International Journal of Electrical and Computer Engineering (IJECE) Vol. 7, No. 6, December 2017, pp. 3292~3298 ISSN: 2088-8708, DOI: 10.11591/ijece.v7i6.pp3292-3298  3292 Journal homepage: http://iaesjournal.com/online/index.php/IJECE Reduction of Total Harmonic Distortion in Cascaded H-Bridge Inverter by Pattern Search Technique Suresh N. 1 , R. Samuel Rajesh Babu 2 1 Faculty of Electrical and Electronics Engineering, Sathyabama University 2 Associate Professor, Departement of Electronics and Instrumentation Engineering, Sathyabama University Article Info ABSTRACT Article history: Received Aug 25, 2016 Revised Sep 8, 2017 Accepted Sep 29, 2017 Pattern Search technique can be used to find the solution for the optimization problem. In this paper, pattern search algorithm has been utilized to calculate the switching angles for the cascaded H-bridge inverter with the consideration of minimizing total harmonic distortion. Mathematical equations for the optimization problem were formulated by fourier analysis technique. Lower order harmonics such as third, fifth, seventh, ninth and eleventh order harmonics were taken into account to mitigate the total harmonic distortion of the inverter. Simulations have been carried out for thirteen level, fifteen level and seventeen level cascaded H-bridge inverter using matlab software. Total harmonic distortion of voltage and current for resistive load, resistive-inductive load and motor load were analyzed. Keyword: Cascaded HBridge inverter Optimization techniques Pattern search algorithm Switching angle Total harmonic distortion Copyright © 2017 Institute of Advanced Engineering and Science. All rights reserved. Corresponding Author: Suresh N., Faculty of Electrical and Electronics Engineering, Sathyabama University, Sholinganallur, Chennai-600119, Tamilnadu, India. Email: mailtonsuresh@gmail.com 1. INTRODUCTION In developing countries, electrical power deficit is a major problem. The gap between the supply and the demand widens with the advent of new machines and devices which rely on electricity. Most of the machines used in the manufacturing sector and home appliances by the consumers like air-conditioner, refrigerator, iron boxes, heaters, etc. require power for its operation. To cope up with the demand, immense research is being carried out in the field of producing electrical power from solar energy, wind energy etc. Power produced from the renewable energies is of direct current. But electricity of alternating current type is utilized by many machines in the automation industry. Hence it is necessary to boost the direct current [1] and convert it into alternating current. When converting the d.c into a.c by the inverters, distortions were produced known as harmonics. A harmonic component in a power system is a sinusoidal component of a periodic waveform having a frequency that is an integral multiple of the fundamental frequency [2]. These harmonic components give rise to undesirable effects [3] on conductors, transformers, circuit breakers, fuses, rotating machines, telephone lines, etc. Harmonics can measured by a parameter called Total Harmonic Distortion (THD) [4]. Since THD affects the operation of machines, it is important to mitigate them. Numerous inverters were designed by the researchers with the intention of reducing harmonics. One such inverter is the multilevel inverter. For medium and high power applications multilevel inverters are applied. Various topologies of multilevel inverters such as cascaded H-bridge inverter, diode-clamped inverter, capacitor-clamped inverter were discussed [5]. THD generated by the diode-clamped inverter and capacitor-clamped inverter is more compared to the cascaded H-bridge inverter for the same number of levels [6]. Hence cascaded H-bridge inverters were considered for analysis.