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