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Full Paper Proc. of Int. Conf. on Advances in Electrical & Electronics 2012

Particle Swarm Optimization based Selective Harmonic Elimination In PWM AC-AC Converter Dr. S. Muralidharan1, Bindu J2, S Selvaperumal2, M Muhaidheen2 1

Mepco Schlenk Engineering College,EEE Dept, India Email:yes_murali@yahoo.com 2 Mepco Schlenk Engineering College,EEE Dept, India Email:jbindunair@gmail.com harmonics like Phase shifting transformer, Passive harmonic filters, Active harmonic filters, DC Choke, Line Reactor Harmonic Trap Filters, Broadband Filters, SHE-PWM etc. Among this Selective Harmonic Elimination (SHE) Pulse-width modulation (PWM) technique can be used for the selective elimination of harmonics. The main challenge involved in SHE-PWM is to solve nonlinear equations involved, which are transcendental in nature and therefore have multiple solutions. The common characteristic of the selective harmonic elimination pulse width modulation (SHE–PWM) method was that the waveform analysis were performed using Fourier theory. Sets of nonlinear transcendental equations were derived, and the solution is obtained using an iterative procedure, mostly by Newton–Raphson method. To avoid this cumbersome procedure, this paper proposes PSO based method to find the switching pattern to eliminate rectifier low input current harmonics, without having initial guess for the switching pattern. PSO was adopted to reduce the lower order line current harmonics by developing N number of pulse per half cycle. The optimal pulse pattern was used to suppress harmonics in PWM inverter. In concise, this paper introduces a technique which reduces the computational burden related with the nonlinear transcendental equations of the SHE–PWM technique by the application of intelligent based technique like Particle Swarm Optimization (PSO) method. By this technique switching angle can be calculated efficiently ensuring in rapid convergence. The results obtained were compared and analyzed.

Abstract -Power Electronics is the field which combines Power, Electronic and Control systems. It deals with the study and design of Thyristorised power controllers for variety of application like Heat control, Illumination control, High voltage power supplies, Vehicle propulsion systems, High voltage direct current (HVDC) transmission. Harmonics were produced due to these devices. Such harmonics leads to switching loss which affects the performance of the system. Hence elimination of these harmonics is essential. This paper analyzes a technique to eliminate pre-specified order of harmonics from the output waveform of AC/AC converters. Selective Harmonic Elimination (SHE) in Pulse-width modulation (PWM) technique was proposed for the elimination of harmonics. This necessitates solving systems of nonlinear equations that are transcendental in nature and therefore have multiple solutions. To minimize the computational burden associated with the nonlinear transcendental equations of the SHE–PWM method, intelligent based techniques was suggested in this paper. Particle Swarm Optimization (PSO) technique was analyzed and compared for calculating the switching angles. Keywords- Particle Swarm Optimization (PSO), Pulse-width modulation (PWM), Selective Harmonic Elimination (SHE).

I. INTRODUCTION Advent of power electronics and proliferation of nonlinear loads in industrial applications, power harmonics and their effects are of great concern. Harmonics are electric voltages and currents that appear on the electric power system as a result of certain kinds of electric loads. Harmonic frequencies in the power grid were a frequent cause of power quality problems. The harmonic distortion travels back into the power source and can affect other equipment connected to the same source. The harmonic currents also resulted in the heating of the connected devices. This heat over a period of time, will raise the temperature of the neutral conductor causing nuisance like tripping of circuit breakers, overvoltage problems, blinking of Incandescent Lights, computer malfunctions etc. High levels of harmonic distortion may lead to problems for the utility’s distribution system. This can cause spurious operation of equipment to a shutdown of important plant equipment. All electrical utilities do not have the same order of harmonics. So it is essential to eliminate those dominant orders of harmonics from the output waveform of AC/AC converters. Several techniques were available to reduce these © 2012 ACEEE DOI: 02.AETAEE.2012.3.20

II. LITERATURE SURVEY The recent developments in the field of power electronics has made it possible to improve the performance of electrical system utilities. An AC voltage regulator can be used to control an output AC voltage due to its simplicity and the ability to control large amount of power economically. Microprocessor based control scheme can be employed to control the firing instance for eliminating harmonics [1]. Selective harmonics can be reduced by Programmed PWM techniques, but this method is derivative-dependent and may end in local optima [2]. Solving linear algebraic equations instead of solving nonlinear transcendental equations using Walsh transformation for harmonic elimination is proposed in [3]. [4] Describes two-phase hybrid optimization algorithm 47


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