware perspective, future versions of the system can transition
to three-phase multilevel inverter configurations, suitable for industrial or large
commercial applications. These inverters, combined with modular battery banks
and advanced control units like DSPs (Digital Signal Processors) or ARM-based
microcontrollers, can handle higher power ratings while maintaining superior
output waveform quality and stability.
Additionally, grid interaction protocols such as smart metering,
bidirectional energy flow, and net metering compliance can be integrated. As
utilities shift toward decentralized generation, incorporating features like grid
feedback management, voltage regulation, and reactive power compensation
becomes crucial. This would make the system not only a power source but also
a smart grid-supportive unit.

39
 Furthermore, the future scope includes research into advanced power
electronics such as SiC (Silicon Carbide) or GaN (Gallium Nitride) based
switching devices. These materials enable faster switching speeds, reduced
losses, and smaller system size, making the inverter more compact and efficient.

From a hardware perspective, future designs can shift toward three-phase

multilevel inverter configurations, suitable for industrial and large-scale
commercial applications. Combined with modular battery banks and advanced
controllers like DSPs or ARM-based microcontrollers, these setups can manage
higher power levels with excellent waveform quality and system stability.

The system can also be enhanced with smart grid interaction protocols,
including bidirectional energy flow, smart metering, net metering, and reactive
power compensation. These features enable the inverter to function not only as
a power source but also as a supportive component of a smart grid.

Further research into advanced power electronics, such as Silicon Carbide

(SiC) or Gallium Nitride (GaN) devices, promises improvements in switching
speed, efficiency, and compactness.

Lastly, the system has potential for expansion into a hybrid energy model,
integrating sources like wind turbines, fuel cells, or EV charging stations.
Managed by a central energy management unit, this configuration can offer
enhanced reliability and sustainability in smart cities, remote areas, and disaster-
prone regions.

By continuously evolving with emerging technologies and adapting to

future grid standards, this system has the potential to become a cornerstone in
the transition toward a more decentralized, intelligent, and environmentally
sustainable energy infrastructure.

Finally, the proposed system can be expanded into a hybrid energy

model, integrating wind turbines, fuel cells, or electric vehicle (EV) charging
stations. This multi-source configuration, when controlled by a central energy
management system, could significantly improve energy reliability and
sustainability in smart cities, remote locations, and disaster-resilient zones.

40
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