project review
DESCRIPTION
Two leg three-phase inverters (FSTPIs) have been proposed to be used in low-power; low-cost applications because of the reduced number of semiconductor devices, and space vector pulse width modulation (SVPWM) techniques have also been introduced to control FSTPIs. However, high-performance controllers are needed to implement complicated SVPWM algorithms, which limit their low-cost applications. To simplify algorithms and reduce the cost of implementation, an equivalent scalar method for SVPWM of FSTPIs is proposed. SVPWM for FSTPIs is actually a sine PWM by modulating two sine waves of 600 phase difference with a triangle wave, but in this method third harmonics doesn’t eliminated. So as to eliminate the third harmonics we have to compose a high frequency sine wave to on existing sine waves. So such a special sine PWM can be used to control FSTPIs. The Mathematical and simulation results demonstrate the validity of the proposed method.http://www.mathworks.com/matlabcentral/fileexchange/authors/126814TRANSCRIPT
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DIFFERENT PWM CONTROLLED BASED
FSTPI FED IM DRIVE
PRESENTED
By
SUDHAKAR AKKISUDHAKAR AKKI
Reg.No:1610910044
UNDER THE GUIDANCE OF
Mr. NALINKANT MOHANTYASST.PROF( Sr.G )
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INTRODUCTION
• Semiconductor switches mainly determine the overall price of power
converters.
• The main objective of this project is to prove 2leg inverters are the best
option for low power applications for getting the good performance.
• Two leg inverter produces the square wave or quasi-square wave. but low
power applications allow the two leg inverter output.
• In many industrial applications, it is often required to vary the output
voltage of the inverter due to the following reasons
To cope with the dc I/p voltage.
To regulate the voltage of inverters
To satisfy the constant voltage & frequency for control requirement.
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Pulse-Width Modulated For VSI
Disadvantages of PWM semiconductor devices must have low turn-on and turn-off times. so, they are very expansive
Reduction of available voltage
Increase of switching losses due to high PWM frequency
Control of inverter output voltage with out any additional components
Reduction of lower harmonics
The most common PWM approach is sinusoidal PWM. In this method a
triangular wave is compared to a sinusoidal wave of the desired frequency and the
relative levels of the two waves is used to control the switching of devices in each
phase leg of the inverter.
Objective of PWM
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Amplitude modulation ratio (ma)
A01A0
10
Vofcomponentfrequecnylfundamenta:)(Vwhere,
,2/
)(
dc
A
tri
controla V
Vofvaluepeak
vofamplitude
vofamplitudepeakm
Frequency modulation ratio (mf)
frequencylfundamentafandfrequencyPWMfwhere,, 1s1
f
fm s
f
mf should be an odd integer
if mf is not an integer, there may exist sub harmonics at output voltage
if mf is not odd, DC component may exist and even harmonics are present at output voltage
mf should be a multiple of 3 for three-phase PWM inverter
An odd multiple of 3 and even harmonics are suppressed
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Space vector modulation
• In sinusoidal PWM, the inverter can be thought of as three separate
push-pull driver stages, which create each phase waveform
independently.
• SVM, however treats the inverter as a single unit
• The space vector method is a d,q model PWM approach
Modulation index is high
SVM produces 15% higher then the sinusoidal PWM in output voltages
Simple, inherently digital calculation of the switching times.
SVPWM has been gaining more attention in the industry.
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Block diagram of the project
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Space Vector PWM for 3leg inverter
Where, upper transistors: S1, S3, S5
lower transistors: S4, S6, S2
switching variable vector: a, b, c Eight possible combinations of on and off patterns for the three upper transistors (S1, S3, S5)
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The eight combinations, phase voltages and output line to line voltages
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Basic switching vectors and Sectors
6 active vectors (V1,V2, V3, V4, V5, V6)
Axes of a hexagonal
DC link voltage is supplied to the load
Each sector (1 to 6): 60 degrees
2 zero vectors (V0, V7)
At origin
No voltage is supplied to the load
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cn
bn
an
q
d
V
V
V
2
3
2
30
2
1
2
11
3
2V
V
frequency)lfundamentaf(where,
t2ππtω)V
V(tanα
VVV
s
ssd
q1
2q
2dref
Voltage Space Vector and its components in (d, q).
cnbnan
cnbnq
cnbnan
cnbnand
V2
3V
2
3V
cos30Vcos30V0V
V2
1V
2
1V
cos60Vcos60VVV
Step 1. Determine Vd, Vq, Vref, and angle () Coordinate transformation
: abc to dq
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Step 2. Determine time duration T1, T2, T0
)60α0(where,
)3/(sin
)3/(cosV
3
2T
0
1V
3
2T
)(sin
)(cosVT
)VTV(TVT
VdtVdtVV
dc2dc1refz
2211refz
T
TT
0
TT
T1
2
T
0
T
0
1ref
z
21
21z 1
π
π
α
α
dc
ref
sz210
2
1
V3
2
Vaand
f
1Twhere,),(
)3/(sin
)(sin
)3/(sin
)3/(sin
TTTT
aTT
aTT
z
z
z
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Switching time duration at any Sector
60α0
6)toSector1is,(that6through1nwhere,,
3
1cossin
3
1sincos
3
3
1sin
3
sin3
coscos3
sin3
3sin
3
3
1
3sin
3
210
2
1
TTTT
nn
V
refVT
n
V
refVTT
nn
V
refVT
n
V
refVT
n
V
refVTT
z
dc
z
dc
z
dc
z
dc
z
dc
z
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Space Vector PWM switching patterns at each sector.
Sector 1. Sector 2.
Step 3. Determine the switching time of each transistor (S1 to S6)
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Switching Time Table at Each Sector
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Simulation Diagram of SVM 3leg inverter
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Time durations T1, T2, T0
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Switching Times
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Line voltages
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Principle of Space Vector PWM
Treats the sinusoidal voltage as a constant amplitude vector rotating
at constant frequency
This PWM technique approximates the reference voltage Vref by a combination
of the Four switching patterns (V1 to V4)
Coordinate Transformation (abc reference frame to the stationary d-q frame)
: A three-phase voltage vector is transformed into a vector in the stationary d-q coordinate
frame which represents the spatial vector sum of the three-phase voltage
The vectors (V1 to V4) divide the plane into Four sectors (each sector: 90 degrees)
Vref is generated by two adjacent non-zero vectors and zero vectors
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Comparison of Sine PWM and Space Vector PWM
Space Vector PWM generates less harmonic distortion
in the output voltage or currents in comparison with sine PWM
Space Vector PWM provides more efficient use of supply voltage
in comparison with sine PWM
Switching losses also reduced by space vector modulation
Voltage Utilization: Space Vector PWM = 2/3 times of Sine PWM
Realization of Space Vector PWM
Step 1. Determine Vd, Vq, Vref, and angle ()
Step 2. Determine time duration T1, T2, T0
Step 3. Determine the switching time of each transistor (S1 to S4)
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SPACE VECTOR PWM FOR 2-LEG INVERTER
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Space vectors representation
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Determine the switching time of each transistor (S1 to S4)
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Switching Time for Each Sector of two-leg inverter
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Simulation of 3phase to 2phase
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Simulation for Sector Identification
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Angle& Sectors
Sector
Angle
Sector
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Simulation circuit for 2 leg inverter by SVM
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Switching time duration for two leg inverter
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Connotative Modulation Functions for 2leg
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Line Voltages
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Third Harmonic Injection
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Third Harmonic Injection to Switching Times
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Third Harmonic Switching Times
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Line voltages for 2 leg Inverter
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Rotor & Stator currents
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Speed& Torque Characteristics
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SVPWM APPLIED TO THE 2-LEG INVERTER UNDER DC-LINKVOLTAGE RIPPLE CONDITIONS
The phase-to zero voltages
under balanced load conditions
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phase-to-neutral voltages VAN, VBN andVCN
The phase-to-neutral output voltages can be transformedinto space vector
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Phase-to-zero and phase-to-neutral output voltages
Voltage vectors in αβ plane
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Unbalanced dc-link voltages
The Time Durations In sector 1: 0≤α≤π
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(a) Timing of gate pulse of space vector PWM (b) Timing of gate pulse of carrier–based PWM In sector 2: π≤α≤2π
V t is the instantaneous carrier signal.
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Simulation Circuit of proposed method
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Reference signals Vrefb and Vrefc
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Line voltages
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Speed & Torque Characteristics
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FFT analysis
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Comparison of Different PWM techniques for FSTPIs
Sine PWM SV PWM Scalar PWM Carrier PWM
Calculation Burden Low Very High Medium Low
THD 20.08% 1.86% 14.79% 4.07%
Output Voltage Normal Normal Maximum Normal
DC-link voltage ripple
Resolved
Switching loss high low low high
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CONCLUSION
• In this work, it is shown that two-leg inverters are the best option for high performance low power applications. It can be resolved by comparing the no of semiconductor switches usage in 2-leg and 3-leg inverters and moreover two leg inverters allow the asymmetrical voltages
• To enable this, space vector pulse width modulation (SVPWM) technique, Scalar PWM & Modified SVPWM of FSTPIs is presented.
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BIBLIOGRAPHYJournals
[1]. “Adaptive Carrier-based PWM for a Three-Phase Inverter under DC-link Voltage Ripple Conditions” Tuyen D. Nguyen*,
Hong-Hee Lee† and Hoang M. Nguyen* Journal of Electrical Engineering & Technology Vol. 5, No. 2, pp. 290~298, 2010
[2]. Jae Hyeong Seo; Chang Ho Choi; Dong Seok Hyun, “A New Simplified space-Vector PWM Method for Three-Level
Inverters”, IEEE Transactions on Power Electronics, Volume 16, Issue 4, Jul 2010, Pages 545 - 550
[3]. “the adaptive space vector pwm for four switch three phase inverter fed induction motor with dc – link voltage
imbalance” by Hong Hee Lee*, Phan Quoc Dzung**, Le Dinh Khoa**, Le Minh Phuong**, Huynh Tan
Thanh***School of Electrical Engineering, University of Ulsan Ulsan, Korea.
[4]. Hind Djeghloud and Hocine Benalla, “Space Vector Pulse Width Modulation Applied to The Three-Level Voltage
Inverter”, 5th International Conference on Technology and Automation ICTA’05, Thessaloniki, Greece, Oct 2010.
Books
[5]. P.S.Bimbhra, “Power Electronics”, Khanna publications.
[6]. Muhammad H.Rashid “Power Electronics Circuits, devices, and Applications”, Prentice-Hall of India Private Limited,
Third Edition, 2004.
Thesis References
[7]. Jin-woo Jung, “Space Vector PWM Inverter”, The Ohio State University, February, 2008.
Website references
[8]. www.ieeexplore.com
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THANK YOU