anfis strategy for windfuel cell power management system in a micro grid

8/10/2019 ANFIS Strategy for WindFuel Cell Power Management System in a Micro Grid

1/49

ANFIS Strategy For Wind/Fuel Cell Power Management System In a Micro Grid

This proect introduces a micro grid! which consists o" di""erent distri#uted

generation units which are connected to the distri#ution grid$ The operations o" the

%G units are coordinated #y the power management algorithm in grid and islanded

operations$ The primary generation unit o" the micro grid is the wind tur#ine and the

proton e&change mem#rane "uel cell is used to supplement the 'aria#ility in the

power$ In micro grid a #attery is incorporated to o'ercome the di""iculty o" shortage

o" power demand during Islanded operation and to impro'e crest demands

throughout grid connected operation$ Pre'iously the power management system was

done using model predicti'e algorithm control design$ Which has comple&

mathematical calculations to "ind out critical 'alues

Now in this proect! ANFIS controller is used as the

control design which reduces the design comple&ity as the logical operations are

per"ormed to "ind out critical 'alues! the power (uality such as harmonic

compensation "or nonlinear loads o" the distri#ution system! will #e impro'ed when

compared to model predicti'e algorithm control design and also It has "ast response$

The complete proposed system will #e tested using MAT)A*/SIM+)IN, and the

simulation results re'eal the attracti'e per"ormance characteristics o" the proposed

system$

1


2/49


1. INTRODUCTION

1.1GENERAL

The aim of this chapter is to present the motivation behind the work done in

this thesis. The chapter also provides the Existing system analysis as well as the thesis

organization.

1.2 MOTIVATION

In the near future, the demand for electric energy is expected to increase

rapidly due to the global population growth and industrialization. This increase in the

energy demand requires electric utilities to increase their generation. ecent studies

predict that the world!s net electricity generation is expected to rise from "#.$ trillion

kilowatt%hours in &''( to &).) trillion kilowatt%hours *an increase of )"+ in &'"(

and $$.$ trillion kilowatt%hours *an increase of -&.(+ in &'$'. urrently, a large

share of electricity is generated from fossil fuels, especially coal due to its low prices.

/owever, the increasing use of fossil fuels accounts for a significant portion of

environmental pollution and greenhouse gas emissions, which are considered the

main reason behind the global warming. 0or example, the emissions of carbon dioxide

and mercury are expected to increase by $(+ and 1+, respectively, by the year &'&'

due to the expected increase in electricity generation. 2oreover, possible depletion of

fossil fuel reserves and unstable price of oil are two main concerns for industrialized

countries. To overcome the problems associated with generation of electricity from

fossil fuels, renewable energy sources can be participated in the energy mix. 3ne of

the renewable energy sources that can be used for this purpose is wind energy that is

atmospheric air in motion. This wind energy can be converted to clean electricity

through the turbine process. The use of wind turbine systems for electricity generation

started in the seventies of the &'th

century and is currently growing rapidly worldwide.

1.3 EXISTING SYSTEM

To reduce the variability in the renewable sources, energy storage devices are

used such as batteries and ultra capacitors. The inclusion of energy storage devices is

also difficult for organizing demands and deviation in the load requirement. In present

pro4ect, a micro grid composed of a 5hotovoltaic array *56 7rray, 5E20 i.e., a

proton%exchange membrane fuel cell, and storage battery *89 is planned. 5E20 *a

proton%exchange membrane fuel cell is employed as a backup generator unit to give

back the power produced by the discontinuous nature of %5hotovoltaic array. The

2


3/49


8torage 9attery is incorporated to overcome the difficulty of shortage of power

demand during Islanded operation and to improve crest demands throughout grid

connected operation. In micro grid to organize the distribution of power between

different :; units an energy%management algorithm is designed. The controller

design proposed for the inverters of :; units is 25 ontroller design. 7s The

existing system consists of an 25 ontroller in which the total harmonic distortion

rate is high because its design complexity is high to find out critical values, so the

power quality will be reduced.

0ig "."


4/49


). hapter ) presents in detail about the 7=0I8

(. hapter ( deals with the 27T>79?8I2@>I=A models and esults .

B. In the last chapter conclusion of the thesis are presented. 2oreover, this

chapter gives the outline of the 5ro4ect and 8cope for future.

This chapter covered the motivation behind the thesis work, 8ummary and

how the organization of thesis is carried out

2. SYSTEM DESCRIPTION

4


5/49


=ow a days, In demand response management large number of consumers are

participated because of increase in smarter electrical facilities like electrical vehicles,

unbalanced systems and smart meters. This pro4ect is on smarter grid through

demand%side management *:82, in which energy reserves and power quality has

improved. These methods make the penetration of renewable generation, such as wind

power and solar power into the grid. The 4oining of renewable energy sources can add

on the generation from the distribution grid. These renewable energy sources are not

constant in their generation and may compromise the consistency and stability of the

distribution network.

To reduce the variability in the renewable sources, energy storage devices are

used such as batteries and ultra capacitors. The inclusion of energy storage devices is

also difficult for organizing demands and deviation in the load requirement. In present

pro4ect, a micro grid composed of a wind turbine, 5E20 i.e.,a proton%exchange

membrane fuel cell ,and storage battery *89 is planned. 5E20 *a proton%exchange

membrane fuel cell is employed as an backup generator unit to give back the power

produced by the discontinuous nature of wind turbine. The 8torage 9attery is

incorporated to overcome the difficulty of shortage of power demand during Islanded

operation and to improve crest demands throughout grid connected operation.

In islanded operation, the function of the 8torage 9attery is to keep up the

power stability in the microgrid which is given by

5:; C5bD5> *"

here,

5:; is the power delivered by the main :; unit

5b is the 8torage 9attery power

5> is the real power delivered to the loads

8torage 9attery power which is sub4ected to the charging and discharging constraints

given by

5bFD 5b,max *&

The energy limitation of the 8torage 9attery is determined based on the state%of%

charge *83 limits which are given as

83min F 83 FD 83max *$

Even though the state%of%charge *83 of the battery cannot be calculated directly, it

can be found by using many estimation methods.

5


6/49


:uring the micro grid operating in islanded operation from the distribution grid, the

8torage 9attery can operate in the charging, discharging, or idle mode depending on

its 8tate of charge *83 and power of storage battery 5b.

0ig &.". 3peration of the 89 during grid%connected operation.

In grid%connected function, the distribution grid is interfaced to the microgrid

through a circuit breaker *9 at the point of common coupling *5. The function

of the main :; unit is to provide voltage and power for the loads therefore it reduces

the burden of generation and delivery of power directly from the distribution grid.

ith the increasing of power%electronics devices being interfaced to the microgrid,

the load currents might be unclear because of the presence of harmonic components.

The purpose of :; units is also to compensate harmonics in the currents drawn by

nonlinear loads in the microgrid, as a result that the harmonics will not spread to other

electrical networks interfaced to the 5.If the power produced by the main :; unit

is higher than the total load demand in the microgrid, then the surplus power be able

to charge the 8torage 9attery or in4ected into the distribution grid, depending on the

8tate of charge *83 of the 8torage 9attery, as shown in 0ig. &." onversely, power

produced by the main :; unit is less than the total load demand in the microgrid, the

6


7/49


8torage 9attery can be controlled to attain various energy%management functions

depending on its 8tate of charge *83 and the T3@ *time of use of electricity.

0or the period of off%peak periods as shown in 0ig. &.", when the cost of

generation from the grid is low and if the 8tate of charge *83 of 8torage 9attery is

less than the maximum 83 limit 83max, the 8torage 9attery will be charged by

the grid and the loads will be supplied by the main :; unit and the grid. In peak

periods, when the cost of generation from the grid is high and if the 8torage 9attery

8tate of charge is greater than the minimum 83 limit 83min, the 8torage 9attery

can distribute power to the grid to attain peak sharing.

hen an error occurs on the network of the distribution grid, the function of

the ircuit 9reaker is to cut off the microgrid from the distribution grid. The 8torage

9attery and The main :; unit are the only power sources left to control the loads. In

the case when the generation of the main :; unit is not capable to meet the total load

demand, the 8torage 9attery is necessary to supply for the deficiency in real and

reactive power to uphold the stability and power balance of the microgrid as shown in

0ig. &.&. hen the total load demand greater the generation capability of the main :;

unit and the 8torage 9attery, the 528 detects a reduction in the system frequency and

load shedding for noncritical loads. It is necessary to restore the system frequency and

uphold the stability of the microgrid.

0ig &.&. 3peration of the 89 during islanded operation.

Inmicro grid to organize the distribution of power between different :; units

an power%management algorithm is designed. The controller design proposed for the

7


8/49


inverters of :; units is 7=0I8 ontroller design. This reduces the design complexity

as the logical operations are performed to find out critical values, the power quality

such as harmonic compensation for nonlinear loads of the distribution system will be

improved.This pro4ect provides a complete solution for the function of a micro grid

which will send out a current and voltage concurrently during both islanded and grid%

connected operations.

0ig &.$


9/49


2.1.1. Feat!e" #$ W%&' P#(e! S)"te*

There are some individual energy features of wind power systems. The

ma4ority wind power sites are located in island, marine or rural areas. Energy

necessities in such places are unique and do not want the high electrical power. 7

power system with varied quality supplies can be a fine match with total. ;rid

systems in ural area are probable to be weak *voltage around $$ A6. Interfacing

weak grids to ind Energy onversion 8ystem *E8 is difficult and harmful to

the workersG safety. There are few periods without wind. Thus, to maintain a power

supplies E8 have to be interfaced to energy storage or parallel generating system.

2.1.2. P#(e! $!#* t+e W%&'

In the wind turbine to rotate the generator Ainetic energy produced by

the wind is used to generate electricity. There are a number of factors that influence

the effectiveness of the wind turbine in extracting the power from the wind. 0irstly,

the speed of the wind is one of the significant factors to determine how much power

can be extracted from the wind. This is due to the power generated as of the wind

turbine is a function of the cubed of the wind speed. Thus, if the wind speed tripled,

the power generated will be enhanced by nine times the original power. Then

secondly, site of the wind farm plays an significant role for the wind turbine to extract

the ma4ority existing power form the wind. The next significant reason of the wind

turbine is the rotor blade. The length of the rotor blades in wind turbine is one of the

significant aspects of the wind turbine because the power generated from the wind is

proportional to the rotor blades swept area. If the diameter of the swept area is

doubled, the power generated will be improved by four times. 8o the rotor blades to

be strong, durable and light. 7s the length of the blade increases, the qualities of rotor

blades become more intangible. 9ut with the current advance technologies in carbon%

fiber and fiber glass technology, the manufacture of less weight and tough rotor blades

between &' to $' meters long is achievable. ind turbines with the size of these rotor

blades are able to generate up to " megawatt of power. The association between the

powers generated by the wind source and the speed of the wind and the swept

diameter of rotor blades is shown below.

5 DH?1d:&6$wind

2.1.3A',a&ta-e" #$ W%&' #(e! /a&t"

9


10/49


Improving price competitiveness

2odular installation

apid onstruction

Improved system reliability

=on%5olluting

omplementary generation

2.1.4 T+e D#0/)$e' %&'t%#& -e&e!at#! (%&' t!0%&e

:0I;T *The :oubly%fed induction generator wind turbine was shown in

the fig &.). The the grid%side converter *grid and rotor%side converter *rotor are the

two components of the 7?:?7 converter. 6oltage%8ourced onverters are grid

and rotorthat use forced%commutated power electronic devices *I;9Ts to convert the

: voltage source to 7 voltage. The : voltage source is the capacitor associated

on the : side. grid is connected to the grid through the coupling inductor > . The

rotor is connected to three%phase rotor winding by sliprings and brushes and the three%

phase stator winding is directly 4oined to the grid. The induction generator converts

power *captured by the wind turbine into electrical power and the stator and the rotor

windings transmits this electrical power to the grid. The pitch angle command and the

voltage command signals 6rand 6gcare generated by the control system for rotorand

gridrespectively in order to control the wind turbine power, the reactive power or the

voltage at the grid terminals and the : bus voltage.

0ig &.)< 3perating 5rinciple of the :oubly%0ed Induction ;enerator wind turbine

8ystem

In this figure the followings parameters are used D I> D I % Iswitch

D I % :I>

I>D

The : component of voltage across the inductor has to be zero if losses are

neglected. The average voltage across the inductor is given byD "?T * C D '

D"?T *6s:TC *6s%vo *"%d TD'

7fter solving we getower

C#/' "ta!t8 Ses =o

Wate! *a&a-e*e&t omplex =one

Table &.&< :ifferences among the low temperature and high temperature 5E20

variants

2.9 POINT OF COMMON COUPLING

The 5 is a point in the electrical system where multiple customers or

multiple electrical loads may be connected. 7ccording to IEEE%("-, this should be a

point which is accessible to both the utility and the customer for direct measurement.

7lthough in many cases the 5 is considered at the metering point, service entrance

or facility transformer, IEEE%("- states that within an industrial plant, the 5 is the

point between the non%linear load and other loads.U It will generally be easier to meet

harmonic distortion limits when the 5 is considered at the metering point, facility

21


22/49


23/49


nature of sinusoidal such that it does not disturb the waveform *0ig &."&. 2ost

household appliances are classified as linear loads. =on%linear loads will draw a

current that is not exact sinusoidal *0ig &."$. 8ince the current waveform departs

from a sine wave, noises in voltage waveform are created.

0ig &."&< Ideal 8ine wave

0ig &."$< :istorted aveform

7s can be seen from the waveform in 0igure $, waveform distortions can significantly

modified the form of the sinusoid. /owever, no matter the level of difficulty of the

fundamental wave, it is in fact 4ust a composite of multiple waveforms called

harmonics.

/armonics have different frequencies that are multiples of the waveformGs

fundamental frequency. Thus, harmonic distortion is the degree to which a waveform

changes from its pure sinusoidal values. 7s a effect of the summing up of all these

harmonic elements. The perfect sine wave has nil harmonic components Total

harmonic distortion, or T/:, is the summing up of all harmonic components of the

current or voltage waveforms compared against the fundamental component of thevoltage or current wavei%ion batteries

L%t+%*%#& 0atte!%e"

>ithium is an attractive material for battery technology as it has a higher reduction

potential and lighter weight V-$W. echargeable >i%ion batteries are commonly found

26


27/49


in consumer electronic products, comprising most of the global generation volume of

"' to "& ;iga%watt hours per year V-$W. These batteries are widely used in plug%in

hybrid electric vehicles *5/E6 and electric vehicles *E6. ompared to the long

history of lead%acid batteries, >i%ion technology is relatively new. It is expected that

the E6 and energy storage market will substantially benefited from advancements in

>i%ion battery technology. The high energy density and relatively low weight results

in a viable choice for electric vehicles and other applications where space and weight

are important. ;iven their long cycle life and compactness, higher roundtrip energy of

1( M -'+ V-(W, >i%ion battery manufacturers may be used for various utility grid%

support applications including distributed energy storage systems at community scale,

commercial end%user energy management, home back%up energy management

systems, frequency regulation and wind and photovoltaic power smoothing

applications.

F/#( 0atte!%e"

7 flow battery is a rechargeable battery where electrolyte containing one or more

dissolved electro%active species flow through an electrochemical cell which converts

chemical energy to electricity . 6anadium redox battery technology is one of the most

mature flow battery systems available, with an expected life of about "( years.

/owever, the physical scale of this battery is mainly due to the large volume of

electrolyte required when sized for utility%scale pro4ects. 0low batteries are an

attractive energy storage option for the grid because of their ability to store a large

amount of energy with a potentially longer life%cycle. /owever, such technology is

still young, with an associated cost barrier. 2oreover, the presence of active species in

the anode and cathode electrolytes may lead to efficiency loss and contamination.

S#'%* "/$! 0atte!%e"

The sodium sulfur battery possesses high energy and power density and electrical

efficiency. Its long life results in an excellent choice for electric power system

applications. 8ulfur is used as an active material at the positive electrode and sodium

is used at the negative electrodes. Electrodes are separated by sodium%ion%conductive

ceramic solid electrolyte. /igh temperature maintains the electrode active materials in

a liquid state while the electrode is solid. This reduces resistance and enables efficient

battery performance averaged over lifetime discharge.

Se!aa%t#!"

27


28/49


8uper%capacitors are devices that store electrical energy as charge separation in porous

electrodes with large surface areas. 8ome key benefits of ultra capacitors include

highest capacitance density of any capacitor technology, low cost per farad, reliable,

long life, high cycle%life, maintenance%free operation, environmentally safe, a wide

range of operating temperatures high power density and good energy density. 3f these

features, the greater power and energy densities bridge the gap between standard

batteries and traditional capacitors for high%power, short%duration energy storage. 7s a

result, they are widely used in utility applications for transmission line stability,

spinning reserve, frequency control, voltage regulation, power quality and

uninterruptible power supply applications.

2.;.2 Me+a&%a/ E&e!-) St#!a-e

5umped hydro, compressed air energy storage and flywheels can be classified as

mechanical energy storage.

P*e' +)'!#

5umped hydro electric storage is the oldest, most widespread commercially available

energy storage technology. 8uch schemes consist of two large reservoirs at different

levels with a store of water. 3ff%peak electricity is used to pump water up to the top

reservoir, which can then be discharged as required, typically to a lower reservoir at

the other end of a height differential. This flow of water drives turbines in the same

way as hydro%electric dams. The technology can provide reliable power at short

notice, typically within one minute, with efficiency in the range of #'%1(+ . 3verall

the technology is one of the most mature on the market and further technological

advances are considered unlikely. 5umped hydro is the main form of energy storage

globally and has been used since the "1-'s. There is approximately -'; of pumped

storage in operation worldwide, accounting for $+ of global generation capacity V-BW.

7 limiting factor is the large capital costs involved in construction *although cost is

highly dependent on local topography and other factors.

F/) (+ee/

0lywheels represent a mechanical form of energy storage in which the kinetic energy

of a fast%spinning cylinder contains stored energy. ecent technological advances of

fly%wheel have improved the efficiency of the traditional flywheel V-$W. 2odern

flywheel systems are typically comprised of a massive rotating cylinder, supported on

28


29/49


a stator by magnetically levitated bearings that eliminate wear and extend system life.

To increase efficiency, the flywheel is operated in a low pressure environment to

reduce air friction. This energy storage system draws electricity from a primary source

to spin the high density cylinder at speeds greater than &',''' rpm. hen the primary

source loses its power, the motor acts as a generator. 7s the flywheel continues to

rotate, this generator supplies power to the grid. 0lywheels have a high energy density

of (' M "'' h?kg and an efficiency of around -'+, depending on the flywheelGs

speed range . ith no chemical management or disposal to consider, flywheels have

certain environmental advantages over battery systems.

C#*!e""e' a%! e&e!-) "t#!a-e

In compressed air energy storage system *7E8, air is compressed into underground

mines or caverns by using off%peak electricity, which improves the efficiency of the

gas turbine. hen required, the compressed air is utilized in con4unction with a gas

turbine to generate electricity, resulting in gas consumption reductions of B'+ relative

to the same amount of electricity generation directly from gas. ompressed air energy

storage can be integrated with a wind farm in order to store additional power during

high wind conditions. The energy efficiency of 7E8 is around 1'+. The availability

or generation of large underground storage spaces can have possible environmental

impacts, and constraint on this technology is constrained by the

absence of suitable locations for underground air storage.

2.;.3 E/et!#*a-&et% "t#!a-e

Se!#&'t%&- *a-&et% e&e!-) "t#!a-e

8uperconducting magnetic energy storage *82E8 can store electrical energy

in a magnetic field within a cooled super%conducting coil. The coil is cooled beyond

its superconducting temperature *%&B-o, where the resistance of the material is very

low. This limited electrical resistance allows 82E8 to achieve high efficiency of up to

-#+. 8ince the 82E8 can release immediate energy, It is useful where customers

require an extremely high quality power output. 7s the 82E8 is currently undergoing

research and development, very limited information available regarding costs.

Extremely low temperatures are required for the superconducting system, representing

a safety issue. >arger scale 82E8 systems could require significant protection to deal

with magnetic radiation in the immediate vicinity.

2.;.4 H)'!#-e& E&e!-) St#!a-e

29


30/49


/ydrogen%based energy storage systems are currently receiving considerable

attention due to the long period over which hydrogen can be stored, and owing to the

potential hydrogen holds for replacing petroleum products as the energy carrier for the

transport sector. hen coupled with a renewable energy source or low carbon energy

technology, hydrogen energy storage has the potential to reduce greenhouse gas

emissions. The essential elements of a hydrogen storage system consist of an

electrolyzer unit, to convert electrical input to hydrogen during off%peak periods, the

storage component and an energy conversion component to convert the stored

chemical energy into electrical energy when demand is high or for use in

transportation systems.

The electrolyzer and fuel cell components can be dedicated or reversibleU filter denoted by fi and >fi to abolish the high

switching frequency harmonics produced by the :; inverter.

0ig $." and $.& show the equivalent single%phase illustration of the :; inverters for

islanded%connected and grid%connected operation.

31


32/49


0ig. $.". Equivalent :iagram for single%phase of the :; inverters for grid connected

operation.

0ig. $.&. Equivalent :iagram for single%phase of the :; inverters islanded operation.

The resistance 4reflects the loss of the :; inverter. Total load current i> is

the summing of the currents given to the load k * kD", &, $, is represented by

and also it can be divided as two components composed of harmonic and

fundamental frequency with amplitudes and and is represented by

where Y>h and Y>f are the phase angles of the harmonic components and fundamental

components of i>and i>f,pand i>f,q are the instant fundamental phase and quadrature

components of i>. To attain unity power factor on the grid side, 9alance for the

harmonics in the load currents and simultaneously attain load sharing, :; unit of the

inverter supplies a current i:;4.

i:;4 D *i>f,p%igC i>f,qC i>h

where igis the grid current. 7s shown in 0ig.$.", the utility substation supplies the

voltage to a distribution grid represented by a voltage source 6gduring grid%connected

32


33/49


operation, and is interfaced to the microgrid and to the loads through a distribution

line with inductance >l and resistance >.

:uring the grid%connected operation, the grid voltage is identified and the

microgrid shares the load requirement with the grid. /ence, to manage the power

delivered to the loads, by using the 2 *current control mode the :; inverter

output current is controlled.

0or the duration of islanded operation, the total load requirement will be

supplied by microgrid as shown in 0ig. $.&, and by using 62 *6oltage control

mode it is necessary that the output voltage can be regulated to a pure sine wave

with a fixed magnitude.

To obtain a state%space model for the :; inverter through both grid%connected

operation and islanded operations, AirchhoffGs current and voltage laws are applied to

the current loop as shown in 0ig. $.$,

0ig $.$. 8ingle%phase illustration of the nth :; inverter inIslanded and grid%connected

operations.

where i4 is the current passing through >fi. therefore, the grid interfaced :; inverter

model can be define as

where the subscripts g and 4 represent the model of :; inverter 4 during grid%

connected operation *4D", &,$ and

7g4 D

33


34/49


g4D" Z :g4"D V '%f4WZ :g4&D'

[g4Di4is the stateZ64GDVv:;4 d v:;4?dtW

Tis the exogenous input. u4is the control input,

with%"FDu4FD"Z and yg4Di:;4is the output.

hile islanded operation, due to the microgrid power disparity the frequency

will differ. 528 will detect the changes in frequency in microgrid, such that 528 is

used to manage and monitor power dispatch by each :; unit. the change in

frequency will be detected by 528 then the 528 will have need of the main :; unit

and the 8torage 9attery to produce the essential power to meet up the overall load

demand in the microgrid as shown in the flowchart of 0ig. &.&, such that *" is

satisfied. In islanded operation, it follows from *# and *1 that :; inverter can be

modelled as

where the subscript i denotes the model of the :; inverter 4 during islanded operation

*4D" , & and

with fGD\&4D"f4 Z xi4DVi4 6:;4W

Tis the state vectorZ

iG4Di>%\n]4in is the exogenous input of the :; inverter

4Z u4is the control input, with %"FD u4FD"and

yi4DV6:;4 i:;4 WT is the output, which will be regulated to find the needed reference

waveform. =ote that even though the importance is on the voltage 6:;4. To ensure that

the power is delivered by using 62 6:;4and i:;4will be regulated. 2oreover it is

believed that the exogenous input i4G in the model is not straightly measurable by the

:; inverter because it involves quantities outside that inverter. specifically, i4Gis the

addition of all load currents minus the addition of all infrom the other :; inverters n

] 4 in the microgrid.

34


35/49


4. ANFIS

4.1 INTRODUCTION

The idea of fuzzy logic and artificial neural network for

organize problems has been grown in recent years. The motive is that the traditional

control theory frequently requires a mathematical model for designing the controller.

The inexactness of mathematical modeling generally degrades the performance of the

controller, particularly for complex and nonlinear control problems. The introduction

of the neural controllers and fuzzy logic controllers *0> based on multi layered

neural networks has motivated new resources for the possible understanding of

improved and high efficient control. In latest years, the combination between fuzzy

logic and neural network that is fuzzy neural network *0== has been pro4ected and

developed. ;enerally the multiplexing of fuzzy logic and neural network is known as

7=0I8 *7daptive =euro 0uzzy Inference 8ystem. =eural system has numerous

inputs and also has many outputs but the fuzzy logic has numerous inputs and only

one output, so the integration of this two is know as 7=0I8 which is used for

nonlinear applications.

4.2 SYSTEM OVERVIEW35


36/49


T%8 fuzzy model was planned in"-1( by Takagi and 8ugeno .>ater on it is

known as 8ugeno fuzzy model. It is a nonlinear model. 8ugeno fuzzy model can

appropriately state the dynamic characteristic of complex systems. in addition,

8ugeno fuzzy model is the fuzzy inference model that is in the most common use. 7

usual fuzzy rule in this model has the following format$?/=*@

here > ^ 2 are fuzzy set antecedent, _Df*x,y is a crisp function in the onsequent.

>et us suppose the fuzzy inference system consist of two inputs x, y with one

output. If the rule base consists of two fuzzy if%then rules of Takagi and 8ugeno!s

type then it is represented as given belowogic. 2any inputs are applied to the neural network

depending upon the inputs the neural network has some standard output, so depending

upon the input and the output the neural network is trained, after training the neural

network the output is applied to the fuzzy logic which generates the I0 T/E= rules

and membership functions.

37


38/49


0ig ).&< 7=0I8 23:E>

. SIMULATION STUDIES

.1 INTRODUCTION TO MATLA5

The name 27T>79 refers to 27Trix >79oratory. 27T>79 was written at

first to afford uncomplicated access to matrix software designed by the >I=57A

*linear system package and EI857A *Eigen system package pro4ects. It is a high%

performance language for technical calculations. It is a combines visualization,

computation, and programming environment. 2oreover, 27T>79 is a contemporary

programming language environment< it has complicated data structures, debugging

tools, built%in editing and supports ob4ect%oriented programming. These reasons make

27T>79 an outstanding tool for research and teaching. 27T>79 has a lot of

advantages over the conventional languages *e.g., , 03T7= for solving

technical efforts. 27T>79 is an interactive system whose basic data element is an

array which do not require dimensions.

It has influential incorporated routines which allow a large range of

computations. In addition to it 27T>79 includes effortless graphics commands

which build the visualization of outputs instantly available. 0ew applications are

gathered in packages known as toolbox.

.1.1 SIMULIN

8imulink is a software add%on to matlab which is a mathematical tool designedby The 2ath works, 2atlab is powered by wide%ranging numerical investigation

38


39/49


ability. 8imulink is used to program visually a system *those governed by :ifferential

equations and look towards results. 8imulink >ibraries has a standard building block

which is used to build logic circuits or control system for a dynamic system. It

contains a range of toolboxes for wide range of techniques, such as =eural =etworks,

0uzzy >ogic, signal processing, 8tatistics etc. are accessible with 8imulink, which

improve the processing power of the tool. The most important advantage is the

accessibility of building blocks, which keep away from the necessity of typing code

for mathematical processes.

8imulink is an interactive tool for modeling, simulating, and analyzing

dynamic systems, including controls, signal processing, communications, and other

complex systems. The version of 8imulink included in 27T>79 ^ 8imulink 8tudent

6ersion provides all of the features of professional 8imulink, with model sizes up to

"''' blocks. It gives you immediate access to the high%performance simulation power

you need. 8imulink is a key member of the 27T>79 family of products used in a

broad range of industries, including automotive, aerospace, electronics,

environmental, telecommunications, computer peripherals, finance, and medical.

2ore than one million technical professionals at the worldGs most innovative

technology companies, government research labs, financial institutions, and at more

than $('' universities, rely on 27T>79 and 8imulink as the fundamental tools for

their engineering and scientific work.

.2 SIMULATION RESULTS

The micro grid is experienced under various conditions to estimate its

capabilities during grid connected and islanded operations from the distribution grid.

39


40/49


0ig (."< configuration of the proposed micro grid architecture.

Three types of loads containing of linear and nonlinear loads are measured in

these conditions. 0or load ", a "(%k67 three%phase 52 ad4ustable speed drive

*78: with its configuration as shown in 0ig.(.& is used and load & is made up of a

three%phase > load rated at 5>&D&1 k and >&D"1.( k67r. >oad $ is a noncritical

three%phase dimmer load rated at5>$D "1 k and >$D"&.$ k67r, which is

nonlinear in nature and will be shed under emergency conditions when the generation

of the microgrid is unable to meet the load demand. The system parameters are given

in Table (.".

0ig. (.&. onfiguration of a "(%k67 three%phase 78: .

Pa!a*ete! Va/e

D%"t!%0t%#& -!%' ,#/ta-e V->23BV

DC /%&6 ,#/ta-e V'>4BBV

40


41/49


D%"t!%0t%#& L%&e I*e'a&e R/>B.BB9= L/>2.9H

LC F%/te! L$>1.2*H= C$>2B H

DG I&,e!te! /#"" !e"%"ta&e R $>B.B1

Table (." 5arameters 3f The 5roposed 8ystem

Te"t Ca"e 1 I*!#,e*e&t O$ a/%t) #$ a #(e! D!%&- G!%'C#&&ete'

Oe!at%#&

0ig (.$< simulation 2odel during grid connected 3peration

The first case shows the ability of the micro grid to enhance the power quality

of the distribution network by compensating for the harmonics in the total load

current i>. 7s the nonlinear loads are interfaced to the distribution network, such that

the harmonics will not spread to the rest of the distribution network in grid%

connected operation. The 8torage 9attery is working in the charging mode to

accumulate energy in off%peak period where the cost of generation from the grid is

short to meet up future unexpected demands for power. The 8torage 9attery current

iband the 83 during charging for 'Q t F '.Bs are shown in 0ig.(.B. The waveforms

of the total load current i>, the current given by the main :; unit i:;and grid current

ig in this case are shown in 0ig. (.). The per%phase currents i> ", i>& and i>$drawn by

loads ", &, and $ for 'Q t Q '.B s are shown in 0ig. (.(.

41


42/49


0ig. (.). three%phase three%phase :; current i:; *top, load current i>*middle, and

three%phase grid current ig*bottom :uring ;rid onnected 3peration.

42


43/49


0ig.(.(. 5er%phase currents drawn by loads ", &, and $ :uring ;rid onnected

3peration.

43


44/49


0ig.(.B< aveform of the 89 current during charging :uring ;rid onnected

3peration.

0ig.(.#


45/49


0ig (.1 < ave forms of ;rid 6oltage and urrent :uring ;rid onnected 3peration.

0ig (.-< The total harmonic distortion *T/: value of load current i>using 7=0I8

The total harmonic distortion *T/: value of load current i>is &-.'&+

as shown in 0ig. (.-. ith the 7=0I8 controller T/: value of is improved to about

")+ when compared to previous methods *25 ontroller as shown in fig.(."'

45


46/49


0ig (."' < The total harmonic distortion *T/: value of load current i>using 25

ontroller

Te"t Ca"e 2 L#a' S+e''%&- D!%&- I"/a&'e' Oe!at%#&

0ig (.""< simulation 2odel during Islanded 3peration

46


47/49


In islanded operation, the total generation power of the micro grid may not be

able to maintain its generation to meet up the power requirement of the loads. :uring

such conditions, consumers will permit the non%critical load to be discarded so as to

keep the constant function of the micro grid. The second test case shows the function

of the microgrid which is islanded from the grid. In this case, the microgrid is

primarily functioning in the grid%connected mode for ' Q t F '.& s. The 8torage

9attery is primarily functioning in the idle mode and its 8tate of charge is 1'+. 7s an

error occurs on the network of the distribution grid, the ircuit 9reaker function is to

disconnect the microgrid from the distribution grid at tD '.& s.

0ig. (."& the waveforms of the real and reactive power supplied by the grid.

The ircuit 9reaker manages to separate the microgrid from the distribution grid,

ensuing in zero real and reactive power delivered by the grid for '.&Q t F '.Bs. The

real power given by :; inverter & of the 8torage 9attery is shown in 0ig. (."&.

47


48/49


0ig (."$< 5ower delivered by 8torage 9attery during Islanded 3peration.

' Q t F '.&s, the 8torage 9attery is in the idle mode. 7fter the beginning of the

islanding operation at tD '.& s, the :; inverter & is tasked by the 528 to enhance its

generation to offer real power of about ) k to the loads.

0ig (.") < aveforms of ;rid urrent :uring Islanded 3peration

0ig (.") shows the grid current during islanded operation in which the grid current is

supplied to the loads till '.&s then between '.&Q t F '.Bs the current reduces to '

because the grid will get disconnected and it is operated in Islanded operation

48


49/49


CONCLUSION AND FUTURE SCOPE

CONCLUSION

In this Thesis, an 7daptive =euro fuzzy Interface control system coordinates

the operation of multiple :; inverters in a micro grid for grid%connected and islanded

operations has been presented. The proposed controller for the :; inverters is

predicated on an incipiently developed 7=0I8 in order to reduce the overall

computation time. The control design is to extract the harmonic spectra of the load

currents and to engender the compulsory references for the controller. The :;

inverters can compensate for load harmonic currents in a homogeneous way as

conventional compensators, such as active and passive filters, and, hence, no

adscititious equipment is required for power%quality amelioration.

To realize the perspicacious grid concept, an assortment of 5ower%

management functions, such as peak shaving and load shedding, have additionally

been demonstrated in the simulation studies. The results have validated that the micro

grid is able to handle different operating conditions efficaciously during grid%

connected and islanded operations, thus incrementing the overall reliability and

stability of the micro grid. The entire proposed system will be tested using

27T>79?8I2@>I=A and the simulation results demonstrate the attractive

performance characteristics of the proposed system.

FUTURE SCOPE

. The proposed controller i.e. 7=0I8 for the :; inverters is

utilized rudimentary 5ulse width 2odulation technique, it can reduces the higher

order harmonics only, that can be elongated to urrent ontrol loop so that, we can

reduce the lower order harmonics also.

anfis strategy for windfuel cell power management system in a micro grid

Documents