This article was downloaded by: [McGill University Library] On: 18 December 2014, At: 07:02 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Electric Power Components and Systems Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/uemp20 Sinusoidal Pulse-width Modulated Three-phase Multilevel Inverter Topology a Charles Ikechukwu Odeh a Department of Electrical Engineering, University of Nigeria, Nsukka, Nigeria Published online: 20 Nov 2014. Click for updates To cite this article: Charles Ikechukwu Odeh (2015) Sinusoidal Pulse-width Modulated Three-phase Multi-level Inverter Topology, Electric Power Components and Systems, 43:1, 1-9, DOI: 10.1080/15325008.2014.963260 To link to this article: http://dx.doi.org/10.1080/15325008.2014.963260 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. 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Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions Electric Power Components and Systems, 43:1–9, 2015 C Taylor & Francis Group, LLC Copyright ISSN: 1532-5008 print / 1532-5016 online DOI: 10.1080/15325008.2014.963260 Sinusoidal Pulse-width Modulated Three-phase Multi-level Inverter Topology Charles Ikechukwu Odeh Department of Electrical Engineering, University of Nigeria, Nsukka, Nigeria Downloaded by [McGill University Library] at 07:02 18 December 2014 CONTENTS 1. Introduction 2. Proposed Three-Phase Multi-Level Inverter 3. Simulation and Experimental Results 4. Conclusions References Abstract—This article presents a sinusoidal pulse-width modulated three-phase multi-level inverter topology. In this configuration, the basic two-level, three-phase inverter is modified to synthesize higher voltage levels by the insertion of two auxiliary switches per phase leg. The multi-level inverter configuration generates output voltage levels similar to the corresponding well-known conventional diode-clamped flying capacitors and cascaded H-bridge inverters but with fewer power circuit components and more simplicity. For output voltage and frequency variations demanded by such applications as variablespeed drives, active power filters, photovoltaic power conversions, etc., the sinusoidal pulse-width modulation technique is employed in the generation of the gating signals for the proposed three-phase multi-level inverter. A balanced three-phase R-L load is applied at the inverter output terminals, and the inverter performance is compared with that of other sinusoidal pulse-width modulated conventional multi-level inverter configurations. The validity of the proposed multi-level inverter topology and the modulation scheme are verified through simulations and experiments. 1. Keywords: Inverter, multi-level, cascaded, pulse-width modulation, H-bridge, total harmonic distortion Received 4 February 2013; accepted 19 July 2014 Address correspondence to Charles Ikechukwu Odeh, Department of Electrical Engineering, University of Nigeria, Nsukka 410, Nigeria. E-mail: charles.odeh@unn.edu.ng Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/uemp. INTRODUCTION Multi-level converters (MLCs) are currently popular for medium-voltage high-power applications due to their reduced rating of power semiconductor devices; improved quality of output voltage; near sinusoidal input currents; lower commonstress; smaller input and output filters; mode voltages; less dv dt and increased efficiency due to the possibility of low switching operation, reduced output torque ripple, reduced electromagnetic interference (EMI) problems, and possible fault-tolerant operation [1–6]. The different topologies mainly reported in the literature for multi-level inverters (Figure 1) include diode-clamped or neutral-point converters (NPCs) [7], flying-capacitor converters (FCs) [8], and cascaded H-bridge converters (CHBs) [9]. In addition, generalized multi-level inverter topology with selfvoltage balancing [10], mixed-level hybrid multi-level cells [11], asymmetric hybrid multi-level cells [12], soft-switched multi-level inverters [13–15], and modular multi-level cascade converters (MMCCs), [16–21] have been proposed. The topology of the NPC inverter is limited to three-level operation 1 Downloaded by [McGill University Library] at 07:02 18 December 2014 2 Electric Power Components and Systems, Vol. 43 (2015), No. 1 due to capacitor voltage balancing issues as well as excessive clamping diodes required for high-level inverters [4]. The topology of capacitor-clamped inverters is limited to three or four levels due to such limitations as capacitor voltage balance requirement, pre-charge of the capacitors at the start, and need of larger number of capacitors. In addition, this topology is not suitable for low and medium switching frequencies due to the high cost of flying capacitors [22]. For higher-level operation, cascaded inverters are preferred as they require the least number of components compared to other topologies as well their modularized circuit layout, packaging is possible because each level has a similar structure [22]. Although the modular structure solves the voltage imbalance problem, this approach requires many isolated DC sources and link voltage controllers. The concept of enhancing the quality of the waveforms of the classical inverter by inserting an auxiliary circuit between the source and the power switches of the basic full-bridge inverter was reported for a single-phase inverter only in [23–28]. In [23], the auxiliary circuit was formed from two switching elements and two diodes, while in [24, 25] the auxiliary circuit contained one switching element and a full bridge of diodes. In [26], a switched capacitor circuit was used, which was formed from two diodes, two capacitors, and a switching element. As a result, a five-level voltage waveform was obtained at the inverter output. An extension of this principle was seen in [27], where two auxiliary circuits were inserted to synthesize a seven-level voltage waveform. In [28], the concept of cascading similar inverter modules was explored, where four of the basic five-level inverter cells proposed in [24] were cascaded. The result is the synthesis of a 17-level output voltage waveform for single-phase applications. In all, the resultant effect is a significant suppression of the load harmonic currents when compared with the classical three-level full-bridge inverter [29–33]. In line with the aforementioned principle and for threephase system, an inverter configuration was presented in [34] wherein the output line voltage of five levels is synthesized. In this referred work, pre-computed switching angles resulted in fixed output voltage. But to be used on such applications as the variable-speed drive, active power filter, photovoltaic power conversion, etc., on-line variation of the inverter output voltage amplitude and frequency is imperative. This article proposes a sinusoidal pulse-width modulated (PWM) three-phase multi-level inverter topology consisting of two bi-directional switches inserted between the DC source and each phase leg of the classical full-bridge three-phase inverter. As a result, a seven-level output line voltage waveform is synthesized per cycle. The multi-carrier sinusoidal pulse-width modulation technique is employed in the generation of the gating signals for the proposed three-phase multi-level inverter for on-line variation of inverter output voltage and frequency. The increased level in the PWM output voltage waveform drastically reduced the harmonic components inherent in the classical three-level, three-phase full-bridge inverter and also in the inverter configuration proposed in [34]. Greater advantage of the proposed three-phase inverter topology is seen in the reduction of the active power semiconductor switches when compared with other classical three-phase, PWM multi-level inverters. Additionally, with this low-power circuit component count, the proposed three-phase inverter achieves a total harmonic distortion (THD) value of the output voltage that is on par with those of the diode-clamped and flying capacitor multi-level inverter configurations of the same level. 2. PROPOSED THREE-PHASE MULTI-LEVEL INVERTER The proposed inverter configuration, operational principles, and modulation scheme are given in this section. Simulation and experimental results are adequately presented to verify the validity of the proposed three-phase PWM inverter configuration. 2.1. Principle and Operation of the Proposed Three-phase Multi-level Inverter The proposed three-phase inverter topology, shown in Figure 2, is a modification of the basic three-phase, three-level inverter configuration, where two (upper and lower) auxiliary circuits are inserted per phase leg. Each auxiliary circuit constitutes one switching element and full-bridge diodes. The DC source is split into three equal parts by capacitor banks. One terminal of each of the upper and lower auxiliary circuits is connected to two-thirds and one-third of the split DC source, respectively, while the other terminals of the upper and lower are hooked to the center of the respective phase leg. In all, only four active switches are utilized per phase leg. Proper switching of the inverter can produce four PWM output voltage levels per phase—0, Vs /3, 2Vs /3, and Vs —and seven PWM line-line output voltage levels—Vs /3, 2Vs /3, Vs , 0, –Vs /3, –2Vs /3, and –Vs —for every cycle. For phase A, the synthesized voltage levels and the corresponding switching states of the proposed three-phase inverter are summarized in Table 1. 2.2. PWM Modulation Scheme The carrier-based modulation scheme for multi-level inverters is adopted in the generation of the gating pulses for the Downloaded by [McGill University Library] at 07:02 18 December 2014 Odeh: Sinusoidal Pulse-width Modulated Three-phase Multi-level Inverter Topology 3 FIGURE 2. Configuration of proposed three-phase, PWM multi-level voltage source inverter. proposed inverter topology. Precisely, the in-phase disposition (IPD) modulation technique of the level-shifted multi-carrier modulation scheme is used, since it provides the best harmonic profile of all the multi-carrier modulation schemes [35]. In this modulation scheme, a multi-level inverter with m voltage levels requires (m – 1) triangular carriers, all having the same frequency, phase, and amplitude. The (m – 1) triangular carriers are vertically disposed such that the bands they occupy are contiguous. The modulating signal is usually a three-phase sinusoidal wave with adjustable amplitude and frequency. The gate signals are generated by comparing the modulating wave with the carrier waves. The frequency modulation index is Switching states Inverter phase voltage, Van g1 ga2 ga1 g4 0 0 0 0 0 0 1 1 0 0 1 0 0 1 0 0 0 VS 3 2VS 3 VS FIGURE 1. Per phase circuit configuration of the conventional multilevel inverters: (a) 4-level diode-clamped multilevel inverter. (b) 4-level flying capacitor multilevel inverter. (c) 4-level CHB multilevel inverter. TABLE 1. Switching states and output voltages of proposed threephase multi-level inverter Downloaded by [McGill University Library] at 07:02 18 December 2014 4 Electric Power Components and Systems, Vol. 43 (2015), No. 1 FIGURE 4. Simulated inverter output line voltages, ma = 0.9. signals. As depicted in Figure 3, line voltage VAB is simply the difference of the two phase voltages VAn and VBn . The logical expressions from which the gating pulses of phase A (g1 , ga2 , ga1 , and g4 ) are derived are given in Eqs. FIGURE 3. Phase A switching patterns and output voltages of the proposed three-phase, PWM multi-level inverter. given by mf = fc , fm (1) where f c and f m are the frequency of the carriers and the modulating signals, respectively; the amplitude modulation index is defined as ma = Vm , Vc (m − 1) (2) where Vm and Vc are the peak amplitude of the modulating wave and peak amplitude of each carrier wave. Figure 3 shows the comparison of the modulating wave (vma ) and carrier signals (T 1 , T 2 , and T 3 ) that generated the four gating pulses (g1 , ga2 , ga1 , and g4 ) for phase A power switches; synthesized phase voltage Van is also shown. Gating pulses and phase voltages for phases B and C are obtained by similar comparison of vmb and vmc with the triangular carrier FIGURE 5. Simulated inverter output line currents, ma = 0.9. Downloaded by [McGill University Library] at 07:02 18 December 2014 Odeh: Sinusoidal Pulse-width Modulated Three-phase Multi-level Inverter Topology 5 FIGURE 8. FFT analysis of synthesized output line voltage of four-level diode-clamped inverter. FIGURE 6. Simulated inverter output line voltages, ma = 0.7. g4 = vma < T3 . (6) (3)–(6): g1 = vma > T1 , (3) ga2 = (vma < T1 ) AND (vma > T2 ) AND vma > 0, (4) ga1 = [(vma > T3 ) AND (vma < 0)] OR [(vma < T2 ) AND (vma > 0)] , (5) FIGURE 7. FFT analysis of synthesized output line voltage of proposed inverter. It is worth mentioning that VAB is composed of three, five, and seven voltage levels for 0 ≤ ma ≤ 0.33, 0.33 ≤ ma ≤ 0.74, and 0.74 ≤ ma ≤ 1.0, respectively. FIGURE 9. FFT analysis of synthesized output line voltage of four-level flying capacitor inverter. 6 Electric Power Components and Systems, Vol. 43 (2015), No. 1 Inverter type Main switching device Main diodes DC bus Balancing capacitor Proposed inverter Diodeclamped Flying capacitors Cascaded H-bridge 4 6 6 12 8 1 0 6 1 0 0 1 6 0 3 0 Downloaded by [McGill University Library] at 07:02 18 December 2014 TABLE 2. Comparison of proposed PWM inverter with well-known three-phase inverters of the same voltage level on the basis of number of power circuit components per phase 3. 3.1. SIMULATION AND EXPERIMENTAL RESULTS Simulation Results To assess the validity of the proposed multi-level inverter topology, simulations are normally carried out in advance. MATLAB SIMULINK (The MathWorks, Natick, Massachusetts, USA) simulated the proposed three-phase inverter topology in accordance to the PWM switching scheme presented in Figure 4 and Table 1. A balanced three-phase starconnected RL load with 40-Ω resistance and 50-mH inductance per phase was used. Figure 4 show the simulated inverter output line voltage waveforms for an amplitude modulation index value of 0.9 and a carrier frequency of 2 kHz. The line-to-line voltage waveS S , −2V , and − VS , forms show seven levels: V3S , 2V3 S , VS , 0, −V 3 3 as earlier predicted. For the indicated loading condition, the simulated output line current waveforms are shown in Figure 5. To typify the voltage variation capability of the proposed PWM three-phase inverter configuration, modulation index ma is reduced to a value of 0.7, and the corresponding synthesized line voltages are given in Figure 6. Spectral analysis of the inverter line voltage waveform in Figure 4 is conducted. The spectral results are displayed in Figure 7, wherein a THD value of 23.0% is achieved in the line voltage waveform. Under the same simulation conditions and voltage level, the diode-clamped and flying capacitor threephase multi-level inverters, the phase configurations of which are shown in Figures 1(b) and 1(c), are simulated. The spectral FIGURE 10. Experimental gate signals for phase A: g1 , ga2 , ga1 , and g4 . analyses results of the individual synthesized line voltages are shown in Figures 8 and 9, respectively, which is in accordance with the results in [35]. In these simulated results, the line voltage waveforms have THD values of 24.67% and 24.63% for the four-level diode-clamped and flying-capacitor multilevel inverters, respectively. With respect to obtaining a quasi-sinusoidal voltage waveform at the output terminal, the proposed inverter topology performance is on par with those of the aforementioned two conventional multi-level inverter configurations. Further comparison of the proposed three-phase inverter configuration with the major topologies in the literature in terms of power circuit component count is given in Table 2. Power switches: IGBT EUPEC BSM 75 GB 120 DLC (EUPEC Power Electronics, Union, NJ, USA) Fast switching diodes in the auxiliary circuits: STTH12012TVL R = 30 Ω, L = 50 mH C 1 , C 2 , C 3 = 5000 µF, 400 V TABLE 3. Prototype specification FIGURE 11. Experimental inverter line vab , vbc , and vca output voltages, ma = 0.9. Downloaded by [McGill University Library] at 07:02 18 December 2014 Odeh: Sinusoidal Pulse-width Modulated Three-phase Multi-level Inverter Topology FIGURE 14. Experimental inverter line vab , vbc , and vca output voltages, ma = 0.7. FIGURE 12. Experimental inverter line iab , ibc , and ica currents. 3.2. Experimental Results Based on the simulation results, a laboratory prototype of the three-phase multi-level inverter was set up and tested to verify its validity. Basic complementary metal-oxide semiconductor (CMOS) logic gates and TL 084 IC (Texas Instruments, Dallas, TX, USA) were deployed in the generation of the inverter 12 gating pulses, four of which were specified in Figure 3 for phase A. Figure 10 shows experimentally obtained gating signals for the switches of one of the inverter legs g1 , ga2 , ga1 , and g4 . The prototype specification is given in Table 3. Shown in Figure 11 are the experimental waveforms of output line voltages vab , vbc , and vca . For the loading condition FIGURE 13. Experimental inverter line vab , vbc output voltages and corresponding iab , ibc line currents. 7 specified in Table 3, the corresponding output line currents are shown in Figure 12. The experimental waveforms for the line a and b voltages are shown in Figure 13, wherein the corresponding line currents are incorporated. For a cycle, these voltage waveforms exhibit seven levels as earlier proposed for line voltages. Experimentally validating the voltage variation capability of the proposed PWM three-phase inverter configuration, modulation index ma is reduced to a value of 0.7 in the built prototype circuit, and the corresponding line voltages are shown in Figure 14. 4. CONCLUSIONS This article has presented a sinusoidal PWM three-phase multi-level inverter topology, where additional auxiliary circuits consisting of six bi-directional switches have been inserted between the DC voltage source and the full-bridge power switches of the classical three-phase inverter configuration. For output voltage and frequency variations, as demanded by some applications, the sinusoidal pulse-width modulation technique has been used in the generation of the gating signals for the power switches. The operational principles and switching functions have been discussed in detail. The proposed PWM multilevel inverter exhibited similar behaviors of the conventional diode-clamped and flying capacitors inverters earlier reported, but with reduced power circuit components and ease of implementation. The spectral analyses of the synthesized output line voltages were given. The proposed three-phase inverter topology has been compared with classical three-phase multi-level inverter configurations of the same voltage level, with respect to the power circuit component count and spectral analysis re- 8 Electric Power Components and Systems, Vol. 43 (2015), No. 1 sults at the same modulation conditions. It has been shown that the harmonic spectrum performance of the proposed inverter is quite on par with those of the diode-clamped and flying capacitor seven-level inverters. However, the proposed inverter topology presents a power circuit of reduced component count. Simulation and experimental results obtained validated the proposed three-phase, PWM, multi-level inverter topology. Downloaded by [McGill University Library] at 07:02 18 December 2014 REFERENCES [1] Abu-Rub, H., Holtz, J., Rodriguez, J., and Baoming, G., “Medium-voltage multilevel converters—state of the art, challenges, and requirements in industrial applications,” IEEE Trans. Indust. Electron., Vol. 57, No. 8, pp. 2581–2596, August 2010. [2] Kouro, S., Malinowski, M., Gopakumar, K., Pou, J., Franquelo, L., Wu, B., Rodriguez, J., Perez, M., and Leon, J. ,”Recent advances and industrial applications of multilevel converters,” IEEE Trans. Indust. Electron., Vol. 57, No. 8, pp. 2553–2580, August 2010. [3] Malinowski, M., Gopakumar, K., Rodriguez, J., and Perez, M., “A survey on cascaded multilevel inverters,” IEEE Trans. Indust. Electron., Vol. 57, No. 7, pp. 2197–2206, July 2010. [4] Franquelo, L., Rodriguez, J., Leon, J., Kouro, S., Portillo, R., and Prats, M., “The age of multilevel converters arrives,” IEEE Indust. Electron. Mag., Vol. 2, No. 2, pp. 28–39, June 2008. [5] Rodriguez, J., Bernet, S., Wu, B., Pontt, J., and Kouro, S., “Multilevel voltage-source-converter topologies for industrial medium-voltage drives,” IEEE Trans. Indust. Electron., Vol. 54, No. 6, pp. 2930–2945, December 2007. [6] Tolbert, L., Peng, F. Z., and Habetler, T., “Multilevel converters for large electric drives,” IEEE Trans. Indust. Appl., Vol. 35, No. 1, pp. 36–44, 1999. [7] Nabae, A., Takahashi, I., and Akagi, H., “A new neutral-pointclamped PWM inverter,” IEEE Trans. Industry Appl., Vol. IA17, No. 5, pp. 518–523, September 1981. [8] Meynard, T. A., and Foch, H., “Multi-level conversion: high voltage choppers and voltage-source inverters,” Conf. Rec. 23rd PESC’ 92, Vol.1, pp. 397–403, 1992. [9] Hammond, P., “A new approach to enhance power quality for medium voltage AC drives,” IEEE Trans. Indust. Appl., Vol. 33, No. 1, pp. 202–208, 1997. [10] Peng, F. Z., “A generalized multilevel inverter topology with self-voltage balancing,” IEEE Trans. Indust. Appl., Vol. 37, No. 2, pp. 611–618, 2001. [11] Hill, W., and Harbourt, C., “Performance of medium voltage multi-level inverters,” Conf. Rec. 1999 IEEE Indust. Appl. Conf. 34th IAS Ann. Meet., Vol. 2, pp. 1186–1192, 1999. [12] Manjrekar, M., Steimer, P., and Lipo, T., “Hybrid multilevel power conversion system: A competitive solution for highpower applications,” IEEE Trans. Indust. Appl., Vol. 36, No. 3, pp. 834–841, 2000. [13] Song, B.-M., Kim, J., Lai, J.-S., Seong, K.-C., Kim, H.-J., and Park, S.-S., “A multilevel soft-switching inverter with inductor coupling,” IEEE Trans. Indust. Appl., Vol. 37, No. 2, pp. 628–636, 2001. [14] Yuan, X., Orglmeister, G., and Barbi, I., “ARCPI resonant snubber for the neutral-point-clamped inverter,” IEEE Trans. Indust. Appl., Vol. 36, No. 2, pp. 586–595, 2000. [15] Yuan, X., and Barbi, I., “Zero-voltage switching for three-level capacitor clamping inverter,” IEEE Trans. Power Electron., Vol. 14, No. 4, pp. 771–781, 1999. [16] Akagi, H., “Classification, terminology, and application of the modular multilevel cascade converter (MMCC),” IEEE Trans. Power Electron., Vol. 26, No. 11, pp. 3119–3130, November 2011. [17] Rohner, S., Bernet, S., Hiller, M., and Sommer, R., “Modulation, losses, and semiconductor requirements of modular multilevel converters,” IEEE Trans. Indust. Electron., Vol. 57, No. 8, pp. 2633–2642, August 2010. [18] Teeuwsen, S. P., “Simplified dynamic model of a voltagesourced converter with modular multilevel converter design,” Proceedings of the Power Systems Conference and Exposition, pp. 1–6, Seattle, WA, 15–18 March 2009. [19] Antonopoulos, A., Angquist, L., and Nee, H. P., “On dynamics and voltage control of the modular multilevel converter,” Proceedings of the European Conference on Power Electronics and Applications, pp. 1–10, Barcelona, Spain, 8–10 September 2009. [20] Gnanarathna, U. N., Gole, A. M., and Jayasinghe, R. P., “Efficient modeling of modular multilevel HVDC converters (MMC) on electromagnetic transient simulation programs,” IEEE Trans. Power Del., Vol. 26, No. 1, pp. 316–324, January 2011. [21] Rohner, S., Bernet, S., Hiller, M., and Sommer, R., “Modelling, simulation and analysis of a modular multilevel converter for medium voltage applications,” Proceedings of the IEEE International Conference on Industrial Technology, pp. 775–782, Vina del Mar, Chile, 14–17 March 2010. [22] Fazel, S., Bernet, S., Krug, D., and Jalili, K., “Design and comparison of 4-kV neutral-point-clamped, flying-capacitor, and series connected H-bridge multilevel converters,” IEEE Trans. Indust. Appl., Vol. 43, No. 4, pp. 1032–1040, August 2007. [23] Agelidis, V. G., Baker, D. M., Lawrance, W. B., and Nayar, C. V., “A multilevel PWM inverter topology for photovoltaic applications,” Proceedings of the IEEE International Symposium on Industrial Electronics (ISIE ‘97), Guimaraes, Portugal, pp. 589–594, 7–11 July 1997. [24] Park, S. J., Kang, F. S., Lee, M. H., and Kim, C. U., “A new single-phase, five-level PWM inverter employing a deadbeat control scheme,” IEEE Trans. Power Electron., Vol. 18, No. 3, pp. 831–843, May 2003. [25] Rahim, N. A., and Selvaraj, J., “Multi-string five-level inverter with novel PWM control scheme for PV application,” IEEE Trans. Ind. Electron., Vol. 57, No. 6, pp. 2111–2121, June 2010. [26] Axelrod, B., Berkovick, Y., and Ioinovici, A., “A cascade boostswitched-capacitor-converter-two level inverter with an optimized multilevel output waveform,” IEEE Trans. Circuits Syst. I: Reg. Papers, Vol. 52, No. 12, pp. 2763–2770, 2005. [27] Rahim, N. A., Chaniago, K., and Selvaraj, J., “Single-phase, seven-level grid-connected inverter for photovoltaic system,” IEEE Trans. Ind. Electron., Vol. 58, No. 6, pp. 2435–2443, 2011. Downloaded by [McGill University Library] at 07:02 18 December 2014 Odeh: Sinusoidal Pulse-width Modulated Three-phase Multi-level Inverter Topology [28] Odeh, C. I., and Nnadi, D. B., “Single-phase, 17-level hybridized cascaded multi-level inverter,” Elect. Power Compon. Syst., Vol. 41, No. 2, pp.182–196, January 2013. [29] Babaei, E., Farhadi Kangarlu, M., and Najaty Mazgar, F., “Symmetric and asymmetric multilevel inverter topologies with reduced switching devices,” Elect. Power Compon. Syst., Vol. 86, pp. 122–130, 2012. [30] Ceglia, G., Guzman, V., Sanchez, C., Ibanez, F., Walter, J., and Gimenez, M. I., “A new simplified multilevel inverter topology for DC-AC conversion,” IEEE Trans. Power Electron., Vol. 21, No. 5, pp. 1311–1319, September 2006. [31] Xue, Y., Chang, L., Kajer, S. B., Bordonau, J., and Shimizu, T., “Topologies of single-phase inverters for small distributed power generators: An overview,” IEEE Trans. Power Electron., Vol. 19, No. 5, pp. 1305–1311, September 2004. [32] Kangarlu, M. F., and Babaei, E., “A generalized cascaded multilevel inverter using series connection of sub-multilevel inverters,” IEEE Trans. Power Electron., Vol. 28, No. 2, pp. 625–636, February 2013. [33] Abu-Rub, H., Holtz, J., Rodriguez, J., and Baoming, G., “Medium-voltage multilevel converters—state of the art, challenges, and requirements in industrial applicatons,” IEEE Trans. Indust. Electron., Vol. 57, No. 8, pp. 2581–2596, 2010. [34] Odeh, C. I., Nnadi, D. B., and Obe, E. S., “Threephase, five-level multi-level inverter topology,” Elect. Power 9 Compon. Syst., Vol. 40, No. 13, pp. 1522–1532, September 2012. [35] Wu, B., “Cascaded H-bridge multilevel inverters” and “Diodeclamped multilevel inverters,” in High-Power Converters and AC Drives, Hoboken, NJ: John Wiley and Sons. Inc., Chaps. 7 and 8, pp. 120–136 and pp. 143–145, 2006. BIOGRAPHY Charles Ikechukwu Odeh received his B.Eng., M.Eng., and Ph.D. in electrical engineering from the Department of Electrical Engineering, University of Nigeria, Nsukka, in 2002, 2006, and 2010, respectively. He is a senior lecturer at the Department of Electrical Engineering, University of Nigeria, Nsukka. From January through September 2011, he was an exchange scholar sponsored by the U.S. Navy at Tennessee Technological University, Cookeville, TN. Currently, he is an Alexandra Von Humboldt (AvH) fellow at E.ON Energy Research Center, RWTH University, Germany. His research interests are power electronics multi-level converter topologies and applications.