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Transcript of Advanced Electrical Drives_unit1
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ADVANCED ELECTRICAL DRIVES
UNIT-I
Prepared by
A.VENKADESANAP/EEE,SRM UNIVERSITY
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Introduction
A Motor with Power Electronics converter
forms a open loop drive.
A Motor with Power Electronics converter and
controller forms a closed loop drive.
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Introduction-Closed Loop Electrical
Drives
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Types of Electrical Drives
DC Motor Drives
AC Motor Drives
Special Motor Drives
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DC Motor Drives
Advantages
The control of DC Motor is simple.
Disadvantages
It is costlier
The dc motor requires regular maintenance
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AC Motor Drives
The AC motor in particular induction motor is
the workhouse of power industries.
The construction of IM is simple and requires
less maintenance.
Hence, induction motor drives are most
popularly used for variable speed control
applications.
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Converters for AC motor drives
AC voltage controllers - variable voltagecontrol
Cyclo-converters - Variable Frequency Control
Inverters V/F Control
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Types of Inverter
Three Phase six switch inverters
Three Phase four switch inverters
Multilevel Inverters Matrix Converters
Soft Switched based Inverters
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Modeling of Inverters
Modeling of inverter assumes importance for
effective analysis and control.
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Types of Modeling - Inverters
Switching function model
Average Model
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Switching Function for Inverters
The switching function modeling of inverters is
a powerful tool in understanding the
operation of inverters and for designing of
controllers.
The inverters are modeled using the switching
states.
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Switching States
The number of switching states depends on
the total number of legs present in the
inverter.
The states can be calculated using the formula
2k , where K is the number of legs.
6 switch 3 leg inverter three phase inverter23=8.
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Switching model of Three Phase Six
Switch Converter
1-denotes leg, 2-denotes switch number
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Switching Constraints
Switching Constraints (no two Switches on the
same leg should be on)
S11
+S12
=1; S21
+S22
=1; S21
+S22
=1
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Definition of Switching States
Leg A Leg B Leg C
S11 S12 Vao S21 S22 Vbo S31 S32 Vco
1 0 Vdc 1 0 Vdc 1 0 Vdc
0 1 0 0 1 0 0 1 0
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Switching States
StatesOn State
SwitchesSa Sb Sc Vao Vbo Vco Vab Vbc Vca Van Vbn Vcn
I S12S22S32 0 0 0 0 0 0 0 0 0 0 0 0
II S11S22S32 1 0 0 Vdc 0 0 Vdc 0 -Vdc 2/3Vdc -1/3Vdc -1/3Vdc
III S11S21S32 1 1 0 Vdc Vdc 0 0 Vdc -Vdc 1/3Vdc 1/3Vdc -2/3Vdc
IV S12S21S32 0 1 0 0 Vdc 0 -Vdc Vdc 0 -1/3Vdc 2/3Vdc -1/3Vdc
V S12S21S31 0 1 1 0 Vdc Vdc -Vdc 0 Vdc -2/3Vdc 1/3Vdc 1/3Vdc
VI S12S22S31 0 0 1 0 0 Vdc 0 -Vdc Vdc -1/3Vdc -1/3Vdc 2/3Vdc
VII S11S22S31 1 0 1 Vdc 0 Vdc Vdc -Vdc 0 1/3Vdc -2/3Vdc 1/3Vdc
VIII S11S21S31 1 1 1 Vdc Vdc Vdc 0 0 0 0 0 0
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Equivalent Circuit Indicating Vnobetween the two neutral point
Three Phase Inverter Three Phase Star Connected Load
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Derivation of Voltages across Load
Vao=Van+Vno----------------(1)
Vbo=Vbn+Vno ---------------(2)
Vco=Vcn+Vno----------------(3) Adding (1)+(2)+(3) and in balanced Three
phase system, Van+Vbn+Vcn=0;
Vao+Vbo+Vco=3Vno
(4)3
ao bo cono
V V VV
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Derivation of Voltages across the
Load
Sub in Vno in (1), (2), (3)
12
31
23
1 23
an ao bo co
bn bo ao co
cn co ao bo
V V V V
V V V V
V V V V
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Voltages across the Load in terms
of Switching Function
12
31
23
1 23
an ao a bo b co c
bn bo b ao a co c
cn co c ao a bo b
V V S V S V S
V V S V S V S
V V S V S V S
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Modeling of Three Phase Inverter
using MATLAB
Sinusoidal unipolar PWM schemes are used.
Vdc=717V
Switching Frequency=10KHz
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Modeling of Single Phase Inverter.
Assignment-I
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Assignment II
Realize the three phase inverter as a switching
model. Simulate the same using MATLAB in
such a way that the magnitude of the
fundamental component of line to line voltageshould be 3005%V. Assume switching
frequency as 15KHz. Use Sinusoidal unipolar
Switching scheme.
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Modeling of Induction Machine
Similar to inverter modeling, induction motor
can be modeled using mathematical
equations.
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Types of induction motor modeling
Steady State Modeling
Dynamic Modeling
Space Vector Model
dq Model
Before going to see about the dq modeling ofinduction motor, it is mandatory to know
about the Reference frame transformation
theory.
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Reference Frame Transformation
The use of reference frame theory can simplify
the analysis of electric machines.
It also provide a powerful tool for the digital
implementation of sophisticated
control schemes for ac drives.
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Reference Frames
Stationary Frame
Synchronous Frame
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Transformation of variables
between the two frames
abc(stationary) ab(stationary)
abc(stationary) dq(Synchronous Frame)
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abc (stationary) to dq
(synchronous)
2 4cos cos cos
3 32
3 2 4-sin -sin -sin3 3
a
d
b
q
c
xx
x
x x
where x represents either current, voltage, or flux linkage, and
is the angular displacement between the a-axis and d-axis of
the three-phase and two-phase reference frames
---------------------------------------------------------------------------------------(4)
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Variables in three-phase (abc) stationary frame
and two-phase (dq) synchronous frame
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abc (stationary) to dq
(synchronous)
The three-phase variables,xa, xband xc, are in
the stationary reference frame which does not
rotate in space.
The two-phase variables, xdand xq, are in the
synchronous reference frame whose direct (d)
and quadrature (q) axes rotate in space at the
synchronous speed e. e= 2fs.
0
( ) ( )
t
et t dt
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abc (stationary) to dq
(synchronous) (other formula)
2 2cos cos cos
3 32
3 2 2-sin -sin -sin3 3
a
d
b
q
c
xx
x
x x
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dq (rotatory) to abc (stationary)
cos -sin
2 2
cos - -sin -3 3
4 4cos - -sin -
3 3
a
d
b
q
c
xx
x xx
---------------------------------------------------------------------------------------(5)
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dq (rotatory) to abc (stationary)-
other formula
cos -sin
2 2cos - -sin -
3 3
2 2cos -sin3 3
a
d
b
q
c
x xx
xx
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MATLAB SIMULATION
abc to dq and dq to abc- MATLAB MODEL
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3/2 or 2/3 Stationary
Transformation
With the rotating speed of the two-phase reference frame set at zeroand its d-axis coincident with the a-
axis of the three-phase frame (e=0 and e = 0), both frames arestationary in space.
Sub e= 0 in equation (4) and (5),equation for 3/2 & 2/3 stationaryreference frames are obtained.
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abc (stationary) to ab (stationary)
1 11 - -
2 2 2
3 3 30 -
2 2
s a
d
bsq
c
xx
xxx
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ab (stationary) to abc (stationary)
1 0
1 3-
2 2
1 3- -2 2
a s
d
b s
q
c
xx
xx
x
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MATLAB SIMULATION
3/2 and 2/3 phase stationary. Model
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Problem 1 on Transformation
Find the voltages in two stationary reference frames
Solution
http://localhost/var/www/apps/conversion/tmp/scratch_2/Solution%20on%20problem%201.ppthttp://localhost/var/www/apps/conversion/tmp/scratch_2/Solution%20on%20problem%201.ppt -
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Transformation Theory
The transformation is valid only for the
balanced three phase system.
xa+ xb+ xc= 0
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If system is not balanced, what happens to the
equations
Answer is ZERO SEQUENCE COMPONENT
should be incorporated in the equation.
b ( ) d
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abc (stationary) to dq
(synchronous) with zero sequence
component
2 2cos cos cos
3 3
2 2 2-sin -sin -sin
3 3 3
0.5 0.5 0.5o
d
q
x
x
x
a
b
c
x
x
x
d ( ) b ( i )
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dq (rotatory) to abc (stationary)
with zero sequence component
cos -sin 1
2 2
cos - -sin - 13 3
4 4cos - -sin - 1
3 3
a
b
c
x
xx
d
q
o
x
xx
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dq modeling of induction motor
D i E i l t i it f
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Dynamic Equivalent circuit for q-
axis
D i E i l t i it f d
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Dynamic Equivalent circuit for d-
axis
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Mathematical Equations
Stator side equations
Rotor side equations
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Flux Linkage equations
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Electromagnetic Torque Equations
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Mathematical Equations
S-laplace operator
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Dq Modeling in various frames
Stationary Frame; e=0 (stanley Equations)
Synchronously Rotating Frame; e= s
Rotor Reference Frame; e
= r
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dq modeling in various frames
Various Frames efor the
machine
Angle for
transformation
Stationary 0 0
Synchronous s Theta derived
from
synchronous
speedRotor r Theta derived
from rotor speed
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MATLAB SIMULATION
DQ MODEL IN VARIOUS FRAMES
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How to reduce switching loss
Decrease switching frequency by optimizing
performance.
Discontinuous PWM Techniques
Resonant Inverters
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Types of Resonant Inverters
Load Resonant Inverters
Resonant circuits in the load
Resonant Switch Inverters
Zero Current Switching
Zero Voltage Switching
Resonant dc link inverters
Resonant circuits in between dc input and inverter
Resonant ac link inverters