DESIGN OF A ROBUST GRID INTERFACE SYSTEM FOR PMSG-BASED WIND TURBINE GENERATOR- Final Year Project in GTU
DESIGN
OF A ROBUST GRID INTERFACE SYSTEM FOR PMSG-BASED WIND TURBINE GENERATOR
A
PROJECT REPORT
Submitted
by
CHAUHAN JAKIRHUSAIN J.
BARIA VIJAYKUMAR M.
KAZI UVEZUDDIN H.
In fulfillment for the award of
the degree
Of
BACHELOR
OF ENGINEERING
IN
ELECTRICAL
DEPARTMENT
OM
INSTITUTE OF TECHNOLOGY
AT.
VANTA-VACHHODA, TA. SHAHERA, DIST. PANCHMAHAL
Gujarat
Technological University,Ahmedabad
December,
2014-2015
TABLE OF
CONTENTS
|
|
Acknowledgement |
4 |
|
|
Certificate of college |
5 |
|
|
Declaration |
6 |
|
Chapter 1 |
Introduction |
7 |
|
|
1.1 wind turbine & PMSG |
8 |
|
|
1.2 wind energy conversion system |
8 |
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|
1.3 problem summary |
9 |
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|
1.4 Aim of project |
9 |
|
|
1.5 problem specification |
9 |
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|
1.6 literature review |
10 |
|
|
1.7 Patent Search |
11 |
|
|
1.8 Planning of work |
12 |
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|
1.9 Materials/Tools |
12 |
|
Chapter 2 |
Design: analysis,
Design methodology & implementation
strategy |
13 |
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2.1 Block diagram |
14 |
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|
2.2 circuit diagram |
16 |
|
|
2.3 description of
used component |
17 |
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2.4 Observation
matrix |
39 |
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|
2.5 Ideation canvas |
39 |
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Chapter 3 |
3.1 Implementation |
40 |
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3.2 Block diagram |
41 |
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|
3.3 Hardware
description |
42 |
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3.4 Result |
45 |
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Chapter 4 |
Summary |
49 |
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4.1 Summary of result |
50 |
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4.2 Advantage |
50 |
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|
4.3 Methodology |
50 |
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4.4 Future work |
51 |
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References |
|
52 |
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| |
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ACKNOWLEDGEMENT
First
of all we thank the almighty for bestowing his blessings on us so that we are
able to complete this project successfully. we feel privileged to express my
deep sense of reverence and gratitude to my revered supervisor, Mr.Bipin
Saksena for her support, immaculate guidance, constant encouragement and in
providing requisite facilities to carry on my research which otherwise would
have remained incomplete. Her nurturing and caring concern has been a stimulus
which I will always cherish.
No
words of mine can express my deep sense of gratitude to my UG Coordinator of
the department PROF. RAVI KHATRI for
his support.
The
successful culmination of this thesis could not have been possible without the
blessing of my loving parents. Without their help we would have been greatly
incapacitated. All may not be mentioned, but no one is forgotten.
Chauhan Jakirhusain J.
Baria Vijaykumar M.
Kazi Uvezuddin H.
CERTIFICATE
Date:-29/05/2015
This is
to certify that the dissertation entitled “DESIGN OF A ROBUST GRID INTERFACE
SYSTEM FOR PMSG-BASED WIND TURBINE GENERATOR” has been
carried out by Mr. CHAUHAN JAKIRHUSAIN, BARIA
VIJAYKUMAR, KAZI UVEZUDDIN under my guidance in fulfillment of the degree of
Bachelor of Engineering in Electrical Engineering 8th
Semester of Gujarat Technological University, Ahmedabad during the academic year 2014-15.
Guides:-
Mr. BIPIN SAKSENA
Head
of the Department
Mr. R.V.KHATRI
DECLARATION
We
hereby certify that we are the sole authors of this UDP project report and that
neither any part of this IDP/UDP project report nor the whole of the UDP
Project report has been submitted for a degree by other student(s) to any other
University or Institution.
We
certify that, to the best of our knowledge, the current UDP Project report does
not infringe upon anyone’s copyright nor violate any proprietary rights and
that any ideas, techniques, quotations or any other material from the work of
other people included in our UDP Project report, published or otherwise, are
fully acknowledged in accordance with the standard referencing practices.
Furthermore, to the extent that we have included copyrighted material that
surpasses the boundary of fair dealing within the meaning of the Indian
Copyright (Amendment) Act 2012, we certify that we have obtained a written
permission from the copyright owner(s) to include such material(s) in the
current UDP Project report and have included copies of such copyright clearances
to our appendix.
We
have checked the write up of the present UDP Project report using
anti-plagiarism database and it is in the allowable limit. In case of any
complaints pertaining to plagiarism, we certify that we shall be solely
responsible for the same and we understand that as per norms, University can
even revoke BE degree conferred upon the student(s) submitting this UDP Project
report, in case it is found to be plagiarised.
Chapter:- 1
INTRODUCTION
1.1 Wind
Turbines & PMSG
Windmills have been
used for many centuries for pumping water and milling grain. The discovery of
the internal combustion engine and the development of electrical grids caused
many windmills to the early part of this century. However, in recent years
there has been a revival of interest in wind energy and attempts are underway
all over the world to introduce cost-effective wind energy conversion systems
for this renewable and environmentally benign energy source. In developing
countries, wind power can play a useful role for water supply and irrigation
(wind pumps) and electrical generation (wind generators). These two variants of
windmill technology are discussed in separate technical briefs. This brief
gives a general overview of the resource and of the technology of extracting
energy from the wind.
1.2 Wind Energy Conversion System (WECS)
Wind
energy can be harnessed by a wind energy conversion system, composed of wind
turbine blades, an electric generator, a power electronic converter and the
corresponding control system. Figure 1.shows the block diagram of basic
components of WECS. There are different WECS configurations based on using
synchronous or asynchronous machines and stall-regulated or pitch regulated
systems. However, the functional objective of these systems is the same:
converting the wind kinetic energy into electric power and injecting this
electric power into a utility grid.
Figure 1:-Wind Energy Conversion System (WECS)
As
mentioned in the previous section, in the last 25 years, four or five
generations of wind turbine systems have been developed. These different
generations are distinguished based on the use of different types of wind
turbine rotors, generators, control methods and power electronic converters. In
the following sections, a brief explanation of these components is presented.
1.3
Problem Summary
Reasons for
connecting a wind plant to a main grid:
• Continuous sources of energy
• Clean source of energy
• No emissions into the atmosphere
• Does not add to thermal burden of the
earth
• Produces no health-damaging air
pollution or acid rain
• Land can be sued to produce energy and
grow crops simultaneously
• Economical
1.4
Aim of project
Aim of our project is
the connect wind power plant to grid source using interfacing converter, give
uninterrupted power supply to consumers, make power system reliable and more
useful.
1.5
Problem Specification
In wind power plant,
main source of energy is wind and it is not available when needed, and also it
is not continuous and constant. So due to this variable speed of wind, output
of PMSG generator is also variable (variable voltage and frequency) that is why
we cannot connect wind power plant to grid like other power plant because of
synchronism problem. And that’s actual problem.
1.6
Literature Review
PWM
techniques are extensively used for the control of voltage fed inverters. it is
possible to control the output voltage as well as optimize the harmonics by
performing semiconductor device in a current fed inverter must with stand
reveres voltage, and there for standard symmetric voltage blocking device are
used. (B.K. BOSE 2002)
z-source
converter employs a unique impedance network (Or circuit) to couple the
converter main circuit to the power source, to thus the providing unique
features that cannot be obtain in traditional voltage-source (or voltage-fed)
and current source (or current fed) converter where capacitor and used
respectively Z-source converter overcome the concept theoretical barriers and
limitation of the traditional voltage source converter and current source
converter and provides a novel power concept the Z-source concept can be
applied to all dc-to-ac, ac-to-dc, ac-to-ac and dc-to dc power conversion. To
describe the operating principle Z-source inverter for dc-ac power conversion
needed in fuel cell application.(Fang Z.Peng,2002)
Limitation
of the traditional inverter, Z-source inverter for fuel cell, unique feature of
the new inverter and proof of concept simulation and experimental results are
discussed (Fang Z.Peng, 2002)
dc-to-ac
converters are called inverter. The function of an inverter is to change a dc
input to ac output of desired magnitude and frequency. Varying input dc voltage
maintaining the gain of the inverter
constant can obtain a variable output voltage. The output voltage waveform of
ideal inverters should be sinusoidal where practical inverter having non
sinusoidal wave forms. Inverter is widely used in industries as: variable-speed
ac motor drives, induction heating, Standby power supplies. U.P.S. the input
may be a battery, fuel cell, solar cell etc. inverters generally use PWM
control signals for producing an ac output voltage, which are thyristor
dependent application. The inverter are fed from a voltage source and the load
current is forced to fluctuate from positive to negative, and vice versa
(M.H.Rashid power electronics 2nd edition1993).
Voltage
source dc-to-ac inverters are described that accept dc voltage source as input
and produce either single phase or three phase sinusoidal output voltage at a
low frequency relative to the switching frequency for current source inverters.
These ac-to-dc inverters can make a smooth transition in to the rectification
mode where the flow of power reverses to be from the ac side to the dc side.
The sinusoidal PWM switching scheme allows control of the boost converter is in
regulated dc power supplies, where a negative polarity output may be desired
with inspect on the common terminal of the input voltage, and output voltage
can be either higher or lower than the input voltage ( N.MOHAN, W.P.Robbin, and
T.Undeland,1998).
1.7
Patent Search
The
present invention is directed to an impedance source power converter that
includes a power source, a main converter circuit and an impedance network. The
main converter circuit is coupled to a load and the impedance network couple
the power source is configured such that the main converter circuit can perform
both buck conversion and boost conversion. (Impedance source power converter,
Fang Z.Peng, Patent No.US 7130205B2)
Various
aspect of the present invention are now summarized to facilitate a basic
understanding of the invention, wherein this summary is not an extensive
overview of the invention, and is intended neither to identify certain elements
of the inventions, nor to delineate the scope thereof. Rather, the primary
purpose of this summary is to present some concepts of the invention in
simplified form prior to the more detailed description that is presented
hereinafter. The present disclosure present power conversion systems and
current source converters and switching controls thereof by which wind energy
and other system may successfully provide reactive power control and gri fault
tolerance while employing current source converter technology(Current source
converter-based wind energy system, Yongqiang Lang, Reza Zargari, Manish Pande,
Bin Wu, Patent No.US8030791B2).
Provide
are methods and system for a control approach that utilizes a
direct-current-based d-q vector control technology for full-converter based
variable-speed PMSG wind turbin; provides a control approach based on a
nonlinear programming configuration for the best performance of PMSG wind
turbine under fuzzy, adaptive, and PID control technologies in an optimal
control configuration; and provides a smart wind turbine control technology for
effective maximum power extraction from the wind (Control of a permanent magnet
synchronous generator wind turbine, Pub.N.US2012/0056602A1)
1.8
Planning of our work
First of all we have
decided that which are the requirements for our Project, after selecting that
we search on the internet, see videos and refer the books related to our
project after that we decide which components we need for our project. After
completed need of the components we have to check their specifications and once
we checked we brought them one by one.
After that we collected all
components and as per circuit diagram we made the design on PCB board and
tested.
1.9 Materials/Tools requirements:-
·
PCB
·
Diode
·
MOSFET
·
Connecting wire
·
Transformer
·
Ammeter
·
Capacitor
·
Inductor
·
Microcontroller
Chapter:- 2
DESIGN:ANALYSIS, DESIGN METHODOLOGY
& IMPLEMENTATION STRATEGY
2 Design: Analysis, Design
Methodology & implementation strategy:-
For our project we design a Circuit diagram,
impedance source inverter &rectifier block diagram.
2.1 Block diagram
Figure 2:- Block diagram of wind power plant
With world electricity
demand growing steadily, demand for renewable energy sources is also expected
to increase drastically. Wind, a free, clean and inexhaustible source of
energy, is increasingly competitive with other energy sources
Typically a grid
operates in parallel with other grid. For wind power plant system, the
interface between renewable energy source and power grid is power electronics.
Inverters convert power from DC to AC with controllable voltage and variable
frequency. The flexibility and control needed by wind power plant with the main
grid is achieved with the help of power electronic interfaces. Each power
electronics interface should provide quality power to the electric grid for the
loads.
Traditionally
there are two inverter namely voltage source inverter and current source
inverter. Each inverter has six switches in the main circuit. These switches
are power switches with ant-parallel diodes. These diodes provide bidirectional
current flow and voltage blocking capability. Variable speed wind turbines are
known to provide more effective power capture than fixed speed wind turbines.
Yet the grid is fixed frequency at most loads. The voltage source inverter
(VSI) with a DC chopper circuit has traditionally been used for this voltage
level and frequency conversion. The traditional VSI, however, has the
limitation only providing output voltages that are lower than input voltages.
For this reason, the DC chopper circuit is used to add the boost feature. Even
though this topology is functional, the extra active devices and controls add
additional system costs and complexities.
Alternatively,
the Impedance source inverter presented recently in not only overcomes the
voltage limitation of the traditional inverter but also uses fewer components.
Moreover, it is more efficient and reduces cost. As a result, it is well suited
for the wind turbine system.
This
project deals with Impedance source inverter for wind power plant to grid
source. Impedance source inverter can be applied to the entire spectrum of
power conversion. It is used as Boost-Buck conversion where capacitors are
used. In this thesis, the Impedance source inverter is considered in place of
voltage source inverter and current source inverter. By using this impedance source
inverter the problems mentioned are rectified and then we can get higher
efficiency.
2.2 Circuit diagram
Figure 3:- circuit diagram
2.3 Description of used component
(1) Rectifier
Ø Types
Rectifier Circuits
One of the important
applications of a semiconductor diode is in rectification of AC signals to DC.
Diodes are very commonly used for obtaining DC voltage supplies from the
readily available AC voltage.
There are many possible
ways to construct rectifier circuits using diodes. The three basic types of
rectifier circuits are:
·
The Half Wave Rectifier
·
The Full Wave Rectifier
·
The Bridge Rectifier
Ø Half-wave
Rectifier
The
easiest rectifier to understand is the half wave rectifier. A simple half-wave rectifier
using an ideal diode and a load is shown in Figure 3.1
Circuit
operation
Let’s
look at the operation of this single diode rectifier when connected across
alternating voltage source vs.
Since
the diode only conducts when the anode is positive with respect to the cathode,
current will flow only during the positive half cycle of the input voltage.
Figure 4:-Simple
half-wave rectifier circuit
We are
interested in obtaining DC voltage across the “load resistance” RL.
During
the positive half cycle of the source, the ideal diode is forward biased and
operates as a closed switch. The source voltage is directly connected across
the load. During the negative half cycle, the diode is reverse biased and acts
as an open switch. The source voltage is disconnected from the load. As no
current flows through the load, the load voltage vois zero. Both the
load voltage and current are of one polarity and hence said to be rectified.
The waveforms for source voltage vS and output voltage voare
shown in figure 3.2.
Figure 5:-Source and output voltages
We notice that the output voltage varies between the
peak voltages Vmand zero in each cycle. This variation is called
“ripple”, and the corresponding voltage is called the peak-to-peak ripple
voltage, Vp-p.
·
The Full-Wave Rectifier
The
full wave rectifier consists of two diodes and a resister as shown in Figure
3.3
The transformer has a centre-tapped secondary
winding. This secondary winding has a lead attached to the centre of the
winding. The voltage from the centre tap to either end terminal on this winding
is equal to one half of the total voltage measured end-to-end.
Circuit Operation
Figure
6 shows the operation during the positive half cycle of the full wave rectifier.
Note that diode D1 is forward biased and diode D2 is reverse biased. Note the
direction of the current through the load.
Figure 6:-Full-wave rectifier- Circuit operation during positive half cycle
During the negative
half cycle, (figure 7) the polarity reverses. Diode D2 is forward biased and
diode D1 is reverse biased. Note that the direction of current through the load
has not changed even though the secondary voltage has changed polarity. Thus
another positive half cycle is produced across the load.
Figure 7:-Full-wave rectifier – circuit operation during negative half cycle
Calculating
Load Voltage and Currents
Using
the ideal diode model, the peak load voltage for the full wave rectifier is m
V . The full wave rectifier produces twice as many output pulses as the
half wave rectifier. This is the same as saying that the full wave rectifier
has twice the output frequency of a half wave rectifier. For this reason, the
average load voltage (i.e.DC output voltage) is found as
Vave
Figure 8 below
illustrates the average dc voltage for a full wave rectifier.
Figure 8:-Average DC Voltage for a Full Wave Rectifier
·
The Full Wave Bridge
Rectifier
In
many power supply circuits, the bridge rectifier (Figure 3.6) is used. The
bridge rectifier produces almost double the output voltage as a full wave
center-tapped transformer rectifier using the same secondary voltage.
The advantage of using this circuit is that no
center-tapped transformer is required.
Basic Circuit Operation
During
the positive half cycle (Figure 9) , both D3 and D1 are forward biased. At the
same time, both D2 and D4 are reverse biased. Note the direction of current
flow through the load.
During
the negative half cycle (Figure 10) D2 and D4 are forward biased and D1 and D3
are reverse biased. Again note that current through the load is in the same
direction although the secondary winding polarity has reversed.
Figure 9: Operation during positive half cycle
Figure 10: Operation during negative half cycle
·
Traditional Source
Inverter
·
Introduction
The objective of this chapter is to
describe traditional source inverter, modes of operations and comparison with
impedance source inverter.
DC to AC converters is known as
inverters. The function of an inverter is to change a dc input of voltage to a
symmetrical ac output voltage of desired magnitude and frequency. The output
voltage could be fixed or variable at fixed or variable frequency. A variable
output voltage can be obtained by varying the input dc voltage and maintaining
the gain of the inverter constant. Inverter broadly classified with two types
(a) Single phase inverter (b) Three phase inverter.
This inverter generally use PWM
control signals for producing an ac output voltage. An inverter is called a
voltage fed inverter if the input voltage remains constant, a current fed
inverter if the current is maintained constant, and a variable dc linked
inverter if the input voltage is controllable.
·
Traditional Source
Inverters
Traditional
source inverters are Voltage Source inverter and Current Source Inverter. The
input of voltage source inverter is a stiff dc voltage supply, which can be a
battery or traditional rectifier both single phase and three phase voltage
source inverter are used in industries. The switching device can be a
conventional MOSFET, Thyristor or a power transistor.
Voltage source
inverter is one which the dc source has a small or negligible impedance. In
other words a voltage source inverter has stiff dc source voltage at its input
terminals. A current fed inverter or current source inverter is fed with
adjustable current source. In current source inverter output current waves are
not affected by load.
·
Voltage Source Inverter
When the power
requirement is high, three phase inverter are used. When three single phase
inverter are connected in parallel, we can get the three phase inverter. The
gating signals for the three phase inverter have a phase difference of 120o.
These inverters take their dc supply from a battery or from a rectifier using
six MOSFET’s and with diodes.
A large capacitor is connected at the input terminals tends to make the
input dc source constant. This capacitor also suppresses the harmonics fed back
to the source. Therefore the voltage source inverter is only buck (step down)
inverter operation for DC to AC power conversion or boost (step up) operation
for AC to DC power conversion.
For application where over drive is desirable and
the available dc voltage is limited, an additional dc-dc boost converter is
needed to obtain a desired ac output. The additional power converter stage
increases system cost and low efficiency.The upper and lower devices of each
phase leg cannot be gate on simultaneously either by purpose or by EMI noise.
Figure 11:- voltage source invertors
Otherwise a shoot through problem by Electromagnetic interference noise’s
misgating-on is major killer to the inverter reliability. Dead time to block
both upper and lower devices has to provide in the voltage source inverter
which causes the waveform distortion, etc. An output LC filters needed for
providing a sinusoidal voltage compared with current source inverter which
causes additional power lose and control complexity.
·
Current Source Inverter
A current source
inverter is fed from a constant current source. Therefore load current remains
constant irrespective of the load on the inverter. The load voltage changes as
per the magnitude of load impedance. When a voltage source has a large
inductance in series with it, it behaves as a current source. The large
inductance maintains the current constant.
The
traditional three phase current source inverter structure is shown in
figure.2.2. A dc current source feeds the three phase main inverter circuit.
The dc current source can be relatively large dc inductor fed by a voltage
source such as a battery or rectifier. It consists of six switches and with
anti-parallel diodes. This diodeprovides the bidirectional current flow and
unidirectional voltage blocking capability.
Figure 12 :- current source inverter
Current source inverter
has the following conceptual and theoretical barriers and limitations. The ac
output voltage has to be greater than the original dc voltage that the feeds
the dc inductor or dc voltage produced is always smaller than the ac input
voltage. Therefore this inverter is a boost inverter for dc to ac power
conversion. For application where a wide voltage range is desirable, an
additional dc to ac buck converter is needed. The additional power conversion
stage increases system cost and low efficiency.
At least one
of the upper devices and one of the lower devices have to be gated on and
maintained on at any time. Otherwise, an open circuit of the DC inductor would
occur and destroy the devices. The open circuit problem by EMI noises
misgatting-off is a major concern of the converters reliability. A current
source inverter is fed from a constant current source. Therefore load current
remains constant irrespective of load on the inverter. The load voltage changes
as per the magnitude of load impedance. When a voltage source has large
impedance in series with it, it behaves as a current source. The large
inductance maintains the current constant.
·
Comparison of CSI, VSI
AND ZSI
Table 1 Comparison of CSI, VSI and Impedance source inverter
|
Sr.no |
Current source inverter |
Voltage source inverter |
Impedance source inverter |
|
1 |
As inductor is used in the dc link, the source
impedance is high. It acts as a constant current source. |
As capacitor is used in the dc link, it acts as a
low impedance voltage source. |
As capacitor and inductor is used in the dc link,
it acts as a constant high impedance voltage source |
|
2 |
A CSI can capable of withstanding short circuit
across any two of its output terminals. Hence momentary short circuit on load
and misfiring of switches are acceptable. |
A VSI cannot accept the misfiring of switches. |
In ZSI misfiring of the switches sometimes are
also acceptable. |
|
3 |
CSI is used in only buck or boost operation of
inverter |
VSI is used in only a buck or boost operation of
inverter. |
ZSI is used in both buck and boost operation of
inverter. |
|
4 |
The main circuit cannot be interchangeable. |
The main circuit cannot be interchanged here also. |
Here the main circuits are interchangeable. |
|
5 |
It is affected by the EMI noise. |
It is also affected by the EMI noise. |
It reduces the here the main circuit can be it is
less affected by the interchangeable EMI noise. |
·
Modes of Operation
Three phase inverter are
normally used for high power application. Three single-phase half or full
bridge inverter can be connected in parallel to the form the configuration of a
three phase inverter. The gating signals of single phase inverter should be
advanced or delayed by 120o with respect to each other in order to
obtain three phase balanced voltages.
The three phase output can be
obtained from a configuration of six switches and six diodes. Two types of
control signals can be applied to the switches: 180oconduction or
120oconduction.
·
180o
Conduction
Each switch conducts for
180o. Three switches remain on at instant of time. When switch 1 is
switches on, terminal ‘a’ is connected to the positive terminal of dc output
voltage. When switch 4 is on, terminal ‘a’ is connected to the negative
terminal of dc source. There are six modes of operation in a cycle and the
duration of each mode is 60o. The switches are numbered in the
sequence of gating the switches 123, 234, 345, 456, 561, 612. The gating signals are shifted from each
other by 60o to obtain three phase balanced voltage
Table:-2 Switch States for Three-Phase VSI ( Based on 180o
Conduction signal)
Figure shows the eight possible
switching states of a six switch inverter and the switching plane represented
by these states.
Figure
13:- Eight possible switching states of a six switch inverter
·
120o Conduction
Each switch
conducts for 120o. Only two switches remains on at any instant of
time. The conduction sequence of switches is 61, 12, 23, 34, 45, 56, and 61.
There are three modes of operation in half cycles and the equipment circuit for
wye connected load is shown in figure 2.3.
During mode 1 for
switches 1 and 6 conducts.
During modes 2 for
, switches 1 and 2 conducts.
During modes 3 for
, switches 3 and 2 conducts.
The
line to neutral voltage can be expressed in Fourier series as given equation
2.1 to 2.3.
∑
……2.1
..…2.2
…..2.3
Figure 14:- voltage source
inverter
The a to b line voltage is 
with a phase advanced of 30o.
There is a delay of 
between the turning off switch 1
and turning on switch 4. Thus there should be no short circuit of the dc supply
through one upper and lower switch. At any time, two load terminals are
connected to the dc supply and the third one remains open. The potential of
this open terminal will depends on the load characteristics and would be
unpredictable. Since one switch conducts for 120o, the switches are
less utilized as compared to that of 180o conduction for the load
condition. The control of output voltage is done using pulse width modulation.
The commonly used techniques are single phase pulse width modulation.
1.
Multiple pulse width modulation.
2.
Sinusoidal pulse width modulation.
3.
Modified sinusoidal pulse width modulation.
4.
Phase displacement control
·
Impedance Source
Inverter
·
Introduction
The objective of this chapter is
to describe theoretical, mathematical analysis and the merits of impedance
source inverter
Bridge rectifier is commonly
used in high power application. The impedance network is a two part network. A
two port network has input terminals and output terminals. This network also
called as lattice network. This lattice network consists of split inductors (L1
phase AC supply is given to the rectifier unit; rectification is a process
converting alternating current or voltage into a direct current or voltage. the
three phase and L2) and capacitor (C1 and C2).
The impedance source inverter consists of voltage source from rectifier supply,
impedance network, and three phase inverter and with grid. This network is
coupled with inverter main circuit and source. This impedance network is a
second order filter, and also this network is energy storage or filtering
element for the impedance source inverter. DC to AC convertor is known as
inverter. The function of an inverter is to change a DC input voltage to AC
output voltage of desired magnitude and frequency. Three phase inverters are
normally used for high power applications. We choose 120 degree conduction for
proper and reliable operation of inverter. MOSFET have chosen for three phase
inverter. There are three modes of operation in one half cycle for Y-connected
load.
This impedance source inverter
is used to overcome the problems in the traditional source inverters. This
impedance source inverter employs a unique impedance network coupled with
inverter main circuit to the power source. This inverter has unique features
compared with the traditional sources
·
Theoretical analysis
Impedance network is a two port
network. A two port network is simply a network inside a box and the network
has only two pairs of accessible terminals. Usually one pair represents the
input and other represents the output. This network also called as lattice
network. Lattice network is the one of the common four terminal two port
network.
The lattice network is used in
filter sections and is also used as alternators. Lattice networks are sometime
used in preference to ladder structure in some special applications. This
lattice network, L1 and L2 are series arms inductances, C1
and C2 are diagonal capacitance. This a two port network that
consists of split inductors L1 and L2 and capacitor C1
and C2 connected in x-shape. This network is coupled with the main
circuits and the source, to describe the operating principle of inverter.
The impedance source inverter
bridge has one extra zero state. When the load terminal are shorted through both
upper and lower devices of any one phase leg or all three phase legs this shoot
through zero state is forbidden in the VSI. Because it would cause a
shoot-through. This network makes the shoot through zero state possible. This
state provides the unique buck-boost features to the inverter.
The equivalent circuit of the
impedance source inverter is shown in fig.5.1. The inverter bridge is
equivalent to a short circuit when the inverter bridge is in the shoot-through
zero state. The equivalent switching frequency from the impedance source
network is six time the switching frequency of the main inverter, which greatly
reduces the required inductance of the impedance source network.
Figure
15:- Equivalent circuit of the impedance network
·
Description of impedance source network
The
impedance source network is a combination of two inductors and two capacitor.
This combine circuit, the impedance source network is the energy storage or
filtering element for the impedance source inverter. This impedance source network provides a second order filter.
This is more effective to suppress voltage and current ripples. The inductor
and capacitor requirement should be smaller compare than the traditional
inverters.
When the two inductors (L1
and L2) are small and approach zero, the impedance source network
reduces to two capacitor (C1 and C2) in parallel and
becomes traditional voltage source. Therefore, a traditional voltage inverters
and capacitor requirements and physical size is the worst case requirement for
the impedance source inverter. Considering additional filtering and energy
storage provided by the inductors, the impedance source network should require
less capacitance and smaller size compare with the traditional voltage source
inverter.
Similarly, when the two capacitors (C1
and C2) are small and approach zero the impedance source
network reduces to two inductors (L1 and L2) in series
and becomes a traditional current source. Therefore a current source inverter
inductor requirements and physical size is the worst case requirement for the
impedance source inverter. Considering additional filtering and energy storage
by the capacitors, the impedance source network should require less inductance
and smaller size compared with the traditional current source inverters.
·
Merits of impedance source inverter
§
The output voltage range is not limited.
§
The impedance source inverter is used as a buck-boost inverter.
§
The impedance source inverter cost is low.
§
The impedance source inverter has low current compared with the
traditional source inverter.
§
The impedance source inverter provides the buck-boost function by two
stage conversion.
§
The impedance source inverter does not affect the electromagnetic
interference noise.
§
The impedance source inverter concept can be applied to all AC-AC, DC-DC,
AC-DC, DC-AC power conversion.
·
AT89S52
Microcontroller
·
DESCRIPTION
The AT89S52 is a low-power,
high-performance CMOS 8-bit microcomputer with 4K bytes of Flash programmable
and erasable read only memory (PEROM). The device is manufactured using Atmel’s
high-density non-volatile memory technology and is compatible with the industry
standard
MCS-51
instruction set and pin out. The on-chip Flash allows the program memory to be
reprogrammed in-system or by a conventional non-volatile memory programmer. By
combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel
AT89S52 is a powerful microcomputer which provides a highly-flexible and
cost-effective solution to many embedded control applications.
·
pin
diagram of AT89S52 Microcontroller
Figure
16:- Pin diagram of microcontroller
·
INTERNAL
ARCHITECTURE OF 8051 MICROCONTROLLER
Figure
17:- architecture of 8051 microcontroller
·
PIN
DESCRIPTION
|
|
|
|
VCC |
Supply
voltage. +5.0V |
|
|
|
|
GND |
Ground. |
|
|
|
|
Port
0 |
Port
0 is an 8-bit open-drain bi-directional I/O port. As an output port, each pin
can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can
be used as high impedance Inputs. Port 0 may also be configured to be the
multiplexed low order address/data bus during accesses to external program
and data memory. In this mode P0 has internal pull-ups. Port 0 also receives
the code bytes during Flash programming, and outputs the code bytes during
program verification. External pull-ups are required during program
verification. |
|
|
|
|
Port
1 |
Port
1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 1
output buffers can sink/source four TTL inputs. When 1s are written to Port 1
pins they are pulled high by the internal pull-ups and can be used as inputs.
As inputs, Port 1 pins that are externally being pulled low will source
current (IIL) because of the internal pull-ups. Port 1 also receives the
low-order address bytes during Flash programming and verification. |
|
|
|
|
Port
2 |
Port
2 is an 8-bit bi-directional I/O port with internal pullups. The Port 2
output buffers can sink/source four TTL inputs. When 1s are written to Port 2
pins they are pulled high by the internal pull-ups and can be used as inputs.
As inputs, Port 2 pins that are externally being pulled low will source
current (IIL) because of the internal pullups. Port 2 emits the high-order
address byte during fetches from external program memory and during accesses
to external data memory that uses 16-bit addresses (MOVX @ DPTR). In this
application, it uses strong internal pull-ups when emitting 1s. During
accesses to external data memory that uses 8-bit addresses (MOVX @ RI), Port
2 emits the contents of the P2 Special Function Register. Port 2 also
receives the highorder address bits and some control signals during Flash
programming and verification. |
|
|
|
|
Port
3 |
Port
3 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 3
output buffers can sink/source four TTL inputs. When 1s are written to Port 3
pins they are pulled high by the internal pull-ups and can be used as inputs.
As inputs, Port 3 pins that are externally being pulled low will source
current (IIL) because of the pull-ups. |
|
|
|
|
RST |
Reset
input. A high on this pin for two machine cycles while the oscillator is
running resets the device. |
|
|
|
|
ALE/PROG |
Address
Latch Enable output pulse for latching the low byte of the address during
accesses to external memory. This pin is also the program pulse input (PROG)
during Flash programming. In normal operation ALE is emitted at a constant
rate of 1/6 the oscillator frequency, and may be used for external timing or
clocking purposes. Note, however, that one ALEpulse is skipped during each
access to external Data Memory. If desired, ALE operation can be disabled by
setting bit 0 of SFR location 8EH. With the bit set, ALE is active only
during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high.
Setting the ALE-disable bit has no effect if the microcontroller is in
external execution mode. |
|
|
|
|
PSEN |
Program
Store Enable is the read strobe to external program memory. When the AT89S52
is executing code from external program memory, PSEN is activated twice each
machine cycle, except that two PSEN activations are skipped during each
access to external data memory. |
|
|
|
|
EA/VPP |
External
Access Enable. EA must be strapped to GND in order to enable the device to
fetch code from external program memory locations starting at 0000H up to
FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally
latched on reset. EA should be strapped to VCC for internal program
executions. This pin also receives the 12-volt programming enable voltage
(VPP) during Flash programming, for parts that require 12-volt VPP. |
|
|
|
|
XTAL1 |
Input
to the inverting oscillator amplifier and input to the internal clock
operating circuit. |
|
|
|
|
XTAL2 |
Output
from the inverting oscillator amplifier. |
·
BASIC
POWER CIRCUIT OF AT89S52
Figure
18:- Basic power circuit of AT89S52
2.4 Observation matrix:-
2.5
Ideation canvas:-
Chapter:- 3
IMPLEMENTATION
3.1
Implementations:-
This
chapter deals with hardware circuit diagram of impedance source inverter for
grid source. It consists of i.e. rectifier circuit, power supply unit circuit,
control circuit and impedance source inverter circuit. The performance of the
proposed impedance source inverter is evaluated on the basis of high-voltage
laboratory scaled-down prototype. The three phase AC voltage for the
experimental circuit is obtained by connecting the three -phase inverter and
delaying the gate signal of 1200 phase angles. The following are the
specification of the experimental circuit.
The
magnitude of input voltage 127
(dc)
The
magnitude of output voltage 83 (ac)
3.2 BLOCK DIAGRAM
Figure
gives the operation details about the hard ware implementation of impedance
source inverter.
Figure
19:- Block diagram of hardware implementation
3.3 HARDWARE DESCRIPTION
The
available AC voltage of 220V is given to the primary side of the transformer
from a source. The transformer is used to step-down the voltage from an AC
voltage of 220V to 24V and 24V is given to the bridge rectifiers. The rectifier
converts the ac voltage into pulsating DC voltage. To filter the pulsations
present in the DC output voltage of the rectifier the capacitor is connected across
them the three-phase inverter is driven by the driver circuit with an angle of
1200 mode. The gate signals are controlled by the micro controller 89C51.
The constant DC voltage as the input
supply of micro controller (5V DC) is
obtained by a circuit which consists of rectifier (W04, 300V, 1A), capacitors
(1000µF, 25PF).
The drive circuits, which are
controlled by micro controller, consist of opto-coupler. Circuits, which are
controlled by micro controller, consist of opto-coupler to isolate the circuits
of controller ad drive circuit operated at different voltage levels. The input
supply for drive circuits is obtained by using the step-down transformer
(230/12) V. The drive-circuit gives 12V to the corresponding gates of MOSFETs.
The
hardware involve the following sections,
·
Main source circuit
·
Micro controller
circuit
·
Driver circuit
·
Inverter circuit
Ø Main source circuit
The
circuit consists of the following parts
·
power supply circuit
·
transformer
·
bridge transformer
·
Power
supply circuit
The main source section of hardware
unit is shown in figure-- .here input voltage is 24V ac which is getting from
step down transformer. This 24V is converted to DC and regulated by means of
regulator by means of regulator 7805. After passing through regulator the
voltage maintain constant value.
Figure
20:- power supply unit
·
TRANSFORMER
It is used to step up/step-down the
ac supply voltage to suit the requirement of the electronics devices and the
circuit fed by the dc power supply line. In this project supply input voltage
is 230v AC and output is step-down voltage of 24V ac is shown in figure
Figure
21:- rectifier circuit
·
Bridge
rectifier
Figure is rectifier circuit, which
converts ac voltage into pulsating dc voltage. In this diagonally opposite pair
of diodes are made to conduct by giving ac supply. The bridge rectifier
converts the given ac voltage to dc voltage.
·
Filter
The function of the circuit element
is to remove the fluctuation/pulsation (called as ripple) present in the output
voltage supplied by the rectifier. It cannot give a ripple free voltage as that
of dc battery, but it approaches so closely that the power supply performs so
well.
·
Voltage
regulator
Its main function is to keep the
terminal voltage of the dc supply constant even when
§ AC
input voltage to the transformer varies
§ The
load varies
§ It
is impossible to get 100% constant voltage but minor variation is acceptable.
Ø Opto coupler
·
As discussed in theory
opto isolator is used for provide optical isolation between microcontroller and
MOSFET bridge. It protects the controller against high voltage and other
occurrence.
·
In this project 4n33
opto-coupler is used, pin diagram is shown below. For high power application we
are using Darlington pair as discussed in theory.
Figure 22:-Opto coupler
·
The output of
microcontroller is given to the optical coupler and output of the opto coupler
is given to the gate of the MOSFET. It is also used as an isolator.
3.4 Result
Switching
pulses for 3-phase full bridge inverter is generated from 89c51
microcontroller, those are shown in below figure, and switching frequency for
inverter is 50Hz.
Gate
Signal 1 to 2
Gate Signal 1 to 3
Gate Signal 1 to 4
Gate Signal 1 to 6
Line Voltage of Isnverter
Chapter:- 4
SUMMARY
4.1
Summary of result
By this method we can improve the phase to phase voltage and phase
to phase current for wind turbine output voltage. But the conventional method
is simple PWM based Z-Source Inverter. By using that simple PWM method we can
improve the phase to phase voltage and phase to phase current for wind turbine
output voltage same as in proposed method. So the maximum constant boost
control with third harmonic injection based Z-source inverter is most efficient
compared to conventional method. The reduction of harmonics in proposed method
sustained as conventional method.
4.2
Advantages
Merits of impedance source inverter
·
The output voltage range is not limited.
·
The impedance source inverter is used as a buck-boost inverter.
·
The impedance source inverter cost is low.
·
The impedance source inverter has low current compared with the
traditional source inverter.
·
The impedance source inverter provides the buck-boost function by two
stage conversion.
·
The impedance source inverter does not affect the electromagnetic
interference noise.
·
The impedance source inverter concept can be applied to all AC-AC, DC-DC,
AC-DC, DC-AC power conversion.
4.3
Methodologies
·
Literature survey was
done by referring to related material and collecting the needed information.
·
A detail study of
impedance source inverters overcoming the problem of traditional inverters.
·
Hardware implementation
of the circuit.
·
Obtaining the result
through CRO, compare theoretical and practical values and to design hardware
kit.
4.4
Future Work
In future work, these
models will be used for the following purposes:
·
To
model inertia/frequency support schemes,
·
To
model sub-synchronous control interactions of wind power plants with the power
system
·
To
model schemes with wind power plants providing other ancillary services, such
as reactive power and voltage control,
·
To
model interaction of wind power plants with storage and conventional
generation, and
·
To
model wind power plant system protection.
References
1. Fang
Zhengpeng, Fellow, IEEE, Alan Joseph, Jin Wang, Student Member, IEEE,
MiaosenShen, Student Member, IEEE, Lihua Chen, Zhiguo Pan, Student Member,
IEEE, Eduardo Ortiz-Rivera, Member, IEEE, and Yi Huang. pp 857-863.
2. Muhammad
H. Rashid, 2011,“ Power Electronics Circuits Devices and Applications”, Third
Edition, pp.237-246, 356-370, 400-402.
3. UthaneSupatti,
Student Member ,IEEE and Fang
Z. Peng, Fellow, IEEE,Z-source Inverter Based Wind Power Generation
System, pp.697-700
4. M.D. Singh, K.B. Khanchandani, 2003, “Power
Electronics”, Tata McGraw Hill Limited, pp.315-326, 349-367, 651-667.
5. D.
MahindaVilathgamuwa, Senior Member,
IEEE; Xiaoyu Wang, Member, IEEE;
King Jet Tseng,Senior Member, IEEE;
C. J. Gajanayake, Member, IEEE “Z-source
Inverter Based Grid-interface For Variable-speed Permanent Magnet Wind Turbine
Generators” pp.1-6.
6. Electrical India,
April 2013 pp. 24-38
7. Fang ZhengePeng, senior
member, IEEE, march/april-2003, “Z-source inverter”, IEEE transaction on
industrial application, vol 39, no.2., pp. 504-510.
8. Robert l. Boylestad
Louis Nashelsky,-2000, “Electronics Devices and Circuit Theory”, Prentice-Hall
of India, New Delhi, pp.238-247.
9. Yingqi Zhang, Student
Member, IEEE, and PareshC,Sen, Fellow, IEEE, November/December-2003, “A New
Soft-Switching Technique for Buck, Boost, and Buck-Boost Converter” IEEE
Transaction On industrial applications,Vol.39. No.6. pp.1775-1783.
10. FengGuo, Student Member, IEEE, Lixing Fu, Student Member, IEEE, Chien-Hui
Lin, Cong Li, Student Member, IEEE,
Woongchul Choi, and Jin Wang, Member,
IEEE,December 2013
“Development of an 85-kW Bidirectional Quasi-Z-Source Inverter With
DC-Link Feed-Forward Compensation for Electric Vehicle Applications”.
IEEEtransactions on Power
electronics, VOL. 28, NO. 12, , pp. 5477-5487