solar colony: designing and economics of rooftop solar pv system
TRANSCRIPT
SOLAR COLONY: DESIGNING AND ECONOMICS OF
ROOFTOP SOLAR PV SYSTEM – A CASE STUDY
Submitted in partial fulfilment of the requirements for the degree of
Bachelor of Engineering
by
Name Roll No.
Akshay Bhirud 401204
Abhishek Desai 401210
Rishi Pant 401241
Pratyush Pasbola 401242
Gaurav Wagh 401264
Supervisors
Dr. Sincy George
Mrs. Uma L
Department of Electrical Engineering
Fr. Conceicao Rodrigues Institute of Technology
Sector – 9A, Vashi, Navi Mumbai – 400703
UNIVERSITY OF MUMBAI
2015-2016
Certificate of Approval
This is to certify that the project entitled “SOLAR COLONY: DESIGNING AND
ECONOMICS OF ROOFTOP SOLAR PV SYSTEM – A CASE STUDY’ is a bonafide work
of:
Name Roll Number
Akshay Bhirud 401204
Abhishek Desai 401210
Rishi Pant 401241
Pratyush Pasbola 401242
Gaurav Wagh 401264
Submitted to the University of Mumbai in partial fulfilment of the requirement for the award of
the degree of Bachelor of Engineering in “Electrical Engineering”.
____________________________ ____________________________
Dr. Sincy George (Project Guide) Mrs. Uma L (Co - Project Guide)
____________________________ __________________________
Dr. Sincy George (Head of Department) Dr. S. M. Khot (Principal)
Project Report Approval for B.E.
This project report entitled “Solar Colony: Designing and Economics of Rooftop Solar PV
System – A Case Study” by Akshay Bhirud (401204), Abhishek Desai (401210),
Rishi Pant (401241), Pratyush Pasbola (401242) and Gaurav Wagh (401264) is approved for
the degree of B.E in Electrical Engineering.
Examiners
1____________________
2____________________
Date:
Place:
Declaration
We declare that this written submission represents our ideas in our own words and where others’
ideas or words have been included, we have adequately cited and referenced the original sources.
We also declare that we have adhered to all principles of academic honesty and integrity and have
not misrepresented or fabricated or falsified any idea/data/fact/source in the submission. We
understand that any violation of the above will be cause for disciplinary action by the Institute and
can also evoke penal action from the sources which have thus not been properly cited or from
whom proper permission has not been taken when needed.
Akshay Bhirud (401204) ____________________
Abhishek Desai (401210) ____________________
Rishi Pant (401241) ____________________
Pratyush Pasbola (401242) ____________________
Gaurav Wagh (401264) ____________________
i
Acknowledgement
First and foremost, we would like to thank University of Mumbai for including group project in
the curriculum which inspired us to carry out the aforementioned project in college which helped
us to utilize our skills and technical knowledge to the maximum extent.
We would like to thank our principal Dr. S M Khot for giving us the opportunity and permission
to undertake this project. We would also like to thank our Head of Electrical Department Dr.
Sincy George for thoroughly supervising the group project activities.
We are grateful to Mr. R.C. Pant, President of Housing Society of Kendriya Vihar, Kharghar for
giving us an opportunity to inspect the site of the colony where the society wants to install the
project and allowing us to carry out the designing and economic calculations for the same.
Our internal guides Dr. Sincy George and Mrs. Uma L have provided us with regular and
efficient guidance throughout this semester and has given us encouragement and constructive
suggestions without which project wouldn’t have reached the current stage. We are thankful for
their contributions.
Lastly, we would like to thank our colleagues and all the staff members in our Department who
have directly or indirectly contributed to the project.
ii
Abstract
Energy is the input required to drive and improve the life cycle. It is the gift of the nature to the
human in various forms. The consumption of the energy is directly proportional to the progress
of the mankind. With ever growing population, improvement in the living standard of the
humanity, industrialization of the developing countries, the global demand for energy is expected
to increase rather significantly in the near future. The primary source of energy is fossil fuel,
however the finiteness of fossil fuel reserves and large scale environmental degradation caused
by their widespread use, particularly global warming, urban air pollution and acid rain, strongly
suggests that harnessing of non-conventional, renewable and environment friendly energy
resources is vital for steering the global energy supplies towards a sustainable path. Solar energy
is one of them.
Solar Energy, a clean renewable resource with zero emission has got tremendous potential of
energy which can be harnessed more efficiently using power electronic converters. With recent
developments, solar energy systems are easily available for industrial and domestic use with the
added advantage of minimum maintenance.
This project work aims for the designing and finding the economics of a roof top solar PV
system for a residential area in Navi Mumbai. Following work is carried out:
Payback period calculation of Solar PV system
MATLAB simulation of DC – DC Converter
Hardware implementation of prototype of Solar PV system using DSP TMS320F28069
Satisfactory results are obtained and are presented in this report.
iii
Table of Contents
Section Topic Page No.
Acknowledgement i
Abstract ii
Table of Contents iii
List of figures v
List of Tables vii
Chapter 1 Introduction
1.1 Objective 2
1.2 Motivation 2
1.3 Work Proposed 3
1.4 Work Completed 3
Chapter 2 Literature Survey
2.1
2.1.1
2.1.2
2.1.3
2.1.4
2.1.5
2.1.6
Renewable Energy Current Scenario
Renewable Energy Worldwide
Renewable Energy in India
Advantages and Disadvantages of Renewable Energy
Scenario of Solar Energy in India
Future of Solar Energy Power in India
Advantages and Disadvantages of Solar energy
5
5
5
6
7
8
9
2.2
2.2.1
2.2.2
Topologies of Solar System
Stand-alone system
Grid connected system
9
9
10
Chapter 3 Designing and Economics of Rooftop Solar PV System
3.1 Existing System 11
3.2 Proposed Rooftop Solar PV System 13
3.3 Design of standalone solar PV system 14
3.3.1 Estimation of Load and Area available for Solar panel
installation
14
iv
3.3.2 Selection of Converter Type and its Rating 16
3.3.3 Sizing of Batteries 16
3.3.4 Sizing of PV Modules 19
3.3.5 Cabling 22
3.3.6 Design of Buck Boost Converter 23
3.3.6.1 Duty Cycle Calculation 24
3.3.6.2 Selection of Inductor 24
3.3.6.3 Selection of Capacitor 26
3.3.7 Payback Period Calculation 26
3.3.7.1 Standalone Solar PV System with Lead Acid battery bank 27
3.3.7.2 Standalone Solar PV System connected directly to the load 28
Chapter 4 Design of DC-DC Converter
4.1 Open loop Simulation 32
4.2 Closed loop Simulation 34
4.2.1 Generation of Pulse for voltage control 35
4.2.2 Simulation Result
36
Chapter 5 Hardware Implementation of Standalone Solar PV
System
5.1 Implementation of Buck Boost Converter using DSP
TMS320F28069
39
5.1.1 Implementation of Power Circuit 40
5.1.2 Implementation of Control Circuit 40
5.1.2.1 Auxiliary Power Supply 41
5.1.2.2 DSP Processor 42
5.1.3 Buck boost converter results 43
5.2 Solar Panel Testing 45
5.3 Implementation of hardware using solar panels 47
Chapter 6 Conclusions and Future Scope 48
v
List of Figures
Sr. No Title Page No
1 2.1 Renewable energy installed capacity in India 6
2 2.2 State wise installed solar capacity 7
3 2.3 Potential of the solar energy in India 8
4 2.4 Stand-alone solar PV system 10
5 2.5 Grid tied roof top solar PV system 10
6 3.1 Basic block diagram of proposed system 13
7 3.2 Satellite View of Kendriya Vihar Colony, Kharghar 15
8 3.3 Battery Connection Diagram 18
9 3.4 Battery Connection Diagram with Autonomy 19
10 3.5 Solar panel connection diagram 21
11 3.6 Ratings of components of Proposed System 23
12 3.7 Standalone Solar PV System directly connected to load 29
13 4.1 MATLAB model of the Buck Boost converter 32
14 4.2 Pulse given to MOSFET 32
15 4.3 Switch and Diode Voltage Waveform 33
16 4.4 Inductor current and Inductor Voltage 33
17 4.5 Output Current and Output Voltage 34
16 4.6 MATLAB model of closed loop simulation 35
17 4.7 Error signal and Repeating signal 35
18 4.8 Pulse for MOSFET 36
19 4.9 Output Voltage waveform for Boost Mode 36
20 4.10 Pulse for Boost Mode 36
21 4.11 Pulse for Boost Mode 37
22 4.12 Pulse for Boost Mode 37
23 5.1 Pulse for Boost Mode 39
24 5.2 Gate – Driver Circuit of HCPL 3120 40
25 5.3 Driver Circuit Output 41
26 5.4 Regulator Circuit 41
vi
27 5.5 Transformer for Auxiliary Power Supply 42
28 5.6 DSP TMS320F28069 42
29 5.7 Pin Details of DSP TMS320F28069 43
30 5.8 Output Voltage Waveform for VIN = 16.89 V 44
31 5.9 Output Voltage Waveform for VIN = 16.89 V 44
32 5.10 Solar Panel Testing 45
33 5.11 I-V characteristics of 75 Wp Solar Panel 46
34 5.12 Hardware Setup 47
vii
List of Tables
Table No Description Page No.
3.1
Details of load estimation
15
3.2
Cost of components of Solar PV system 27
3.3
Cost of components of Solar PV system 29
4.1
Components to simulate Buck Boost converter 31
4.2
Output Parameters 34
4.3
PI controller parameters 34
5.1
Component Specifications 39
5.2
Measured values of VOC and ISC of at 11.30 am on 22nd
March, 2016
45
5.3
Measured values of voltage and current for different values
of resistances
46
1
Chapter 1
Introduction
Power or electricity is very essential constituent of infrastructure affecting economic growth and
welfare of the country. India is the 5th largest producer of electricity in the world. World
electricity demand is likely to reach 155 GW by 2016-17 & 217 GW by 2021-22 whereas peak
demand will reach 202 GW & 295 GW over the same period respectively [1].
Despite an ambitious rural electrification programme, India is facing frequent blackouts. While
84.9% of Indian villages have at least an electricity line, just 46 percent of rural households have
access to electricity. Electricity grids in the developed markets expect losses below 15%, but the
losses by India's state utilities, over the past five years, were as high as 30% [2].About one-third
of that loss is technical, but the rest is either given away for free or at subsidized rates to farmers,
or lost to theft. Utility generation companies have little control over that.
2
In India, the total power generated has been 1048.5 Billing Unit (BU) during the FY 2014-15. By
using renewable energy sources like solar energy, we reduce our dependence on fossil fuel gas
and oil reserves, which are becoming more expensive and difficult to find. It also reduces our
dependence on imported fossil fuels, improving our energy security.
India's cumulative grid interactive or grid tied renewable energy capacity (excluding large hydro)
has reached 33.8 GW, of which 66% comes from wind, while solar PV contributed nearly 4.59%
along with biomass and small hydro power of the renewable energy installed capacity in India.
Realising the importance of renewable energy this project work is undertaken to transfer the
common loads (corridor lights) in a residential colonies on renewable energy sources by
installing an integrated system of solar PV cells and battery, along with the estimation and
calculation of the payback period for this installation of solar PV panels. A site in Kendriya
Vihar Colony, Kharghar, Navi Mumbai has been chosen for implementation of proposed system.
Details of the required equipments (solar PV panels, LED lamps, Converter, etc) have been
introduced in the report. A financial analysis on the payback period is also done from the derived
data.
1.1 Objective
The objective of the project is to study the feasibility of replacing CFL in a corridor of a
residential colony by LED which is fed by solar PV system. Selection of proper DC-DC
converter along with PV panel to maintain supply voltage to LED light system is also proposed.
Based on payback period calculation feasibility of solar PV installation in the colony is to be
decided. Solar PV system with battery as energy storage is proposed as main application of
corridor lightning is during night period.
1.2 Motivation
Theoretically, Solar PV possesses great potential to make a significant contribution to the ever
increasing energy demands. However, the high cost of its implementation and maintenance
renders it unworthy for an individual to replace the traditional sources. Therefore, it is essential
3
to harness this energy step by step and encourage people to gather in groups for the
implementation of it.
The motivation behind this project is:
Increasing costs of conventional electricity is a major boost to promote solar PV energy. The
potential of solar PV energy is considerably large to reduce the load drastically on the traditional
sources. People are keen on reducing the problems caused due to greenhouse gases and thus,
cleaner energy is the solution readily available. PV costs have decreased substantially in the
recent years. Also, the project further delineates the economical benefits through calculations of
payback period. Thus this project work is a small initiative to make the society aware of the
benefits and the positive impacts of solar energy.
1.3 Work Proposed
Selection of complete solar PV system to light corridor in the residential building
Payback period calculation
Simulation of DC – DC Converter
Hardware implementation of solar PV system
1.4 Work Completed
Sizing of PV modules, battery autonomy along with sizing of batteries and selection of
converter rating through load estimation was carried out for selection of solar PV system.
Payback period is calculated based on Initial investment considering the operating and
maintenance cost and replacement cost
MATLAB simulation of DC – DC Converter is carried out
A prototype of solar PV system is implemented using DSP TMS320F28069
4
Chapter 2
Literature Survey
The dawn of a new era is here. Renewable energy which was unimaginable a century ago is now
on our doorsteps. In matter of a decades, it has grown from a fringe player to a mainstream actor
in the energy sector. Renewable energy sources are expensive compared to fossil fuels today but
will be cheaper tomorrow.
A literature survey is carried out to:
1. Study the existing status and future plan of implementation of renewable energy in India
as well as in the world.
2. To study stand-alone and grid connected Solar PV system.
5
2.1 Renewable Energy Current Scenario [3]
With the ever increasing demand for the always depleting fossil fuels, the much needed shift in
attention towards renewable energy was a must and gas reserves are estimated to last for 45 and
65 years respectively whereas coal deposits are estimated to last a little longer than 200 years. In
2012, renewable energy sources together comprised for around 13.2% of the total energy supply
of the world, and in 2013 renewables accounted for almost 22% of global electricity generation,
which was a 5% increase from 2012.
2.1.1 Renewable Energy Worldwide [4]
The use of renewable energy without doubt, renewable energy is on the verge of increase.
Denmark is producing 43% of its energy from renewables, targets 70% by 2020. Germany, at
about 30% soon, will aim for 40% to 45% clean power by 2025, 55% to 60% by 2035, and a
whopping 80% by 2050. China, overcoming numerous challenges, is the world’s leading source
of renewable investment, as well as the largest solar manufacturer.
The United States, with about 13% renewable energy generation, lags to some extent, though
California points the way forward. The Solar Energy Industries Association reports that the solar
market in the U.S. grew by 41% in 2013, and that it made up 20% of all new generating capacity
in that year.
2.1.2 Renewable Energy in India [5]
Renewable energy installation for electricity in India as increased at a rapid annual rate of 25%,
in the past decade. It was about 30,000 MW in January 2014. In this period, wind power
installation increased tenfold while solar energy increased to 2500 MW from nothing.
Renewables presently accounts for about 12 per cent of the total electricity generation capacity
and contributes about 6 per cent of the electricity produced in the country. Renewables, produce
more than twice the amount of electricity produced by all nuclear power plants in the country. In
2012-13, the electricity produced by renewable energy was equivalent to meeting the per capita
annual electricity requirement of about 60 million of the population. Solar energy is responsible
for meeting the basic electricity needs of more than 60 million people in India.
6
The following diagram shows the renewable energy installed capacity in India.
Fig 2.1 Renewable energy installed capacity in India
2.1.3 Advantages and Disadvantages of Renewable Energy
Advantages of renewable energy are:
• Limitless Availability
• Environment-friendly
• Reliability of the sources
• Economically beneficial
• Stabilized Prices
Disadvantages of renewable energy are:
• Unreliable Supply
• Cannot be produced in large quantities
• High Capital Cost
• Large Requirement of Land
7
2.1.4 Scenario of Solar Energy in India [6]
India has tremendous scope of generating solar energy. The geographical location of the country
stands to its benefit for generating solar energy. The reason being India is a tropical country and
it receives solar radiation almost throughout the year, which amounts to 3,000 hours of sunshine.
This is equal to more than 5,000 trillion kWh. Almost all parts of India receive 4-7 kWh of solar
radiation per m2. This is equivalent to 2,300–3,200 sunshine hours per year. States like Andhra
Pradesh, Bihar, Gujarat, Haryana, Madhya Pradesh, Maharashtra, Orissa, Punjab, Rajasthan, and
West Bengal have great potential for tapping solar energy due to their location. Dharnai village
became first fully powered village of India. State wise installed solar capacity is shown in the
following Fig 2.2. It is seen that Gujarat and Rajasthan are the leading states in solar installations
which have more than 50% of the installations in the country.
Fig 2.2 State wise installed solar capacity
The potential of the solar energy in India is as shown in Fig 2.3. It is seen that India has lot of
potential, which can completely suffice the electricity needs of the nation, with Rajasthan, North
Gujrat and Karnataka receiving the maximum solar radiation.
8
Fig 2.3 Potential of the solar energy in India
2.1.5 Future of Solar Energy Power in India [7]
Many large projects have been proposed in India in the near future. Thar Desert has been
estimated to generate 700 to 2,100 GW. Gujarat aims at generating 1000MW from solar energy
through its various policies. A $19 billion solar power plan was proposed in July, 2009 which
projected to produce 20 GW of solar power by 2020. About 66 MW is installed for various
applications in the rural area, amounting to be used in solar lanterns, street lighting systems and
solar water pumps, etc.
India is slowly gaining its prominence in the generation of solar power due to the comprehensive
and ambitious state and the Centre’s solar policies and projects and National Solar Mission. In
the latest 2014 budget, Finance Minister Jaitley declared that the Government has proposed an
amount of 500 crore rupees to develop few mega solar power plants in Gujarat, Tamil Nadu,
Rajasthan, and Ladakh. He also said that solar power-driven agricultural water pumping stations
and 1 MW solar parks on canal banks will be developed in the country at an estimated cost of
$74 million and $18.5 million, respectively. With respect to all of the above projects, India
seems to driving nation in the development of solar energy.
9
2.1.6 Advantages and Disadvantages of Solar energy
Advantages:
• Prevention of global warming
• Solar power is economically advantageous
• Provides energy reliability
• Provides energy security
• Provides energy independence
• Creates stable Jobs Opportunities
Disadvantages:
• Technology Cost
• Highly Weather Dependent
• Expensive Energy Storage
• Space Consuming
2.2 Topologies of Solar System
Generally two types of topologies are used in case of Solar PV System:
(i) Standalone System
(ii) Grid connected System
2.2.1 Stand-alone system [8]
A Stand-Alone Power System (SAPS or SPS), also known as Remote Area Power Supply
(RAPS), is an off-the-grid electricity system for locations that are not fitted with an electricity
distribution system. Typical SAPS include one or more methods of electricity generation, energy
storage, and regulation.Storage is typically implemented as a battery bank, but other solutions
exist including fuel cells. Power drawn directly from the battery will be direct current extra low
voltage (DC ELV), and this is used especially for lighting as well as for DC appliances. An
inverter is used to generate AC low voltage, which more typical appliances can be used with. A
typical standalone PV system is shown in Fig 2.4.It consists of a solar panel, DC to DC
converter, DC link capacitor, inverter, AC distribution panel and AC load.
10
Fig 2.4 A stand-alone solar PV system
2.2.2 Grid connected system [9]
A grid-connected photovoltaic power system, or grid-connected PV system is an electricity
generating solar PV system that is connected to the utility grid. A grid-connected PV system
consist of solar panels, one or several inverters, a power conditioning unit and grid connection
equipment. They range from small residential and commercial rooftop systems to large utility-
scale solar power stations. Unlike stand-alone power systems, a grid-connected system rarely
includes an integrated battery solution, as they are still very expensive. When conditions are
right, the grid-connected PV system supplies the excess power, beyond consumption by the
connected load, to the utility grid, shown in Fig 2.5.
Fig 2.5 Grid tied roof top solar PV system
Based on the literature survey, a rooftop solar PV system is designed and explained in the next
chapter.
11
Chapter 3
Designing and Economics of Rooftop Solar PV System
Objective of project work is to design a Roof Top Solar PV Standalone System for Kendriya
Vihar Colony, Kharghar for staircase lighting system by replacing existing CFL with LED lights
which will be lit during night time by means of battery storage. Also calculation of the cost
associated, minimization of the cost and estimation of the payback period of this installation to
be done.
3.1 Existing System
The colony consists of:
(i) Ground (Parking) + Seven Storied Building: 5 Nos.
(ii) Ground (Accommodation) + Three Storied Building (No Parking): 1 No.
For each building:
(i) Each floor has Three CFL lamps
(ii) Ground Floor (Parking) has Nine lamps
12
Ratings of CFL Lamp:
Voltage, V = 220 - 240 V
Wattage, W = 23 W
Frequency, f = 50 Hz
Lumen Output = 1400 lumen
Number of CFL lamps for each seven storied building (N7),
N7 = (7 x 3) + 9 = 30 … (Eqn 3.1)
Number of CFL lamps for three storied building (N3),
N3 = 4 x 3 = 1 … (Eqn 3.2)
Total number of CFL lamps = (5 x N7) + N3 = (5 x 30) + 12 = 162
Considering 5% extra lamps, number of extra CFL lamps, Ne = 8 lamps
Therefore, Total number of CFL lamps, NT = 162 + Ne = 162 + 8 = 170 lamps
Number of hours of staircase lights operation,
T = 12 hours (7 pm to 7 am)
Energy consumed by seven storied buildings (E7),
E7 = 5 x N7 x W x T = 5 x 30 x 23 x 12 = 41.4 kW-hr. … (Eqn 3.3)
Energy consumed by three storied building (E3),
E3 = N3 x W x T = 12 x 23 x 12 = 3.312 kW-hr. … (Eqn 3.4)
Energy consumed by 5 % extra lamps (Ee),
Ee = Ne x W x T = 8 x 23 x 12 = 2.208 kW-hr. … (Eqn 3.5)
Total power consumed (PT),
PT = NT x W = 170 x 23 = 3.91 kW … (Eqn 3.6)
13
Energy Consumed per day,
E = PT x T = 3.91 x 12 = 46.92 kW-hr … (Eqn 3.7)
Or, E = E7 + E3 + Ee = 41.4 + 3.312 + 2.208 = 46.92 kW-hr … (Eqn 3.8)
Cost of 1 unit (1 kW-hr) of energy consumed, CU = INR 4.5
Total Energy cost per month,
CM = E x 31 x CU = 46.92 x 31 x 4.5 = INR 6545.34 … (Eqn 3.9)
Total Energy cost per year,
CA = E x 365 x CU = 46.92 x 365 x 4.5 = INR 77,066.1 … (Eqn 3.10)
3.2 Proposed Rooftop Solar PV System
The proposed work deals with replacing CFL lights with LED lights of same Lumen output
which will be supplied by a battery source during night time (7pm to 7am). Batteries will be
charged during day by the Solar PV Installation through converter. A DC-DC converter is to be
selected to charge the battery properly. During night time battery will supply energy to the load
through the DC-DC converter. The block diagram of proposed system is shown in Fig 3.1.
Fig 3.1 Basic block diagram of proposed system
14
3.3 Design of standalone solar PV system [10]
Typically in a Solar PV System Design the order of components from Source to Load is as
follows:
Solar PV Panels
Converter
Battery
Inverter
Load.
The proposed system consists of DC Load and hence, inverter will not be considered. Thus,
order of components in the proposed system will be: Solar PV Panels, Converter, Battery, DC
Load. Block diagram of the system is shown in Fig 3.1. Designing procedure will start with load
calculation and end with panel selection.
Following analysis is carried out for calculating payback period:
(i) Load Estimation
(ii) Selection of Converter rating
(iii) Selection of Batteries
(iv) Selection of Solar Panels
(v) Cabling
(vi) Payback Period Calculation
3.3.1 Estimation of Load and Area available for Solar panel installation
Estimation of load:
In load estimation, total load to be supplied by the Solar PV module is calculated. Solar PV
installations can be of two types, namely Stand Alone System and Grid Connected System.
The proposed system is a Standalone system. Details of the load is given in Table 3.1.
15
Table 3.1 Details of load estimation
Load Type Power (Watts) Working
Hours/Day
Number of
Lamps
Energy (kW-hr)
LED Lights 14W 13 170 30.94
Power consumed by load = Number of lamps x Wattage rating of each lamp
= 170 x 14 = 2380 W … (Eqn 3.11)
Energy consumed is obtained by multiplying the load connected to the system multiplied by its
number of hours of operation.
Total Energy consumed,
E = Wattage Rating of LED x Numbers of hours of Operation x Number of Lights
Number of hours of operation per day is 12 from 7am to 7pm.
Considering worst case scenario, assuming number of hours of operation as 13 hours, energy is
calculated. Thus, total energy required is calculated as 30.94 kW-hr.
Estimation of Area available for Solar panel installation:
Layout of the plot for Solar PV installation is shown in Fig 3.2.
Area available for installation = 1200 m2
Fig 3.2 Satellite View of KendriyaVihar Colony, Kharghar
16
3.3.2 Selection of Converter Type and its Rating [11]
Daily energy consumed is 30.94 kW-Hr. The energy supplied by the battery should be more than
daily energy consumption as practical converters have energy losses. Therefore, power output of
battery that is input to converter should be more than 30.94 kW-Hr.
For more reliable system, PV system voltage is considered as 24 V. The solar panels selected
have VOC (or VM) greater than system voltage. Hence, if the solar panel output voltage is greater
than system voltage, the converter needs to buck the solar panel output voltage to 24 V and if
solar panel output voltage is less than system voltage, converter needs to boost the solar panel
output voltage to 24 V.
Considering DC-DC Buck – Boost Converter efficiency as 92%,
Energy supplied by Battery = Enerygy RequirementConverter Efficiency
= 30.940.92
= 33.58 kW-Hr … (Eqn 3.12)
The power ratings of converter should be specified in the Solar PV System design. It is estimated
based on total load connected to the converter. In this system, Total Load connected to the
converter is 2380W which is given by Eqn 3.11. Therefore, keeping a margin of safety so that
limits are not exceeded, the converter’s power handling capacity is set at 3000W.
3.3.3 Sizing of Batteries
Typically the terminal voltage of batteries used in a Solar PV System is 12V. Terminal voltage
of batteries is increased to decrease the current carried by the cables, to decrease Power Loss.
Terminal voltage is multiple of 12V (12V, 24V, 36V, 48V). To decide system voltage, we need
to consider whether system voltage is more important or we need less power loss.
As system should be more reliable consider the PV system voltage as 24 V. Therefore the size of
the batteries required will depend on the following three parameters:
Depth of Discharge (DoD) of battery
Voltage and Ampere-Hour (Ah) capacity of battery
Number of days of Autonomy
Depth of Discharge is the amount of rated capacity of the battery which is usable. Usually in
Solar PV, batteries having DoD in the range 60 – 80% are used.
17
From Eqn 3.12,
Energy supplied by Battery = 33.58 kW-Hr.
Now, Required Charge Capacity = Energy supplied by the battery
Terminal Voltage of the battery
Therefore,
Required Charge Capacity = 33.58 x 103
24= 1399.2 A-hr = Approximately 1400 A hr
… (Eqn 3.13)
Taking Battery terminal voltage as 12V and capacity of each battery as 100 A-hr.
Actual Charge Capacity of Batteries = Required Charge Capacity
Depth of Discharge
Taking average Depth of Discharge as 70%,
Actual Charge Capacity of Batteries = 1400
0.7= 2000 A-hr … (Eqn 3.14)
Number of battery links to be connected in parallel = Actual Charge Capacity of Batteries
Ah capacity of each battery
= 2000
100 = Twenty 24 V batteries in parallel
… (Eqn 3.15)
For 24V as system voltage, two 12V batteries need to be connected in series. Therefore, each
link should have two 12V batteries.
Hence, Total number of batteries = Battery links in parallel x No of batteries in each link
= 20 x 2 = 40 batteries … (Eqn 3.16)
Battery connection diagram is given in Fig 3.3.
18
Fig 3.3 Battery Connection Diagram
Battery Autonomy:
Autonomy of a battery is defined as number of days battery should be able to supply the energy
to the load when primary source of energy is absent for those number of days. The number of
batteries will be more when Battery Autonomy is considered.
If total daily A-hr requirement is X and the number of days of autonomy is n days, then total A-
hr required including autonomy,
Total A-hr = X + (n x X)
In Navi Mumbai, maximum number of days of autonomy required will be 2 as in the worst case
scenario sunshine will not be available for maximum 2 days.
Therefore, Total A-hr = 2000 + (2 x 2000) = 6000 A-hr … (Eqn 3.17)
From above calculation we can see that battery bank size is 3 times that of without autonomy
battery bank. Hence, total number of batteries required will also be 3 times of that without
autonomy.
Total batteries required = 3 x 40 = 120 batteries … (Eqn 3.18)
The connection of these extra 80 batteries will be the same as for battery bank without
autonomy.
Battery connection diagram with autonomy considered is shown in Fig 3.4.
19
Fig 3.4 Battery Connection Diagram with Autonomy
3.3.4 Sizing of PV Modules
For sizing of PV Modules following parameters are important:
(i) Voltage, current and wattage of the module
(ii) Solar radiation at the proposed site
(iii) Efficiency of the batteries
(iv) Temperature of the module
(v) Efficiency of converter
(vi) Dust level in working environment
The energy required by the load is supplied by the battery bank on daily basis. As the battery is
being designed for autonomy total energy stored in the battery is much than energy required by
load on daily basis. The extra energy which is stored in the batteries is only to be used during the
autonomy days. Therefore, PV Module capacity should only be designed to supply load on daily
basis.
Energy supplied by the batteries is 33.58 kW-hr. Therefore, naturally energy input to the
batteries or the energy obtained from PV Modules should be more than this considering the
efficiency of the battery.
20
Considering efficiency of batteries as 80%,
Energy supplied at input of battery terminal = 33.58
0.8 = 41.975 kW-hr … (Eqn 3.19)
The input to the batteries will pass through a converter, hence the efficiency of converter also
need to be considered.
Output energy required from PV Modules = Energy supplied at input of battery terminal
Converter efficiency
= 41.975
0.92 = 45.625 kW-hr … (Eqn 3.20)
As the system voltage considered is as 24V,
Total Ah to be generated by the PV panels = Output Energy required from PV modules
System Volatge
= 45.625 x 103
24 = 1901 A-hr … (Eqn 3.21)
Other factors that degrade the solar cell performance should be taken into account. High module
operating temperature, dust settlement on PV modules should increase the A-hr produced by the
PV Modules.
The contribution of dust to PV module degradation is ranged from 18% to 29%. Dust particles
consists of clay, silt and are very fine grained. O, Si, Ca, Al, Fe and K are the elements of dust
accumulated on PV modules. Transmittance decreases as dust density increases.
On an average considering the degradation of Solar PV modules’ performance by 20%,
Actual A-hr to be generated by PV Modules = 1901
0.8= 2376.25 A-hr … (Eqn 3.22)
In India the average solar radiation available is 800W/m2. The solar radiation varies significantly
during the course of the day. At the site, 800W/m2 of constant insolation is considered available
for a duration of 5 hours (11 am – 4 pm).
21
Total Current (Amperes) that should be obtained from PV Modules = 2376.25
5= 475.25 A
… (Eqn 3.23)
Solar PV panels selected are manufactured by Renogy and have following characteristics [12]:
250Wp, 24V Monocrystalline Panels
VOC = 37.5V and ISC = 8.87A
VM = 30.1V and IM = 8.32A
Weight = 40 lbs, Dimensions = 64.5 x 39 x 1.6 inches (1.64 x 1 x 0.0406 meters)
Since one module can provide 8.32A of current,
Number of modules required = 475.25 A
8.32 A = 57.12 ≈ 58 … (Eqn 3.24)
Rounding the number of modules required to 58 modules, all these modules need to be
connected in parallel. As the voltage of each PV Module is 30.1V only one panel is sufficient in
each link.
Area required by each 250W module is 1.64 x 1 = 1.64 m2.
Total Area required for complete Solar PV Installation = Number of modules x Area required by
each module = 58 x 1.64 x 1 = 95.12 m2. … (Eqn 3.25)
Fig 3.5 Solar panel connection diagram
22
3.3.5 Cabling
Appropriate dimensions of wires and cables for interconnection of modules, batteries and loads
should be decided. The size of wires should be such that there should not be excessive voltage
drop in the wires. Usually, the voltage drop in the wire from battery to load should not be more
than 5% of the battery voltage. Therefore, the voltage of battery should be more than the load
voltage as there will be voltage drop in the wires connecting batteries and load.
The voltage drop for a given cable can be estimated as,
Vd = 2 x I x 𝜌𝐿
𝐴 … (Eqn 3.26)
where,
I is the current carried by the cable,
𝜌 is specific material resistivity,
L is length of the wires and
A is the cross section area.
For DC System, the diameter of cables used for wiring will be more than that used for same
amount of AC Load. In case of Solar PV System Wiring, usually Copper wiring is used.
Resistivity of Copper = 1.678 x 10-8 Ω-m.
The distance from solar panels to the actual load is maximum of 100 m.
Voltage drop in wires for 100 m of wiring = 2 𝑥 1.678 𝑥 10−8 𝑥 100
5 𝑥 10−6 = 0.67V … (Eqn 3.27)
Also, % Voltage drop = Voltage Drop
System Voltage =
0.67
24= 2.78 % … (Eqn 3.28)
The voltage drop in the wires generally should be less than 4% of system voltage. In this case it
is 2.78%, which is less than 4%. Hence, Cu wires with cross sectional area of 5 mm2 can be used.
23
Therefore, the system has been designed and the ratings of components are shown in Fig 3.6.
Fig 3.6 Ratings of components of Proposed System
3.3.6 Design of Buck Boost Converter [13]
In study state, the time integral of inductor voltage over one time period should be zero.
∫ 𝑉𝑙 𝑑𝑡 = 0𝑇𝑠
0
∫ 𝑉𝑑 𝑑𝑡𝐷𝑇𝑠
0
+ ∫ −𝑉𝑜 𝑑𝑡 = 0𝑇𝑠
𝐷𝑇𝑠
𝑉𝑑(𝐷𝑇𝑠) − 𝑉𝑜(1 − 𝐷)𝑇𝑠 = 0
𝑉𝑜
𝑉𝑑=
𝐷
1 − 𝐷
Abbreviation:
(VIN)MAX = Maximum Input Voltage, (VIN)MIN = Minimum Input Voltage, VOUT = Output
Voltage, IOUT = Output Current, D = Duty Cycle, η = Efficiency
24
3.3.6.1 Duty Cycle Calculation
The first step after selecting the operating parameters of the converter is to calculate the
minimum duty cycle for buck mode and maximum duty cycle for boost mode. These duty cycles
are important because at these duty cycles the converter is operating at the extremes of its
operating range. The duty cycle is always positive and less than 1.
Dbuck =Vout × η
Vinmax
Dbuck =24×0.9
30.1= 0.717 … (Eqn 3.29)
Dboost = 1 −Vin × η
Vout
Dboost = 1 −30.1×0.9
24 = 0.4 … (Eqn 3.30)
3.3.6.2 Selection of Inductor
𝑉𝑖𝑛𝑚𝑖𝑛 = 16𝑉
𝑉𝑖𝑛𝑚𝑎𝑥 = 30.1𝑉
𝐼𝑜𝑢𝑡 = 99.167𝐴
𝑉𝑜𝑢𝑡 = 24𝑉
𝜂 = 0.9
Buck Mode:
𝐿 =𝑉𝑜𝑢𝑡×(𝑉𝑖𝑛𝑚𝑎𝑥−𝑉𝑜𝑢𝑡)
𝐾𝑖𝑛𝑑×𝐹𝑠𝑤×𝑉𝑖𝑛𝑚𝑎𝑥×𝐼𝑜𝑢𝑡
Usually 0.2 < 𝐾𝑖𝑛𝑑 < 0.4.
Assuming 𝐾𝑖𝑛𝑑 is 0.3,
∆𝐼𝑙=𝐾𝑖𝑛𝑑 × 𝐼𝑜𝑢𝑡 = 0.3 × 99.167
∆𝑰𝒍= 29.75 A
𝐿 =24×(30.1−24)
0.3×20× 103×30.1×99.167 = 8.174 µH … (Eqn 3.31)
25
Boost Mode:
𝐿 =𝑉𝑖𝑛𝑚𝑖𝑛2×(𝑉𝑜𝑢𝑡−𝑉𝑖𝑛𝑚𝑖𝑛)
𝐾𝑖𝑛𝑑×𝐹𝑠𝑤×𝑉𝑜𝑢𝑡2×𝐼𝑜𝑢𝑡
𝐿 =162×(24−16)
0.3×20× 103×242×99.167 = 5.975 µH … (Eqn 3.32)
Usually larger value of inductor is selected so that it has higher current rating than the Switch
Current. Therefore, we select inductor of value 8.174µH.
L = 8.174 µH
E =1
2× LIm2 =
1
2× 8.1 × 10−6 × (239.98)2 = 0.2333J … (Eqn 3.33)
AP =
2E
Kw×Kc×J×Bm=
2×0.2333
0.2×0.6×3×106 = 129.61 x 104 mm4 … (Eqn 3.34)
Selection of core for Inductor [14]
Core: UU-100
Apnew = 187.95mm4
Acnew = 645mm4
Awnew = 2914mm2
Number of turns, N = L×Im
Bm×Acnew
N = 8.1×10−6×239.98
0.2×645×10−6 = 15.06 ≈ 16 turns … (Eqn 3.35)
Selection of Wire gauge [15]
a =I
J=
99.1667
3×106 = 3.3055 x 10-6 … (Eqn 3.36)
Wire of gauge SWG14 and cross sectional area anew = 3.243 mm2 is selected.
26
3.3.6.3 Selection of Capacitor
Output capacitance that is larger than both minimum required output capacitance for buck and
boost mode operation is selected.
Assuming ΔV = 1% of VOUT = 0.01 x 24 = 0.24 V
Buck mode:
Coutmin1 =Kind×Iout
8×Fsw×∆Vout=
0.3×99.167
8×20000×0.24 = 774 µF … (Eqn 3.37)
Coutmin2 =(Kind×Iout)
2×L
2×∆Vout×Vout=
(0.3×99.167)2×8.2×10−6
2×0.24×24 = 629 µF … (Eqn 3.38)
Boost Mode:
Coutmin3 =Iout×Dboost
Fsw×∆Vout =
99.167×0.4
20000×0.01×24 = 8.26 mF … (Eqn 3.39)
Hence, output capacitor with maximum value is selected is of 8.26 mF.
C = 8.26 mF
3.3.7 Payback Period Calculation
After investing money into a Solar PV System, it is desirable to find out in what time the
invested money is going to be recovered. The comparison has to be made with other electricity
source that is used currently i.e. grid electricity. The period within which the invested money can
be recovered is known as Payback Period.
The Payback Period is the amount of time that is obtained by dividing the initial investment and
operating and maintenance cost and replacement cost by the cost of annual energy savings due to
the PV system in which money is invested.
Payback period is calculated considering following three cases:
(i) Standalone Solar PV System with Lead Acid battery bank
(ii) Standalone Solar PV System connected directly to the load during day time
27
3.3.7.1 Standalone Solar PV System with Lead Acid battery bank
Initial Investment Calculation:
Details of components for solar PV system with its cost is given in Table 3.2.
Table 3.2 Cost of components of Solar PV system
Material Quantity Unit Cost (INR) Total (INR)
Renogy 250W Solar
Panel 58 18,525 10,74,450
Batteries
(24 V, 100 A-h ) 40 11,600 4,64,000
DC-DC
Buck-Boost
Converter
1 6,700 6,700
Wiring Length = 300m 40/m 12,000
SYSTEM COST 15,50,450
VAT 4% on System Cost 62,018
Labour Cost Approximately 10%
of System Cost 1,55,045
TOTAL COST INR 17,67,513
MNRE provides 30% capital subsidy on capital expenditures for rooftop solar system for
both commercial and residential entities for systems up to 100 kW. The government also
provides loans at 5% per annum for 50% of the capital expenditure for 5 years tenure for both
commercial and residential entities. Commercial entities can claim either capital or interest
subsidies.
Therefore, 30% of initial investment = 0.3 x 17,67,513 = INR 5,30,254 … (Eqn 3.40)
This project is eligible for the subsidy from MNRE for INR 5, 30,254 which will be paid directly
to you after the completion of installation and submitting relevant documents.
28
Effective Initial Investment = INR 17,67,513 – INR 5,30,254
= INR 12,37,259 … (Eqn 3.41)
Operating and Maintenance Cost:
Operating and maintenance cost is approximately 1-2% of the system cost per annum.
Therefore, operating and maintenance cost = 1% of INR 15,50,450 = INR 15,505 … (Eqn 3.42)
Replacement Cost:
Life of the lead-acid batteries used in this system is around 3-5 years. Therefore, they need to be
replaced approximately after every 4 years. That is, after every 4 years, colony will have to pay
INR 928000 for replacing batteries. Generally, life cycle of solar PV plant is 25 years. Therefore,
batteries need to be replaced at least 5 times after 4 years.
Total replacement cost = 4,64,000 x 5 = INR 23,20,000 … (Eqn 3.43)
Lifecycle cost of the system (CL),
CL = Effective Initial Investment + Operating and maintenance cost + Replacement cost
= 12,37,259 + 15,505 + 23,20,000 = INR 35,72,764 … (Eqn 3.44)
Total Energy Cost per year = INR 77,066.1
Payback Period:
Payback period = Life Cycle Cost of system
Total Energy cost per year=
35,72,764
77,066.1= 46.36 years ≈ 47 years … (Eqn 3.45)
Typically life of Solar Panels is 25 years and Payback period with Lead Acid battery bank is
calculated to be 46 years. This topology using Lead Acid battery bank wherein energy is stored
in batteries during day and used from the batteries during night time is not feasible as payback
doesn’t occur because batteries need to be replaced every 4 years which cost INR 4, 64,000 per
replacement.
29
3.3.7.2 Standalone Solar PV System connected directly to the load
Initial Investment Calculation:
In this topology, the battery bank is eliminated and the Solar Panels are directly connected to the
load through DC-DC Buck Boost Converter as shown in Fig 3.7.
Fig 3.7 Standalone Solar PV System directly connected to load
Details of components for solar PV system connected directly to load with its cost is given in
Table 3.3.
Table 3.3 Cost of components of Solar PV system
Material Quantity Unit Cost (INR) Total (INR)
Renogy 250W Solar
Panel 58 18,525 10,74,450
DC-DC Buck-Boost
Converter 1 6,700 6,700
Wiring Length = 300m 40/m 12,000
SYSTEM COST 10,93,150
VAT 4% on System Cost 43,726
Labour Cost Approximately 10% of
System Cost 1,09,315
TOTAL COST INR 12,46,191
MNRE provides 30% capital subsidy on capital expenditures,
Therefore, 30% of initial investment = 0.3 x 12,46,191 = INR 3,73,857 … (Eqn 3.46)
30
This project is eligible for the subsidy from MNRE for INR 3, 73,857which will be paid
directly to you after the completion of installation and submitting relevant documents.
Effective Initial Investment = INR 12,46,191 – INR 3,73,857
= INR 8,72,334 … (Eqn 3.47)
Operating and Maintenance Cost:
Operating and maintenance cost is approximately 1-2% of the system cost per annum.
Therefore, operating and maintenance cost = 1% of INR 10,93,150 = INR 10,932 … (Eqn 3.48)
Replacement Cost:
Only replacement cost in this topology will be that of capacitors and wires. Considering
replacement cost to be 10 % of system cost, we get,
Replacement Cost = 10% of 10,93,150 = INR 1,09,315 … (Eqn 3.49)
Lifecycle cost of the system (CL),
CL = Effective Initial Investment + Operating and maintenance cost + Replacement cost
= 8,72,334 + 10,932 + 1,09,315 = INR 9,92,581 … (Eqn 3.50)
Total Energy Cost per year = INR 77,066.1
Payback Period:
Payback period = Life Cycle Cost of system
Total Energy cost per year=
9,92,581
77,066.1= 12.87 years ≈ 13 years … (Eqn 3.51)
Therefore, if the Solar PV System supplies energy to the load during day time, Payback period
is 13 years. As life of solar PV panels is typically 25 years and after the initial investment is
recovered in 13 years, the profit period of the system begins.
31
Chapter 4
Simulation Results of Buck Boost Converter
To analyse the operation of Buck Boost converter simulation is carried out using MATLAB
software. The specification of the converter is Vin = 20V, Vout = 24V, f = 20kHz,
Iout = 0.5A, RL = 48Ω. Components designed and selected are given in Table 4.1
Table 4.1 Components to simulate Buck Boost converter
Components Value
Source Voltage (solar PV) 20𝑉
Inductance 2𝑚𝐻
Capacitance 100𝜇𝐹
Load Resistance 48Ω
32
Simulation is carried out into two parts:
1) Open loop simulation
2) Closed loop simulation
4.1 Open loop Simulation
MATLAB model of the Buck Boost converter is given in Fig 4.1.
Fig. 4.1 MATLAB model of the Buck Boost converter
By controlling the switching of MOSFET i.e. (Duty Cycle) it is possible to control the output
voltage. For above simulation duty cycle is assumed to be 0.545 (or 54.5%) and output voltage
theoretical value is given by the equation 𝑉𝑜 =𝑉𝑖𝑛∗𝐷
(1−𝐷) = 24V.
A pulse with 54.8% Duty is shown in Fig 4.2 which is given to MOSFET.
Fig 4.2 Pulse given to MOSFET
33
It is seen that, when pulse is given, switch will be on, and hence voltage across the switch will be
zero, and inductor will charge. When pulse is off voltage across the switch will be Vin-Vout= 20-
(-24) = 44V. When switch is off, diode will be reversed biased (open) hence there will be voltage
across the diode will be Vin-Vout=20-(-24) = 44V. When switch is on diode will be forward
biased and voltage will drop to zero. Simulated voltage across switch and Diode is shown in
Fig. 4.3.
Fig 4.3 Switch and Diode Voltage Waveform
When switch is on, input voltage source is directly connected to the inductor L. Also when
switch is on inductor current will start increasing and when switch is off inductor current will
start decreasing but inductor current never falls to zero. Hence average value of inductor current
calculated is 1.106A and measured as 1.15A Also inductor voltage when switch is on is +20V
and when switch is off is -25V as shown in Fig 4.4.
Fig 4.4 Inductor current and Inductor Voltage
34
From the Fig 4.5 it is clear that the measured value of output voltage is 24.1V which matches
with calculated value of 24V as shown in Fig 4.5.
Fig 4.5 Output Current and Output Voltage
The Table 4.2 shows calculated and measured values.
Table 4.2 Output Parameters
Parameters Calculated Measured
Inductor Current 1.106A 1.15A
∆𝐼𝑙(Inductor current ripple) 30% 25%
Output Current 0.5A 0.498A
Output Voltage 24V 23.9V
∆𝑉𝑜 (Output Voltage ripple) 5% 2%
4.2 Closed Loop Simulation
A closed loop simulation for implementation of buck boost converter is done using a PI
controller to regulate output voltage to 24V. Output voltage is sensed and compared with
reference voltage of 24 V and error is used to generate the pulse. I controller coefficient (𝐾𝑝 , 𝐾𝐼)
values are given in Table 4.3.
Table 4.3 PI controller parameters
Proportional Controller gain (𝐾𝑝) Integral Controller gain(𝐾𝑖)
0.5 10
35
MATLAB model of closed loop voltage control is shown in Fig 4.6.
Fig 4.6 MATLAB model of closed loop simulation
4.2.1 Generation of Pulse for voltage control
The output voltage 𝑉𝑜 is sensed and compared with reference voltage 24 V. Sensed voltage is
multiplied by -1 as it is negative .Error which is difference between measured and reference
value is given as input to PI controller block, then PI controller will produced an error signal
which is then compared with triangular waveform of frequency 20KHz using relational operator.
The waveforms of error signal and repeating signals are as shown in Fig 4.7. The output of
relational operator is the desired pulse and is shown in Fig 4.8.
Fig 4.7 Error signal and Repeating signal
36
Fig 4.8 Pulse for MOSFET
4.2.2 Simulation Result
To verify the operation of Buck Boost converter in both buck and boost mode simulation is
carried out by giving input voltage both greater and less than the output system voltage.
Case 1: Boost Mode
Assume supply voltage of 20V, which is less than the desired output voltage of 24V, Closed loop
system automatically change the duty cycle and regulate output voltage
Fig 4.9 Output Voltage waveform for Boost Mode
Fig 4.10 Pulse for Boost Mode
37
Case 2: Buck Mode
Assume supply voltage of 30V, which is greater than the desired output voltage of 24V, Closed
loop system automatically change the duty cycle and regulate output voltage
Fig 4.11 Output Voltage waveform for Buck Mode
Fig 4.12 Pulse for Buck Mode
38
Chapter 5
Hardware Implementation of Standalone Solar PV System
A 75 Wp Solar panel with VOC = 20.6 V, ISC = 3.64 A is used for hardware implementation. It is
connected to a load of 100 Ω resistor through a buck boost converter.
Implementation of Hardware was done in the following steps:
1. Implementation of Buck – Boost Converter
(a) Implementation of Power Circuit
(b) Implementation of Control Circuit
2. Testing of Solar PV Panel
3. Implementation of Hardware for complete Solar PV system
39
5.1 Implementation of Buck Boost Converter using DSP TMS320F28069
The Buck Boost Converter is built up of MOSFET switch, inductor, diode and output side
capacitor as shown in Fig 5.1. Buck Boost Converter consists of 2 circuits namely Power Circuit
and Control Circuit. Buck Boost Converter steps up or steps down the input voltage depending
on the duty cycle of the pulses fed to the MOSFET switch by Control Circuit. Therefore, Control
Circuit ensured that proper pulses are given to the MOSFET and it is fired when desired. As the
system voltage is considered as 24 V, hence output voltage of Converter is 24 V. A DSP
TMS320F28069 is used for generation of pulses for MOSFET and switching frequency is
selected as 20 kHz. Table 5.1 gives the component specifications.
Fig 5.1 Buck Boost Converter Power Circuit
Table 5.1 Component Specifications
MOSFET Switching
Frequency Inductor Capacitor Diode
Fuse
Capacity Load
IRF 840N 20 kHz 2 mH 100 µF MVR 160 1 A 100 Ω
40
5.1.1 Implementation of Power Circuit
Hardware of power circuit of buck boost converter is implemented and is shown in Fig 5.1 and
the output voltage waveforms are obtained on Digital Storage Oscilloscope (DSO). The input
voltage is varied in such a way that the converter is made to operate in both boost and buck
mode. As the output voltage of converter is 24 V, if the DC input supply is greater than 24 V it
will buck the input voltage with duty cycle being less 50% and if DC input supply is less than 24
V it will boost the input voltage with duty cycle greater than 50%.
5.1.2 Implementation of Control Circuit
Gate – Driver Circuit of HCPL 3120 provides isolation between control and power circuit.
Otherwise any undesirable power circuit conditions result in damage to control circuit also. The
Gate – Driver Circuit is implemented using HCPL 3120 as shown in Fig 5.2.
Fig 5.2 Gate – Driver Circuit of HCPL 3120
Input to gate driver circuit are gate pulses from DSP and 330 Ω resistance is provided to limit the
input current within the limit of HCPL 3120. The 10 Ω resistor at pin 6 (or pin 7) is selected in
such a way that maximum peak output current rating of gate driver optocoupler is not exceeded.
10 kΩ resistor is added to ensure MOSFET locking even when driver supply voltage is turned
off and voltage is applied to power circuit. Operating voltage applied between pin 8 and pin 5
determines peak voltage of output pulse. DC supply for driver circuit must be from isolated AC
supply.
For 60% duty cycle, the output of Gate – Driver Circuit is obtained as shown in Fig 5.3 having
peak to peak value of 14.2 V.
41
Fig 5.3 Gate – Driver Circuit Output
5.1.2.1 Auxiliary Power Supply
Auxiliary power supply is required to provide DC supply to gate driver circuit. HCPL A3120
requires 15V supply and is provided by 7815 regulator circuit. Fig 5.4 shows 7815 regulator
circuit.
Fig 5.4 Regulator Circuit
42
The 18 V AC supply at the input of regulator circuit is converted to DC by diode bridge rectifier
IC DB107. For providing 18 V AC supply, conventional transformer with primary winding of
230 V and seven secondary windings of 18 V each and two secondary windings of 9 V each is
used as shown in Fig.5.5.
Fig 5.5 Transformer for Auxiliary Power Supply
5.1.2.2 DSP Processor
Digital Signal Processor used is TMS320F28069 and control stick has a total of 32 pins and is
shown in Fig 5.6.
Fig. 5.6 DSP TMS320F28069
43
Code composer studio is the software used for coding, debugging, loading and running programs
in DSP. Control Suite provides sample project CPU TIMER in which code for pulses is written.
Fig 5.7 shows pin details of DSP.
Fig 5.7 Pin Details of DSP TMS320F28069
5.1.3 Buck boost converter results
Load connected to the system is 100 Ω (10 W). Therefore, as system voltage is 24 V, output
current Io is given by,
Io = 24
100= 0.24 A. ... (Eqn 5.1)
Now, VO = 24 V, VIN = 16.89 V and for buck boost converter, duty cycle (D) can be found out
by,
Vo
𝑉𝑖𝑛=
𝐷
1−𝐷 … (Eqn 5.2)
By substituting values of VO and VIN in Eqn 5.2, we get value of duty cycle D as 0.587.
44
The waveform of output voltage for VIN = 16.89 V and D = 0.587 is shown in the Fig 5.8. For
these specifications, converter works in boost mode.
Fig 5.8 Output Voltage Waveform for VIN = 16.89 V
For VIN = 30 V, Duty cycle D = 0.44 from Eqn 5.2 and output voltage waveform is shown in
Fig 5.9. For these specifications, converter works in buck mode.
Fig 5.9 Output Voltage Waveform for VIN = 30 V
45
5.2 Solar Panel Testing
Testing of Solar Panel is done to find out the Open Circuit Voltage (VOC) and Short Circuit
Current (ISC) of the panel at a particular radiation. VOC gives us the information about the
maximum voltage that can be obtained from the panel and ISC tells us about the maximum
current that the panel can supply.
Solar Panel testing was carried at 11.30 am on 22nd March, 2016 to measure VOC and ISC of 75
Wp Solar Panel. Measured values are given in Table 5.2 and connection diagram for this testing
is shown in the Fig 5.10 (a) and Fig 5.10 (b).
Table 5.2 Measured values of VOC and ISC of at 11.30 am on 22nd March, 2016
VOC ISC
20.6 V 3.6 A
(a) Open Circuit Voltage (b) Short Circuit Current
Fig 5.10 Solar Panel Testing
The voltage supplied by the panel is less than VOC when solar panel works at Maximum Power
Point (MPP) and is generally 80 to 90% of VOC.
46
Therefore, Voltage supplied by panel VM = 0.82 x 20.6 = 16.89 V.
Solar panel V-I characteristics is obtained by connecting different values of resistances across
the panel and measuring voltage across it and current flowing through the resistances. The
voltage and current are measured for values of resistances specified in Table 5.3.
Table 5.3 Measured values of voltage and current for different values of resistances
Resistance (Ω) Voltage (V) Current (A)
75 17.1 2.4
150 10 3.5
As per the values of voltage and current from Table 5.3, I-V characteristics of Solar Panel is
plotted in Fig 5.11.
Fig 5.11 I-V characteristics of 75 Wp Solar Panel
Fig 5.11 shows that operating point depends on load connected to the system. It is seen that at
this point, the system is not extracting maximum power from the panel. To extract maximum
power, the operating point of the Solar panel should be at Maximum Power Point (MPP). This
can be achieved by using DC-DC converter.
47
5.3 Implementation of hardware using solar panels
The Hardware setup of complete solar PV system to light LEDs is shown in Fig 5.1. The input
supply is given by the solar panels and is fed to buck boost converter. The output of buck boost
converter is given to LED lights.Pulses required for operation of MOSFET IRF 540N is given
through gate driver circuit by DSP TMS320F28069. Fig 5.12 shows photograph of hardware
setup.
Fig 5.12 Hardware Setup
The components are numbered and are as follows:
1. Conventional transformer
2. Regulator Circuit
3. Buck Boost Converter (12W)
4. Solar PV panels (75 WP)
5. Code Composer Studio (v6.1.2)
6. DSP TMS320F28069
7. LED Lights (24V, 12W)
48
Chapter 6
Conclusions and Future Scope
The objective of the National Solar Mission is to establish India as a global leader in solar
energy. With about 300 clear, sunny days in a year, India's theoretically calculated solar energy
incidence on its land area alone, is about 5,000 trillion kilowatt-hours (kWh) per year [16].
The Indian government has launched Jawaharlal Nehru National Solar Mission (JNNSM) with a
target of achieving 20000 MW by 2022. The goal is to make India one of the leaders in solar
energy. Although solar energy is still expensive today, but costs are coming down with
technology development, right governmental policies and research and development.
49
In this project work efforts have been made to join the hands with current scenario of solar
energy in the nation. The design of Solar PV system along with the batteries and converters is
carried out and payback period is calculated. The payback period for solar PV system for
corridor lighting using LED lights is calculated. It is found that with Lead Acid Battery as energy
storage device, payback period is 46 years. This period is quite large especially when the life
span of Solar Panel is considered which is usually about 25 years. So, payback period calculation
is done for system connected to day time loads only, without the battery bank. The payback
period is found to be 13 years which is less than life span of Solar Panel.
A standalone system without battery bank for a 75W solar panel using a 12W buck boost
converter for a 24V LED strip using DSP TMS320F28069 is developed and tested.
Even though this system will be used only for day time loads, it will go a long way in reducing
the use of conventional energy and to promote clean energy in the future. Thus the Kendriya
Vihar colony authorities are suggested to go for this system at least on part load basis. They have
taken the case study for a further in depth review and are happy with the efforts.
To increase the efficiency of the roof top solar PV system implantation of Maximum Power
Point Tracking (MPPT) can be done which is not included in this report. In this method, both the
voltage and current of PV are instantaneously measured to distinguish between irradiance change
and the occurrence of partial shadow when the output power of PV changes. The method can
successfully operate even though a partial shadow arises.
The installation of solar system will make the dream of solar colony true. Thus this project work
is a small initiative to reduce electricity prices to some extent. Also, by making the society aware
of the benefits and the positive impacts of solar energy, we hope to increase the reach of
renewable sources in our city and to somewhat reduce the burden on the ever depleting fossil
fuels.
50
References
[1] Solar Power in India – Wikipedia, the free encyclopedia –
http://en.Wikipedia.org/wiki/solar_power_in_India
[2] National Institute of Solar Energy – Ministry of New and Renewable Energy -
Mnre.gov.in/centers/about-sec- 2/
[3] https://beeindia.gov.in/sites/default/files/1Ch1.pdf
[4] http://knowledge.wharton.upenn.edu/article/can-the-world-run-on-renewable-energy/
[5] http://www.downtoearth.org.in/news/growth-of-renewable-energy-in-india-43605
[6] www.mapsofindia.com/my-india/india/scope-of-solar-energy-in-india-pros-cons-and-the-
future
[7] http://tejas.iimb.ac.in/articles/75.php
[8] https://en.wikipedia.org/wiki/Stand-alone_power_system
[9] https://en.wikipedia.org/wiki/Grid-connected_photovoltaic_power_system
[10] Chetan Singh Solanki, Solar Photovoltaics: Fundamentals Technologies and Applications
[11] Ned Mohan, Tore M. Undeland, William P. Robbins, Power Electronics: Converters,
Applications, and Design, 3rd Edition, September 2002, ©2003
[12] http://renogy.com/renogy-solar/pv-modules/
[13] http://www.ti.com.cn/cn/lit/an/slva535a/slva535a.pdf
[14] Z Umanand, S.P. Bhat, Design Of Magnetic Components for Switched Mode Power
Converters, 01-Dec-1992, Appendix 1
[15] Z Umanand, S.P. Bhat, Design Of Magnetic Components for Switched Mode Power
Converters, 01-Dec-1992, Appendix 2
[16] http://www.mnre.gov.in/