1. MAJOR PROJECT ON
INTEGRATION OF RENEWABLE ENERGY SOURCES IN PSCAD
Submitted by
Sandiip Guptaa (Reg.No: 200913072)
In partial fulfilment of
VIII Semester B.Tech (Electrical & Electronics Engineering)
Under the Guidance of:
Sandip Kumar Gupta
Asst. professor, Electrical and Electronics department, SMIT
Electrical and Electronics Department
Sikkim Manipal Institute of Technology
Majhitar, Rangpo, East Sikkim - 737132

2. Sikkim Manipal Institute of Technology
(Constituent College of Sikkim Manipal University)
This is to certify that Sagnik Sinha Roy (Reg. No: 200913069), Prabhat Giri (201113513)
and Sandiip Guptaa (Reg. No: 200913072) have successfully completed their major project on
“INTEGRATION OF RENEWABLE SOURCES IN PSCAD” in partial fulfilment of the
requirements of the VIII Semester Electrical & Electronics Engineering of Sikkim Manipal
Institute of Technology under the supervision and guidance of Mr. Sandip Kumar Gupta, Asst.
professor, Electrical And Electronics department, SMIT.
Prof. D. Suryanarayana Mr. Sandip Kumar Gupta
H.O.D. (Deptt. of E&E) Internal Guide
SMIT (Deptt. Of E&E)
SMIT
ACKNOWLEDGEMENT

3. At the very onset, we would like to offer our sincere gratitude to Sikkim Manipal Institute of
Technology’s Electrical and Electronics Department for allowing us to pursue our research on
the major project.
Our special thanks and gratitude goes to our guide and mentor – Mr. Sandip Kumar Gupta for
incessantly offering us a share of his vast knowledge and sparing his precious time to teach us
new things. We are thankful to him for offering insightful suggestions during the project work
and guiding us during the entire project with encouragement.
Last but not the least; I would like to express my sincere thanks to our senior guides, Head of
the Department, Prof. D. Suryanarayana SMIT for giving us the opportunity to present our
research in their august presence.
Special thanks to Amalnath Mani (TECHNICAL ANALYST AT MANITOBA HVDC
RESEARCH CENTRE, WINNIPEG, CANADA.
Sagnik Sinha Roy
Prabhat Kumar Giri
Sandiip Guptaa

4. LIST OF FIGURES
Figure Number Figure Name Figure Page Number
1. Microgrid model 9
2. Equivalent Circuit For Modelling of Solar
System
10
3. Equivalent Circuit For Modelling of Wind
System
11
4. Micro grid Layout 13
5. Micro grid Architecture 17
6. Doubly Fed Induction Generator 23
7. Super synchronous Mode;
Sub synchronous Mode
24
8. Equivalent Circuit of PV module 29
9. Wind Energy Source Configuration 32
10. Wind Energy Associated Models 33
11. PSCAD Modelling of Wind System 34
12. PSCAD model of wind generator
connected to grid
35
13. Equivalent Circuit of Solar PV Module 37
14. Grid-Tied PV Model in PSCAD 40
15. PI controller 41
16. Hybrid model 52

5. LIST OF TABLE
S.No. Name Page No.
1. Micro grid Classification 18
2. Classification Of Control Strategies
For Electronically Coupled DER Units
20
3. PV Module Characteristics 28
4. Wind Turbine Parameters 33
5. PV Array Parameters 37
6. State/UT wise Details About Micro
grid
47

6. CONTENTS
S.NO TOPIC PAGE NO.
1 List of figure 4
2 List of tables 5
3 Abstract 7
4 Introduction 8
5 Modelling of Energy Resources
# PV System
# Wind System
10,11
6 PSCAD Simulation Tool 12
7 Micro grid
#Requirements of Micro grid
#Sources of Micro grid
#Architecture of Micro grid
#Micro grid Operation
13-18
8 DER Control Technique 19-21
9 Wind Energy
#Modes of Operation of DFIG
#Power Output of Wind Turbine
22-26
10 Solar Energy
#PV Module
#Working Principle of PV Module
27-30
11 PSCAD Modelling
#Wind Model
#Output Graphs of Wind Model
#Solar Model
#Output Graphs of Solar Model
31-45
12 Protection Scheme 46
13 Present Ventures 47-48
14 Advantages of Micro grid 48
15 Cost of Micro grid 49
16 Problems and Challenges Faced in Micro grid 50
17 Future Developments 51-52
18 Conclusion 53
19 Reference 54

7. ABSTRACT
Increasing environmental concerns, consumer expectations in terms of reliability & better
quality of power supply and improving economics of distributed energy resources (DER)
based on renewable, is making Micro Grid a viable proposition. Hybrid Micro grid utilising
diversity of various energy resources including Wind, Solar, Biomass, and Energy Storage
Batteries is found to be a better solution than single source Micro grid system. However,
integration of multiple resources poses many issues & challenges. Moreover, present
distribution system offers many technical & operational glitches for successful integration of
Micro Grid Technologies. The Micro Grid resources optimization is generally being done
based on self-sufficiency criterion which utilizes the grid support only in the event of
contingencies like fault, generation disruptions (DER) etc.

8. INTRODUCTION
In the view of increasing environmental concerns and consumer expectations in terms of
reliability & satisfactory power quality, energy access to farthest located consumers, increasing
technical & commercial losses etc. is indicating need of paradigm shift from centralized
electricity system to decentralised & distributed electricity system.
These challenges give a thrust to micro grid concepts. A micro grid is a system that has at least
one distributed energy resource (DER) and associated loads in it and can form intentional island
in electrical distribution system.
The desire for a more resilient and reliable energy system—especially one with fewer blackouts
in emergency situations—is just one factor driving the development of micro grids .Other factors
include low gas prices, dropping costs in renewable energy technology, and the desire of green-
minded communities to integrate local renewable resources, such as wind and solar plants,
directly into their energy systems
Through micro grids, remote villages in India and Africa may receive reliable power for the first
time, increasing quality of life and decreasing poverty rates. In the U.S., micro grids have the
potential to prevent massive blackouts bought about by intense storms and exacerbated by the
country’s aged infrastructure system
A micro grid can operate either in grid connected or islanded mode. The available power of all
DG units should meet the total load demand for islanded operation; otherwise load shedding
need to be implemented. The control of real and reactive power output of the sources is
essential to maintain a stable operation in a micro grid, especially when it operates in the
islanded mode. The frequency and voltage in an islanded (autonomous) micro grid should be
maintained within predefined limits. The frequency variations are very small in strong grids;
however, large variations can occur in autonomous grids.
Thus power management strategies are vital for an autonomous micro grid in the presence of
few small DG units, where no single dominant energy source is present to supply the energy
requirement. Also, fast and flexible power control strategies are necessary to damp out

9. transient power oscillations in an autonomous micro grid where no infinite source available.
The models developed in this work include fundamental power system components, three DER
units with control (including a wind energy source, a solar energy source and an energy storage
source component), the protective relays, and other necessary components for a micro grid.
Microgrid Model

10. MODELLING OF ENERGY RESOURCES
MODELLING OF PV SYSTEM:
The use of equivalent electric circuits makes it possible to model characteristics of a PV cell.
There are two key parameters frequently used to characterize a PV cell. Shorting together the
terminals of the cell, the photon generated current will follow out of the cell as a short-circuit
current (Isc). Thus, Iph = Isc, when there is no connection to the PV cell (open-circuit), the
photon generated current is shunted internally by the intrinsic p-n junction diode. This gives
the open circuit output voltage (Voc).

11. MODELLING OF WIND SYSTEM:
The wind turbine depends on the flow of air in a rotor consisting of two or three blades
mechanically coupled to an electrical generator. It is a process of power translation from
wind energy to electricity. The difference between the upstream and downstream wind
powers is actual power extracted by the rotor blades.

12. PSCAD SIMULATION TOOL
PSCAD is an industry standard simulation tool for studying the transient behavior of
electrical networks. Its graphical user interface enables all aspects of the simulation to be
conducted within a single integrated environment including circuit assembly, run-time
control, analysis of results, and reporting.
Its comprehensive library of models supports most ac and dc of power plant components and
controls, in such a way that FACTS, custom power, and HVDC systems can be modelled
with speed and precision. It provides a powerful resource for assessing the impact of new
power technologies in the power network.
Simplicity of use is one of the outstanding features of PSCAD. Despite its small size, this
system was specifically designed to mimic very closely the behavior of typical systems in
actual operation.
The time required for simulation in PSCAD is much less than other simulation software such
a Simulink Sim Power Systems. . Another advantage of PSCAD is its ability to interface with
Simulink. This feature enables the researchers to combine the flexible power systems
simulation of PSCAD with the rich and ready-to-use control systems library of Simulink
which helps in minimizing the modelling time. Also, PSCAD’s interface is designed in a way
that is easily used by the researchers and the developers in power systems.
For the purpose of system assembling, the user can either use the large base of built-in
components available in PSCAD or to its own user-defined models.
One of the aims of the paper is to act as a tutorial in the subject of custom power modelling
using PSCAD.

13. MICRO GRID
Micro grids, technically known as distributed generation, are small-scale energy grids. Like a
typical electrical grid, they store, transmit and distribute electricity. But they function in two
ways: many can and do link to a main power grid, operating in parallel on a local level.
Micro grids are also defined by their ability to work independently, sometimes called
“islanding.”
This flexibility makes them ideal in both industrialized urban areas and developing rural
areas. According to World Bank statistics, more than 1 billion people globally don’t have
access to electricity. This statistics can be changed with the introduction and implementation
of micro grids.
Layout of micro grid

14. REQUIREMENTS OF MICRO GRID
In December 2011, over 300 million Indian citizens had no access to frequent electricity.
Over one third of India's rural population lacked electricity, as did 6% of the urban
population. Of those who did have access to electricity in India, the supply was intermittent
and unreliable.
In 2010 and 2012, blackouts and power shedding interrupted irrigation and manufacturing
across the country. In the summer of 2012 India faced the biggest the biggest blackout in the
power sector. Extreme heat and lack of monsoon had resulted in huge draw of electricity
from the grid resulting in its failure.
Through micro grids, remote villages in India and Africa may receive reliable power for the
first time, increasing quality of life and decreasing poverty rates. Micro grids have the
potential to prevent massive blackouts brought about by both natural and man-made reasons.
There are many applications that require a high level of reliability and robustness in the
electrical infrastructure. While a telecommunications network has a never-fail requirement,
response time is short for disaster relief efforts and very little site engineering can be done in
advance of setting up an electrical distribution network.
Department of Defence applications have another set of unique challenges that require an
adaptable, robust and reliable electrical network. This creates a security issue since the
installation’s mission can be severely compromised if the power supply from one of the
feeder lines is interrupted for natural or unnatural reasons. It would be desirable if these
installations had an adaptable power system that would detect instability in the system while
utilizing a controller that would help the system absorb and dampen the effects of the
disturbances avoiding a total system collapse.
The ability to create a power system that can be easily changed with little engineering would
provide the flexibility to add generators and loads as the relief effort evolved. At the same
time, this system should also provide energy to critical structures such as field hospitals and
communication centres. Coupled with priority-based load shedding and intelligent power
sharing, such a system would insure that power is delivered to critical loads and while
keeping the installation at a high state of readiness.

15. Micro grids are quickly becoming a popular since it can address the above problems. A micro
grid is defined as a subsystem of distributed energy sources and their associated loads. This
approach allows for the local control of the distributed generation, thereby reducing or
eliminating the need of a central controller. A micro grid can be a stand-alone system or it
can be tied to a stiff ac grid that it separates from during disturbances.
A micro grid offers major advantages over a traditional electricity supply involving central
generation stations, long distance energy transmission over a network of high voltage lines,
then distribution through medium voltage networks.
 Opportunities to tailor the quality of power delivered to suit the requirements
of end users
 Create a more favourable environment for energy efficiency and small-scale
renewable generation investments
SOURCES OF MICRO GRID
The sources of micro grid can be classified as:
a) In terms of power flow control-
i) Dis patchable sources – The output power can be controlled to maintain the
desired system frequency and voltages. E.g. - fuel cells, bio diesel generators.
ii) Non-dis patchable sources-The output power depends on the environmental
conditions and is expected to be controlled on the basis of maximum power
point tracking. E.g. - wind, photo voltaic.
b) On the way they are connected to the system-
i) Inertial sources – the output power through these sources are difficult to
change. E.g. diesel generator and hydro generators.
ii) Non-inertial sources – the output power through these sources can be
changed instantaneously. E.g. fuel cell, photo voltaic.

16. The output power of dispatchable DGs such as micro turbines, fuel cells and bio-diesel
generators are controlled to maintain the desired system frequency and voltage in an
autonomous micro grid. On the other hand, non dispatchable DGs such as wind and PV, in
which the output power depends on the environmental conditions, are controlled in maximum
power point tracking (MPPT) to harness as much energy as possible.
The dynamic response of inertial and non-inertial DGs is different. The response of inertial
DGs (rotary machine based) will be slower compared to the non-inertial DGs (converter
interfaced). For example, a diesel generator and a hydro generator are inertial sources since
they include synchronous generators with their rotating inertial masses.
Thus, a finite time is required to change output power of an inertial DG. On the other hand,
the DGs connected through converters such as PVs, fuel cells and batteries are non-inertial
and they can respond to change real and reactive power output very quickly. This mismatch
in response rate can create power and frequency fluctuations in an autonomous micro grid
where no single dominant energy source is present. Therefore, the control and power
management strategies are vital for an autonomous micro grid in the presence of few
different types of DGs.
To maximize the efficiency of the unit, the sources need to be placed close to the heat load
rather than the electrical load since it is easier to transport electricity over longer distances.
Distributed energy sources have the potential to increase system reliability and power quality
due to the decentralization of supply. Increase in reliability levels can be obtained if
distributed generation is allowed to operate autonomously in transient conditions, mainly if
there is an outage or disturbances upstream in the electrical supply. Distributed generation
can ease the burden of high penetration of renewable sources by filling in when intermittent
generation is low and by smoothing the transmission system loading.

17. MICRO GRID ARCHITECTURE
A traditional architecture of a micro grid is shown in Figure with a micro grid connected to a
larger system and a disconnect switch that “islands” the distributed generation units to protect
sensitive loads. A major factor in micro grids is the creation of the disconnect switch that will
enable the micro grid to maintain compliance with current commercial standards. Such a
switch is necessary to realize the high reliability and power quality that micro grids offer.
Micro grid Architecture
Having multiple distributed generators available makes the chance of an all-out failure less
likely, especially if there is backup generation capable of being quickly and easily connected
to the system.
It is also efficient than relying on a single large generator. Small generators have a lower
inertia and are better at automatic load following and help avoid large standby charges that
occur when there is only a single large generator.
This configuration of multiple independent generators creates a peer-to-peer network that
insures that there is no master controller that is critical to the operation of the micro grid.
Having a component such as a master controller creates a single point of failure which is not
the ideal situation when the end user demands high reliability in the electrical system.
A peer-to-peer system implies that the micro grid can continue to operate with the loss of
any component or generator. With the loss of one source, the grid should regain all its

18. original functionality with the addition of a new source, if one is available. This ability to
interchange generators and create components with plug-and-play functionality is one
requirement of micro grids.
Extra load demands are picked up by the distributed energy sources and so the micro grid
looks like a constant load to the utility grid. With this configuration the micro grid becomes a
dispatchable load as seen from the utility side, allowing for demand-side management.
Micro grid Classification
Micro grid Operation
Micro grids generally operate in three modes namely Grid Connected Mode, Stand Alone Mode
(Islanded Mode) and Battery Charging Mode.
Grid Connected Mode:
In this mode of operation, the converter connects the power source in parallel with other sources
to supply local loads and possibly feed power into the main grid. Parallel connection of
embedded generators is governed by national standards The power injected into the grid can be
controlled by either direct control of the current fed into the grid, or by controlling the power
angle.

19. Stand Alone Mode (Islanded Mode):
In this stand-alone mode the converter needs to maintain constant voltage and frequency
regardless of load imbalance or the quality of the current. A situation may arise in a micro grid,
disconnected from the main grid .In this case; these converters need to share the load equally.
The frequency and voltage in an islanded micro grid should be maintained within pre-defined
limits. The variations in frequency are very small; however in the case of large variations power
management strategies are needed. The equal sharing of load by parallel connected converter
operating in stand-alone mode requires additional control. There are several methods for parallel
connection, which can be broadly classified into two categories:
1) Frequency and voltage droop method, where each DG in the system uses its real output to set
the frequency at its point of connection.
2) Master-slave method, whereby one of the converters acts as a master setting the frequency
and voltage, and communicating to the other converters their share of the power.
Battery Charging Mode:
In a micro grid, due to the large time constants of some micro sources, storage batteries
should be present to handle disturbances and fast load changes. In other words, energy
storage is needed to accommodate the variations of available power generation and demand.
The power electronic converter could be used as a battery charger thus improving the
reliability of the micro grid.
DER CONTROL TECHNIQUES
Distributed energy resources (DERs) are the key components in micro grid systems. DERs
are small-scale power generation or storage technologies that are located close to the load
they serve. The typical range of the DERs is between 3kW to 10kW. The small-scale power
generation is called distributed generation (DG), and the small-scale storage is called
distributed storage (DS). They play essential roles in the micro grids.

20. Power electronics technologies, such as rectifiers, inverters and DC to DC converters are
involved to integrate DERs into micro grid systems.
Control strategies for DER units within a micro grid should be selected based on the required
functions and possible operational scenarios. The main control functions for a DER unit are
voltage/frequency control (V/F control) and active/reactive power control (PQ control).
A general categorization of the major control methods of a DER unit is shown in the below
table
Grid-following control means the voltage and frequency of a DER unit follow those of the
utility grid or other sources, thus it is mainly applied in grid-connected mode. In contrast,
grid-forming control means a DER unit itself determines the voltage and frequency in
islanded mode.
Each of the two ways can be classified into non interactive control and interactive control.
The term “interactive” means the output power of DER unit depends on the conditions of
other units or loads.
Local frequency control is always one of the main issues when a micro grid operates in
islanded mode. The reason is that an electronically coupled DG unit does not exhibit any
inertia during the micro grid transients and thus has no capability to maintain the micro grid
frequency. When a micro grid transfers from grid-connected mode to islanded mode, the DG
units in the micro grid need to maintain the frequency.

21. The Grid-Forming control strategy emulates behaviour of a “swing source” in an islanded
micro grid. The reason is when the micro grid transfers from grid-connected mode to islanded
mode, the power balance between supply and demand do not match at the moment. Due to
the low inertia of the system, the system frequency may fluctuate. The grid-forming strategy
as a “swing source” picks up the unbalanced load and maintains the system frequency in a
tight range.
If only one DER unit is in the system, it can be assigned to regulate the voltage at the
interconnecting point and dominantly set the system frequency. When two or more DER
units exist in a micro grid, the droop control technique is one technique that is commonly
used. Droop control technique is a method to achieve the peer-to-peer
The droop control technique includes frequency-droop (f-P droop) and voltage-droop (v-Q
droop). This technique is a way to make the inverters in the micro grid system to perform a
load sharing function in islanded mode.
Besides the peer-to-peer control, another class of micro grids uses master control method. In
the master control class micro gird, the droop control technique is not necessarily applied in
DER units.
When the micro grid transfers from grid-connected mode to islanded mode and there is no
droop control to perform load sharing functions to pick up the unbalanced load, a “swing
source” with enough reserved energy is used. This “swing source” performs function of load
sharing and maintains the system voltage and frequency. Obviously, in this situation, some
energy storage source (ESS) must be included in the micro grid system to balance the load
requirement. The ESS plays an important role to maintain the system frequency and voltage
in this type of micro grid.

22. WIND ENERGY
Renewable energy is energy generated from natural resources which are renewable (naturally
replenished) such as sunlight, wind, rain, tides and geothermal heat. Renewable energy
sources (RESs) such as wind turbine and photovoltaic systems are favoured for DERs for
their advantages, such as low maintenance and low pollution.
In recent decades, wind energy has become increasingly important throughout the world.
Through wind turbines, wind energy is converted into electrical energy. Wind turbines are
mechanical devices designed to convert the kinetic energy of the wind into useful mechanical
energy that can be later converted into electricity. Wind turbine generators may be
categorized into two major types (i) constant speed units, and (ii) variable speed units.
Constant speed wind turbine generators essentially run at a relatively fixed mechanical speed.
These units are most typically induction machines; that is, high-efficiency induction motors
running at super-synchronous speed. Slight variations in the generator speed may result from
changes in system conditions.
The most common type of variable-speed wind generation is through the use of doubly-fed
induction generators (DFIG). This design employs a series voltage-source converter to feed
the wound rotor of the machine. By operating the rotor circuit at a variable AC frequency one
is able to control the mechanical speed of the machine. In this design the net power out of the
machine is a combination of the power coming out of the machine’s stator and that from the
rotor and through the converter into the system.
With DFIG (Doubly Fed Induction Generator) based Variable-speed wind turbines, has an
increased energy capture, improved power quality and reduced mechanical stress on the wind
turbine. The performance of DFIG is quite different from conventional induction generators.
It consists of a wound rotor induction machine with slip rings, and power electronic
converters between the rotor slip-rings and the grid. The stator of DFIG is directly connected
to the grid while the rotor fed at variable frequency through converter cascade (AC/DC/AC)
via slip rings and brushes to allow the DFIG to operate at variable wind speeds in response to

23. changing wind speeds. Both the stator and rotor windings are able to supply power to the
grid. The direction of the power flow in the rotor circuit depends on the variation of the wind
speed. The power electronic converters control both the direction and magnitude of the power
flow of the machine.
In addition to DFIG's ability to feed the rotor with ac power of variable frequency (thus
allowing for variable speed operation) a distinct aspect of DFIG is the fact that currents are
tightly controlled (with loop speeds typically ranging in the thousands of rad/sec). This
means that, for example, controls have the ability to, within limits, hold electrical torque
constant. Thus, rapid fluctuations
in mechanical power can be temporarily “stored” as kinetic energy, thus improving power
quality.
. Doubly-fed induction generator
Modes of operation of DFIG

24. DFIG can be operated in two modes of operation namely; sub-synchronous and super-
synchronous mode depending on the rotor speed below and above the synchronous speed.
Depending on wind speed, a doubly fed induction generator (DFIG) based variable speed
wind turbine is capable of operating in sub-synchronous or super synchronous mode of
operation using power electronic converters.
The power flowing in the rotor of a doubly fed induction machine (i.e. of the wound rotor
type) has three components. These are a) the electromagnetic power transferred between the
stator and the rotor through the air gap which is known as the air gap power Ps; b) the
mechanical power Pm transferred between the rotor and shaft; c) the slip power Pr which is
transferred between the rotor and any external source or load (e.g. a converter) through the
rotor slip-rings.
These three components of rotor power are interrelated, under sub- and super-synchronous
modes of operation, as shown in figure.

25. Power output of a wind turbine
The total amount of energy extractable from a wind turbine can be calculated theoretically,
using translational momentum theory. Power extractable from the wind passing across an
area A, when the wind speed is v can be expressed as,
PW = 0.5 ρA v3
Here, ρ is the density of air, which depends on the pressure and moisture levels of air. Betz’s
law states that the maximum fraction of power extracted by a wind turbine would be
theoretically 16/27 of Pw. However in practice, turbines would extract a significantly lesser
portion of wind power. Even modern commercial wind turbines extract about 0.45 of Pw.
Thus, a coefficient is defined to express the useful mechanical power extracted from the wind
by the turbine. It is called the power coefficient or the Betz factor, cp, and defined as the ratio
of the turbine power to the power of the wind.
Power coefficient, cp, is a function of two variables, namely, tip speed ratio, λ, and pitch
angle, β. Tip speed ratio, λ, is the ratio between the speed of the tip of the blade, ωR, and the
velocity of wind, v. Here, ω is the rotational speed of the turbine rotor and R is the radius of
the turbine blade.
Therefore the power extractable is,
PW = 0.5 ρ CpAv3
In Equation the circular swept area of the turbine πR2 is given as A. Further it can be seen that
for a given wind speed, tip speed ratio, λ, is a function of ω only and hence, cp becomes a
function of ω only. Therefore, the power extracted by a fixed pitch wind turbine, Pt, is a
function of its rotor speed, ω, only, provided that the wind speed remains constant.

26. The above graph shows how with the increase of the wind speed leads to a gradual increase
to the power output of the wind turbine.
is the break down point where the output power does not increase anymore with respect
to the wind speed. After the break down point if the wind speed increases anymore the
turbine output power gradually decrease down and at a point reaches zero. To control the
output power with respect to the wind speed a governor is connected to the wind turbine
which controls the wind speed in a limited boundary.

27. SOLAR ENERGY
Solar energy refers to energy that is collected from sunlight. By the photovoltaic effect, the
energy from the sunlight can be directly converted into electricity by using a photovoltaic cell
(PV cell). Besides the wind energy source, solar energy source with PV cells is another
favoured source as distributed generation.
The sun is a tremendously powerful energy source; in fact the earth’s surface receives enough
energy from the sun in one hour to meet its energy requirements for one year. With the
decreasing cost, increasing efficiency and government incentives the demand and use of solar
technology is rising.
PV Module
Photovoltaic cell is the basic semiconductor device that generates electricity by the
photovoltaic effect when exposed to radiant energy such as sunlight. The default parameters
which were used to define the PV module in PSCAD are shown in Table I. The model
enables the user to specify the number of series and parallel cells per module and the number
of modules connected in series and in parallel which helps in building PV systems with high
power rating. By using the default values, the final output of the single module is 650 watt
and 260 kilo-watt for the total 400 modules.

28. The maximum number of modules in series and in parallel in the PSCAD PV model is 20.
The total number of cells/models connected in series determines the total voltage of the
module/array, respectively. The total number of cells/models connected in parallel
determines the total current of the module/array, respectively.
The I-V curve of ideal solar cell is square (Fill Factor = 1), yielding a cell conversion
efficiency of 100%. But in reality, the cell I-V curve exhibits an exponential behaviour (Fill
Factor = 0.89) due to losses that arise from the parasitic series and shunt resistances. Series
resistance is the sum of all resistance due to all the components that come in the path of
current like base, emitter, semiconductor-metal contact resistance and resistance of metal
contact. It is desirable to have the series resistance as low as possible, in the order of few m-
ohms per cm-2 (from 0 to 1600 mΩ.cm-2). If the series resistance increases, the maximum
power point decreases and for very large values of series resistance the short circuit current
starts decreasing without affecting the open circuit voltage. Shunt resistance is due to the
leakage in the p-n junction because of the crystal defects and the impurities in the junction
region. It is desirable to have the shunt resistance as high as possible, in the range of several
hundred ohms. If the shunt resistance decreases, the maximum power point decreases and for

29. very small values of shunt resistance the open circuit voltage starts decreasing without
affecting the short circuit current.
Band gap energy of the solar cell is the minimum energy necessary to elevate an electron to
the excited state, or upper energy level, so that it can be conducted through the solar cell to
the load. Too large a band gap and the solar cell will only absorb short wavelengths of light
(photon with high energy) and so a small photocurrent will be produced. Too small a band
gap and the solar cell will produce a large photocurrent, but a small voltage and lower
efficiencies will result.
WORKING PRINCIPLE OF A PV MODULE
A simplified equivalent circuit model which represents the electrical behavior of the actual
cell module is shown in below figure.
Fig. Equivalent circuit of a PV module

30. I = Ig – Id = Ig – I0 [exp (V + IRsr / nVT) – 1]
Where,
I = output current of PV module ( A )
Id = Diode Current (A)
Ig = Short circuit current of PV module (A)
Io = Diode Saturation Current (A)
V = Terminal voltage of PV module (V)
Rsr = Series Resistance ( )
n = Ideal Constant of diode (1- 2)
VT = Thermal Potential of PV Module (V)
The output current of a PV array can be obtained from
I = NP Ig – NP I0 [exp (V + IRsr / n NS VT) – 1]
Where, NP = Number of parallel PV modules in an array
NS = Number of series PV modules in an array
The current versus voltage and power versus voltage characteristics of a PV array are,

31. PSCAD MODELLING
The implementation of the simulation model of the proposed micro grid system in PSCAD
includes several parts:
1) Develop the fundamental power system component models.
2) Develop the DER unit models and their controller including wind energy, solar energy,
diesel generator and energy storage sources.
3) Integrate the individual component models into the system and develop the protection
scheme and component models.
The implementation process includes modelling all of the necessary component models of the
micro grid system. Some of the component models exist in the PSCAD library. The
parameters needed in PSCAD were specified based on the functions and ratings for each of
these components. Some other component models are not directly available in the PSCAD
library, thus they were developed in PSCAD.

32. WIND MODEL
In the micro grid system, a wind energy source model is designed. After comparing these
configurations, the variable speed wind turbine with a synchronous machine was chosen for
this model. A wind turbine having the advantages of full variable-speed control maximum
power point tracking (MPPT) capabilities with proper control method. The configuration is
shown in figure below. Wind energy source model includes three main parts: wind source,
wind turbine, synchronous generator. The wind turbine output torque serve as the input
torque of the synchronous generator. The three phase output voltages of the synchronous
generator are input to a step up transformer that steps up the output before supplying it to the
grid.
Fig. Wind Energy Source Configuration
Among these parts, the wind turbine component and synchronous generator component are
available in the PSCAD library directly. The model in the PSCAD library was used with
proper parameters based on the ratings.
In PSCAD, the wind source model generates the wind speed variable. The wind speed
variable can be composed by four components as shown in equation below. The values of
those four components can be independently set when necessary.
V Wind = V base + V gust +V ramp + V noise
Where,
V base = Base Wind Speed (m/s) V ramp = Ramp Wind Speed (m/s)
V noise = Noise Wind Speed (m/s) V gust = Gust Wind Speed (m/s)

33. For simplicity purposes we consider only the Vbase. All the other velocity components are
considered to be zero.
The wind turbine model produces the output torque Tm.

34. Fig. pscad modelling of wind system
The above figure is a model of wind turbine simulated in PSCAD software. The figure shows
that there is a wind source model supplying wind velocity to the wind turbine. We consider
that the wind source only supplies base or mean wind. The output of the wind turbine is
mechanical energy which is coupled with a generator thus producing electrical energy.
A governor is connected to the wind turbine. The wind turbine governor in the PSCAD
library is designed for enabling the pitch control function when necessary. Their outputs pitch
angle value as “Beta” shown in above figure. In order to accommodate more wind pitch angle
is increased, thus increasing the output power but does not make use of the highest power
capacity for the wind generator for higher wind speeds. It is possible to develop a complex
control system in which the pitch angle is changed dynamically to power during high wind
speeds.

35. PSCAD Model of Wind Generator Connected to Grid
The Wind Generator is connected to a transformer. The input to the transformer is 13.46 V
where as its output is 115.9V. Transmission lines are connected with the grid to minimize the
losses. To the grid one local load is connected which causes load sharing between the load
and the utility grid. Suppose the wind generator produces 5 units of power. Among them 2
units are used by the local load. The remaining 3 units are supplied to the utility grid. The
grid output is again connected to a step up transformer which gives the output as 345 KV.

36. OUTPUT GRAPHS OF WIND MODULE
Circuit Breaker is set to operate at 10 seconds.
The above two graphs are VRMS VS Time curve and Active and Reactive power VS Time
curve.
In the first curve the VRMS starts from zero and gradually increases and decreases till 10
seconds after which the breaker closes. This causes the VRMS to decrease and gradually
become zero.
The second curve denotes active and reactive power with respect to time. The active power
increases from zero and after ten seconds when the breaker closes the active power gradually
becomes zero. On the other hand the reactive power is initially negative and after ten seconds
when the breaker closes the reactive power increases gradually to zero.

37. SOLAR MODEL
Energy from PV cells is another favoured resource as distributed generation. PV energy
source model mainly includes three parts namely PV arrays, DC/DC converter and an
inverter.
PV Module
Two PV modules are connected in series and then a large capacitor is connected in parallel
with them to serve as energy buffer for the transient.
Fig. solar PV model
PV Array Parameters

38. DC-DC converter
DC-DC converter is used for Maximum Power Point Tracking (MPPT) by controlling the
voltage across the DC link capacitor and the PV array. This is achieved by first creating a
reference voltage that is then supplied to a PI controller which creates switching signals that
force the voltage across the PV array to follow the reference voltage. A case, the MPPT
generates a reference voltage (Vmppt) at which the PV array is forced to operate.
The algorithm decrements or increments Vmppt to track the maximum power point when
operating under varying atmospheric conditions. This reference voltage Vmmpt is used as an
input to the DC-DC Converter Control model.
DC-DC converter is an electronic circuit that is used either to step down the input voltage
(buck converter) or to step up the input voltage (boost converter). In this PSCAD model, the
converter was used that consists of a Pulse Width Pulse Width Modulation circuit, Insulated
Gate Bipolar Transistor (IGBT) switch, inductor, and capacitor and free-wheel diode.
DC-DC converter duty cycle
The above graph shows the variation of duty cycle with respect to time. The duty cycle,
defined as the fraction of the period during which the switch is on, ranges between 0 and 1. A
duty cycle value of 0.5 means on and off time are equal, a value greater than 0.5 means on
time is greater and a value less than 0.5 means off time is greater. The comparator sets its
output to 1 or 0 otherwise creating pulses with a magnitude of 1 and with pulse widths which
depend on the duty cycle.

39. By supplying the gate terminal of the IGBT switch with the PWM signal (T1), the converter
could be switched on (when T1 = 1) and off (when T1 = 0) and for the time durations which
are determined by the widths of the pulses.
When the IGBT switch is on, the free-wheel diode is reverse biased (open circuit) and current
flows through the inductor causing it to be charged with energy. The capacitor is also charged
and provides a filtering action by minimizing the voltage ripple produced at the output of the
converter.
When the IGBT switch is off, the free-wheel diode is forward biased (short circuit for ideal
diode) providing a path for the discharge current from the inductor. The capacitor is also
discharged. This continuous charging and discharging process of the inductor and the
capacitor forces PV output voltage (Vpv) to track and follow the reference voltage (Vmppt)
to operate at the MPP, even when the irradiation decreased from 1000 W/m2 to 500 W/m2.
Inverter
In order to be able to tie a PV system with the utility grid, the DC output power of the DC-
DC converter should be converted into a three phase AC power using a three phase inverter.
IT is part of inverters’ task to keep the DC voltage across its input (DC-DC converter’s
output) at a constant value. In this PSCAD model, the three phase inverter consists of a
simple P and Q regulation circuit, a firing pulse generator and a three phase inverter bridge.
Output Voltage without Filtering

40. The output voltage of the inverter has distortion involved, thus an AC filtering stage is
required to further smoothen the output and limit the voltage drop in the AC side of the
inverter when operating under variable atmospheric conditions. In this paper, the AC filter is
implemented using a inductor. Although the irradiation might decrease due to atmospheric
conditions, the inductor resisted the drop in the voltage and maintained it constant. The
inductor also improves the shape of the output voltage to an almost sinusoidal wave.
Output Voltage with Filtering
Grid tied PV Model in PSCAD
The above figure shows the PV model in the PSCAD. The PV module is connected with solar
radiation and cell temperature controllers. There is a capacitor connected across the PV
module. Initially the voltage across the capacitor is zero. When the breaker connected to the
circuit closes the capacitor starts charging and VPV rises. The output of PV module is

41. connected to a DC/DC converter which acts as a buck converter and as well as a maximum
power point tracking (MPPT) device. The MPPT device causes the PV module output
voltage (Vpv) to track and follow the reference voltage (Vmppt) to operate at the MPP, even
when the irradiation decreased from 1000 W/m2 to 500 W/m2.
In order to establish a constant DC bus voltage between the DC-DC converter and the
inverter, a PI controller, is used to set this voltage at 0.5 kV. Another PI controller sets the
reactive power (Q) of the grid to zero which forces the inverter to operate at unity power
factor so that it produces sinusoidal voltage and current which are in phase.
PI Controllers
The output of the inverter is full of distortions and this filtered by an ac filter. The
transformers are attached for voltage adjustments after which the output is connected to the
utility grid. The utility grid system is represented only as an equivalent 11 kV and 60 Hz
source.
Transformers in grid connected PV can be used for voltage adjustment. One way to omit the
bulky transformer is to use high frequency transformers. Another emerging topology is the
transformer-less inverter which has less overall losses, lighter in weight and it is cheaper than
conventional grid frequency transformer. In addition, model without transformer increases
the control over the system voltage and power since transformer limits the control of the grid
current.
The low voltage side of the transformer (230 V) was connected to the inverter while the high
voltage side (11 kV) was connected to the grid
Harmonics are sinusoidal components of a periodic wave having a frequency that is a
multiple of the fundamental frequency. Harmonics in PV systems are generated by the

42. converters which use switching techniques that generate signals that are not perfect
sinusoidal. Connecting PV systems to the utility grid, which is already being injected with
harmonics by the non-linear loads connected to the power network, will add a stress on the
power quality of the grid.
In order to maintain acceptable levels of grid power quality, standards that regulate the effects of
PV systems on the utility grid should be developed. One such standard is IEEE Std 929- 2000
“IEEE Recommended Practice for Utility Interface of Photovoltaic (PV) Systems” which
ensures compatible operation of photovoltaic (PV) systems that are connected in parallel with
the electric utility.
The droop control method is not used for the inverter control for DER units in the micro grid
system. During the micro grid islanding process, the energy storage source (ESS) device is used
to pick up the load immediately and enable the voltage and frequency control (V/F control) in
the micro grid island operation mode. The most common energy storage devices include battery,
super-capacitor, flywheel, superconducting magnetic energy storage (SMES).

43. OUTPUT GRAPHS
The breaker time is fixed at 10 secon after which the circuit breaker closes.
Vmppt VS Time
The output graphs of the solar PV are shown above. The first is the curve of the voltage of
maximum power point tracking device with respect to time. The voltage gradually increases
with the increase in the cell temperature and after a certain amount of time it starts
depreciating.
The second curve is the PV current versus time. The current remains constant at the
beginning till a certain interval of time. When after 10 seconds the circuit breaker closes the
current doesnot flow anymore through the capacitor and the current gradually decreases and
remains constant for the rest of the time.

44. The third curve represents the PV output voltage (Vpv) with respect to time. Initially the
voltage across the capacitor is at terminal voltage. After that when the breaker is closed after
10 seconds voltage flows across the capacitor and the VPV gradually rises and remains
constant for the rest of the time.
The fourth curve is the output power of the PV array versus time. The output power remains
constant initially due to constant current and voltage. After 10 seconds when the breaker is
closed the output current of the PV module decreases resulting in the decrease of output
power of the PV module.
Active Power VS Time

45. The active and reactive power graphs with respect to time are shown in the above figures.
The active power increases for a certain amount of time and then starts decreasing and
becomes constant for a certain period after which it again decreases slightly and becomes
constant for the rest of the time.
Reactive Power VS Time
The same way the reactive power first decrease from its initial value and then start
increasing and becomes constant for rest of the time.
VRMS VS Time
The last graph is the rms voltage curve with respect to time. The graph shows that the rms
voltage remains constant after a few instance of time.

46. PROTECTION SCHEME
Based on the system model, a protection scheme and the corresponding protective relay
component models were developed. The relay components are able to monitor the currents
and voltages in both phase and time domain. The protection components were coordinated so
that they can protect the micro grid system from different faults, including single-line-to-
ground (SLG) fault, line-to-line (LL) fault, etc.
The protection schemes used in the micro grid are as follows:
1) Primary protection uses differential current and symmetric approach to protect a micro
grid against all SLG and LL faults;
2) If the primary protection fails, the conventional over-current protection is the first back-
up;
3) The second back-up are mainly under voltage monitoring.
The interconnection switch is also controlled by protective relay. Basically, the
interconnection switch should be able to disconnect the micro grid from the utility grid under
the following conditions:
1) Poor voltage quality from the utility, like unbalances due to nearby asymmetrical loads;
2) Frequency of the utility falls below a threshold, indicating lack of generation on the utility
side;
3) Voltage dips that last longer than the local sensitive loads can tolerate;
4) Faults in the system that keeps a sustained high current injection from the grid;
5) Any current that is detected flowing from the micro grid to the utility system for a certain
period of time.

47. PRESENT VENTURES
The Ministry of New and Renewable Energy has sanctioned to State Renewable Energy
Development Agencies along with small agencies have implemented solar PV mini/micro grid
projects in 176 villages in six States during last 2 years.
State/ UT wise details including are given below:
S.No Name of State No. of
Villages
1 Bihar 12
2 Haryana 7
3 West Bengal 5
4 Madhya Pradesh 29
5 Rajasthan 24
6 Uttar Pradesh 101
7 Karnataka 23
Although no comprehensive statistics exist on the number of micro grids, a conservative count
shows that they serve at least 125,000 households in India, divided mostly between large,
government-sponsored projects in the North Indian states of Haryana and West Bengal and
private ventures centered on Uttar Pradesh and Bihar.
Thanks to an LED light powered by a micro grid, women in the village of Muglinkuha in
Uttar Pradesh are able to work at night and glue beads to a sari. Each village has a generator
powered by burning and gasifying rice husks, a by product of farming that is otherwise
wasted.

48. Nearly all micro grids in India are powered by solar photovoltaic panels, with the exception
of 20 to 30 networks that run on hydropower in the states of Karnataka and Uttar Pradesh and
the biomass-powered grids operated by husk.
By illuminating an entire village at once, a micro grid can spread light more quickly than
government hand-outs of solar-powered lanterns. It can also scale up far faster than
traditional power lines, which are often promised in India but seldom delivered. By deriving
their power from biomass or solar panels, micro grids raise the possibility that large regions
could stay off the coal-fired power grid forever.
In the U.S., micro grids have the potential to prevent massive blackouts brought about by
intense storms and exacerbated by our country’s aged infrastructure system.
The super storm Sandy, and the resulting widespread power outages opened the door to micro
grid interest, particularly in Mid-Atlantic States. In the U.S., micro grids are primarily being
tested on university and hospital campuses, as well as military bases, before being tested in
commercial settings. For example, the Galvin Centre for Electricity Innovation at the Illinois
Institute of Technology operates a micro grid system that has been running for a few years
ADVANTAGES OF MICRO GRID
The Micro grid, even though not a replacement of the national grid, improves certain aspects
especially for communities and regions that have adequate renewable resources.
The advantages of micro grid are:
 They have much smaller financial commitments.
 They use renewable resources and are therefore more environmentally friendly.
 They require fewer technical skills to operate and rely more on automation.
 Once installed the cost of maintenance is low.
 They are isolated from any grid disturbance or outage.
 They place the consumer out of the grip of large corporations that run the generation
networks.

49. COST OF A MICRO GRID
The government is providing huge cuts and incentives for projects involving the
implementation of micro grids.
The initial cost of the system is high - each micro grid costs around Rs 65,000. The company
invests that money and expects to recoup its costs in three years. Solar projects get a capital
subsidy on purchase of solar panels and batteries from the central government.
Once installed, micro gird system has no operational cost and only needs occasional
maintenance. The solar powered micro grid functions well even on cloudy days. Many
villagers have now stopped buying torch batteries or using kerosene lamps since they no
longer need them.
In India four companies are working on micro grid projects namely
Mera Gao Power, Naturetech Infrastructure, Minda NexGenTech, and Husk. All of these
companies have received grants and subsidies from the Ministry of New and Renewable
Energy. These grants have helped the companies hugely in formulating their projects.
Mera Gao’s customers pay about 100 rupees and receive enough electricity to power two
LED lights and a mobile phone charger for seven hours a night. Husk can supply about 400
households from one of its rice husk gasifiers. Two stories tall and painted green,
the gasifiers are usually situated near the centre of town, next to a giant pile of rice husks and
surrounded by a rickety fence. Also for 100 rupees, a Husk user gets two CFL light bulbs and
a cell phone charger, along with a power cable that supplies electricity for five hours a night.

50. PROBLEMS AND CHALLENGES FACED BY MICRO GRIDS
In India micro grid installation may be easy, but that is often where the simplicity ends. Some
high-caste farmers demand that lines be rerouted because they can't bear to have electricity
flowing from the house of the low-caste cobbler next door. Some
Hindu neighbourhoods don't want to be on the same grid as Muslims. One resident who
breaks the rules and takes too much power, for a ceiling fan or television, can make the whole
grid crash.
The weather also poses difficulties for micro grids. The North Indian winter can offer a
month of nonstop grey skies, which is a problem for solar systems that need three hours of
sunlight to store enough energy for the night.
In case of Husk Power, its demand for rice husks — once not even useful for cow fodder —
has started to drive up the price, forcing the company to hunt for corncobs or river grasses
that have even less market value.
The biggest difficulty by far is getting paid. India's farmers have irregular incomes and aren’t
used to monthly bills. In tiny villages, forgiving one person's debt means that next month no
one will pay.
This has forced micro grid entrepreneurs, many of whom got in the business for social good,
into uncomfortable new roles as debt collectors. In response they have sought out new
models that assure payment, from installing meters that dole out electricity in chunks like a
prepaid cell phone, or hiring local franchisees that can use their stature to bring deadbeats
into line.

51. FUTURE DEVELOPMENTS
As the renewable resources generally suffers with the limitations of intermittency and
variability, use of more than one distributed resource i.e. resource diversity, improves reliability
and security of power supply. Thus hybrid Micro grid system is preferred over the use of single
resource Micro grid System, but challenge lies in integration of all such resources based
generations to meet consumer demand with reliability, security and best of quality.
The hybrid Micro grid may consist of Solar Photovoltaic array (PV), Wind turbine (WT),
Biomass Gassifier (BG), Diesel Generator (DG) and Battery Energy Storage (BES). The figure1
shows grid-interfaced Hybrid Micro grid architecture. In such systems, two types of control i.e.
sources control and load control is designed.
Source control is achieved primarily through generation control of Diesel Generator or Battery
energy storage systems which serves as flexible generation whereas Solar PV and Wind,
considering its nature of resources, is never controlled or backed down and so it involves load
control.
Hybrid micro grid
In the above figure we are modelling a hybrid micro grid by integrating two diesel unit both
500kw, 300kw with a PV module of 250kw operating in an islanded mode of operation with a
fuel cell or battery. The diesel generator operates at the times when the output power of the PV
module due to atmospheric conditions is low. Hence at these conditions to fulfil the demand of

52. the users diesel generator is used. The load sharing occurs between the diesel generators and the
PV modules.
The droop control method is not used for the inverter control for DER units in the microgrid
system. During the microgrid islanding process, the energy storage source (ESS) device is used
to pick up the load immediately and enable the voltage and frequency control (V/F control) in
the microgrid island operation mode. The most common energy storage devices include battery,
super-capacitor, flywheel, superconducting magnetic energy storage (SMES), hydrogen, and
compressed air. In this microgrid system, a DC battery was chosen to serve as the ESS unit.

53. CONCLUSION
In this project the modelling and performance of wind, solar, Wind_grid, solar_grid is simulated
with the aid of PSCAD/EMTDC software package.
A wind turbines and solar pv’s power outputs depends on the wind speed and solar irradiations
which is quite unpredictable. The objective in this project was to investigate the behaviour of
wind farms under wind speed changes, the behaviour of solar grid system under different
atmospheric conditions and to construct a microgrid which has better structural and operational
advantages over the conventional grid.
From an energy production point of view it is desirable to have as much renewable energy
resources as possible. The integration of the model presented in this project will provide a
general tool for the accurate assessment of power system stability and reliability.
With the help of PSCAD/EMTDC we could construct two separate microgrids powered by wind
and solar energy respectively and study its output power, voltage and current characteristics.
Thus after completing this project we get an appropriate idea about the working of renewable
sources of energy integrated to the microgrids which if applied practically would be very
reliable in terms of power quality and also economically viable to the society.

54. REFERENCE
[1]. Abdulrahman Y. Kalbat “PSCAD Simulation of Grid-Tied Photovoltaic systems.”
PSCAD/EMTDC [Pursued B.S degree in United Arab Emirates in year 2011.]
[2]. P. Pourbeik Senior Member, R.J. Koessler Senior member, D.L. Dickmander member and
W. Wong Member ABB Inc. ”Integration of Wind farms into Utility Grids.”
[3].Amit Kumar Jindal, Aniruddha M.Gole. “Modelling and Performance Analysis of Wind
Power Systems for Off-Grid locations.”[University of Manitoba, Winnipeg, MB, Canada]. IEEE
Power Engineering Society.
[4].Amalnath Mani. “Wind farm simulation using PSCAD” [Special Analyst at Manitoba
HVDC Research Centre, Winnipeg, Canada.]
[5].Ajit Gopi. [Principal Engineer]. Gopi.ajith@pbworld.com. “Modelling and Simulation of
Photovoltaic Components of a Solar power Systems”.
[6].Ashfaq Husain. “Electrical Power Systems” 4th Revised Edition.[Reader in Electrical
Engineering, Aligarh Muslim University, Aligarh, U.P.
[7]. P. Kundur, Power System Stability and Control, McGraw-Hill, New York, 1994.