 Open Access
 Total Downloads : 409
 Authors : S Manivannan, S. Veerakumar, P. Karuppusamy, A. Nandhakumar
 Paper ID : IJERTV3IS061018
 Volume & Issue : Volume 03, Issue 06 (June 2014)
 Published (First Online): 21062014
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
Certain Investication in Performance of Three Phase Voltage Sourse Inverter Fed Induction Motor Drive by Various Pulse Width Modulation Techniques
S. Manivannan, S. Veerakumar, P. Karuppusamy, A. Nandhakumar
Department of Electrical and Electronics Engineering, Bannari Amman Institute of Technology, Erode, Tamilnadu, India
ABSTRACTThe Three Phase Voltage Source Inverter supplies invariably required variable voltage and frequency of the adjustable speed drive system. A number of pulse width modulation (PWM) schemes are used to obtain variable voltage and frequency supply from an inverter. The most widely used PWM scheme for a Three Phase Voltage Source Inverter is carrier based sinusoidal PWM and Space Vector Pulse Width Modulation (SVPWM). There is an increasing trend of using SVPWM, because of their easier digital realization and better DC bus utilization. The study of SVPWM technique reveals that this technique utilizes DC bus voltage more efficiently and generates less harmonic distortion when compared with sinusoidal PWM techniques. The SVPWM technique has become one of the important PWM technique for Three Phase Voltage Source Inverter for the control of AC induction motor, Brushless DC motor, Switched Reluctance motor and Permanent Magnet Synchronous motor. In this paper having collection of different schemes in SVPWM. Specifically various schemes are Center aligned two level SVPWM, Level shifted multi carrier concepts based SVPWM, and carrier waveform based modulated reference waveform generation and comparison in SVPWM. This paper having simulation results of all the three schemes of SVPWM by using MATLAB/SIMULINK software. The performance of Three Phase Voltage Source Inverter fed induction motor drive based on various SVPWM schemes are analyzed by various reference parameters like DC bus utilization, Total harmonic distortion (THD), switching stress and efficiency. As a result of these analysis this paper recommends which scheme is more suitable for variable voltage and various frequency drives. The simulation results are provided to validate the proposed model approaches.
Keywords: Three Phase Voltage Source Inverter, Space vector Pulse width Modulation (SVPWM), Modulated reference waveform, Center aligned, Total Harmonic Distortion (THD), and Switching Stress.

INTRODUCTION
Three phase voltage source inverters are widely used in variable speed AC motor drive applications since they provide variable voltage and variable frequency output through pulse width modulation control [1] [2]. The most widely used PWM method is the carrierbased sinetriangle PWM method due to simple implementation in both analog
and digital realization [2] [3]. However in this method the DC bus utilization is low (0.5Vdc). This has led to the investigation into other techniques with an objective of improving in the DC bus utilization [1] [3]. The PWM technique termed as Space Vector PWM based on space vector theory was proposed by de Broeck et. Al (1988) and Ogasawara et.al (1989) which offers superior performance compared to the carrier based sinetriangle PWM technique I terms of higher DC bus utilization and better harmonics performance [3]. Further, this technique offers easier digital realization. The research in PWM schemes has intensified in the last few decades. The main aim of any modulation technique is to obtain a variable output with a maximum fundamental component and minimum harmonics [3] [4].
The problem of underutilization of the DC bus voltage led to the development of the Third harmonic injection PWM (THIPWM) and Space Vector PWM (SVPWM) [5] [6]. In 1975, Buja developed this improved sinusoidal PWM technique which added a third order harmonic content in the sinusoidal reference signal leading to a 15.5% increase in the utilization rate of the DC bus voltage. In 1988, Van Der Broeck developed the SVPWM technique which has also increased the utilization of DC bus voltage by 15.5% [7] [8].
In the last three decades there are different SVPWM schemes are developed by various authors. But this paper is mainly focus on important five schemes in SVPWM. The various schemes in SVPWM are a) Center aligned two level SVPWM, b) Level shifted multicarrier concepts based SVPWM, and c) carrier waveform based modulated reference waveform generation and comparison in SVPWM. Here these three techniques have similar results, but their methods of implementation are completely different. With the development of microprocessors SVPWM has become one of the most important PWM methods for three phase inverter. The maximum peak fundamental magnitude of the SVPWM technique is about 90.6% increase in the maximum voltage compared with conventional sinusoidal modulation [12] – [16].
This paper having some collective information regarding various schemes as mentioned above presents in the two level SVPWM based Three Phase Voltage Source Inverter fed induction motor drive. This paper covers entire concepts presents in all the three schemes and also this paper gives a comparative statement regarding all those five schemes. The comparative statement is developed by the following valuable parameters. The parameters are THD, DC bus utilization, switching stress and efficiency. As a result of this comparative statement the reader can identify which scheme is more suitable for particular drive operation. The simulation results are provided to validate the proposed approaches.
The paper organized in ten sections. Section II gives some basic introduction regarding SVPWM techniques. Section III introduces the detailed discussion regarding Center aligned two level SVPWM. Section IV introduces the detailed discussion regarding Level shifted multicarrier concepts based SVPWM. Section V introduces the detailed discussion regarding carrier waveform based modulated reference waveform generation and comparison in SVPWM. Section VI gives the detailed comparison between the above mentioned schemes. Section VII shows the extension of the proposed scheme to the Z source and T source inverters. Section VIII concludes the paper.

SVPWM PRINCIPLES
Space Vector Modulation (SVM) was originally developed as a vector approach to pulse width modulation (PWM) for three phase inverter. It is a more sophisticated technique for generating sine wave that provides a higher voltage to the motor with lower harmonic distortion [13]. The main aim of any modulation technique is to obtain variable output having a maximum fundamental component with minimum harmonics. SVPWM method is an advance: computation intensive PWM method and possibly the best techniques for variable frequency drive applications.
The principle of pulse width modulation is explained by using the figure1 [22]. The figure1 (a) shows a circuit model of a single phase inverter with a centertapped grounded DC bus. The figure1 (b) illustrates principles of pulse width modulation.
Figure1 (a) circuit model of a single phase inverter
Figure1 (b) pulse width modulation
From the figure1 (b), the inverter output voltage is determined by the following ways.

When V control > V triangle means VAO = VDC/2

When V control < V triangle means VAO = – VDC/2
Also the inverter output voltage has the following features.

PWM frequency as same as the V triangle frequency.

Amplitude is controlled by the peak value of V
triangle.

The fundamental frequency is controlled by the frequency of V control.

Modulation index (M) is defined as
M Vcontrol ; 0 M
Vtriangle
The circuit model of a typical three phase voltage source inverter is shown in figure2. S1 to S6 are the sin's power switches that shape the output, which are controlled by the switching variables a, a, b, b, c, and c. When an upper switch (a, b, c) are switched ON ie) a, b and c = 1, the corresponding lower switches (a, b, c) switched OFF myself ie) a, b and c = 0. The upper switches and lower switches are complimentary to each other. Therefore the ON and OFF states of the upper and lower switches determines the output voltages [22]. The SVPWM is a different approach from PWM modulation based on space vector representation of the voltage in the – plane.
Figure2 Three phase voltage source inverter with a load and
neutral point
The space vector concept, which is derived from the rotating field of the induction motor, is used to modulate the inverter output voltage. In the modulation
technique the three phase quantities can be transformed into their equivalent twophase quantity either in synchronously rotating frames or stationary frame. From these twophase components, the reference vector magnitude can be found and used for modulating the inverter output [6] [13] [16] [19]. The process of obtaining the rotating space vector is explained in the following section. Considering the stationary reference frame, let the three phase sinusoidal voltage component be
Va = Vmsinwt
Vb = Vmsin(wt2/3)
Vc = Vmsin(wt4/3) [1]
When these three phase voltages are applied to the AC machine it produces a rotating flux in the air gap of the AC machine. This rotating resultant flux can be represented as a single rotating voltage vector. The magnitude and angle of the rotating vector can be found by means of clarks transformation as shown in figure3. This gives the relationship between the abc reference frame to the stationary reference frame [22].
Figure3 the relationship between abc reference frame to the stationary dq reference frame
f dqo = Ks fabc [2]
Where
Ks = ,
f dqo = T,
fabc = T
and f denotes either a voltage or a current variable.
The relationship between the switching variable vector [a b c] T and the linetoline voltage vector [Vab Vbc Vca] T is given by
= Vdc [3]
Also the relationship between the switching variable vector [a b c] T and the phase voltage vector [Van Vbn Vcn] T is given by
= [4]
Table1 Switching vectors, Phase voltages and Output Line to Line voltages
By referring the figure2 there are eight possible switching combinations of ON and OFF patterns for the three upper power switches. The ON and OFF states of the lower power devices are opposite to the upper one and so are easily determined once the states of the upper power switches are determined. According to equation3 and 4, the eight switching vectors, output line to neutral voltage (phase voltage), and output line to line voltages in turns of DC link Vdc are given in the table1. The figure4 shows the eight inverter voltage vectors (V0 to V7).
For 180Â° mode of operation, there exist six switching states and additionally two more states, which make all three switches of either upper arms or lower arms ON. To code these eight states in binary (onezero representation), it is required to have three bits (2 3 = 8). And also, as always upper and lower switches are committed in complementary fashion, it is enough to represent the status of either upper or lower arm switches [22]. In the following discussion, status of the upper bridge switches will be represented and the lower switches will its complementary. Let "1" denote the switch is ON and "0" denote the switch in OFF. Table1 gives the details of different phase and line voltages for the eight states.
As described in Figure3. This transformation is equivalent to an orthogonal projection of [a b c] T onto the twodimensional perpendicular to the vector [1 1 1] T (the equivalent dq plane) in a threedimensional coordinate system. As a result, six nonzero vectors and two zero vectors are possible. Six nonzero vectors (V 1 to V 6) sharp the axes of a hexagonal as depicted in Figure3, and supply power to the load. The angle between any
adjacent two nonzero vectors is 60 degrees. Meanwhile, two zero vectors (V 0 and V 7) and are at the origin and apply zero voltage to the load. The eight vectors are called the basic space vectors and are denoted by (V 0, V 1, V 2, V 3, V 4, V 5, V 6, V 7).
Va = Vmsinwt Vb = Vmsin(wt2/3) Vc = Vmsin(wt4/3)
Where w = 2f and f = 50Hz.
The second step is transforms abc parameters into dq parameters
Vb Vc
Vd Va cos 0 Vb cos120 Vc cos 240 Va 2 2
Vq Va cos 270 Vb cos30 Vc cos150 0
3Vb
2
3Vc 2
1 1
1
2 2
V 2
Va
3 3
d 0
V
[5]Figure4 The eight inverter voltage vectors (Vo to V7)
V 3
2 2 b
q 0 0 0
Vc
The same transformation can be applied to the desired output voltage to get the desired reference voltage vector, Vref in the dq plane. The objective of
The third step is to calculate Vref magnitude and angle () values from equation 5.
SVPWM technique is to approximate the reference
voltage vector Vref using the eight switching patterns.
V V jV V 2 V 2
One simple method of approximation is to generate the
ref d q d q
[6]average output of the inverter in a small period T to be the same as that of V ref in the same period [6] [13]. The following figure5 represents the identification of sectors by vector locations. This figure5 represents all the
tan1
Vq
V
d
eight vectors and sectors with 60Â° displacement with each other.
Figure5 Basic switching vectors and sectors


CENTER ALIGNED TWO LEVEL SVPWM
By referring the above introductory parts, the SVPWM can be implemented in the following steps. The first step is to generate three phase waveforms Va, Vb, Vc by referring the equation 1.
The fourth step is to identify the sector in which
the reference voltage space vector is present. It is necessary to know in which sector the reference output lies in order to determine the switching time and sequence. The identification of the sector where the reference vector is located is straight forward. The phase voltage corresponding to eight switching states: six nonzero vectors and two zero vectors at the origin. Depending on the reference voltages, the angle of the reference vector can be determined the sector as per the table2 [22].
Table2 Sector Definition
Sector
Degrees
1
0 < 60Âº
2
60Âº < 120Âº
3
120Âº < 180Âº
4
180Âº < 240Âº
5
240Âº < 300Âº
6
300Âº < 360Âº
The fifth step is switching time calculation: to determine the time duration of Ta, Tb and To. Consider the reference vector in sector 1 as shown in figure6.
The voltsecond product in sector1 can be written
as
Where
Vref Ts V1 T1 V2 T2 V0 T0
Vref
Vref
2
cos j Vref
sin
V1 3 Vdc j(0),
V0 0,
[7]Figure6 Vref position in sector1
Substitute equation 9 in equation 8 we get a T1
2 V
cos j 2 V
sin
V2 3 dc
3 3 dc 3
sin
T T
a 3
The equation7 can be written as
1 s
sin
3
cos
2 1
2 cos 3
[8]now,T
T (T T )
[10]Ts Vr sin T1 ( 3 Vdc ) 0 T2 ( 3 Vdc )
0 T0
0 s a b
sin
From equation 8
3
because, Ts Ta Tb T0
Now generalizing the switching time calculation for entire 6 sectors, therefore
T V sin T
2 V
sin
3V T
n
s r 2 3
dc 3
T ref s sin
a V 3
V sin
dc
T r T
3V T
(n1)
b
2 2 V
s sin
T ref s sin
[11]3 dc 3
Vdc
3
T2
Ts

a sin
sin
3
[9]T0 Ts Ta Tb
Where n=1, 26 and = 0 to 60Â°. The figure6 shows the reference vector as a combination of adjacent vectors at
where, a
Vr
2 V
3 dc
sector1. The following table3 gives the exact location of Vref and its Dwell time in each sector [18].
Table3 Vref location and Dwell time
With the space vectors, selected and the switching times or dwell times calculated, the next step is to arrange possible switching sequences. In general the switching
sequence design for a given
Vref
is not unique, but it
should satisfy the following two requirements for the minimization of the device switching frequency [18].

The transition from one switching state to the next involves only two switches in the same
inverter leg, one being switched ON and other being switched OFF.
The figure7 space vector diagram for twolevel inverter shown below should satisfy the above two requirements. This space vector diagram is common to all

The transition of
Vref
moving from one
the four possible switching sequences. Only changes in this
sector in the space vector diagram to the next requires no or minimum number of switches.
space vector diagram are the various possibilities of reference vector rotation in each sectors.
Figure7 General space vector diagram for two level inverter Figure7.1 Space vector diagram for two level inverter with Vref rotation
The possible switching sequence in each sector is like, starting with [000] switching sequence and also ends with [000] switching sequence. This will be shown in figure7.1The seven segments switching sequence and switching time calculation for each switch for each sector is shown in figure 8.1 to 8.6. The circuit diagram is shown in figure 7.2.
Figure7.2 Center aligned SVPWM fed induction motor drive
Figure8.1 Figure8.2
Figure8.3 Figure8.4
Figure8.5 Figure8.6
Figure8.1 to 8.6 shows seven segments switching sequences for Vref
in sector 1 to 6.
Figure 8.1 to 8.6 shows a typical seven segment switching sequence and inverter output waveforms for Vref in each sectors.
Here
Vref is synthesized by
V1,V2 &V0 . The sampling period Ts is divided into seven segments for the selected vectors. The
following can be observed.
The dwell time for the seven segments adds up to the sampling periods, Ts = Ta + Tb + T0. The design requirement (a) is satisfied. For instance the transition from [000] to [100] is accomplished by turning S1 ON and S4 OFF, which involves only t wo switches. The redundant switching state Error! Bookmark not defined. are utilized to reduce the number of switchings per sampling period. For T0/4 segment in the center of the sampling period, the switching state [111] is selected, whereas for the T0/4 segments on both sides, the state [000] is used. Each of the switches in the inverter turns ON and OFF once per sampling period. The switching frequency fsw of the devices are thus equal to the sampling frequency fsp, ie) fsw = fsp = 1/Ts [18].
The performance parameters of the three phase two level inverter fed induction motor drive are measured and shown in the figure9.1 to 9.6.
Line voltage
Figure9.1 Line voltage in volts
Figure9.2 Line voltage THD
Stator currents
Rotor current
Figure9.3 Stator current in Amperes
Figure9.4 Rotor current in Amperes
Rotor speed
Electromagnetic torque
/td> Figure9.5 Rotor speed in rpm
Figure9.6 Electromagnetic torque in Nm
4
x 10
2
1.8
1.6
1.4
1.2
0.8 1
Time in seconds
0.6
0.4
0.2
0
100
0
100
200
300
400
500
4
x 10
2
1.8
1.6
1.4
1.2
0.8 1
Time in seconds
0.6
0.4
0.2
0
200
0
1600
1400
1200
1000
800
600
400
200
4
x 10
2
1.8
1.6
1.4
1.2
0.8 1
Time in seconds
0.6
0.4
0.2
0
50
100
150
200
0
200
150
100
50
4
x 10
2
1.8
1.6
1.4
1.2
0.8 1
Time in seconds
0.6
0.4
0.2
0
50
100
150
0
200
150
100
50
300
250
200
100 150
Harmonic order
0 50
0
0.1
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
Fundamental (50Hz) = 622 , THD= 0.02%
0
4
x 1
1.6 1.8 2
1.4
0.8 1 1.2
Time in seconds
0.6
0.4
0.2
0
200
400
600
800
0
800
600
400
200
Rotor speed in rpm
Line voltage in volts
Stator current in Amperes
Rotor current in Amperes
Electromagnetic torque in Nm
Magnitude
Figure9.1 to 9.6 Performance of Three phase 2level SVPWM Inverter fed induction motor drive


LEVEL SHIFTED MULTICARRIER CONCEPTS BASED SVPWM
With reference to the figure 15.1 to 15.6 takes the output from the switches 1 to 6 and compare with carrier signals to produce the pulses for each switches presents in the three phase 2level SVPWM Inverter power circuit. The circuit diagram is shown in figure10.
Figure10 Level shifted multicarrier concepts based SVPWM
50
0
50
100
150
50
0
50
100
150
250 300
200
100 150
Harmonic order
50
0
0.8
0.6
0.4
0.2
1
1.2
Fundamental (50Hz) = 397.2 , THD= 1.64%
0
4
x 1
100
200
300
400
500
0
500
400
300
200
100
Stator current in Amperes
Line voltage in volts
Magnitude (% of Fundamental)
Rotor current in Amperes
The performance parameters of the three phase two level inverters are measured and shown in the figure10.1 to 10.6.
Line voltage
1
1.1
1.2
1.3
1.4 1.5 1.6
Time in seconds
1.7
1.8
1.9 2
0
Figure10.1 Line voltage in volts
Figure10.2 Line voltage THD
Stator current
Rotor current
0
0.5
1
1.5
2
2.5
4
0
0.2
0.4
0.6
0.8 1
Time in seconds
1.2
1.4
1.6
1.8
2
Rotor speed
Electromagnetic torque
Figure10.5 Rotor speed in rpm
Figure10.6 Electromagnetic torque in Nm
4
x 10
2
1.8
1.6
1.4
1.2
0.8 1
Time in seconds
0.6
0.4
0.2
0
50
0
50
100
150
200
4
x 10
2
1.8
1.6
1.4
1.2
0.8 1
Time in seconds
0.6
0.4
0 0.2
1600
1400
1200
1000
800
600
400
200
0
200
Figure10.4 Rotor current in Amperes
4
x 10
150
100
x 10
Time in seconds
Figure10.3 Stator current in Amperes
150
100
Rotor speed in rpm
Electromagnetic torque in Nm
Figure10.1 to 10.6 Performance of Three phase 2level SVPWM Inverter fed induction motor drive

CARRIER WAVEFORM BASED MODULATED REFERENCE WAVEFORM GENERATION AND COMPARISON IN SVPWM
There is an increasing trend of using space vector pulsewidth modulation (SVPWM) schemes for driving voltage source inverters because of their easier digital realization and better DC bus utilization.
Figure11 Carrier waveform based modulated reference waveform generation and comparison in SVPWM
This paper introduces an carrier waveform based modulated reference waveform generation and comparison in SVPWM technique as shown in figure11 based on a reduced computation method, which is much simpler and more executable than conventional means without lookup tables or complex logical judgments. The SVPWM scheme is modeled and simulated using MATLAB/SIMULINK and experimentally implemented and verified. The simulation procedure for the above Matlab/Simulink circuit is given below.

The first step is to generate three phase sinusoidal waveforms with magnitude = 0.8V.
Va = Vmsinwt Vb = Vmsin(wt2/3) Vc = Vmsin(wt4/3)

The second step is to find out the maximum value and minimum value among these three waveforms by using minmax block in Matlab/Simulink.

The third step is to add the maximum and minimum values getting from step2.

The fourth step is, divide the values getting from step3 by 2. Because the magnitude values of waveform get reduced and the waveforms get opposite polarity.

The next step having steps

For phase a add Va with step4 waveform

For phase b add Vb with step4 waveform

For phase c add Vc with step4 waveform
a) The last step is to compare step5 waveforms with respect to carrier waveform and generates the pulses for that switch presents in the three phase voltage source inverter circuit.
f) The simulated waveforms are available in figure12 that shows the performance characteristics of three phase voltage source inverter fed induction motor drive.
Stator Current
Rotor current
0 0.2 0.4 0.6
0.8 1 1.2
Time in seconds
1.4 1.6 1.8 2
0
0.2
0.4
0.6
0.8 1 1.2
Time in seconds
1.4
1.6
1.8 2
Figure12.3 Stator current in Amperes
Figure12.4 Rotor current in Amperes
Speed
Electromagnetic torque
0
0.2 0.4
0.6
0.8 1
Time in seconds
1.2
1.4
1.6
1.8
2
0
0.5
1
1.5
2
2.5
4
x 10
Time in seconds
Figure12.6 Electromagnetic torque in Nm
20
40
60
80
100
120
0
40
20
Figure12.5 Rotor speed in rpm
4
x 10
0
1600
1400
1200
1000
800
600
400
200
0
4
x 1
20
40
60
80
0
80
60
40
20
0
4
x 1
20
40
60
80
0
100
80
60
40
20
Figure12.2 Line voltage THD
0
Figure12.1 Line voltage in volts
0
4
x 1
1.8 1.9 2
1.7
1.4 1.5 1.6
Time in seconds
1.3
1.1 1.2
1
100
200
300
400
500
0
500
400
300
200
100
Line voltage
Speed in rpm
Stator current in Amperes
Line voltage in Volts
Magnitude (% of Fundamental)
Electromagnetic torque in Nm
Rotor current in amperes
Fundamental (50Hz) = 415 , THD= 1.36%
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
50
100
150
Harmonic order
200
250
300
Figure12.1 to 12.16 Performance of Three phase 2level SVPWM Inverter fed induction motor drive



COMPARATIVE RESULTS OF ALL FIVE POSSIBLE SWITCHING SCHEMES
The main aim of any modulation technique is to obtain variable output having maximum fundamental component with minimum harmonics. The objective of SVPWM technique is to enhance the fundamental output voltage and the reduction of harmonic content in three phase voltage source inverter fed induction motor drive. In this paper having different possibilities of switching schemes present in two level SVPWM are compared in terms of THD. The Simulink model has been developed for SVPWM modulated two level three phase voltage source inverter fed induction motor drive. The simulation work is carried in MATLAB/SIMULINK.
The simulation parameters used are; AC input voltage = 440V, fundamental frequency = 50Hz, ODE solver = ode45 (DormandPrince), switching frequency = 12 kHz, modulation index = 0.87, Rated power = 3HP, Type of motor = Three phase squirrel cage induction motor, Discrete solver model = forward Euler, Reference frame = Stationary, Stator resistance = 0.4355, Stator inductance = 4mH, Rotor resistance = 0.816, Rotor inductance = 2mH, filter = second order filters. The results for three phase voltage source inverter fed induction motor drive for all the possible switching sequences are given in the table4.
Table4 Comparative results statement of all three possible switching schemes
Sl.No
Performance Parameters
MethodI
MethodII
MethodIII
1
Line voltage
600V
440V
440V
2
Stator current
20A
15A
20A
3
Rotor current
1.1A
2A
1.4A
4
Speed in rpm
1420
1395
1470
5
Electromagnetic torque in N m
11.9
11.9
15.9
6
Line voltage THD
0.02%
(622)
1.64%
(397.2)
1.36%
(415)
The above table provides a detailed comparison between all three types of switching schemes presents in the SVPWM techniques. From the details presents in the table we can conclude like the speed can be controlled by each method is unique one. So depending upon our speed requirement we can choose any one control methods and also the methodI provide lower values of THD compared with other methods. Each method had unique features and characteristics that will be varying with respect to types and load parameters.

SVPWM TECHNIQUE FOR ZSOURCE AND TSOURCE INVERTERS
All the above section represents the basic concepts recording SVPWM, the various switching schemes in SVPWM and the performance of 2level three phase voltage source inverter. The same concepts can be represented in the Z – Source inverter (ZSI) and TSource inverter (TSI) also. The procedure for switching sequence in ZSI and TSI are same as three phase voltage source inverter except the introduction of a shoot though zero state in ZSI. The following subsequent paper should explain these concepts in details.

CONCLUSION
The SVPWM technique can only be applied to a threephase inverter and it increases the overall system efficiency. The SVPWM is used for controlling the switching of the machine side converter. Advantages of this method include a higher modulation index, lower switching losses, and less harmonic distortion compared to SPWM. SVPWM research has been widespread in recent years, making it one of the most popular methods for three
phase inverters because it has a higher fundamental voltageoutput than SPWM for the same DC bus voltage. The SVPWM is significantly better than SPWM by approximately 15.5%. However, the SVPWM technique is complex in implementation, especially in the over modulation region. SVPWM technique has become the most popular and important PWM technique for three phases VSI for the control of AC induction. This paper has provided a thorough review of the each technique with a special focus on the operation of SVPWM in all the three possible switching schemes. In this paper, Simulink models for all three possible switching schemes has been developed and tested in the MATLAB/SIMULINK environment. This paper discusses the advantages and drawbacks of each switching schemes and their simulation results are compared and analyzed by plotting the output harmonic spectra of various output voltages and computing their total harmonic distortions (THD). As seen from the simulation results the DC bus utilization will be variable for all the three possible switching schemes, but the THD will be varied for every switching sequence. From the simulation results we can come to the conclusion like the methodsII and III switching schemes having high THD when compared to the other method of switching schemes. In the future researches there are some possibilities are available for implementing the same switching schemes in three phase ZSI and TSI. Definitely the performance of ZSI and TSI fed induction motor drive will be varied with respect to its different switching schemes.
REFERENCE

J. Holtz, Pulse Width Modulation A Survey, IEEE Transaction on Industrial Electronics, Vol. 39, no. 5, Dec. 1992, pp. 410420.

Granado, J., Harley, R.G., Giana, G, Understanding and Designing a Space Vector PulseWidthModulator to Control a Three Phase Inverter, Transaction Of the SAIEEE (1989), Vol.80, Sept.1989, pp. 2937.

Holtz, J. (1994). Pulse Width Modulation for Electronic Power Conversion, Proceedings of the IEEE, Vol.82, No.8, pp. 1194 1214.

Holms, D.G. (1996). The Significance of Zero Space Vector Placements for CarrierBased PWM Schemes, IEEE Transactions on Industry Applications, Vol. 32, No. 5, pp. 1122 1129.

Zhai, L. and Li, H. (2008) Modeling and Simulation of SVPWM Control System of Induction Motor in Electric Vehicle, IEEE International Conferences on Automation and Logistics, pp. 20262030.

Bose, B. K, 2002, Modern Power Electronics and AC Drives, Prentice Hall PTR, New Jersey.

J. H. Seo, C. H. Choi, and D.S. Hyun, A new simplified space vector pwm method for threelevel inverters, IEEE Transaction on Power Electronics, vol. 16, no. 4, pp. 545550, Jul. 2001.

T. Bruckner and D. G. Holmes, Optimal pulsewidth modulation for threelevel inverters, IEEE Transaction on Power Electronics, vol. 1, no. 20, pp. 8289, Jan. 2005.

O. Ogasawara, H. Akagi, and A. Nabae, A Novel PWM Scheme of Voltage Source Inverters Based on Space Vector Theory, EPE Europ. Conference in Power Electronics and Applications, Aachen, 1989, pp11971202.

G. S. Buja and G. B. Indri, Optimal Pulse width Modulation for Feeding AC Motors, IEEE Transaction on Industrial Applications, Vol. IA13, No. 1, Jan. /Feb. 1977, pp. 3844.

A. Nabae, S. Ogasawara and H. Akagi, A Novel Control Scheme for PWM Controlled Inverters, IEEE Industrial Applications Society Annual Meeting, Toronto, 1985, pp. 473478.

M. Rajender reddy, T. Brahmananda reddy, D. Subba rayudu, Simple and novel unified pulse width modulation algorithm for voltage source inverters in the entire modulation range Acta Electrotechnica et Informatica, Vol. 13, No. 3, 2013, 4855, DOI: 10.2478/aeei20130040.

JBV Subrahmanyam, Sankar, Application of svpwm technique to three level voltage source inverter International Journal of Engineering and Technology Volume 1 No. 1, October, 2011.

K. Mounika, B. Kiran Babu, Sinusoidal and Space Vector Pulse Width Modulation for Inverter International Journal of Engineering Trends and Technology (IJETT) – Volume4Issue4 April 2013.

S.Meenakshi Sundaravel and Dr.S.Murugan, Modified Cascaded HBridge Multilevel Inverter topology with Reduced Number of Power Electronic Switching Components International Journal of Electrical Engineering. ISSN 09742158 Volume 6, Number 2 (2013), pp. 137149.

K. Vinothkumar, Simulation and Comparison of SPWM and SVPWM Control for Three Phase Inverter, ARPN Journal of Engineering and Applied Sciences, Vol. 5, No. 7, July2010.

D. G. Holmes and T. A. Lipo. 2003. Pulse Width Modulation for Power Converters: Principles and Practice. New Jersey: IEEE Press, Wiley Publications, New York, USA.

Bin Wu HighPower Converters and AC Drives, IEEE Press, WileyInterscience. pp. 95117.

Zhou, K., and Wang, D. Relationship between spacevector modulation and threephase carrierbased PWM: A comprehensive analysis, IEEE Trans. Industrial Electronics., 2002, 491, pp. 186196.

N. Mohan, T. R. Undeland, W. P. Robbins, Power Electronic Converters, Applications, and Design, John Wiley & Sons, Inc. Media Enhanced Third Edition.

Phuong Hue Tran, Matlab/Simulink implementation and analysis of three pulsewidthmodulation (PWM) techniques, Master of Science in Electrical Engineering, Boise State University, May 2012.

JinWoo Jung, Space Vector PWM Inverter, Ph.D., Thesis, Department of Electrical and Computer Engineering, The Ohio State University, Feb.20, 2005.

Muhammad H. Rashid, Power Electronics Handbook, Academic Press Series in Engineering.