ABSTRACT
The potentials of large scale solar photovoltaic power generation in Sokoto
State, North -Western Nigeria and Port Harcourt, Southern Nigeria were
evaluated through the application of solar PV Sys computer software. Daily
average solar radiation in both locations and average relative humidity from
2001 to 2010 was obtained from Nigerian Metrological Weather Forecast
Centre, Abuja. The data together with recorded Minimum/Maximum
Temperatures were applied as simulation input parameters to activate the
computer program. Results obtained were used to estimate the total energy
production capacity of a 200kW and 500kW photovoltaic power plant in Sokoto,
as compared to the same capacity of power plant located in Port Harcourt. It
was observe that, the total energy production capacity of a 200kW PV power
plant in Sokoto state is 532MWhr/yr, while the same power plant in Port
Harcourt could only produce 223MWhr/yr. The economic analysis also indicate
that the cost of 200kW PV power plant in Rivers state is higher than the same
power plant located in Sokoto state, North Western Nigeria. Furthermore,
economic analysis of large scale solar photovoltaic power generation was made
and a model of 4 x 250kW mini grid systems was developed.
TABLE OF CONTENTS
TITLE PAGE ………………………………………………………………………………………….. i
DEDICATION ………………………………………………………………………………………… ii
CERTIFICATION …………………………………………………………………………………… iii
ACKNOWLEDGEMENTS ………………………………………………………………………. iv
TABLE OF CONTENTS ………………………………………………………………………….. v
LIST OF FIGURES ……………………………………………………………………………….. vii
LIST OF TABLES ………………………………………………………………………………… viii
ABSTRACT ………………………………………………………………………………………….. ix
CHAPTER ONE
1.0 INTRODUCTION AND LITERATURE REVIEW ………………………………… 1
1.1 Introduction ………………………………………………………………………………….. 1
1.1.1 Research Problem ………………………………………………………………………… 2
1.1.2 Scope and Delimitation …………………………………………………………………. 2
1.1.3 Independent Power Projects (IPP) ………………………………………………….. 6
1.1.4 National Integrated Power Projects (NIPP) ………………………………………. 6
1.2 Literature Review …………………………………………………………………………. 7
1.2.1 Classification of Solar PV Power Plants …………………………………………. 17
1.2.2 Stand Alone Solar PV System ………………………………………………………. 18
1.2.3 Hybrid System ……………………………………………………………………………. 18
1.2.4 Grid Connected ………………………………………………………………………….. 18
1.2.5 Characteristics of Grid Connected Solar PV System ………………………… 18
1.2.6 PV Sys V5.0 Computer Software ………………………………………………….. 20
1.2.7 Aim and Objectives …………………………………………………………………….. 22
CHAPTER TWO
2.0 MATERIALS AND METHODS ………………………………………………………. 23
2.1 Materials ……………………………………………………………………………………. 23
2.2 Methods…………………………………………………………………………………….. 24
2.2.1 Modeling of the nth Year Cumulative Energy Produced in Sokoto …….. 24
2.2.2 Modeling 1.0MW PV Power System ………………………………………………. 25
2.2.3 Modeling Details …………………………………………………………………………. 25
vi
2.2.4 Project Design ……………………………………………………………………………. 28
2.2.5 Simulation Variant ………………………………………………………………………. 28
2.2.6 Selection of Grid Inverters ……………………………………………………………. 29
2.2.7 Economic Analysis of Solar PV Energy Cost Per Unit of Installation in
Sokoto State ………………………………………………………………………………. 31
2.2.8 Economic Analysis of Solar PV Energy Cost Per Unit of Installation in
Port Harcourt, Rivers State ……………………………………………………………………. 32
CHAPTER THREE
3.0 RESULTS AND DISCUSSION ……………………………………………………… 35
3.1 Results ……………………………………………………………………………………… 35
3.1.1 200kW PV power losses in a year …………………………………………………. 37
3.1.2 500kW PV power losses in a year …………………………………………………. 38
3.2 Discussion …………………………………………………………………………………. 39
3.2.1 Solar PV Equipment Costing ………………………………………………………… 39
3.2.2 Simulation Result in Case of Three Phase Fault Connection …………….. 41
3.2.3 Solar PV Arrangement and Overall System Rating ………………………….. 43
3.2.4 Configuration Details …………………………………………………………………… 43
3.2.5 Inverter Specifications Details ………………………………………………………. 45
3.2.6 D.C Side Protections …………………………………………………………………… 46
3.2.7 Solar SCADA System ………………………………………………………………….. 47
CHAPTER FOUR
4.0 CONCLUSIONS AND RECOMMENDATIONS ……………………………….. 48
4.1 Conclusions ……………………………………………………………………………….. 48
4.2 Recommendations ……………………………………………………………………… 49
REFERENCES…………………………………………………………………………………….. 50
APPENDICES
Maximum Temparature Monthly Average…………………………………………52
Monthly Average Solar Radiation ………………………………………………………54
Mean (Monthly Average) Wind Speed………………………………………………….55
Monthly average Relative Humidity…………………………………………………….56
CHAPTER ONE
1.0 INTRODUCTION AND LITERATURE REVIEW
1.1 Introduction
Nigeria has an installed generation capacity of 8,644MW of electricity (Energy
Commission of Nigeria, 2003). But the increase in population as a result of
urbanization has results in to severe shortage of electricity. According to an
estimate, 70% of Nigerian population does not have access to electricity. The
degree of development and civilization of a country is measured by the amount
of utilization of energy by human beings. At present only 10% of rural
households has access to electricity, (Sambo 2007).
Nigeria is endowed with vast oil and gas reserves and also an abundance of
renewable energy potentials. Yet the country is suffering from an energy crisis,
which has a major impact on its ability to reduce poverty and achieve the
millennium development goals. Solar energy is the most promising of the
renewable energy sources in view of its apparent unlimited potentials. (Energy
Commission of Nigeria, 2003)
Nigeria is situated approximately between 4⁰ N and 13⁰ E and with land mass of
9.24 x 105km2 enjoys an average daily sunshine of 6.25hrs, ranging between
about 3.5hrs at the coastal areas and 9.0hrs at the Northern boundary. This is
equivalent to an annual average daily solar radiation of about 5.25kw/m2/day
varying between about 3.5kw/m2/day at the coastal area and 7.0kw/m2/day at
the Northern boundary (Bugaje, 2011). Despite its relative abundance and
2
pollution free nature, the use of solar energy is at present very limited, although
its application potentials are believed to be significant.
The time is ripe to become aware of the direct contributions of what large scale
solar photovoltaic power generation can make to our lives and economy
especially during this time of erratic power supply by the power holding
company of Nigeria (PHCN).
1.1.1 Research Problem
The depletion of fossil fuel resources on a worldwide basis has necessitated an
urgent search for alternative energy resources to meet up the present day
energy demands. In Nigeria, more than 70% of the power generation is from
fossil fuel power stations (Remote area power supply in Nigeria, 1999).
Therefore in order to satisfy the load demand and provide affordable energy to
rural areas, grid connected solar photovoltaic system can be considered. Solar
energy is clean, inexhaustible and environment – friendly potential resource
among renewable energy options. This natural resource can be channeled
towards provision of electricity to the rural communities.
Despite the abundant availability of solar energy resource in Nigeria, the
contribution of photovoltaic to power generation is less than 1% and is largely
restricted to street lights, pumping and charging of storage batteries.
1.1.2 Scope and Delimitation
The research work will explore the possibility of setting up a large scale solar
photovoltaic power plant in Sokoto state of North Western Nigeria. Availability of
an annual average solar radiation will be obtained and applied for the
3
development of large scale solar photovoltaic power plant. The research will
also examine the difference in locating a photovoltaic power generation in
savannah region and Sudan savannah desert region of Northern Nigeria and a
coastal area of Southern Nigeria. Attempt will be made at identifying the best
site location for the power plant.
The economic evaluation of the large scale PV power plant will also be
considered. However, Load flow and power flow analysis of the large scale PV
system is not part of this study.
Study of the contribution of existing electricity generation facilities in Nigeria,
such as the thermal power plants, the hydro power and the Independent power
projects will also be considered.
4
Table 1.1 shows the existing thermal power stations across Nigeria and the
gross contribution of each to the National energy demand. Total installed
capacity is the estimated capacity of the generators in the power plant, while the
available capacity is the production capacity of the power plant less
depreciation factors.
Table 1.1 Existing FGN Power Stations – Thermal
S/N Name of Power
Station
Year Location Installed
Capacity
(MW)
Available
Capacity
(MW)
1 Egbin Power
station
1986 Egbin, Lagos 1320 1100
2 Garegu Power
Station
2007 Garegu, Kogi 414 276
3 Omotosho Power
Station
2007 Omotosho,
Ondo
304 76
4 Olorunsogo
Power Station
2008 Olorunsogo,
Ogun
304 76
5 Delta Power
Station
1966 Ughelli, Delta 900 300
6 Sapele Power
Station
1978 Sapele, Delta 1020 90
7 Afam IV-V 1963 Afam, Rivers 726 60
8 Calabar Power
Station
1934 Calabar,
Cross River
6.6 Nil
9 Orji River Power
Station
1956 Orji, Enugu
State
10 Nil
Total – – 5,004.6 1978
Source: Power Holding Company of Nigeria, Key Performance Indicators Unit
(KPI)
5
Table 1.2 shows the existing hydro power stations across Nigeria and the gross
contribution of each hydro station to the National energy demand. When
Mambilla hydro power stations is completed the available capacity of the hydro
power stations will increases significantly with additional 3.050MW. Both
Challawa, Kiri and Tiga are classified as Small Hydro Power (SHP) projects
Table 1.2 Independent Power Plants – Thermal
S/n Name of power plant Location Installed
cap (mw)
Avail. Cap
(mw)
1 AES Power station Egbin, Lagos 224 224
2 Shell power station Afam, Rivers 650 650
3 Agip power station Okpai, Delta 480 480
4 ASG Ibom power station Akwa Ibom 155 76
5 RSG Power station Omoku, Rivers 150 30
Total – 1759 1484
Source: Power Holding Company, Project Monitoring Unit (PMU)
6
1.1.3 Independent Power Projects (IPP)
The IPP’s are the non- Federal Government funded investment in the Nigerian
power generation industry. From the table below, it can be seen that there is no
much difference between the installed and available capacities apart from the
power plants in Akwa Ibom and Omoku Rivers.
Table 1.3 NIPP Power Projects
S/N Name of power plant Location Designed cap
(MW)
Current cap.
(MW)
1 Calabar power project Cross Rivers 563 Nil
2 Egbeme power project Imo state 338 Nil
3 Ihorvor Power project Edo state 451 Nil
4 Gbarau Power project Bayelsa state 225 Nil
5 Sapele power project Delta state 451 Nil
6 Omoku power project Rivers state 225 Nil
7 Alaoji power project Abia state 961 Nil
8 Olorunsogo phase II
project
Ogun state 676 676
9 Omotosho phase II
project
Ondo state 451 451
10 Garegu phase Ii project Kogi state 434 434
Total – 4,775 1,561
Source: National Integrated Power Projects NIPP
7
1.1.4 National Integrated Power Projects (NIPP)
The National Integrated Power Projects (NIPP) is funded and owned by the
three tiers of government (Federal, States and LGA’s) these facilities are
currently being constructed and will be operated via operation and maintenance
contract when commissioned, prior to the privatization of the power stations.
However, most of the projects are at various stages of completion largely due to
poor funding from the government. Three power plants, namely Omotosho,
Oluronshogu and Garegu has been completed and commissioned to the grid.
8
1.2 Literature Review
The conversion of light energy into electricity was invented by Edmund
Becquerel in 1839, but the practical solar cell and their applications did not
appear until 1950’s (Barnett, 1996). By the beginning of 1960’s solar power was
used in small power applications to provide small power requirements. The
following list indicates how the solar power levels have grown over the years to
produce MW scale large power system in numerous applications.
Figure 1.1: Stages of solar photovoltaic power generation (Barnett, 1996)
Remote application in satellite
communication stations etc
Application in solar home system
(50W)
Application in small drip irrigation
systems (100W)
Powering computers in remote
schools and road signage (500-
1000W) range
Solar power applications on
buildings (rooftop) 1kW range
Large scale power generation in
desert for electricity generation
in (MW) range
Low power applications in
calculators, wristwatches etc
(mW and W range)
9
It is important to state that the amount of literature on solar energy, the solar
energy system and photovoltaic grid connected system is enormous. So much
study is needed to design a grid – connected photovoltaic system.
Kumar and Bigger (1993) assessed different PV systems based on their types,
output characteristics, various system configurations, modeling, design and
economic considerations. Their assessment also includes some specific areas
for further research and development. Although no major technical barriers are
evident the entry of PV, as the level of penetration increases, several key issues
identified in this paper will need further consideration. Photovoltaic’s is still
evolving and has not reached its full potential. It is likely to grow for decades to
come, however the rate of growth may be dependent on several exogenous
factors such as the cost of conventional energy sources and the people desire
to improve the global environment.
Gupta (1994) presented a paper about design, development and installation of
100kW utility grid connected solar photovoltaic power plants for rural
application. This paper briefly describes title features of the two power plants,
the developmental approach adopted based on “Building block Philosophy” with
25kV system as the basic unit with the attendant advantages. It includes the
indigenous design and development effort made for grid connected operation
and most importantly the special design features incorporated to ensure a very
high degree of safety and protection so necessary in the rural areas with
predominantly non-literate user. Title paper is concluded with some import
lessons learnt from both the technical and logistics point of view for guiding
10
installation of similar such plants in the remote rural areas in India and other
developing countries in the future.
Alonso and Pedro (1994) examines the intelligent PV module concept a low –
cost – high – efficiency dc-dc converter with maximum power point tracking
(mppt) functions control and power line communications (plc) in addition they
analyses the alternatives for the architecture of grid connected PV systems
centralized string, and modular topologies. The proposed system i.e. the
intelligent PV module fits within the last group. Its principles of operation, as
well as the topology of boost dc – dc converter, were analyzed. This paper
describes powerful tool especially designed to evaluate all kinds of PV systems.
Large grid connected photovoltaic power plants, aimed at delivering energy to
the grid, however the cost of 1 kWh of PV energy is still very high compared to
conventional fossil fired power plants.
Sugihara (1995) presented paper about the cost analysis of very large scale PV
system on the world desert. A 100MW very large scale photovoltaic power
generation (VLS-PV) system was estimated assuming that it is installed on the
world deserts, which are Sahara, Negev, Thar, Sonora, great sandy, and Gobi
desert. Photovoltaic array layout, support, foundation, wiring and so on. Then
generation cost of the system life cycle cost (LCC) As a result of the estimation,
the generation cost was estimated
Azeved (1996) carried out a comparative study on the efficiency of Topologies
in photovoltaic energy conversion systems. In special, a study of losses was
presented and the methodology was used to compare different topologies for
grid connected photovoltaic systems. The systems were also tested with
11
photovoltaic generation as well as current harmonic and reactive power
compensation simultaneously. Using the loss models, it is possible to estimate
efficiency and make a comparative study of different conversion systems.
Alsema(1997) presented a paper about a cost and environmental impact
comparison of grid connected rooftop and ground based PV systems. The
environmental impact and total system costs have been investigated for rooftop
and ground based crystalline silicon PV systems by using environmental and
cost life cycle assessment. Green house gas emissions and other
environmental impacts from Balance – of the – system component are relatively
small, in comparison with present day modules frameless laminates are largely
preferred from an environmental point of view, and the extra impacts from a
somewhat heavier mounting structure are more than compensated by the
avoided impacts of the frames. Roof systems clearly have a lower
environmental impact of the balance of system compounds in comparison to on
– the roof and ground-based systems.
Alsema (1997) gave an idea about environmental aspect of photovoltaic power
systems. During normal operations, photovoltaic (PV) power systems do not
emit substances that are harmful to normal health or the environment. In fact,
the savings in conventional electricity production can lead to significant
emission reductions. However there are several indirect environmental impacts
related to PV power systems that require further considerations. The production
of present generation PV power systems is relatively energy intensive, it
invokes the use of large quantities of bulk materials and (smaller) Quantities of
substances that are scarce are or Toxic. During operations damaged modules
12
or fire may lead to the release of hazardous substances. Finally, at the end of
their useful lifetime PV power systems may have to be decommissioned, and
resulting waste flows have to be managed.
Jose and Lo’pez (1998) carried out the economic and environmental studies on
PV solar energy installations connected to the Spanish electric grid system.
First, an economic study was performed, proposing different scenarios where
different values of interest rate and energy tariff were considered. The following
parameters were used to determine the profitability of a PV installation, the net
present value and the pay-back-period. Furthermore the environmental benefits
of PV systems connected to the grid have been evaluated. This has been
accomplished using the life cycle analysis theory of the systems, calculating the
recuperation time of the invested energy, the contamination or emissions
avoided and the externality costs.
Elliot, T. C. (1998). The analysis performed in his paper suggests
recommending centralized power electronic conditioning systems together with
the use of proper simulation – aided design tools.
Recent advances in semiconductor technology have reduced the number of
power conditioners required in a PV system. The power conditioner is an
indispensable component of a photovoltaic power generation system. On the
other hand, power conditioners do have a serious problem. They generate
electromagnetic noise. To make matter worse, the electromagnetic noise that is
generated at power conversion is transmitted to the solar cells through electric
wires, the solar cells serving as an antenna to radiate the electromagnetic
13
noise. The radiated electromagnetic noise may cause operation and
communication failures in other electronic equipment.
Oparaku, (2002), studied the application of Photovoltaic Systems for Power
Supply in Nigeria. The paper extensively evaluated the operations of
Large size grid connected PV systems with storage capacity.
Bacha (2003) proposes evaluation criteria for comparing and choosing
topologies compatible with user’s demands. After presenting an overview of
current architectures used in grid connected systems, five (5) key points for
comparison based on topology upgradeability, performance under shaded
conditions, degraded made operations, investment costs and ancillary service
participation were discussed. The proposed method can be adapted to the
user’s particular needs and expectations of the photovoltaic plant. These
evaluation guidelines may assist grid – tied PV system users to choose the
most convenient topology for their application by weighting the evaluation
criteria.
Marion (2005) studied the performance parameters of grid connected PV
systems. Three performance parameters were used to define the performance
of grid – connected PV systems: final PV system yield (Yf), reference yield (Yr),
and performance ratio (PR). The Yf and PR are determined using the name
plate D.C power rating. The Yf is the primary measures of performance and is
expressed in units of kWh/kW. It provides a relative measure of the energy
produced and permits comparisons of PV systems of different size, design or
technology. If comparisons are made for different time provide or locations it
should be recognized that year-to-year variations in the solar resource will
influence Yf, the PR factors out solar resource variations, resource year. This
14
provides a dimensionless quantity that indicates the overall effect of losses and
may be used to identify when operational problems occur or to evaluate long
term changes in performance. As part of operational and maintenance
program, the PR may be used to identify the existence of performance issues.
Holloway (2005) studied the performance of grid connected PV system with
energy storage. One kilo Watt (1kW) amorphous photovoltaic system has been
operated in a grid connected mode with energy storage. The purpose of the
system development and performance experiment is to investigate the
additional value of a grid connected system garners with dispatch able battery
energy against the added cost of the system and in efficiencies incurred in the
charging and discharging of the batteries.
Stritataew and Sangwang (2006) examined the issues related to the distribution
system reliability improvement using (PV) photovoltaic grid connected system.
The output characteristics of a PV system were experimentally measured. The
measured data were used to investigate the effects of PV system installation to
improve the distribution system’s reliability. The system constraints such as,
recovered real power, and loading reduction of the tie line / switch after the
installation of PV grid-connected systems are concentrated. Simulation results
show that with the action of the tie switch, system losses and loading level of
the tie switch can be reduced with proper installation location.
Wang (2007) researched two grid connected PV photovoltaic power system.
The first one is 10kW located in Beijing, the second one is 100kW located in
Northern china. For 10kW photovoltaic power system, single phase
transformers less – grid connected inverters are applied to this system. The
15
inverters have two stage structures, AC – DC and DC – AC, but they often
operates only with DC – AC stage according to the panel string output voltage.
For 100kW photovoltaic power system, three – phase transformer less grid
connecting inverters were used. But they concluded that although all the
inverters in the two systems have two stage structures, only single stage were
designed to work during most of the time, because their system efficiency can
be readily increased. Large PV system should adopt series wound and for high
operating voltage and minimum less. The research shows the correlations the
output power quality of one inverter of 10kw system was also analyzed.
Chang (2007) presented a paper about effects of the solar Module installing
Angles on the output power. In his paper he – discussed that the output power
increment of photovoltaic cells is mainly based on two factors one is decreasing
the cell modules temperature and the other is increasing the cells received solar
illumination intensity. The former is maintaining a proper radiating space
between the modules and the ground while the later is more complicated. One
needs to consider the installation of cells modules and then the maximum
power output which can be derived. This paper theoretically calculated the
solar orbit and position at anytime and any location they can derived the output
power of the solar module cell at any tilt angle and orientation. The simulated
results could be utilized in large scale photovoltaic power generation systems
when considering placement for optimal installation. It also provides a useful
evaluation for the output power of photovoltaic cells mounted on roofs and on
walls of buildings.
16
Several gird connected photovoltaic system topologies are used in existing
installations.
Ofualagba (2008) in his paper first explained the reasons for mounting interest
in photovoltaic technology and has provided a quick synopsis of the operation of
these technology and their applications and markets. Photovoltaic technology
has received increasing attention over the past decade as one response to the
challenge of global warming, increasing demand for energy, high full costs, and
local pollution (Gupta, 1994). This paper describes (PV) photovoltaic system
(Modules, batteries, power conditioning, generators and pumps) and discussed
the photovoltaic markets including on – grid, off – grid and water pumping
applications.
Jenkins (2009) studied the technical aspect of using photovoltaic systems for
small power supplies, and the overall system design. Typical applications of
photovoltaic system are also described.
Sunandra and Sinha (2009) estimated the grid quality solar photovoltaic power
generation potentials and its cost analysis in some districts of west Bengal. The
objective of their work was to generate solar photovoltaic power in some
districts of west Bengal (Birbhum, Burdwan, Hooghly, Howrah and Kolkata),
Study the solar radiation level and potential of the above mentioned districts
and finally develop a system corresponding to the available potentials.
Equipment specifications were provided based on the system developed and
finally cost analysis was also carried out.
Pavan (2009) reported some of the most promising research approaches
currently in progress on new PV materials and devices, focusing on the
17
reduction of PV generation cost expected from the technological implementation
of such research, their paper reported the main features and the expected
economical effect of two of these researches: The first regard the use of
cadmium telluride thin films, the second concerns the development of novel
non-structured PV materials.
Bugaje, M (2011) Rural electrification with renewable energy. An alliance for
rural electrification with the application of solar photovoltaic technology.
1.2.1 Classification of Solar PV Power Plants
A solar PV power plant can be categorized based on the way it supplies power
to the consumer, as enumerated in Table 1.4
Table 1.4 Types of Solar PV Power Plants
S/no Type of system Application Features
1 Off-Grid Domestic To meet the energy
demand of remote house
– holds and villages,
which are located far
from the grid
Most appropriate technology
utilized globally to provide
electricity for off-grid
communities
2 Off-grid non –
domestic
Provide power for
telecommunication,
water pumping, vaccine
refrigeration and
navigational aids
The first commercial
application of PV system
instigated competition with
small conventional generation
technologies
3 Grid connect and
centralized
Provide backup power as
a centralized power
station
Oil independence and
reduction in green- house
gasses with minimum
operation and maintenance
expenditure
4 Grid connected
distributed
Provide power to a
number of grid
connected customers on
their premises or directly
to the grid
Can be integrated in to the
customer’s premises to
increate reliability and reduce
dependency on the grid.
Plays a role in the smart grid.
18
1.2.2 Stand Alone Solar PV System
This is the type of system which is not connected to the grid. There is a
photovoltaic array that converts sunlight in to electricity and then the energy is
stored in a battery as chemical energy. The stored energy is utilize when the
need arise. It is also known as an off-grid photovoltaic system (Jenkins, 2009).
Application of standalone system are commonly found in calculators,
wristwatches, cell phone towers, road traffic signals, street light, road sign and
water pumping (Jenkins,2009).
1.2.3 Hybrid System
The hybrid PV systems are used in remote areas. They combine a diesel
generator or storage with PV panels. The PV systems are added to provide
24hr power in a more economical and efficient way. The aim of these hybrid
systems is to save diesel and reduce the maintenance and operation cost.
1.2.4 Grid Connected
The PV systems are connected to the grid without battery storage through an
inverter. The PV system must be synchronized with the grid in voltage and
frequency. These systems can be divided into small systems which are usually
located on roof tops and large grid connected.
1.2.5 Characteristics of Grid Connected Solar PV System
The characteristics of the inverter suitable for grid connected system are as
follows
19
The response time; the inverter has to be extremely fast, this is governed
by the bandwidth of the control system.
Power factor; means it has to be locked to the grid.
Harmonic output; traditionally harmonic output is very poor and can be
injected to the grid, which will increase the losses and the power might
have a very poor quality.
Synchronization; It usually uses zero crossing detection on the voltage
waveform.
Fault current distribution; the current is proportional to the amount of light.
The panels are usually rated to produce 1000W/m2. Under these
conditions, the short circuit current possible for these panels is typically 20
times higher than the nominal rate current. If the solar radiation is low, then
the maximum current under short circuit is going to be less than the
nominal full load current (Marion, 2005).
Protection requirement; Four protection requirements has to be taken in to
consideration. Those are; overvoltage, under voltage, over frequency and
under frequency protection schemes.
Photovoltaic LV; this is a low voltage bus which is modeled by an a.c bus
bar with a nominal voltage of 0.4kV (line to line). The steady state voltage
limits are 0p.u and 1.05p.u. In modeling this different busses are
considered as one bus since transmission losses are very negligible.
Step up transformers; In order to raise the voltage level, three phase
transformers are used. Each transformer has a rated power of 250kVA
with a nominal frequency of 50 Hz. The nominal primary/secondary
20
voltages are 0.4/11kV and the vector group is Dyn11. The short circuit
voltage is considered as 6% while no copper loss is assumed.
MV bus; The Medium voltage bus is also modeled by an a.c bus bar with
nominal voltage of 11kV (line to line). The steady state voltage limits are
0p.u and 1.05p.u. This bus bar represents the connection point of the
power plant to the grid.
1.2.6 PV Sys V5.0 Computer Software
PV Sys V5.0 Computer Software is a software package for the study, sizing and
Data analysis of complete PV systems. It deals with grid connected, stand
alone, pumping and DC – grid PV systems. The software is geared to the needs
of Engineers and Researchers. It is also very useful for educational training.
PV Sys V5.0 offers 3-level of PV system study, roughly corresponding to the
different stages in the development of real project. The stages are
a. Preliminary design, project design
b. Project design and
c. Measured data analysis
a. Preliminary Design: this is the pre-sizing step of the project. In this
mode the system yield evaluations are performed very quickly in monthly
values, using only a very few general system characteristics or
parameters without specifying actual system components (Marion, 2005).
For grid connected systems, PV Technology, colors, transparency etc
and all the information required. For standalone systems; this tool allows
sizing the required PV power and battery capacity, given the load profile
and probability that the user will not be satisfied (Marion, 2005).
21
b. Project Design: The first step is aimed at performing total system design
using detail hourly simulations. Within the frame work of a project, it can
perform different system simulation and make comparison. Plane
orientation can also be defined in this mode.
In the second step, the user can specify more detailed parameters and analyze
fine effects like thermal behavior, wiring, module quality, mismatch and incident
angle losses, horizon for shading or partial shadings of near objects on the
array. For pumping system several system designs may be tested and
compared to each other, with a detailed analysis of the behaviors and
efficiencies. Results include several dozens of simulation variables, which may
be displayed in monthly, daily or hourly values. The loss diagram is particularly
useful for identifying the weaknesses of the system design (Chang, 2007).
An engineering report may be printed for each simulation that was run, including
all parameters used for the simulation and the main results. A detailed
economic evaluation can also be performed using real components prizes and
any additional costs and investment conditions (Holloway, 2005).
c. Measured Data Analysis
When a PV system is running and carefully monitored, this part (located in the
tools part) permits the import of the measured data (in almost any ASCII format)
to display tables and graphs of the actual performances, and to perform close
comparisons with the simulated variables. This gives a means of analyzing the
real simulation parameters of the system, and identifies even very little misrunnings
(Kumar and Bigger, 1993).
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