ADVANCES in NATURAL and APPLIED SCIENCES

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1 ADVANCES in NATURAL and APPLIED SCIENCES ISSN: Published BY AENSI Publication EISSN: Special 10(14): pages Open Access Journal High VoltageLift QuasiZSource fed Modified Cascaded HBridge Multilevel Inverter 1 G. Prem Sunder, 2 Dr. B. Shanthi, 3 Dr.Alamelu Nachiappan, 4 Dr. S. P. Natarajan 1 Associate professor, Department of Electrical and Electronics Engineering, Mailam Engineering College. 2 Professor, Centralized Instrumentation and Service Laboratory, Annamalai University. 3 Professor & Head, Department of Electrical and Electronics Engineering, Pondicherry Engineering College. 4 Professor & Head (Retd), Department of Instrumentation Engineering, Annamalai University. Received 7 June 2016; Accepted 12 October 2016; Available 20 October 2016 Address For Correspondence: G. Prem Sunder, Associate professor, Department of Electrical and Electronics Engineering, Mailam Engineering College. premgsunder@gmail.com. Copyright 2016 by authors and AmericanEurasian Network for Scientific Information (AENSI Publication). This work is licensed under the Creative Commons Attribution International License (CC BY). ABSTRACT QuasiZSource Cascaded Hbridge Multilevel inverters (qzschbmli) have attracted much interest in recent research works due to its rewarding advantages when compared with traditional voltage source inverters and Zsource Inverters. The qzschbmli has limited output voltage boosting capability, and requires more number of switches as the number of levels increases. This increases the volume and cost of the qzschbmli with limited voltage boosting capability. In order to surmount these problems, a new VoltageLift QuasiZSource Modified Cascaded HBridge Multilevel Inverter (VLqZSMCHBMLI) is presented in this paper. The proposed topology utilizes lower number of switches for generating seven level output voltage as compared with traditional qzschbmli for the same voltage level. The presence of voltagelift cell in the proposed topology significantly increases the voltage boosting capability, providing boosted output voltage with reduced Total Harmonic Distortion (THD). The performance of the proposed topology is confirmed through simulation results obtained using multicarrier PDPWM with simple boost control technique. KEYWORDS: QuasiZSource, VoltageLift cell, Modified CHB MLI,PDPWM, Simple Boost Control INTRODUCTION In modern research activities, multilevel inverters have absorbed everincreasing applications in renewable energy sources such as Photovoltaic (PV) and wind energy systems [1]. CHB multilevel inverter has more advantages over diode clamped and capacitor clamped multilevel inverters for a given number of levels[24]. The Zsource based multilevel inverters have attracted much interest in recent research works due to its rewarding advantages compared with traditional voltage source inverters and Zsource Inverters (ZSI) [5]. The quasizsource concept has been applied to cascaded Hbridge multilevel inverter (CHBMLI) that provides the combined advantages of traditional CHBMLI and qzsi[6].the ZSI makes use of shootthrough and nonshootthrough states of the inverter bridge to provide boosted output voltage with singlestage power conversion capability, thus providing high immunity to the EMI noise [710]. Conversely, it has perceptibledefectsincluding high voltage stress across the capacitors and switching devices, high inrush current, and limited voltage boosting caability. The major limitation of the ZSI is the discontinuous input current,which may lead to low utilization and permanent damage of the dc source.to overcome the problems associated with the ZSI, a variety of improved circuit topologies were presented in [1115]. To Cite This Article: G. Prem Sunder, Dr. B. Shanthi, Dr.Alamelu Nachiappan, Dr. S. P. Natarajan., High VoltageLift Quasi ZSource fed Modified Cascaded HBridge Multilevel Inverter. Advances in Natural and Applied Sciences. 10(14); Pages:

2 177 G. Prem Sunder et al., 2016/ Advances in Natural and Applied Sciences. 10(14) Special 2016, Pages: A new extendedboost ZSIs is presented in [11], where a diode or capacitor is included to provide increased boost factor and continuous input current, but it has complex circuit structure. QuasiZsource inverter (qzsi) is presented in [12], achieving the advantages of lower number of power devices with lower power rating, continuous input current and reduced current stress in dc source. QuasiZsource cascaded multilevel inverter (qzschbmli) providesplentiful merits over traditional CHB multilevel inverter in distributed generation applications. A new quasizsource Modified Cascaded HBridge multilevel inverter with voltagelift cell (VLqZSMCHBMLI) is presented in this paper to further increase the boost ability of the qzschbmli, and to decrease the number of switching devices. The new proposed topology provides higher boost ability with the same shootthrough duty ratio, while maintaining the advantages of the qzschbmli.the proposed topology is reliable against short circuits, and has lower THD, higher efficiency and higher voltage boosting capability as compared to traditional inverters. The performance analysis of the proposed topology in terms of the THD for a seven level output voltage is presented with the simulatedresults using MATLAB. The traditional qzschbmli is explained in section 2 with circuit topology and characteristics of boost factor and shootthrough duty ratio. The proposed VLqZSMCHBMLI is explained in section 3. The PWM control strategy of the proposed VLqZSMCHBMLI is given in section 4. The simulationresults of the proposed topology are presented in section 5. Finally, the conclusion is given in section 6. Traditional QzsChbMli: The traditional qzschbmli is shown in Fig 1. It has qz source network consisting of two inductors (L 1, L 2 ), capacitors (C 1, C 2 ) and one diode (D 1 ). The qz source network shares the common ground with inverter, and the current drawn by the dc source is continuous. The boost factor(b) of the qzschbmli is given in (1) = = ( ) (1) S11 S13 S12 S14 S21 S23 Vin2 S22 S24 S31 S33 Vin3 Fig. 1: Traditional qzschbmli S32 S34 Proposed VlQzsMchbMli: To improve the voltage boost capability of the traditional qzsmchbmli, a voltagelift cell is incorporated by replacing inductor L 2 in that topologyto form a new proposed topology VLqZSMCHBMLI as shown in Fig. 2. In the proposed topology, lower number of switches are utilized for generating seven level output voltage as compared with traditional qzschbmli for the same voltage level.

3 178 G. Prem Sunder et al., 2016/ Advances in Natural and Applied Sciences. 10(14) Special 2016, Pages: Shootthrough control state: The equivalent circuit representing the shootthrough control state is shown in fig.3. In this circuit, L 2, L 3 and C 3 are connected in parallel where the diodes D 2 and D 3 are in ON state and D 1 is in OFF state. The capacitor C 3 is charged, while and C 2 are discharged. The inductors L 1, L 2 and L 3 store energy during this state. During this state, the inductor voltages (V, V, V ) and capacitor voltages (V, V, V C3 ) are as given below in (2) = (2) = = = D2 C3 D3 Sa1 Sa2 D2 C3 S1 S3 D3 Sb1 Vin2 Sb2 S4 S2 D2 C3 D3 Sc1 Vin3 Sc2 Fig. 2: Proposed VLqZSMCHBMLI i i i ic3 i C3 i Fig. 3: Equivalent circuit of the proposed VLqZSMCHBMLI under shootthrough 3.2 Nonshootthrough control state: The equivalent circuit of the nonshootthrough control state is shown in figure.4. In this circuit, L 2, L 3 and C 3 are connected in series, where the diodes D 2 and D 3 are in OFF state and D 1 is in ON state. The capacitor C 3 is discharged, while C 1 and C 2 are charged. The inductors L 1, L 2 and L 3 transfer energy from the dc voltage source to the load during this state. The inductor voltages and capacitor voltages as given in (3).Fig.5 depicts the

4 179 G. Prem Sunder et al., 2016/ Advances in Natural and Applied Sciences. 10(14) Special 2016, Pages: boost ability of the proposed topology which is drastically higher when compared with traditional topology for the same shootthrough duty ratio. Simple boost control strategy is utilized for the proposed topology, which is well known for its easy implementation and reduced current stress across the components. = = (3) = i i i i C3 i C3 i V dc Fig. 4: Equivalent circuit of the proposed VLqZSMCHBMLI under nonshootthrough VLqZSCHBMLI qzschbmli Boost Factor, B Shootthrough Duty Ratio, D sh Fig. 5: Comparison of boost ability between qzschbmli and VLqZSMCHBMLI Pwm Control Strategy Of The Proposed SlQzsMchbMli: The phase disposition pulse width modulation (PDPWM) technique is used to generate switching signals for the proposed topology. In PDPWM, the triangular carriers are in phase with each other, having same frequency f c and same amplitude A c. In this technique, the reference signal with an amplitude A m and frequency f m is compared with each of the triangular carrier signals to generate gate pulses. Shootthrough states can be introduced by simple, maximum and constant boost control methods. In this paper, the shootthrough states are introduced in the generated pulses by using Simple boost control method. The shootthrough states enables extended boost operation of the proposed topology. The simple boost control method employs a straight line, whose amplitude is equal to or greater than the peak value of the modulating signal in order to produce the shootthrough states which are introduced at the zero states. For simple boost control method, the shootthrough duty ratio is given in (4)!" = # # =1 & (4) The relationship between modulation index M and shootthrough duty ratio is given in (5)

5 180 G. Prem Sunder et al., 2016/ Advances in Natural and Applied Sciences. 10(14) Special 2016, Pages: &<1!" (5) The boost factor of VLqZSMCHBMLI is shown in (6) Boost Factor, = (6) VLqZSCHBMLI qzschbmli 10 Gain, G Moduation Index, M Fig. 6: Voltage conversion ratios of the traditional and proposed topology. Table 1: Simulation parameters of the VLqZSMCHBMLI Input dc voltage V in 40V VLqZS network L=L 1=L 2=L 3 40 mh C=C 1=C 2=C µf Switching frequency f s 5 KHz Resistive Load R 50Ω The proposed topology utilises lower shootthrough duty ratio when compared with qzschbmli for attaining the same boost gain. This advantage of the proposed topology provides the larger improvement in the output voltage. This can be well understood from figure 6, which describes the relationship between gain and modulation index. Results And Analysis: The FFT analysis of output voltage and the fundamental output voltage of the new voltagelift quasiz Source Modified Cascaded MLI is evaluated in this section. The simulation results are presented in Figs. 7, 8 and 9and their simulation parameter are provided in Table 1. As shown in Fig. 9 during the steady state, DC link voltage V dc is boosted to 120V for the input dc voltage of 40V. Fig. 7: Load Voltage of the VLqZSMCHBMLI

6 181 G. Prem Sunder et al., 2016/ Advances in Natural and Applied Sciences. 10(14) Special 2016, Pages: Fig. 8: FFT Spectrum of the Load Voltage Fig. 9: DC Link Voltagesof the VLqZSMCHBMLI Conclusion: This paper has presented a new voltagelift quasizsource Modified Cascaded MLI with higher boost ability compared with traditional quasizsource Cascaded MLI, which improves the quality of the output waveformwith reduced number of switches and lower THD. The performance of the proposed topology is verified by the simulation results using simple boost control method. REFERENCES 1. Yuan, Li., Shuai Jiang, J.G., CintronRivera, Fang Zheng Peng, "Modeling and control of quasizsource inverterfor distributed generation applications," IEEE Transactions on IndustrialElectronics., 60(4): Rodriguez, J., S. Bernet, B. Wu, J.O. Pontt and S. Kouro, Multilevel voltagesourceconverter topologies for industrial mediumvoltage drives, IEEE Trans. Ind. Electron., 54(6): Miao Changxin, Shi Liping, Wang Taixu and Cui Chengbao, Flying capacitor multilevel inverters with novel PWM method, Procedia Earth and Planetary Science, 1(1): Kang, LeeB.K., J.H. Jeon, T.J. Kim and D.S. Hyun, A symmetric carrier technique of CRPWM for voltage balance method of flying capacitor multilevel inverter, IEEE Trans. Ind. Electron., 52(3): Banaei, M.R., A.R. Dehghanzadeh, E. Salary, H. Khounjahan, R. Alizadeh, "Zsourcebased multilevel inverter with reduction of switches, IET Power Electron., 5(3): Yushan Liu, Baoming Ge, H. AbuRub, F.Z. Peng, "An effective control method for quasizsource cascade multilevel inverterbased gridtie singlephase photovoltaic power system," IEEE Transactionson Industrial Informatics, 10(1): Miaosen Shen, Joseph, A., Jin Wang, F.Z. Peng, D.J. Adams, "Comparison of Traditional Inverters and Z Source Inverter for Fuel Cell Vehicles," IEEE Transactions on Power Electronics, 22(4): Yi Huang, Miaosen Shen, Peng, F.Z., Jin Wang, "ZSource Inverter for Residential Photovoltaic Systems," IEEE Transactions on Power Electronics, 21(6): I776l Peng Fang zheng, "Zsource inverter," IEEE Transactions on Industry Applications, 39(2):

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