1. i
Integration of DC micro grid using wind energy
By
VENKATA SIRISH KUMAR.A
This is an Engineering project submitted to the Gannon University graduate faculty in
Partial fulfillment for the degree Master of Science in Engineering.
Major Subject: Electrical Engineering
Approved:
Advising Professor in Charge of Major Work
Director of Major Department
Chairman of Graduate Programs
Gannon University
Erie, Pennsylvania 16541
May, 2016
2. ii
Abstract
This project describes the integration of wind power by interconnecting it to the
micro grid that stores and transforms DC power. Nowadays, renewable energy is
frequently used. Distributed energy sources such as wind power, solar power and so on
that can be operated in parallel with a wider utility. This project illustrates the storage and
utilization of DC power by using a micro grid. Droop control of power electronics is used
to charge the battery and functions as set of storage state of charge. While keeping state-
of-charge (SOC) within a target range to maintain terminal voltage, equilibrium of micro
grid’s real-time supply and demand. The primary purpose is to ensure local, reliable and
flexible power for urban and rural communities, at the same time, providing solutions for
commercial, industrial and federal government consumers. A micro grid also consists of
distributed energy resources like wind energy and solar PV systems that have several
electrical loads. Integration of DC micro grid has been proposed, operational
optimization was plotted using SIMULINK. Our main aim is to minimize cost and
emissions.
3. iii
Acknowledgements
I take this chance to express my most significant appreciation to every person
who gave me the probability to complete this report. An unprecedented gratefulness I
give to my guide Dr. Lin, Zhao, whose dedication in fortifying proposals and
consolation, helped me to mastermind my endeavor especially in forming this report.
Also, I am very thankful to Dr. Lee, Head of the Department, who has assumed
the part of tutor for me in my graduate degree program in Gannon University.
I additionally take this chance to express a profound feeling of appreciation to the
Department of Electrical Engineering of Gannon University for giving me permission to
start this Project.
I might likewise want to thank my family to support and urging me to accomplish
my objectives.
4. iv
Table of Contents
ACKNOWLEDGEMENTS.................................................................................................................................III
LIST OF FIGURES ...................................................................................................................................... V
LIST OF TABLES .....................................................................................................................................VI
LIST OF SYMBOLS ....................................................................................................................................VII
CHAPTER 1. INTRODUCTION..........................................................................................................................1
CHAPTER 2. POWER FLOW ANALYSIS USING POWER WORLD.......................................................................4
2.1 Introduction.........................................................................................................................4
2.2 A 3-Bus 345-KV System without Susceptance...................................................................4
2.3 A 3-Bus 345-KV System with Susceptance........................................................................7
2.4 Conclusion ..........................................................................................................................9
CHAPTER 3. TORQUE VS. SLIP CHARACTERISTICS OF 3PH INDUCTION MOTOR
………………………………………………………………......................................10
3.1 Introduction and Background Theory ...............................................................................10
3.2 Torque Vs. slip and Analysis ............................................................................................12
3.3 Conclusion ........................................................................................................................14
CHAPTER 4. STEADY STATE AND DYNAMIC MODEL OF 3PH INDUCTION MACHINE ....................................
.....................................................................................................................................15
4.1 Introduction and Background Theory ...............................................................................15
4.2 Problem Statements...........................................................................................................16
4.3 Dynamic Design of 3 Phase Induction Machine using SIMULINK .................................17
4.4 Simulation Results for Dynamic Design and Analysis .....................................................17
4.5 Conclusions.......................................................................................................................22
CHAPTER 5. WIND ENERGY.........................................................................................................................23
5.1 Introduction.......................................................................................................................23
5.2 Simulation Specification of Integration of DC micro grid using wind..............................23
5.3 Simulation Results and Analysis.......................................................................................25
5.4 Conclusions.......................................................................................................................27
CHAPTER 6. INTEGRATION OF DC MICRO GRID .........................................................................................28
6.1 Circuit and Block Diagram ...............................................................................................28
6.2 Operational Optimization of Micro grid ...........................................................................29
6.3 Simulation Result and Analysis ........................................................................................32
6.4 Conclusion ........................................................................................................................34
BIBLIOGRAPHY .....................................................................................................................................35
APPENDIX .....................................................................................................................................36
5. v
List of Figures
Figure 1: A three-bus 345-KV system................................................................................ 5
Figure 2: power flow diagram ignoring susceptance.......................................................... 6
Figure 3: System for assembling Y- matrix........................................................................ 7
Figure 4: Power Flow Diagram with Susceptance.............................................................. 8
Figure 5: equivalent circuit............................................................................................... 11
Figure 6: Torque vs. slip................................................................................................... 13
Figure 7: Torque (various resistances) vs. slip ................................................................. 13
Figure 8: Simulink Model................................................................................................. 17
Figure 9: Input voltages when Wd is Wsyn ........................................................................ 17
Figure 10: Stator currents when Wd is Wsyn...................................................................... 18
Figure 11: Rotor currents when Wd is Wsyn ...................................................................... 18
Figure 12: Currents when Wd is Wsyn ............................................................................... 19
Figure 13: speed and torque curve when Wd is Wsyn ........................................................ 19
Figure 14: Input voltages when Wd is 0............................................................................ 19
Figure 15: Currents when Wd is 0..................................................................................... 20
Figure 16: Torque vs. slip................................................................................................. 20
Figure 17: Torque vs. speed.............................................................................................. 20
Figure 18: Torque vs. speed.............................................................................................. 21
Figure 19 : Wind Turbine Block....................................................................................... 23
Figure 20: Parameters for Wind Turbine Block ............................................................... 23
Figure 21: Asynchronous block........................................................................................ 24
Figure 22: parameters for Asynchronous block................................................................ 24
Figure 23 : Power Conversion Block................................................................................ 24
Figure 24: Simulink Model............................................................................................... 25
Figure 25: V& I curve....................................................................................................... 25
Figure 26: Torque and Speed curves ................................................................................ 26
Figure 27: Output Voltage Waveform .............................................................................. 26
Figure 28: Circuit diagram of DC micro grid ................................................................... 28
Figure 29: Block diagram for DC micro grid ................................................................... 28
Figure 30: Wind or solar power forecast uncertainty for 1 h............................................ 29
Figure 31: Aggregation of wind and solar power forecast in micro grid.......................... 29
Figure 32: Battery storage capacity allocation for optimized scheduling......................... 31
Figure 33: Simulation circuit of proposed system ............................................................ 32
Figure 34: Solar current & voltage waveform .................................................................. 32
Figure 35: Battery SOC, voltage & current waveform..................................................... 33
Figure 36: Grid voltage waveform.................................................................................... 33
Figure 37: Load voltage & current waveform .................................................................. 33
6. vi
List of Tables
Table 1: List of Symbols...................................................................................................vii
Table 2: Input data .............................................................................................................. 5
Table 3: Per unit values....................................................................................................... 5
Table 4: power flow diagram ignoring susceptance .......................................................... 6
Table 5: per unit Susceptance ............................................................................................. 7
Table 6 : Results of power flow diagram adding susceptance............................................ 8
Table 7: Name Plate details and Input Parameters ........................................................... 12
Table 8: Name plate details............................................................................................... 16
Table 9: wind and solar power forecast data .................................................................... 30
Table 10 : Combined states of wind and solar power forecast ......................................... 30
Table 11 : Three hours of aggregated three-state power forecast model.......................... 30
7. vii
List of Symbols
Table 1: List of Symbols
BESS Battery energy storage system
DC Direct current
EV Electric vehicle
MES Multilevel energy storage
NR Negative energy reserve of BESS
PR Positive energy reserve of BESS
PV Photovoltaics
RES Renewable energy sources
SOC State of charge
UPS Uninterruptible power supply
WECS Wind energy conversion system
DOD Depth of discharge
EBESS State of charge of BESS
EBESS-0 Initial state of charge of BESS
ECBESS Energy capacity of BESS
ECNR-3h Energy capacity allocated for NR in 3-h window
ECPR-3h Energy capacity allocated for PR in 3-h window
ECUPS Energy capacity reserved for UPS service
ECEVF Energy capacity for fast charging demand
EMS Emission in system for 1 kWh power generation
EPBF Emission penalty–bonus factor
F function of micro grid optimized scheduling
K Number of individual states
L Number of combined states giving aggregated state
l, m, n Counters for states
P Power
8. 1
Chapter 1.Introduction
Wind power is mainly produced by utilizing wind. It is the energy that utilizes
wind through wind turbines, which turn and produce power. For generating wind power
we have numerous wind power hardware like wind turbines, windmills and water plants.
There are numerous favors of wind energy, for example, wind turbine power generation,
mechanical force with windmills, pumping water utilizing wind pumps, and so on.an
electrical generator is combined with a wind turbine, and it is named as a wind turbine
generator. There are different sorts of wind turbine generators and these wind turbine
generators can be specifically connected to the power grid or loads with the force. The
generation wind power is mainly through the force of wind flows through wind turbine,
where as soon as wind strikes the turbine it converts mechanical energy to electrical
energy.
DFIG double fed induction generator with 3-phase rotor and stator. An AC
current is conveyed in the rotor windings because of 3-phase AC signal nourished to rotor
windings. As a result of mechanical power created from wind energy the rotor begins
revolution and produces magnetic field. The rotor speed and frequency of the AC signal
connected to rotor windings are relative to each other. This steady magnetic flux going
through the stator windings produces AC current in the stator winding. Because of variety
of rate in wind speed there will be AC signal with an increasing frequency. Along these
lines, by changing the frequency of AC input signal given to the rotor windings we can
acquire an AC output signal with a consistent frequency. Grid side converter can be
utilized for giving directed DC voltage to charge batteries. Rotor side converter can be
utilized for giving controlled AC voltage to the rotor.
“The frequency (F) of a synchronous generator is directly proportional to its speed
(N). When multiple synchronous generators are connected in parallel to electrical grid,
the frequency is fixed by the grid, since individual power output of each generator will be
small compared to the load on a large grid. Synchronous generators connected to the grid
9. 2
run at various speeds but they all run at the same frequency because they differ in the
number of poles (P).
A speed reference as percentage of actual speed is set in this mode. As the
generator is loaded from no load to base load, the actual speed of the prime mover tend to
decrease. In order to increase the power output in this mode, the prime mover speed
reference is increased. Because the actual prime mover speed is fixed by the grid, this
difference in speed reference and actual speed of the prime mover is used to increase the
flow of working fluid (fuel, steam, etc.) to the prime mover, and hence power output is
increased. The reverse will be true for decreasing power output. The prime mover speed
reference is always greater than actual speed of the prime mover. The actual speed of the
prime mover is allowed to "droop" or decrease with respect to the reference, and so the
name.
For example, if the turbine is rated at 3000 rpm, and the machine speed reduces
from 3000 rpm to 2880 rpm when it is loaded from no load to base load, then the
droop % is given by”[1]
In this paper, it is proposed to set droop as a function of state of charge (SOC) of the
battery according to its operational optimization set point versus the actual real time
SOC. The proposed operational optimization is renewable generation forecast, emission
constraints, and EV fast charging.
In this paper, the proposed micro grid system composed with renewable energy sources,
for example, wind power system which is interfaced to the DC bus with the assistance of
the power electronic segments which is known as a micro grid. The micro grid generates
one output from the diverse accessible input power sources to control electrical loads. We
can straightforwardly supply to the DC loads utilizing the power generated from wind
power generating stations or we can store the DC power in battery.
10. 3
ROUTE TO REPORT
This project illustrates the process of integration of Dc micro grid using wind
energy and solar energy. Firstly process goes by simulating 3 bus systems with
susceptance and ignoring susceptance using power world, steady state and dynamic
model results torque vs. speed/slip, I and V (current and voltage) curve of induction
machine were simulated using MATLAB/SIMULINK.
11. 4
Chapter 2. Power flow analysis using
power world
2.1 Introduction
“In power engineering, the power-flow study, or load-flow study, is a numerical
analysis of the flow of electric power in an interconnected system. A power-flow study
usually uses simplified notation such as a one-line diagram and per-unit system, and
focuses on various aspects of AC power parameters, such as voltages, voltage angles, real
power and reactive power. It analyzes the power systems in normal steady-state
operation.
Power-flow or load-flow studies are important for planning future expansion of
power systems as well as in determining the best operation of existing systems. The
principal information obtained from the power-flow study is the magnitude and phase
angle of the voltage at each bus, and the real and reactive power flowing in each line.”[2]
“Power World simulator is an interactive power system simulation package
designed to simulate high voltage power system operation on a time frame ranging from
several min to several days. The software is capable of efficiently solving systems of up
to 100,000 buses.”[3]
2.2 A 3-Bus 345-KV System without Susceptance
2.2.1 Problem Statements
A 3-Bus 345-KV system without susceptance is shown in Figure-1 below.
Calculate the power flow using Power World simulator using data provided in Table-1
and Table-2.
12. 5
Figure 1: A three-bus 345-KV system
Table 2: Input data
Bus no: Real power
(pu)
Reactive power
(pu)
Voltage
(pu)
Nominal Voltage
(KV)
Angle
(deg)
1(slack bus) 0 (we assumed
3pu)
0 1 345 0
2(PV bus) 2 0 1.05 345 0
3(Load bus) -5 -1 1 345 0
Table 3: Per unit values
13. 6
Problem Solutions
Power flow analysis without susceptance
Figure 2: power flow diagram ignoring susceptance
In Figure-2 a 3-Bus 345-KV system without susceptance, we observe that real and
Reactive power at bus 1, 2 and 3 is changing. And also voltage and Power Angle at bus 1,
2 and 3 is also changing. The direction of green arrow states the power flow through load.
Table 4: power flow diagram ignoring susceptance
DATA
(P)Real
Power
(MW)
(Q)Reactive
Power
(MVar)
(V)Voltage
(pu)
Power
Angle
(deg)
Comments
Bus 1 308 -81 1 0 P at bus1 increased
Bus 2 200 267 1.05 -2.07
Change in power
angle
Bus 3 500 100 0.98 -8.79 Decrease in (v)
Line(1-3)
At bus 1
239 29 1 0 -
Line(1-3)
At bus 3
236 7 0.98 -8.79
Change in power
angle
Line(1-2)
At bus 1
69 -111 1 0 -
Line(1-2)
At bus 2
68 119 1.05 -2.07
Change in power
angle
Line(2-3)
At bus 2
268 306 1.05 -2.07
Change in power
angle
Line(2-3)
At bus 3
264 -107 0.98 -8.79
Change in power
angle
14. 7
In Table-4, we observe that Real Power, reactive Power, Voltage and power
Angle has been changing at different buses and in different transmission line connected
to bus. Respective comments have given for changes occur at buses and transmission
lines.
2.3 A 3-Bus 345-KV System with Susceptance
2.3.1 Problem Statements
One a 3-Bus 345-KV system adding susceptance is shown in Figure-3 below.
Calculate the power flow using Power World simulator using data provided in Table-4.
Figure 3: System for assembling Y- matrix
Table 5: per unit Susceptance
15. 8
Problem Solutions
Power Flow using Susceptance:
Using data from Figure-1, Figure-2, Table-1 and susceptance values in Table-4
we designed circuit as shown in Fig-4. And the results are tabulated in the Table-5.
Figure 4: Power Flow Diagram with Susceptance
In Figure-2 a 3-Bus 345-KV system with susceptance, we observe that real and
Reactive power at bus 1, 2 and 3 is changing. And also voltage and Power Angle at bus 1,
2 and 3 is also changing. The direction of green arrow states the power flow through load.
Table 6 : Results of power flow diagram adding susceptance
DATA
(P)Real
Power
(MW)
(Q)Reactive
Power
(MVar)
(V)Voltage
(pu)
Power
Angle
(deg)
Comments
Bus 1 308 -217 1 0 Q lagging power increased
Bus 2 200 119 1.05 -2.05
Change in power angle and
Q
Bus 3 500 100 1 -8.72
Voltage restored as initial
value
Line(1-3)
At bus 1
240 -66 1 0 Q lagging power increased
Line(1-3)
At bus 3
236 -5 1 -8.72
Change in power angle, V
and Q
Line(1-2)
At bus 1
68 -151 1 0 Change in Q
Line(1-2)
At bus 2
67 75 1.05 -2.05
Change in power angle and
Q
Line(2-3)
At bus 2
267 271 1.05 -2.05
Change in power angle and
Q
Line(2-3)
At bus 3
264 -95 1 -8.72
Change in power angle, V
and Q
16. 9
In Table-6, we observe that Real Power, reactive Power, Voltage and power Angle
has been changing at different buses and in different transmission line connected to bus.
Respective comments have given for changes occur at buses and transmission lines.
2.4 Conclusion
A 3-Bus, 345-KV system for assembling Y-matrix with shunt Susceptance at each
end of the transmission line leads to change in voltage at load bus; this change is due to
effect of adding lagging reactive power to the system. As real power changes the power
angle also changes.
So, we conclude that to regulate the voltage in the system we need to modify lagging
reactive power by adding susceptance to the lines.
17. 10
Chapter 3.Torque Vs. Slip characteristics
of 3Ph Induction Motor
3.1Introduction and Background Theory
“One of the most common electrical motor used in most applications which is known
as induction motor. This motor is also called as asynchronous motor because it runs at a
speed less than synchronous speed. An induction motor always runs at a speed less than
synchronous speed because the rotating magnetic field which is produced in the stator
will generate flux in the rotor which will make the rotor to rotate, but due to the lagging
of flux current in the rotor with flux current in the stator, the rotor will never reach to its
rotating magnetic field speed i.e. the synchronous speed” [4].
Torque and Slip of Induction Motor
(1)
(2)
(3)
(4)
18. 11
(5)
Electromagnetic Torque of Induction motor is represented as
(6)
So, to find the (Pem) we used the equivalent circuit of 3ᴓ Induction motor in Figure-5
Figure 5: equivalent circuit
(7)
To find (Tem), By applying potential divider rule in the thevenin equivalent circuit
shown in Figure-5
(8)
19. 12
3.2 Torque Vs. slip and Analysis
Torque vs. Slip characteristics are described with an example
Table 7: Name Plate details and Input Parameters
For these parameters, torque versus slip results was obtained using MATLAB code.
This code is present in APPENDIX.
20. 13
RESULTS:
Figure 6: Torque vs. slip
Figure 7: Torque (various resistances) vs. slip
Analysis
In Figure-6 initially Induction Motor at no load conditions , we observe speed
decreases and slip increases ,and when in Induction Motor load conditions (as we know
torque depends on slip) so slip changes automatically torque as we observed in (s=0 to
s=1).In Figure-7 Change in resistance leads to change in starting torque and maximum
torque remains constant.
21. 14
3.3 Conclusion
In this Chapter, studied about the rotor speed, synchronous speed, slip speed, and also
torque vs. slip characteristics. Observed about generator mode and motoring mode.
Initially Induction Motor at no load conditions, observed speed decreases and slip
increases ,and when in Induction Motor load conditions (as we know torque depends on
slip) so slip changes automatically torque as we observed in (s=0 to s=1).Change in
resistance leads to change in starting torque and maximum torque remains constant.
22. 15
Chapter 4.Steady State and Dynamic
model of 3Ph Induction Machine
4.1 Introduction and Background Theory
“The induction machine is also called as the asynchronous machine. Most induction
motors are of the rotary type with basically a stationary stator and a rotating rotor. When
the induction motor is connected to the appropriate ac voltage source, there is a revolving
flux in the air-gap. If there is a difference in between revolving field speed and rotor
speed then the revolving field induces a voltage in the rotor winding. The difference
between the rotor and the revolving field speeds is called the slip speed. The induced
voltage results in a rotor current that generates a flux in the counter direction to the flux
generated by the stator windings. However, the speed control of the induction motor is
not easier when compared with the dc motors. At light load conditions, the induction
motors take large starting currents and operate at a poor lagging power factor. The 3-
phase induction machine with a balance input voltage can be evaluated by single-phase
equivalent circuit. In the steady state mode, the per-phase equivalent circuit of the
induction motor is given in fundamental frequency. The simplified per-phase equivalent
circuit model of the machine provides good performance prediction for steady state
operation of the machine with sinusoidal supply voltages. But, it fails to give a good
model for dynamic performance. In an adjustable speed drives, the machine normally 43
constituted as element within a feedback loop, and therefore its transient behavior has to
be taken into consideration.”[5]
(9)
24. 17
4.3 Dynamic Design of 3 Phase Induction Machine using SIMULINK
The dynamic model of this type of machine is presented. In addition, the dynamic
Simulink model is also attached (with its initial m file).This code is present in
APPENDIX.
Figure 8: Simulink Model
4.4 Simulation Results for Dynamic Design and Analysis
a) Respective graphs are obtained by using MATLAB code and SIMULINK,
Compared with the change in Wsyn valve and ‘zero’ in the Simulink.
Figure 9: Input voltages when Wd is Wsyn
25. 18
Figure 10: Stator currents when Wd is Wsyn
Figure 11: Rotor currents when Wd is Wsyn
26. 19
Figure 12: Currents when Wd is Wsyn
Figure 13: speed and torque curve when Wd is Wsyn
Figure 14: Input voltages when Wd is 0
27. 20
Figure 15: Currents when Wd is 0
b) Torque vs. slip
Figure 16: Torque vs. slip
c) Torque vs. speed
Figure 17: Torque vs. speed
28. 21
d) In above case, given voltage Vrd as 5% of 460 volts to check the speed.
Figure 18: Torque vs. speed
Analysis
For Results (a): From (Figure -9 to Figure-14), Change in reference leads to sin
wave in the output and from (Figure -12 to Figure-15) there is no change in output.
For Results (b): Initially Induction Motor at no load conditions, we observe
speed decreases and slip increases ,and when in Induction Motor load conditions (as we
know torque depends on slip) so slip changes automatically torque as we observed in
(s=0 to s=1).
For Results (c): From the Figure-17 we observe that the torque is inversely
proportional to each other.
For Results (d): From the Figure-18 we observe that speed decreases and torque
will be in negative.
29. 22
4.5 Conclusions
To validate the proposed induction motor displaying approaches, numerical
simulation part have been done by utilizing MATLAB/SIMULINK. The simulation
parameters and particulars of induction motor used in this project are given in
APPENDIX. The induction motor responses such as current, torque and speed using
stationary reference frame. From simulation results it can be observed that results are
based on d-q modeling and real time implementation.
30. 23
Chapter 5.Wind Energy
5.1 Introduction
Wind power is mainly produced by utilizing wind. It is the energy that utilizes wind
through wind turbines, which in turn produces power. Wind strikes the turbine directly
which in turn converts the kinetic energy into electrical energy and this electrical energy
is send to the grid through transmission lines and generates wind power.
5.2Simulation Specification of Integration of DC micro grid using wind
5.2.1 Wind Turbine
Figure 19 : Wind Turbine Block
Parameters used in this block for the simulation are
Figure 20: Parameters for Wind Turbine Block
31. 24
5.2.2 Asynchronous Machine
Figure 21: Asynchronous block
Parameters used in this block for the simulation are
Figure 22: parameters for Asynchronous block
5.2.3 Wind Power Conversion
Figure 23 : Power Conversion Block
32. 25
Figure 24: Simulink Model
5.3 Simulation Results and Analysis
Voltage and current waveform
Figure 25: V& I curve
33. 26
Torque and Speed
Figure 26: Torque and Speed curves
Grid Voltage
Figure 27: Output Voltage Waveform
Analysis
By the graphs we plotted that in Figure-25 voltage and current waveform of wind, in
Figure-26 we plotted that torque and speed curve (as we know that torque is inversely
proportional to speed) and in Figure-27 we plotted DC voltage curve.
34. 27
5.4Conclusions
This chapter presents the modeling of DC Micro grid with wind as input source.
These renewable sources are integrated into the main DC bus through bi directional AC-
DC converter. Wind energy variation was taken consideration in order to explore the
effect of such environment variations to the proposed Micro grid. In addition the
proposed Micro grid is equipped with energy storage system and it is connected to
distributed system. This micro energy resource can improve the Micro grid efficiency and
reduce variations in the input system. The is also cost effective and smaller in size.
35. 28
Chapter 6.Integration of DC micro grid
6.1 Circuit and Block Diagram
Figure 28: Circuit diagram of DC micro grid
Figure 29: Block diagram for DC micro grid
WECS (Wind Energy Conversion System), PV panels (Photovoltaic panels)
The dc bus associates with wind energy conversion system (WECS), PV panels,
and battery energy storage system (BESS).The WECS is connected to the DC bus via
AC–DC converter, PV panels are connected to the DC bus via a DC–DC converter. The
BESS is also connected DC bus via DC-DC converter .From DC bus it is connected to
DC-AC converter and connected to load.
36. 29
6.2 Operational Optimization of Micro grid
In the first stage optimization of micro grid is scheduled, wind and solar power
forecasts are to produce total renewable power. The power generation data are used to
assign as positive energy and negative energy is reserved by BESS (Battery Energy
storage system) for the micro grid operation. BESS can operate in charged and
discharged in operation conditions; reserved positive energy from BESS gives the energy
that is fed up to a DC bus on demand and reserved negative energy will remain
uncharged. The aim of the optimization is to minimize operation cost of the micro grid.
In the operation, an adaptive droop control is devised for the BESS, which is selected on
the basis of the deviation between the optimized and real-time (SOC) state-of-charge of
the BESS.
Figure 30: Wind or solar power forecast uncertainty for 1 h
Three stages are low, high and average power, this forecast is considered for an
hour of average power in urban micro grid.
6.2.1 Aggregated Model of Wind and Solar Power Forecast
Figure 31: Aggregation of wind and solar power forecast in micro grid
37. 30
Table 9: wind and solar power forecast data
In Table-9 it shows that the wind and solar power generation forecast for a 1hour.
The aggregated model has two power resources (N = and it has three states so K=3,
then 9 combination states are defined.
Table 10 : Combined states of wind and solar power forecast
6.2.2 Energy Reserve Assessment for Operation of Micro grid
Table 11 : Three hours of aggregated three-state power forecast model
In Table-11 it shows that the probability of real time power for three hours in state
1 is equal to the product of probability in those three hours, then the probability would be
= 0.00659 and this probability is same foe state 3.This probability is small, in
order to cover up that, the reserved negative energy from BESS is supplied for those
uncertainty demand.
38. 31
(13)
Figure 32: Battery storage capacity allocation for optimized scheduling
Similar reserved negative energy, we can calculate reserved positive energy from BESS
(14)
Both the positive and negative reserved energy are stored in BESS, depth-of-
discharge (DOD), positive energy reserve (PR), negative energy reserve (NR) are in
BESS. . BESS can operate in charged and discharged in operation conditions; reserved
positive energy from BESS gives the energy that is fed up to a DC bus on demand and
reserved negative energy will remain uncharged.
6.2.3 Formulation of Optimized Scheduling of Micro grid
(15)
39. 32
6.3 Simulation Result and Analysis
Figure 33: Simulation circuit of proposed system
Figure 34: Solar current & voltage waveform
40. 33
Figure 35: Battery SOC, voltage & current waveform
Figure 36: Grid voltage waveform
Figure 37: Load voltage & current waveform
41. 34
Analysis
In Figure-36 we plotted solar voltage and current waveform.
In Figure-37 we plotted battery SOC, voltage and current waveform.
In Figure-38 we plotted grid voltage waveform.
In Figure-39 we plotted load voltage and current waveform.
6.4 Conclusion
Integration of DC micro grid has been proposed, operational optimization was
plotted using SIMULINK. Our main aim is to minimize cost and emissions. Aggregated
model is to forecast power generation of wind and solar using BESS (Battery energy
storage system) associated with AC and DC adaptive droop control. This droop control
supports the SOC (state-of-charge). For the special case of an urban location, wind and
solar power were harvested on the top, energy delivery at the bottom on the ground level
and this energy delivered to local stationary and mobile EV charges.
42. 35
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43. 36
Appendix
In chapter three, the torque and speed curves are plotted using MATLAB code
----------------------------PROJECT-2-------------------------------%
%-----------------------------GECE567---------------------------------%
%--AUTHORS:Roma Harshan Eskala, Sirish Kumar Alahari, Akhil Adrash----%
clear all;
clc;
%-------------------------Name Plate Details---------------------------%
Po = 2.4;
Vs = 460/sqrt(3);%----------Voltage phase conversion----------%
f = 60;
Ph = 3;
Ifload = 4;
Speed = 1769;
Efficiency = 88.5;
Pf = 0.8;
P = 4;
slip = 1.72;
J = 0.025;
%------------------------Per-phase Motor circuit Parameters-------------%
Rs = 1.77;
Xs = 5.25;
Xr = 4.57;
Xm = 139.0;
Rr = 1.34;
%-----------------------------------------------------------------------%
%------------------------Solution---------------------------------------%
%-----------------------------------------------------------------------%
pts =100000;
s=linspace(1,-1,pts);
%s= 0.06;
%----------------------From Thevenin's Circuit--------------------------%
Vth=Vs*(1*i*Xm)/(Rs+1*i*Xm+1*i*Xs);
ang=angle(Vth)*180/pi;
Vth=abs(Vth);
Zth=((1*i*Xm)*(Rs+1*i*Xs))/(1*i*Xm+Rs+1*i*Xs);
Rth=real(Zth);
Xth=imag(Zth);
W=2/P*(2*pi*f);
i = 1;
%k(i)= 1;%-----------Omitted for the part c-----------------------------%
while i<7;
K=[1 2 4 6 8 10];
for j=1:pts
T(j)=(1/W)*(3*(Vth.^2)*(Rr*K(i)/s(j)))/((Rth+(Rr*K(i)/s(j))).^2+((Xth+Xr).^2));
end
%---------------Ploted Graph for Torque vs Slip---------------------%
plot(s,T);hold on;
i=i+1;
grid on;
end
title('Torque vs slip');
xlabel('slip');
ylabel('torque(N-M)');
44. 37
In chapter four, the torque and speed curves are plotted using MATLAB code
clear;
clc;
% Calculation of Initial Conditions for line directly start
% Induction Motor Parameters
Rs=1.77;
Rr=1.34;
Xls=5.25;
Xlr=4.57;
Xm=139;
Jeq=0.025;
p=4;
% Steady State Operating Condition
f=60; VLLrms= 460; s=-0.0172; % phase-a voltage is at its positive
peak at t=0
Wsyn=2*pi*f; % synchronous
speed in electrical rad/s
Wm=0
%Wm=(1-s)*Wsyn; % rotor
speed in electrical rad/s
% Phasor Calculations
Va = VLLrms * sqrt(2)/ sqrt(3); % Va phasor
Zrotor = j*Xlr + Rr/s; % Equivalent
Rotor Branch Impedance
Zm = j*Xm; % Magnetizing
Impedance
Zeq = (Rs + j*Xls) + (Zm * Zrotor) / (Zm + Zrotor); % Equivalent
Impedance
Ia = Va / Zeq; % Ia phasor
Ema = Va - (Rs + j*Xls) * Ia; % Voltage
across the magnetizing branch
Iraprime = Ema / Zrotor; % Rotor
branch current phasor
% Space Vectors at time t=0 with stator a-axis as the reference
Vs_0 = 0; %Vs_0 = (3/2) * Va;
% Vs(0) space vector
Is_0 = 0; %Is_0 = (3/2) * Ia;
% Is(0) space vector
Theta_Is_0 = angle(Is_0); % angle of
Is(0) space vector
Ir_0 =0; %Ir_0 = (-1) * (3/2) * Iraprime;
% Ir(0) space vector; notice factor of (-1); see Fig. 3-11
Theta_Ir_0 = angle(Ir_0); % angle of
Ir(0) space vector
% We will assume that at t=0, d-axis is aligned to the stator a-axis.
Therefore, Theta_da_0=0
Theta_da_0 = 0;
Isd_0 = sqrt(2/3) * abs(Is_0) * cos(Theta_Is_0 - Theta_da_0) % Eq. 3-
64
Isq_0 = sqrt(2/3) * abs(Is_0) * sin(Theta_Is_0 - Theta_da_0) % Eq. 3-
65
Ird_0 = sqrt(2/3) * abs(Ir_0) * cos(Theta_Ir_0 - Theta_da_0)
Irq_0 = sqrt(2/3) * abs(Ir_0) * sin(Theta_Ir_0 - Theta_da_0)
% Calculation of machine inductances
Ls = (Xls + Xm) / (2*pi*f);
Lm = Xm / (2*pi*f);
Lr = (Xlr + Xm) / (2*pi*f);
45. 38
% Inductance matrix M in Eq. 3-61
M = [Ls 0 Lm 0 ;...
0 Ls 0 Lm;...
Lm 0 Lr 0 ;...
0 Lm 0 Lr];
% Flux Linkages
fl_dq_0 = M * [Isd_0; Isq_0; Ird_0; Irq_0]; % dq-winding
fluxes in vector form, Eq. 3-61
fl_sd_0 = fl_dq_0(1)
fl_sq_0 = fl_dq_0(2)
fl_rd_0 = fl_dq_0(3)
fl_rq_0 = fl_dq_0(4)
% Electromagnetic Torque, which equals Load Torque in Initial
Steady State
Tem_0 = 12.466;
%Tem_0 = (p/2) * Lm * (Isq_0 * Ird_0 - Isd_0 * Irq_0) % Eq. 3-
47
TL_0 = Tem_0
% Wmech = rotor speed in actual rad/s
Wmech_0= 0
%Wmech_0=(2/p)*Wm %Eq. 3-34
sim('fac_zhao001_linestart.mdl')
