A MULTI-LEVEL INVERTER FOR SOLAR ENERGY APPLICATIONS J.Harshavardhan V.Ghouse Basha III B.Tech III B.Tech Department of EEE Department of EEE SSITS.Rayachoti, A.P, India, SSITS,Rayachoti, A.P, India, Mobile:+91-8464836628 Mobile:+91-8790060994 E-mail:royalharsha111@gmail.com E-mail:ghouse.basha131@gmail.com

ABSTRACTA new multi-level inverter topology based on a H-bridge structure with four switches connected to the dc-link. Based on a new PWM method which requires only one carrier signal is suggested.The switching sequence to balance the capacitor voltage.The proposed topology requires minimum number of component count to increase the number of voltage level.

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Presentation outlineIntroductionVarious topologies of multilevel invertersModulating strategies & features of MLICircuit Diagram & its implementationSimulation implementation & its results Advantages & ApplicationsConclusionFuture-scope

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INTRODUCTIONMLI produces nearly sinusoidal outputMLI control the lower order harmonicsMLI introduced by grid connected systemTopologies of MLINeutral point clamped typeFlying capacitor type Cascade type

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*VARIOUS TOPOLOGIES OF MULTILEVEL INVERTERS:

comparisons of components requirements per phase multilevel inverters

TYPES OF CONNECTIONS: Diodes protect the circulating current Capacitor gives the supply to switches

Neutral point clamped (NPC) type:*

Capacitors are directly connected to the switches capacitors are used to charging and discharging at unbalance voltages*Flying capacitor type

There is no interruption Levels can be increased by cascade connection*Cascade type:

Modulation strategies for multilevel inverters:

Features of Multilevel Inverters:

It may be easier to produce high voltage, high power inverter with multilevel structure

They can operate with a lower switching frequency

By increasing number of voltage levels the harmonic content of output voltage waveform decreases

CIRCUIT DIAGRAM OF THE PROPOSED SYSTEM:Fig.1: Single- phase MLI*

Output voltage(Vo)Switching conditionTp+Tp-TN +TN -TA+ TB-TA- TB+VdcONOFFOFFONONOFF0.5VdcOFFONOFFONONOFFONOFFONOFFONOFF0OFFONONOFFONOFFOFFONONOFFOFFON-0.5Vdc OFFONOFFONOFFONONOFFONOFFOFFON-VdcONOFFOFFONOFFON

SWITCHING STATESVo= -VdcVo= Vdc*

Vo=0.5VdcVo=-0.5Vdc*Switching states (contd.)Vo=0Vo=0

Vo=-0.5VdcVo=0.5Vdc*Switching states(contd.)

SOLAR INPUT CIRCUIT DIAGRAMFig.2: Single phase inverter system of solar input*

DC-link voltage200VOutput voltage110 VrmsDC- link capacitor2200 FFilter inductor(Lf)300 HFilter capacitor(Cf)150 FSwitching frequency(Fsw)5 KHzOutput frequency(fo)60 Hz

SIMULATION DIAGRAM:*

SIMULATION DIAGRAM FOR SOLAR INPUT:*

SIMULATION RESULTS:*Fig.3:Out put voltage and current wave form for R = 9.3 (R-load)Fig.4:Out put voltage of a 5-level multi-inverter

ADVANTAGES:Simple structure Low power Consumption Reduces the switching lossesOperating at fundamental frequencyMore reliable

APPLICATIONS:Applicable for Solar/wind power generation Hybrid vehicles Grid energy supply

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CONCLUSION:

Number of devices of the proposed multi-level inverter is fewer than that of the conventional multi-level inverters. The proposed system is more reliable and cost effective than the conventional two-level and multi- level inverters. Switching loss of the four switches (TA+, TA-, TB+, TB-) is almost negligible. Only one carrier signal is required to generate the PWM signals for 4 switching devices (TP+, TP-, TN+, TN-).

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FUTURE SCOPE:The proposed topology can be easily extended to 7-level or higher level with minimized active device component count.

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REFERENCES: Gui- jia su, senior member ,IEEE Multilevel DC-Link Inverter , IEEE Trans. on Indapplications, vol.41, issue 4, pp.724-738,may/june 2005. Zhong Du, Member,IEEE, Leon M.Tolbert, senior member Fundamental Frequency Switching Strategies of a Seven level Hybride Cascaded H-Bridge MultiLEVEL Inverter , IEEE Transactions on, vol.24, no.1, JANUARY 2009 J. Rodriguez, J. Lai, F.Z. Peng: Multilevel inverters: a survey of topologies,controls, and applications, IEEE Trans. on Ind. Electronics, vol.49, issue 4, pp.724-738, 2002. Baiju, M.R., Gopakumar, K., Somasekhar, V.T., Mohapatra, K.K., and Umanand, L.: A space vector based PWMmethod using only the instantaneous amplitudes of reference phase voltages inverters, IEEE, Trans. Ind. Appl 2005, pp. 297309. B.P. McGrath and D.G. Holmes, Multi-carrier PWM strategies for multilevel inverters, IEEE Transactions on Industry Applications, vol.49, no.4, pp.858-867,August 2002.

T.P.Chen, Y.S.Lai, and C.H.Liu, New space vector modulation technique for inverter control, IEEE Power Electronics Specialists Conference,Vol.2,1999,pp.777-782.

P. Hammond, A new approach to enhance power quality for medium voltage ac drives, IEEE Trans. Ind. Applicat., vol. 33, pp. 202208, Jan./Feb. 1997.

J. S. Lai and F. Z. Peng, Multilevel convertersA new breed of power converters, IEEE Trans. Ind. Applicat., vol. 32, pp. 509517, May/June 1996.

C. Hochgraf, R. Lasseter, D. Divan, and T. A. Lipo, Comparison of multilevel inverters for static var compensation, in Conf. Rec. IEEE-IAS Annu. Meeting, Oct. 1994, pp. 921928.

References (Contd)

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