DELHI TECHNOLOGICAL
UNIVERSITY
PROJECT
REPORT
ASYNCHRONOUS AND
SYNCHRONOUS
MACHINES
SEM-IV
(2020-2021)
SUBMITTED TO:
Prof. Sikandar Ali Khan
Assistant Professor, DTU
SUBMITTED BY:
Asif Akhtar 2K20/EE/68
Ghanmohan Dangi 2K20/EE/106
ASM FINAL REPORT
ACKNOWLEDGEMENT
We express the deepest gratitude to our respected Professor
Sikandar Ali Khan, Faculty, Department of Electrical Engineering,
Delhi Technological University (DTU) for his benevolent guidance in
the accomplishment of this project successfully.
He inspired us to work hard and gave us enough time and support
whenever needed. We feel extremely fortunate to have worked
under his kind supervision. His active encouragement has enabled
us to complete the project in the due course of time. We gratefully
acknowledge the precious advice and suggestions received from
the other faculty members and the knowledge gained during the
discussions in the class.
We express our special thanks to the university library, for help in
accessing online journals and research papers and my parents and
friends for their cooperation and constant support.
Team:
Ghanmohan Dangi (2K20/EE/106)
Asif Akhtar (2K20/EE/68)
DELHI TECHNOLOGICAL
UNIVERSITY
MODELING &
SIMULATION OF
VARIOUS
ENERGY
CONVERSION
SYSTEM AT
CONSTANT AND
VARIABLE
SPEEDS USING
PMSG
SUBMITTED BY:
Ghanmohan Dangi 2K20/EE/106
Asif Akhtar 2K20/EE/68
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CONTENTS
1. Abstract And Ideation
2. Literature review
a. Introduction
b. Permanent magnet synchronous
generator (PMSG)
c. Doubly fed induction generator (DFIG)
d. WIND energy conversion system
(WECS)
e. Mathematical model of the system
3. Work done in the project
(Simulations And Results)
a. PMSG BASED WECS MODEL
i. Constant Speed Model
ii. Variable Speed Model
b. Comparative Analysis of PMSG and
DFIG based Wind Turbines
4. Conclusion
5. References
ASM FINAL REPORT
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ABSTRACT AND IDEATION
It is important to find an alternative form of energy before the world’s fossil fuels are depleted.
It is predicted that oil and gas reserves will be depleted by 2032. Due to the combustion of
fossil fuels, carbon dioxide is released into the atmosphere causing the atmosphere to trap solar
radiation that then leads to global warming or the “greenhouse effect”.
Wind power has played an important role in the history of human civilization. Windmills (or
wind turbines) have been used for at least 3000 years, mainly for grinding grain or pumping
water. The wind has been an essential source of power for even longer. From as early as the
13th century, horizontal-axis wind turbines were an integral part of the rural economy and only
fell into disuse with the advent of cheap fossil-fuelled engines and then the spread of rural
electrification.
the applications of wind energy develop much more rapidly than the other renewable resources
such as solar, geothermal, etc. in the 21st century. It becomes the third core energy resource
following non-conventional fuels as oil and chemical. The electrical energy generated by wind
power plants is the fastest developing and most promising renewable energy source. The wind
is a clean, free, and inexhaustible energy source. The origin of wind is simple.
Wind turbines are classified into two types as fixed speed and variable speed wind turbine. A
variable speed wind turbine provides more energy than the fixed speed wind turbine, reduces
power fluctuations, and improves reactive power supply. Basically, direct-drive PMSG
(Permanent Magnet Synchronous Generator) and DFIG (Double Fed Induction Generator) are
used in variable speed wind turbine generators.
In this project, we aim to present a detailed analysis of the Wind Energy Conversion System (WECS)
using PMSG in both constant and variable speed models. The project will be realized in the MATLAB
Simulink environment and the generated results will be interpreted to understand the efficiency of
PMSG. Finally, we draw out a theoretical differentiation between Wind Energy Conversion using
PMSG and DFIG and the efficiency of one another in different parametric situations.
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LITERATURE REVIEW
To lay out the introduction to the project, we will be broadly covering the following topics:
1.
2.
3.
4.
Permanent Magnet Synchronous Generator (PMSG)
Double Fed Induction Generator (DFIG)
Introduction to Wind Energy Conversion System (WECS)
Components: Drive Train and Pitch Angle Control
1. PERMANENT MAGNET SYNCHRONOUS GENERATOR (PMSG)
Fig: Permanent Magnet Synchronous Generator (PMSG)
A permanent magnet synchronous generator is a generator where the excitation field is
provided by a permanent magnet instead of a coil. The term synchronous refers here to the
fact that the rotor and magnetic field rotate with the same speed because the magnetic
field is generated through a shaft-mounted permanent magnet mechanism and current is
induced into the stationary armature.
Synchronous generators are the majority source of commercial electrical energy. They are
commonly used to convert the mechanical power output of steam turbines, gas turbines,
reciprocating engines, and hydro turbines into electrical power for the grid. Some designs of
Wind turbines also use this generator type.
Working Principle: The working principle of a permanent magnet synchronous motor is the
same as that of a synchronous motor. When the three-phase winding of the stator is
energized from 3 phase supply, the rotating magnetic field is set up in the air gap. At
synchronous speed, the rotor field poles lock with the rotating magnetic field to produce
torque and hence rotor continues to rotate.
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2. DOUBLY FED INDUCTION GENERATOR (DFIG)
Fig: Doubly Fed Induction Generator (DFIG)
Doubly-fed electric machines also slip-ring generators are electric motors or electric
generators, where both the field magnet windings and armature windings are separately
connected to equipment outside the machine.
By feeding adjustable frequency AC power to the field windings, the magnetic field can be
made to rotate, allowing variation in motor or generator speed.
Working Principle: The principle of the DFIG is that stator windings are connected to the
grid and rotor winding are connected to the converter via slip rings and a back-to-back
voltage source converter that controls both the rotor and the grid currents. Thus rotor
frequency can freely differ from the grid frequency (50 or 60 Hz).
3. WIND ENERGY CONVERSION SYSTEM (WECS)
Wind turbines generate electrical power in the same
way as all other generation technologies. The only
difference is in the source of the mechanical power
supplied to the electrical generator: wind, rather than
a diesel engine or steam turbine, provides the energy.
Blades capture energy in the wind and turn the
turbines. Control mechanisms point the blades into
the wind (yaw control) and, on large wind turbines,
adjust the pitch of the blades (blade angle) as wind
speeds change. Typically, a gearbox connects the
shaft from the blades (rotor) to the electrical
generator.
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4. MATHEMATICAL MODEL OF THE SYSTEM
The following equation represents the kinetic energy store in the wind as follows:
where, 𝑚 = air mass
𝑣 = wind speed
𝜌 = air density
𝑆 = surface area of the turbine
Thus, the wind power can be written as:
After that wind turbine is used to convert the wind energy into mechanical torque. It can be
determined from mechanical power at the turbine extracted from wind power. The power
coefficient of the turbine (𝐶𝑝) is applied. It is defined as the ratio between mechanical
power (𝑃𝑚) and wind power (𝑃𝑤). It is shown below:
The power coefficient(𝐶𝑝) can also be expressed in terms of pitch angle (𝛽) and tip-speed (𝜆)
as:
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5. DRIVE TRAIN MODEL
A Drive train is considered as a mechanical system of a wind turbine comprising of the
turbine, generator, and gearbox. The gearbox converts the low speed of the wind turbine
into the desired speed of the generator turbine. The mathematical model of a two-mass
drive train is expressed as follows:
where
𝐻𝑡 = Inertia constant of the turbine
𝜃𝑠𝑡𝑎 = Shaft twist angle
𝑤𝑡 = Angular speed of the wind turbine
𝑤𝑟 = Rotor speed of generator
𝑤𝑒𝑏𝑠 = Electrical base speed
𝑇𝑠 = Shaft torque
𝐾𝑠𝑠 = Shaft stiffness
𝐷𝑡 = Damping Coefficient
6. PITCH ANGLE CONTROLLER
This control strategy is applied to control the mechanical power input at the nominal value
and also prevent the electrical power output from becoming so high. It is usually active in
the condition of high wind speed. In those situations, the rotor speed can't be controlled by
increasing the generated power because this would make the overloading of the generator.
That's why the blade pitch angle is modified for limiting the aerodynamic efficiency of the
rotor which helps to control the rotor speed to become high.
As we discussed earlier, the power coefficient, 𝐶𝑝 is a function of tip-speed, λ, and blade
pitch angle, β. So modifying the β would also modify the 𝐶𝑝 and therefore it will help to
control the rotational speed as well as the generator output. We know that the maximum
value of 𝐶𝑝 is attained when blade pitch angle, β is zero which defines the condition when
pitch angle control is not required which means the turbine is operating at the nominal
wind speed. But when the wind speed exceeds the rated wind speed by some extent where
the rotor speed exceeds its rated value then this control method must be applied. Then the
value of pitch angle β will be increased by some mechanism to decrease the value of 𝐶𝑝 to
maintain the balance between input and output power.
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WORK DONE UNDER THIS PROJECT
This project covers the following topics :
Design and Simulation of PMSG based Wind Energy Conversion System
Constant Wind Speed Model
Variable Speed Model based on Muppandal Wind Farm, Kanyakumari
Analysis of DFIG based Wind Energy Conversion System.
A detailed comparative analysis of PMSG vs DFIG based Wind Energy Conversion
Systems.
PMSG BASED WECS MODEL :
FOR CONSTANT WIND SPEED
Fig: Simulink Model for Constant Speed
Till now, we have seen all the components of WECS individually. The model in the above
figure brings all the parts together. The wind turbine model being used is a predefined
block in the Simulink library, with some customizable constants, and this is also the case
with the PMSG being used. Whereas the PID-based Pitch Angle Controller and the 2-Mass
Drivetrain have been designed using the mathematical model of both components.
Fig: 2-Mass Drivetrain
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Fig: PID BPitch Angle Controller
Simulation Results
RMS Current
RMS Voltage
Line Current
Line Voltage
3 Phase Voltage and Current
Rotor Speed And Torque
FOR VARIABLE WIND SPEED
For the application of the above system in real life as a standalone power source, the wind
turbine should be able to provide consistent Voltage and Current without much fluctuation
corresponding to the variation in the wind speed. If the speed of the wind is more than the
base speed of the turbine then this can cause overloading of our generator as the torque
provided by the turbine is directly proportional to the wind speed. This is the place where
the pitch angle controller comes into play.
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As soon as the speed of the generator increases above the base speed, the pitch angle is
increased by the controller, which decreases the aerodynamic efficiency, in turn decreasing
the torque being provided to the generator.
For making this project more relevant to the real world, the wind speed pattern has been
modeled according to the real-world data collected by the National Renewable Energy
Laboratory, USA, for the State of Gujarat, INDIA.
The pattern of average daily wind speed variation, at a height of 50m, over the period of 24
hours has been provided below.
Hours of the Day
After studying the graph provided above,
The base speed is taken to be 5 m/s.
The wind speed in the simulation will reach a peak of 7 m/s gradually.
After reaching the peak, wind speed will start decreasing back to 5 m/s
Fig: Simulink Model for Variable Speed
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Simulation Results :
---- Pitch Angle
---- Rotor Speed
---- Wind Speed
The graph above shows the role of the pitch angle controller in stabilizing the output of the
wind turbine.
The base speed of the PMSG model taken here is 152.8 rad/s, so as soon as the increase in
wind speed causes the rotor speed to go above the base speed, the pitch angle controller
tries to reduce the speed and bring it down within the acceptable range for obtaining a
consistent output.
The Pitch angle controller reaches a peak of approximately 18 degrees.
Line Voltage
RMS Voltage
RMS Current
Line Current
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3 Phase Voltage and Current
Active Power
The graphs shown above indicate that the pitch angle controller was successful in
minimizing the fluctuations and hence avoiding any overloading of the generator.
COMPARATIVE ANALYSIS OF DFIG VS PMSG
The efficiency of a permanent magnet synchronous generator is higher than a doubly-fed
induction generator because of the fact that excitation can be provided without an energy
supply. The other advantage of a permanent Magnet Synchronous generator is that
according to conditions power can be generated at any speed.
The stator of the latter is wound and the rotor consists of a permanent magnet pole system.
On the other side, the materials used for manufacturing permanent magnets are expensive
and also are sensitive to temperature therefore they require cooling systems.
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ASM FINAL REPORT
Another issue with this type of generator is a problem encountered during start-up due to
its synchronous nature and hence there will be difficulty in getting constant voltage. Doubly
Fed Induction Generator (DFIG) on the other hand has good control over generating reactive
power which can be delivered to the stator by grid side converter. Due to the presence of
gearbox in DFIG, there is additional maintenance cost and hence less reliable than PMSG.
Variable speed operation is attractive in today’s world because of the fact that machine with
this technology exhibits more power capture and less mechanical stress.
CONCLUSION
A brief synopsis of the wind energy conversion system has been
covered under this project, along with an overview of different
generator types being used for these systems, namely Permanent
Magnet Synchronous Generators and Doubly Fed Induction
Generators.
The design and successful simulation of PMSG based Wind Turbine
system for constant Wind speed prove its proper functionality,
whereas, with the help of the variable wind Speed model, we are
able to see its practical usability in real-life situations.
The last portion of this report covers a detailed comparative analysis
between the two existing generator topologies, DFIG and PMSG, from
which we are able to infer the superiority of using PMSG for the Wind
Energy Conversion Systems.
FUTURE SCOPE OF WIND ENERGY CONVERSION
With the right steps, India’s wind industry is poised to
meet the government’s revised target of 67 GW ahead of
2022. Moreover, the wind is riding strong on the
competitive bidding regime and increased demand for
green energy that is reliable, affordable, and a
mainstream source of energy. The Wind Industry is
regaining momentum, considering there is clear visibility
of 10-12 GW with a plan of further bids by the ministry of
new and renewable energy (MNRE).
Some Indian states have also come up with novel schemes
by identifying areas where agriculture is not very
intensive and remunerative. Such initiatives do not
involve the process of land acquisition while making use
of the land for a fixed annual payment carried through a
partnership between the government and farmers.
Piloting technologies such as the wind-solar hybrid,
where both windmills and solar panels are put up on the
same piece of land, are also paying off well.
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REFERENCES
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International Conference on Recent Developments in Control, Automation and Power
Engineering (RDCAPE), Noida, India, 2015, pp. 199-203, doi:
10.1109/RDCAPE.2015.7281395.
A. Rolan, A. Luna, G. Vazquez, D. Aguilar, and G. Azevedo, "Modeling of a variable speed
wind turbine with a Permanent Magnet Synchronous Generator," 2009 IEEE
International Symposium on Industrial Electronics, Seoul, Korea (South), 2009, pp. 734739, doi: 10.1109/ISIE.2009.5218120.
T. H. M. Sumon Rashid." A Novel Approach to Maximize Performance and Reliability of
PMSG Based Wind Turbine: Bangladesh Perspective.”American Journal Of Engineering
Research (AJER), Vol. 7, No. 6, 2018, Pp.17-26.
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http://www.iaeme.com/IJEET/issues.asp?JType=IJEET&VType=10&IType=3
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Montserrat. (2006). Modeling and control of the doubly-fed induction generator wind
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with Autonomous Control", Mathematical Problems in Engineering, vol. 2014, Article ID
856173, 9 pages, 2014. https://doi.org/10.1155/2014/856173
Fatima Zohra Naama, Abdallah Zegaoui, Yssaad Benyssaad, Fatma Zohra Kessaissia,
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https://www.researchgate.net/publication/333045908_Modeling_and_Simulation_of_PM
SG-Based_Wind_Power_Generation_System
SUBMITTED BY:
Lakshay Chandna 2K19/EE/146
Manika Jain 2K19/EE/151