Mitigation of Harmonics in Seven Level Inverter by using PSO Algorithm

Mitigation of Harmonics in Seven Level Inverter by using PSO Algorithm
Authors:B.RAJITHA

Abstract: In nowadays the multilevel inverters are increased due to their ability to generate high quality output wave forms with low switching frequency. The different multilevel inverter structures are Cascaded H-Bridge, diode clamped and flying capacitor multilevel inverter. A Cascaded H-bridge Inverter (CHB) is a multilevel topology which is formed from the series connection of H-bridge cells. In this paper the Selective harmonic elimination pulse width modulation strategy is eliminating low-order harmonics by solving nonlinear equations. The selective harmonic elimination method (SHE-PWM) at fundamental frequency switching scheme has been implemented using the Particle Swarm Optimization (PSO) Algorithm that produces all possible solution sets when they exist. In comparison with other suggested methods, the proposed technique has many advantages such as: it can produce all possible solution sets for any numbers of multilevel inverter without much computational burden; speed of convergence is fast etc. This paper is to reduce the total harmonic distortion (THD) and elimination of selective lower order harmonics such as 5thand 7th order with minimum harmonic distortion and obtain desired fundamental voltage. The results prove that the PSO algorithm converges successfully to the global solution faster than other algorithms. The simulation will be obtained by using MATLAB/SIMULINK. 

Keywords: Multilevel Inverters, Selective Harmonic Elimination (SHEPWM), Cascaded H-Bridge, Particle Swarm Optimization. 

INTRODUCTION 

        In recent years, Multilevel Inverters have received more attention because of their ability to generate high quality output waveforms with low switching frequency. Multilevel Inverters have been considered as an optimum choice to provide better quality power to the load. In Multilevel Inverters the desired output voltage is achieved by Suitable low combination of multiple low dc voltage sources used at the input side. As the number of dc sources increases the output voltage will be pure closer to sinusoidal waveform. In this paper, an attempt has been made to improve the quality of power. There are three types of conventional structures for multilevel inverters such as diode clamped multilevel inverter, flying capacitor multilevel inverter and cascaded multilevel inverter. There are many popular methods are used to reduce the harmonics in order to get an effective results. The methods for high switching frequency are Sinusoidal PWM and Space Vector PWM. For low switching frequency methods are space vector modulation and selective harmonic elimination. The spwm, svpwm techniques are don’t eliminate low order harmonics. So the selective harmonic mitigation (SHM-PWM) technique for generating pwm signals that can be eliminate selected lower order harmonics from voltage sources inverter.

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