Comparison of modulation techniques for cascaded h bridge type multilevel current
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This document compares different modulation techniques for a five-level cascaded H-bridge multilevel current source inverter. It simulates the inverter using selective harmonic elimination angle control, phase-shifted multicarrier PWM, and different level-shifted carrier PWM schemes (in-phase disposition, alternative phase opposite disposition, and phase opposite disposition). The total harmonic distortion is calculated and compared for each modulation technique. The results show that the phase-shifted multicarrier and level-shifted carrier PWM methods achieve THD values between 2.7-2.99%, while selective harmonic elimination has a higher THD of 18.22%. The level-shifted carrier PWM schemes all perform similarly with POD modulation having the lowest THD of 2.7
![International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976
– 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME
181
COMPARISON OF MODULATION TECHNIQUES FOR CASCADED
H-BRIDGE TYPE MULTILEVEL CURRENT SOURCE INVERTER
Vinesh Kapadia1
and Dr. Hina Chandwani2
1
Research Scholar at CHARUSAT, Changa, Gujarat & Associate Prof. Dept of E.C.,
SNPIT & RC, Umrakh, Bardoli, Gujarat, India
2
Associate Professor, Dept of Electrical Engineering, The M.S.University of Baroda,
Vadodara, India
ABSTRACT
This paper presents a comparison of the different modulation techniques for a single
phase five level cascaded h-bridge (CHB) type multilevel current source inverter. Majority
of the multilevel inverters are voltage sourced based. The popular carrier based PWM
switching techniques for MVSI are the phase shifted and level shifted modulation
techniques, the same techniques are tried out for the MCSI along with Selective Harmonic
Elimination method using angle control and the results have been presented.
Index Terms: APOD, CHB, IPD, Multilevel Current Source Inverter (MCSI), Multilevel
Voltage Source Inverter (MVSI), POD, PWM, THD.
I. INTRODUCTION
MULTILEVEL voltage source inverters are very common and now in wide use.
Compared to two-level inverters, multilevel inverters have advantages for higher power
applications, including reduced harmonics and reduced switching device voltage and
current stresses. The CSIs have some advantages over VSIs such as more stable operating
conditions, direct control of the output current, faster dynamic response (in some cases) and
easier fault management [1]. In this paper a single phase five level MCSI with symmetric
DC current sources is simulated with popular Multilevel Modulation techniques and results
are compared with respect to total harmonic distortion (THD).
INTERNATIONAL JOURNAL OF ADVANCED RESEARCH IN
ENGINEERING AND TECHNOLOGY (IJARET)
ISSN 0976 - 6480 (Print)
ISSN 0976 - 6499 (Online)
Volume 4, Issue 2 March – April 2013, pp. 181-190
© IAEME: www.iaeme.com/ijaret.asp
Journal Impact Factor (2013): 5.8376 (Calculated by GISI)
www.jifactor.com
IJARET
© I A E M E](https://image.slidesharecdn.com/comparisonofmodulationtechniquesforcascadedh-bridgetypemultilevelcurrent-130502085528-phpapp02/85/Comparison-of-modulation-techniques-for-cascaded-h-bridge-type-multilevel-current-1-320.jpg)
![International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976
– 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME
183
III. MODULATION TECHNIQUES
A. Angle Control Method (Selective Harmonic Elimination)
By proper selection of the firing (displacement angles α ) angles it is possible to try
and eliminate or say minimize those particular harmonics.
The fourier series for unipolar output voltages per half cycle can be expressed as (due to
symmetry):
vo = ∑ ܤ sin ݊߱ݐ∞
ୀଵ,ଷ,ହ,..
Bn =
ସೞ
గ
ሾ 1 ∑ ሺെ1ሻ
ୀଵ cosሺ݊ߙሻሿ ݂ݎ ݊ െ 1,3,5, …
Where ߙଵ ൏ ߙଶ … ൏ ߙ ൏
గ
ଶ
The third and fifth harmonics would be eliminated if
1 - cos 3ఈଵ cos 3ఈଶ ൌ 0
1 - cos 5ఈଵ cos 5ఈଶ ൌ 0
[2]-[3] Assuming and initial value of α1 = 0 and calculating in an iterative manner till the
results become stable we get;
Initial Values α1= 0 , hence
α2 = 0.52359
1st
Iteration α1= 0.28728
α2 = 0.64242
2nd
Iteration α1= 0.31366
α2 = 0.66478
3rd
Iteration α1= 0.31084
α2 = 0.66229
4th
Iteration α1= 0.31127
α2 = 0.66268
5th
Iteration α1= 0.31121
α2 = 0.66262
6th
Iteration α1= 0.31122
α2 = 0.66263
The values are radians , hence in degrees, α1= 17.831o
and α2= 37.966 o
.](https://image.slidesharecdn.com/comparisonofmodulationtechniquesforcascadedh-bridgetypemultilevelcurrent-130502085528-phpapp02/85/Comparison-of-modulation-techniques-for-cascaded-h-bridge-type-multilevel-current-3-320.jpg)
![International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976
– 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME
184
Fig-2 Output Current Waveform of the 5 level MCSI with Angle Control Method
Fig-3 Harmonic Spectrum of the 5 level MCSI with Angle Control Method
B. Carrier Based PWM Schemes
The carrier-based modulation schemes for multilevel inverters can be generally
classified into two categories: phase-shifted and level-shifted modulations. Both the
techniques have been applied
1. Phase Shifted Multicarrier Modulation
In general, a multilevel inverter with m voltage levels requires (m – 1) triangular carriers. In
the phase-shifted multicarrier modulation, all the triangular carriers have the same
frequency and the same peak-to-peak amplitude, but there is a phase shift between any two
adjacent carrier waves, given by
Øcr = 360°/(m – 1) [4]-[7]
Fig-4 Triangular Carriers compared with Reference Sine
0 100 200 300 400 500 600 700 800 900 1000
0
2
4
6
8
10
12
Frequency (Hz)
Fundamental (50Hz) = 1.108 , THD= 18.22%
Mag(%ofFundamental)](https://image.slidesharecdn.com/comparisonofmodulationtechniquesforcascadedh-bridgetypemultilevelcurrent-130502085528-phpapp02/85/Comparison-of-modulation-techniques-for-cascaded-h-bridge-type-multilevel-current-4-320.jpg)
![International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976
– 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME
185
Fig-5 Output Current Waveform of the 5 level MCSI with Phase Shifted MultiCarrier
Modulation
Fig-6 Harmonic Spectrum of the 5 level MCSI with Phase Shifted MultiCarrier Modulation
2. Level Shifted Carrier Modulation Schemes
Similar to the phase-shifted modulation, an m-level Cascaded H-Bridge inverter using
level-shifted multicarrier modulation scheme requires (m – 1) triangular carriers, all having
the same frequency and amplitude. The (m – 1) triangular carriers are vertically disposed
such that the bands they occupy are contiguous. The frequency modulation index is given
by mf = fcr/fm, which remains the same as that for the phase-shifted modulation scheme
whereas the amplitude modulation index is defined as
ma =
^
ೝ
^ ሺିଵሻ
for 0 < ma < 1
(in our case m = 5) where ܸ
^
is the peak amplitude of the modulating wave Vm and ܸ
^
is
the peak amplitude of each carrier wave.
Here three schemes for the level-shifted multicarrier modulation are simulated (a) in-phase
disposition (IPD), where all carriers are in phase; (b) alternative phase opposite disposition
(APOD), where all carriers are alternatively in opposite disposition; and (c) phase opposite
disposition (POD), where all carriers above the zero reference are in phase but in opposition
with those below the zero reference [4]-[7].
0 100 200 300 400 500 600 700 800 900 1000
0
0.05
0.1
0.15
Frequency (Hz)
Fundamental (50Hz) = 0.9998 , THD= 2.92%
Mag(%ofFundamental)](https://image.slidesharecdn.com/comparisonofmodulationtechniquesforcascadedh-bridgetypemultilevelcurrent-130502085528-phpapp02/85/Comparison-of-modulation-techniques-for-cascaded-h-bridge-type-multilevel-current-5-320.jpg)
![International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976
– 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME
189
Fig-16 Circuit Diagram of the 5 level CHB MVSI
IV. RESULT
Repeating the simulations with different frequencies for lowest THD has been done
and then the modulation index ( M.I.) has been varied to further reduce the THD , the
optimum frequency and modulation index in each case was found to be 900Hz and 1(for
phase shifted multicarrier) and 0.25 (for level shifted ) respectively. The same cases were
also tried out for a similar 5 level CHB MVSI (figure 16 shown above [8]-[9]) , the THD
for each modulation technique is as follows :
TABLE II
THD (%) Results for Different Modulation Techniques for both MVSI and MCSI
Modulation Technique MVSI MCSI
Angle Control Method 18.30 18.22
Phase Shifted Multicarrier 2.99 2.92
IPD 2.82 2.8
APOD 2.90 2.88
POD 2.72 2.7](https://image.slidesharecdn.com/comparisonofmodulationtechniquesforcascadedh-bridgetypemultilevelcurrent-130502085528-phpapp02/85/Comparison-of-modulation-techniques-for-cascaded-h-bridge-type-multilevel-current-9-320.jpg)
![International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976
– 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME
190
V. CONCLUSION
It is concluded that for such a 5 level MCSI in CHB configuration for both the
MVSI and MCSI the results are very similar moreover the prominent multilevel inverter
modulation topologies (i.e., Phase shifted multicarrier, IPD, APOD and POD) are also
giving similar results a minimum THD of 2.7 % has been obtained using the POD
modulation scheme in both the MVSI and MCSI cases.
VI. REFERENCES
[1] Jian-yu Bao, Wei-bing Bao and Zhong-chao Zhang, “High Generalized multilevel
current source inverter topology with self-balancing current” , Journal of Zhejiang
University-SCIENCE C (Computers & Electronics), ISSN 1869-1951 (Print); ISSN
1869-196X (Online), 2010,pp. 555-561.
[2] Muhammad H. Rashid, “Power Electronics Circuits, Devices and Applications”,
Pearson Seventh Impression, 2009, pp. 280-282.
[3] Jagdish Kumar, Biswarup Das, Senior Member, IEEE, and Pramod Agarwal,
“Selective Harmonic Elimination Technique for a Multilevel Inverter”, Fifteenth
National Power Systems Conference (NPSC), IIT Bombay, December 2008.
[4] Bin Wu, “High-Power Converters and ac Drives” ,The Institute of Electrical and
Electronics Engineers, Published by John Wiley & Sons Inc, 2006.
[5] Ilhami Colak, Ersan Kabalci and Ramazan Bayindir “A Review of multilevel voltage
source inverter topologies and control schemes” Energy Conversion and Management,
Elsevier September 2010 pp. 1-2.
[6] T.Prathiba, P.Renuga , “A comparative study of Total Harmonic Distortion in
Multilevel inverter topologies”, Journal of Information Engineering and Applications,
Vol 2, No.3, 2012.
[7] Annetla Ramakrushna, Reddy & Suresh Kumar K S, “Comparative Study of Multi
Carrier Sine and Space Vector Modulation Techniques for Cascaded H-Bridge
Inverter”, International Conference on Electrical and Electronics Engineering, ISBN :
978-93-81693-85-8, 9th
June, 2012.
[8] Ganesh Prasad Reddy, K. Ramesh Reddy , “ Design and Simulation of Cascaded H-
Bridge Multilevel Inverter Based DSTATCOM”, International Journal of Engineering
Trends and Technology- Volume3Issue1- 2012, ISSN: 2231-5381.
[9] M.Murugesan, R.Sakthivel, E. Muthukumaran and R.Sivakumar , “Sinusoidal PWM
Based Modified Cascaded Multilevel Inverter”, International Journal Of
Computational Engineering Research, ISSN: 2250–3005, Mar-Apr 2012, Vol. 2,
Issue No.2, pp.529-539.
[10] Vinesh Kapadia and Dr.Hina Chandwani, “A Review on Current Source Inverter Fed
Ac Drives and Multilevel Current Source Inverters: Part -1: CSI Fed Ac Drives”
International Journal of Electrical Engineering & Technology (IJEET), Volume 3,
Issue 3, 2012, pp. 80 - 88, ISSN Print : 0976-6545, ISSN Online: 0976-6553.
[11] Vinesh Kapadia and Dr.Hina Chandwani, “A Review on Current Source Inverter Fed
Ac Drives and Multilevel Current Source Inverters: Part -2: Multilevel CSIS”
International Journal of Electrical Engineering & Technology (IJEET), Volume 3,
Issue 3, 2012, pp. 102 - 109, ISSN Print : 0976-6545, ISSN Online: 0976-6553.](https://image.slidesharecdn.com/comparisonofmodulationtechniquesforcascadedh-bridgetypemultilevelcurrent-130502085528-phpapp02/85/Comparison-of-modulation-techniques-for-cascaded-h-bridge-type-multilevel-current-10-320.jpg)
Comparison of modulation techniques for cascaded h bridge type multilevel current
- 1. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME 181 COMPARISON OF MODULATION TECHNIQUES FOR CASCADED H-BRIDGE TYPE MULTILEVEL CURRENT SOURCE INVERTER Vinesh Kapadia1 and Dr. Hina Chandwani2 1 Research Scholar at CHARUSAT, Changa, Gujarat & Associate Prof. Dept of E.C., SNPIT & RC, Umrakh, Bardoli, Gujarat, India 2 Associate Professor, Dept of Electrical Engineering, The M.S.University of Baroda, Vadodara, India ABSTRACT This paper presents a comparison of the different modulation techniques for a single phase five level cascaded h-bridge (CHB) type multilevel current source inverter. Majority of the multilevel inverters are voltage sourced based. The popular carrier based PWM switching techniques for MVSI are the phase shifted and level shifted modulation techniques, the same techniques are tried out for the MCSI along with Selective Harmonic Elimination method using angle control and the results have been presented. Index Terms: APOD, CHB, IPD, Multilevel Current Source Inverter (MCSI), Multilevel Voltage Source Inverter (MVSI), POD, PWM, THD. I. INTRODUCTION MULTILEVEL voltage source inverters are very common and now in wide use. Compared to two-level inverters, multilevel inverters have advantages for higher power applications, including reduced harmonics and reduced switching device voltage and current stresses. The CSIs have some advantages over VSIs such as more stable operating conditions, direct control of the output current, faster dynamic response (in some cases) and easier fault management [1]. In this paper a single phase five level MCSI with symmetric DC current sources is simulated with popular Multilevel Modulation techniques and results are compared with respect to total harmonic distortion (THD). INTERNATIONAL JOURNAL OF ADVANCED RESEARCH IN ENGINEERING AND TECHNOLOGY (IJARET) ISSN 0976 - 6480 (Print) ISSN 0976 - 6499 (Online) Volume 4, Issue 2 March – April 2013, pp. 181-190 © IAEME: www.iaeme.com/ijaret.asp Journal Impact Factor (2013): 5.8376 (Calculated by GISI) www.jifactor.com IJARET © I A E M E
- 2. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME 182 II. THE POWER CIRCUIT DIAGRAM Shown below is the circuit for 5 level single phase MCSI along with the switching table TABLE I Switching Combination for the 5 level MCSI Fig-1 Circuit Diagram of the 5 level CHB MCSI The above table shows one of the possible combinations for obtaining the desired current amplitudes. Current Amplitude “ON” Switches 0 S11, S12, S21, S22 I S11, S14, S21, S22 2I S11, S14, S21, S24 -I S12, S13, S23, S24 -2I S12, S13, S23, S22
- 3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME 183 III. MODULATION TECHNIQUES A. Angle Control Method (Selective Harmonic Elimination) By proper selection of the firing (displacement angles α ) angles it is possible to try and eliminate or say minimize those particular harmonics. The fourier series for unipolar output voltages per half cycle can be expressed as (due to symmetry): vo = ∑ ܤ sin ݊߱ݐ∞ ୀଵ,ଷ,ହ,.. Bn = ସೞ గ ሾ 1 ∑ ሺെ1ሻ ୀଵ cosሺ݊ߙሻሿ ݂ݎ ݊ െ 1,3,5, … Where ߙଵ ൏ ߙଶ … ൏ ߙ ൏ గ ଶ The third and fifth harmonics would be eliminated if 1 - cos 3ఈଵ cos 3ఈଶ ൌ 0 1 - cos 5ఈଵ cos 5ఈଶ ൌ 0 [2]-[3] Assuming and initial value of α1 = 0 and calculating in an iterative manner till the results become stable we get; Initial Values α1= 0 , hence α2 = 0.52359 1st Iteration α1= 0.28728 α2 = 0.64242 2nd Iteration α1= 0.31366 α2 = 0.66478 3rd Iteration α1= 0.31084 α2 = 0.66229 4th Iteration α1= 0.31127 α2 = 0.66268 5th Iteration α1= 0.31121 α2 = 0.66262 6th Iteration α1= 0.31122 α2 = 0.66263 The values are radians , hence in degrees, α1= 17.831o and α2= 37.966 o .
- 4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME 184 Fig-2 Output Current Waveform of the 5 level MCSI with Angle Control Method Fig-3 Harmonic Spectrum of the 5 level MCSI with Angle Control Method B. Carrier Based PWM Schemes The carrier-based modulation schemes for multilevel inverters can be generally classified into two categories: phase-shifted and level-shifted modulations. Both the techniques have been applied 1. Phase Shifted Multicarrier Modulation In general, a multilevel inverter with m voltage levels requires (m – 1) triangular carriers. In the phase-shifted multicarrier modulation, all the triangular carriers have the same frequency and the same peak-to-peak amplitude, but there is a phase shift between any two adjacent carrier waves, given by Øcr = 360°/(m – 1) [4]-[7] Fig-4 Triangular Carriers compared with Reference Sine 0 100 200 300 400 500 600 700 800 900 1000 0 2 4 6 8 10 12 Frequency (Hz) Fundamental (50Hz) = 1.108 , THD= 18.22% Mag(%ofFundamental)
- 5. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME 185 Fig-5 Output Current Waveform of the 5 level MCSI with Phase Shifted MultiCarrier Modulation Fig-6 Harmonic Spectrum of the 5 level MCSI with Phase Shifted MultiCarrier Modulation 2. Level Shifted Carrier Modulation Schemes Similar to the phase-shifted modulation, an m-level Cascaded H-Bridge inverter using level-shifted multicarrier modulation scheme requires (m – 1) triangular carriers, all having the same frequency and amplitude. The (m – 1) triangular carriers are vertically disposed such that the bands they occupy are contiguous. The frequency modulation index is given by mf = fcr/fm, which remains the same as that for the phase-shifted modulation scheme whereas the amplitude modulation index is defined as ma = ^ ೝ ^ ሺିଵሻ for 0 < ma < 1 (in our case m = 5) where ܸ ^ is the peak amplitude of the modulating wave Vm and ܸ ^ is the peak amplitude of each carrier wave. Here three schemes for the level-shifted multicarrier modulation are simulated (a) in-phase disposition (IPD), where all carriers are in phase; (b) alternative phase opposite disposition (APOD), where all carriers are alternatively in opposite disposition; and (c) phase opposite disposition (POD), where all carriers above the zero reference are in phase but in opposition with those below the zero reference [4]-[7]. 0 100 200 300 400 500 600 700 800 900 1000 0 0.05 0.1 0.15 Frequency (Hz) Fundamental (50Hz) = 0.9998 , THD= 2.92% Mag(%ofFundamental)
- 6. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME 186 (a) IPD : Fig-7 Triangular Carriers compared with Reference Sine for IPD Modulation Fig-8 Output Current Waveform of the 5 level MCSI with IPD Modulation Fig-9 Harmonic Spectrum of the 5 level MCSI with IPD Modulation 0 100 200 300 400 500 600 700 800 900 1000 0 2 4 6 8 10 12 14 16 18 Frequency (Hz) Fundamental (50Hz) = 1 , THD= 2.80% Mag(%ofFundamental)
- 7. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME 187 (b) APOD : Fig-10 Triangular Carriers compared with Reference Sine for APOD Modulation Fig-11Output Current Waveform of the 5 level MCSI with IPD Modulation Fig-12 Harmonic Spectrum of the 5 level MCSI with IPD Modulation
- 8. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME 188 (c) POD : Fig-13 Triangular Carriers compared with Reference Sine for POD Modulation Fig-14 Output Current Waveform of the 5 level MCSI with POD Modulation Fig-15 Harmonic Spectrum of the 5 level MCSI with POD Modulation 0 100 200 300 400 500 600 700 800 900 1000 0 1 2 3 4 5 6 7 8 9 10 Frequency (Hz) Fundamental (50Hz) = 1 , THD= 2.70% Mag(%ofFundamental)
- 9. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME 189 Fig-16 Circuit Diagram of the 5 level CHB MVSI IV. RESULT Repeating the simulations with different frequencies for lowest THD has been done and then the modulation index ( M.I.) has been varied to further reduce the THD , the optimum frequency and modulation index in each case was found to be 900Hz and 1(for phase shifted multicarrier) and 0.25 (for level shifted ) respectively. The same cases were also tried out for a similar 5 level CHB MVSI (figure 16 shown above [8]-[9]) , the THD for each modulation technique is as follows : TABLE II THD (%) Results for Different Modulation Techniques for both MVSI and MCSI Modulation Technique MVSI MCSI Angle Control Method 18.30 18.22 Phase Shifted Multicarrier 2.99 2.92 IPD 2.82 2.8 APOD 2.90 2.88 POD 2.72 2.7
- 10. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 2, March – April (2013), © IAEME 190 V. CONCLUSION It is concluded that for such a 5 level MCSI in CHB configuration for both the MVSI and MCSI the results are very similar moreover the prominent multilevel inverter modulation topologies (i.e., Phase shifted multicarrier, IPD, APOD and POD) are also giving similar results a minimum THD of 2.7 % has been obtained using the POD modulation scheme in both the MVSI and MCSI cases. VI. REFERENCES [1] Jian-yu Bao, Wei-bing Bao and Zhong-chao Zhang, “High Generalized multilevel current source inverter topology with self-balancing current” , Journal of Zhejiang University-SCIENCE C (Computers & Electronics), ISSN 1869-1951 (Print); ISSN 1869-196X (Online), 2010,pp. 555-561. [2] Muhammad H. Rashid, “Power Electronics Circuits, Devices and Applications”, Pearson Seventh Impression, 2009, pp. 280-282. [3] Jagdish Kumar, Biswarup Das, Senior Member, IEEE, and Pramod Agarwal, “Selective Harmonic Elimination Technique for a Multilevel Inverter”, Fifteenth National Power Systems Conference (NPSC), IIT Bombay, December 2008. [4] Bin Wu, “High-Power Converters and ac Drives” ,The Institute of Electrical and Electronics Engineers, Published by John Wiley & Sons Inc, 2006. [5] Ilhami Colak, Ersan Kabalci and Ramazan Bayindir “A Review of multilevel voltage source inverter topologies and control schemes” Energy Conversion and Management, Elsevier September 2010 pp. 1-2. [6] T.Prathiba, P.Renuga , “A comparative study of Total Harmonic Distortion in Multilevel inverter topologies”, Journal of Information Engineering and Applications, Vol 2, No.3, 2012. [7] Annetla Ramakrushna, Reddy & Suresh Kumar K S, “Comparative Study of Multi Carrier Sine and Space Vector Modulation Techniques for Cascaded H-Bridge Inverter”, International Conference on Electrical and Electronics Engineering, ISBN : 978-93-81693-85-8, 9th June, 2012. [8] Ganesh Prasad Reddy, K. Ramesh Reddy , “ Design and Simulation of Cascaded H- Bridge Multilevel Inverter Based DSTATCOM”, International Journal of Engineering Trends and Technology- Volume3Issue1- 2012, ISSN: 2231-5381. [9] M.Murugesan, R.Sakthivel, E. Muthukumaran and R.Sivakumar , “Sinusoidal PWM Based Modified Cascaded Multilevel Inverter”, International Journal Of Computational Engineering Research, ISSN: 2250–3005, Mar-Apr 2012, Vol. 2, Issue No.2, pp.529-539. [10] Vinesh Kapadia and Dr.Hina Chandwani, “A Review on Current Source Inverter Fed Ac Drives and Multilevel Current Source Inverters: Part -1: CSI Fed Ac Drives” International Journal of Electrical Engineering & Technology (IJEET), Volume 3, Issue 3, 2012, pp. 80 - 88, ISSN Print : 0976-6545, ISSN Online: 0976-6553. [11] Vinesh Kapadia and Dr.Hina Chandwani, “A Review on Current Source Inverter Fed Ac Drives and Multilevel Current Source Inverters: Part -2: Multilevel CSIS” International Journal of Electrical Engineering & Technology (IJEET), Volume 3, Issue 3, 2012, pp. 102 - 109, ISSN Print : 0976-6545, ISSN Online: 0976-6553.