K Ravi Chandrudu* et al / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 6, Issue No. 2, 224 - 229
stage converters. Z – Source inverters are mostly used and tested for various applications in drive control and fuel cells etc. Where the DC voltages generated by the sources are constant magnitude.
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Abstract
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In this work, EZ source inverters are proposed to control a load. DC is boosted using Z network and the switches. The boosted voltage is converted into 3 – phase balanced AC using the converter. Z Source inverters have recently been proposed as an alternative power conversion concept as they have both voltage buck and boost capabilities. Believing in the prospects of Zsource inverters, this paper contributes by introducing a new family of embedded EZ-source inverters that can produce the same gain as the Z-source inverters but with smoother and smaller current/voltage maintained across the dc input source and within the impedance network. These latter features are attained without using any additional passive filter, which surely is a favorable advantage, since an added filter will raise the system cost and, at times, can complicate the dynamic tuning and resonant consideration of the inverters. The output of the inverter is used to control the harmonics presented in the load digital simulation is done and results are presented to verify the proposed idea.
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Fig. 1. Z – Source voltage – type Inverter
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Also traditional voltage source inverters VSI, CSI [2] can be used for such applications. The VSI based system has the following theoretical barriers and limitations. The ac output voltage is limited below and cannot exceed the dc bus voltage.
Keywords – Z –source inverters, EZ – source inverters, voltage sag, Harmonic distortion, Neutral point clamped source.
The upper and lower devices of each phase leg cannot be switched on simultaneously.
I. Introduction
An output LC filter is needed for providing a sinusoidal voltage.
Z – Source inverters, first proposed in [1] and shown in fig. 1(a) are considered for single –
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K Ravi Chandrudu* et al / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 6, Issue No. 2, 224 - 229
The CSI based system has the following theoretical barriers and limitations.
be used for controlling EZ- and Z-source inverters [3 – 4 papers].
At least one of the devices gated on and maintained on at any time. Overlap time needed, other wise cause’s waveform distortion, etc. Fig. 2. Embedded EZ – Source Inverter
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On the other hand, Z – source inverters are designed with maximum modulation ratio, hence any surge in energy demand is managed by varying the inverter shoot – through time duration, which in effect for gaining voltage boosting in Z – source inverters. Both VSI and CSI based systems have poor harmonic performance compared.
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Performing state-space averaging then results are as
II. Embedded EZ source inverter
Despite the modifications, the voltage or current gain of the inverters is kept unchanged, as can be proven mathematically, these are same as like in Z – source type inverters [p]. The proposed EZ-source inverters [p] are therefore competitive alternatives that can be used for cases where implicit source filtering is critical. The proposed concept has been simulated in MATLAB/Simulink and the corresponding results are presented, and also the Z – source inverter simulation results presented, these are compared.
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The proposed Embedded EZ-source inverter shown in Fig. 2, it has dc sources embedded within the X-shaped LC impedance network with its inductive elements L1 and L2 now, respectively, used for filtering the currents drawn from the two dc sources without using any external LC filter. Quite obviously, the immediate disadvantage shown in Fig. 2 is that two dc sources of Vdc/2, instead of the single dc source shown in Fig. 1, are needed for the EZsource inverter. Although this requirement can at times translate to a slightly higher cost. It is not viewed as serious limit. These advantages are more clearly illustrated by analyzing the inverter operating principle, which again involves shoot through and nonshoot-through states produced by a modulator that can equally
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III. Simulation Results The simulation is done using MATLAB/ SIMULINK and the results are presented here.
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K Ravi Chandrudu* et al / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 6, Issue No. 2, 224 - 229
Fig. 3. (b). Capacitor Voltage
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Fig. 3. (d). Line Currents
Fig. 3. (e). FFT analysis for current
Fig. 3. (c). Line Voltages
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K Ravi Chandrudu* et al / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 6, Issue No. 2, 224 - 229
Fig. 4. (d). Line Currents
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Fig. 4. (b). Capacitor Voltage
Fig. 4. (e). FFT analysis for current
Fig. 4. (c). Line Voltages
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K Ravi Chandrudu* et al / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 6, Issue No. 2, 224 - 229
The SIMULINK model of Z – Source Inverter with load application is shown in fig -3.(a). The capacitor voltage is shown in figure –3.(b). Line voltages are shown in fig –3. (c). Line currents are shown in fig –3. (d). The F.F.T. analysis for current is done and spectrum is shown in fig –3. (e). The T.H.D. is 4.83%. The SIMULINK model of proposed Embedded EZ source inverter with load application is shown in fig – 4. (a). The capacitor voltage is shown in figure – 4.(b). The increase in ripple due to the shifting of the source. Line voltages are shown in fig – 4. (c). They are displaced by 1200. The F.F.T analysis is done for the line currents and the spectrum is shown in fig – 4. (f). The T.H.D is 3.13%. Thus the T.H.D. of Embedded E - Z source inverter with load application is less than that of conventional system.
[1]. F. Z. Peng, “Z – Source inverter,” IEEE Transactions on Industry applications, vol. 39. pp. 504 – 510, Mar – Apr 2003.
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[2]. S. Miaosen, A. Joseph, W. Jin, F. Z. Peng and D.J. Adams, “Comparison of traditional inverters and Z – Source inverter,” 2005 IEEE 36th Power Electronic Specialists Conference (IEEE Cat. No. 05CH37659C), PP. 1692 – 8/ CD – ROM, 2005.
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[3]. M. S. Shen, J. Wang, A. Joseph, Z. Peng, L. M. Tolbert, and D.J. Adams, “ Constant boost control of the Z – source inverter to minimize current ripple and voltage stress,” IEEE Transactions an Industry Applications, vol. 42, pp. 770 – 778, May – Jun 2006. [4]. T. Meenakshi, K. Rajambal, “Identification of an Effective Control Scheme for Z-source Inverter,” Asian Power Electronics Journal, Vol. 4 No.1, April 2010.
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IV. Conclusion
References
Embedded E - Z source inverter with load application modeled and simulated using MATLAB/SIMULINK. The results of ZSI and E – ZSI with load application are presented. It is observed that the ripple in the output of E – ZSI system is higher than that of ZSI system. Frequency spectrum indicates that T.H.D of E – ZSI system is 1.7% less than that of ZSI system. The E – ZSI system has advantages like shoot – through capability, boosting ability and reduces the T.H.D. Therefore, E – ZSI with load is viable alternative to the existing drive systems. The simulation results are inline with predictions.
[5]. J. Anderson and F. Z. Peng, “Four quasi-Zsource inverters,” in Proc. IEEE PESC, 2008, pp. 2743–2749.
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[6]. F. Gao, P. C. Loh, F. Blaabjerg and C. J. Gajanayake, “Operational Analysis and Comparative Evaluation of Embedded Z-Source Inverters” IEEE xplore VOL 1, NO 1, 2757 -63 April 08. [7]. G. Pandian, S. Rama Reddy, “Embedded Controlled Z Source Inverter Fed Induction Motor Drive” Journal of Applied Sciences Research, 4(7): 826-832, 2008. [8]. Poh Chiang Loh, Feng Gao, Frede Blaabjerg,
”Embedded
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EZ-Source
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Inverters”
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transactions on industry applications, VOL. 46, NO. 1, Jan/Feb 2010.
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K Ravi Chandrudu has obtained his B.E. from Andhra University in the year 1998. He obtained his M. Tech from S.V. University, A.P, India in 2005. He is presently a Research scholar in S. V. University, A.P. India. His research area is on Induction Motor drives.
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Dr. P Sangameswara Raju currently working as professor in E.E.E. Department, S.V.University, A.P, India. His research work on Power systems, operation protection &control of drives. He presented thirty papers in various International / National Conferences/Journals.
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G V P Anjaneyulu has obtained his B.E. degree from Andhra University, A.P. , India in 2005. He obtained his M.Tech degree from NIT Calicut, Kerala in 2009. Currently working as Lecturer in EEE department, E.V.M.C.E.T.
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