ABC, an effective tool for harmonic

elimination and optimization in

multilevel inverter

By

Shridhar B. Kulkarni

RIT, Islampur

M.Tech - I

1529010

Contents • Introduction• Multilevel inverter• Selective harmonic elimination• ABC algorithm• Implementation • Conclusion• References

Introduction

• For improving inverter performance and power quality there are different methods

• Harmonics• Main objective is elimination of harmonics• Use of multilevel inverter is increases• Iterative methods of optimization are used to

find best switching angle

Multilevel inverter

• What is multilevel inverter? What are the types?

• Why multilevel inverter?• What are the applications?

Concept – multilevel inverter

A multilevel inverter is a power electronic device which is capable of providing desired alternating voltage level at the output using multiple lower level DC voltages as an input.

Types

1) diode-clamped multilevel inverter

2) flying capacitor multilevel inverter

3) cascaded multilevel inverter

Why multilevel inverter?

1)Output voltages levels are doubled the number of sources2) The absence of extra clamping diodes or voltage balancing capacitors3)Sine wave can be approximated to a stepped waveform having larger no. of steps4) As no. of levels increases very fine staircase waveform is obtained

Applications

• Flexible ac transmission system (FACTS)• High voltage direct current lines• Electric vehicle drives • DC power source utilization • Power factor compensators • Back to back frequency link systems • Interfacing with renewable energy resources

etc.

Cascaded H-bridge multilevel inverterEach full-bridgecan generate three different voltage outputs: +Vdc, 0, and −Vdc.

The number of output phasevoltage levels in a cascaded multilevel inverter is 2S + 1

Each H-bridge unit generates a quasi-square waveform by phase-shifting theswitching timings of its positive and negative phase legs.

Output Waveforms

Artificial bee colony algorithm• The artificial bee colony algorithm (ABC) is an optimization algorithm

based on the intelligent foraging behaviour of honey bee swarm, proposed by Karaboga in 2005

• A bee colony consists of three kinds of bees: employed bees, on-looker bees, and scout bees

• Functions of employed bees• Functions of onlooker bees• Functions of scout bees

ABC Flowchart

Implementation

• The size of population of BA is 100.In addition, the number of iterations for each run is 200 and assumed as a termination criterion

• Objective function is,

Selective harmonic distortion• three variables θ1 , θ2 , and θ3 , where Vdc1, Vdc2, and Vdc3 are assumed to be

equal• Considering equal amplitude of all dc sources, the Fourier series expansion of the

output voltage waveform will be written as

• The objective of SHEPWM is to eliminate the lower order harmonics while remaining harmonics are removed with filter.

• To satisfy fundamental harmonic and eliminate fifth and seventh harmonics, three nonlinear equations with three angles are generated

Conclusion• We can eliminate low order harmonics by

using SHEPWM strategy• Bee algorithm is used to solve nonlinear

equation• Best switching angle can be calculated by

using ABC

REFERENCES • Application of the Bee Algorithm for Selective Harmonic Elimination Strategy in Multilevel Inverters

Ayoub Kavousi, Behrooz Vahidi, Senior Member, IEEE, Reza Salehi, Mohammad Kazem Bakhshizadeh, Naeem Farokhnia, Student Member, IEEE, and S. Hamid Fathi, Member, IEEE

• W. Fei, X. Ruan, and B. Wu, “A generalized formulation of quarter-wave symmetry SHE-PWM problems for multilevel inverters,” IEEE Trans. Power Electron., vol. 24, no. 7, pp. 1758–1766, Jul. 2009.

• [9] M. T. Hagh, H. Taghizadeh, and K. Razi, “Harmonic minimization in multilevel inverters using modified species-based particle swarm optimization,” IEEE Trans. Power Electron., vol. 24, no. 10, pp. 2259–2267, Oct. 2009.

• T. Tang, J. Han, and X. Tan, “Selective harmonic elimination for a cascade multilevel inverter,” in Proc. IEEE Int. Symp. Ind. Electron., Jul. 2006, vol. 2, pp. 977–981.

• Z. Du, L. M. Tolbert, and J. N. Chiasson, “Active harmonic elimination for multilevel converters,” IEEE Trans. Power Electron., vol. 21, no. 2, pp. 459–469, Mar. 2006.

• M. G. Hosseini-Aghdam, S. H. Fathi, and G. B. Gharehpetian, “Elimination of harmonics in a multilevel inverter with unequal DC sources usingthe homotopy algorithm,” in Proc. IEEE Int. Symp. Ind. Electron., Jun. 4–7, 2007, pp. 578–583.

Contact details --

Shreedhar.kulkarni65@gmail.com

THANK YOU