IJMTES | International Journal of Modern Trends in Engineering and Science ISSN: 2348-3121 HARMONIC ANALYSIS BY SQUARE WAVE PWM TECHNIQUE AND SELECTED HARMONIC ELIMINATION IN INVERTER USING PARTICLE SWARM OPTIMIZATION Jayanta Kumar Sahu 1 , Radhakrishna Das 2 1 (Electrical Engineering, C.V. Raman College of Engineering, Bhubaneswar, India, jayanta_jks@yahoo.com) 2 (Electrical Engineering, C.V. Raman College of Engineering, Bhubaneswar, India, rups.krishna@gmail.com) ______________________________________________________________________________________________________ Abstract—Converters are used in the utility interface of renewable energy system to reduce harmonic contents in line current/voltage and to increase reliability. These converters suffer from high level of Total Harmonic Distortion (THD) in the utility line currents/voltages which creates a lot of problems in the power system. In this paper harmonics are reduced by pwm technique and selected harmonic elimination technique. Pulse width modulation (PWM) is a powerful technique for controlling analog circuits with a processor's digital outputs. PWM is employed in a wide variety of applications, ranging from measurement and communications to power control and conversion. Selective harmonics are eliminated to reduce the THD, that is, the problem is to determine optimal switching angles for eliminate harmonics while maintaining the required fundamental currents/ voltages. The THD reduction is achieved by the help of multilevel inverter equal separate dc sources using particle swarm optimization. Keywords—Inverter, pwm, THD, pso ______________________________________________________________________________________________________ 1. INTRODUCTION The word ‘inverter’ in the context of power-electronics denotes a class of power conversion (or power conditioning) circuits that operates from a DC voltage source or a DC current source and converts it into AC voltage or current. Pulse width modulated (PWM) inverters are the most used power-electronic circuits in practical applications. These inverters are capable of producing ac voltages of variable magnitude as well as variable frequency. These converters suffer from high level of Total Harmonic Distortion (THD) in the utility line currents/voltages which creates a lot of problems in the power system. In this project selective harmonics are eliminated to reduce the THD, that is, the problem is to determine optimal switching angles for eliminate harmonics while maintaining the required fundamental currents/ voltages. By optimizing the non linear equations in the inverter, the optimal switching angles are generated, selected harmonics are eliminated and consequently THD of output voltage is minimized. 2. HARMONICS – ORIGIN AND EFFECTS: • Harmonics are defined as the sum of all components generated as a percentage of the fundamental waveform. • Non-linear loads generate current harmonics. • Harmonic currents flow largely through capacitors. • The flows of harmonic currents cause voltage harmonics. • Harmonics are thus injected to other linear loads connected in the same bus. • Harmonics injected into the network flow towards other users connected to the network. 3. LOADS GENERATING HARMONICS: • Equipments using switched mode power supply : ~ Television ~ Computers and other IT loads • Equipments using power electronic devices : ~ AC & DC drives ~ Frequency converters ~ Rectifiers ~ Arc & induction furnaces ~ UPS ~ Compact fluorescent & other discharge lamps Fig. (1) Voltage and Current Waveforms for Linear and Non-Linear Loads The main effects of voltage and current harmonics include: Volume: 03 Issue: 06 2016 www.ijmtes.com 133