A Modified Nearest Level Modulation Scheme for a Symmetric Cascaded H-Bridge Inverter

Year 2019, Volume: 32 Issue: 2, 471 - 481, 01.06.2019

Rakesh Kumar , Deepa Thangavelusamy

Abstract

An efficient pulse width modulation scheme for
Cascaded H-Bridge inverter (CHBI) is proposed in this paper. The proposed
modulation scheme is a low switching frequency modulation scheme termed as
modified Nearest Level Modulation (mNLM) scheme. Compared to the conventional
nearest level modulation (NLM) scheme, the proposed modulation scheme reduces
the total harmonic distortion (THD) at the ac output of the inverter. The mNLM
follows an algorithm presented in the paper in order to arrive at a set of
switching angles for MLI which offers reduced THD. Simulation is carried out
using MATLAB/Simulink 2015b software and hardware is presented which validates
the simulation results. Results show that there is a notable reduction in the
THD content with the use of proposed modulation scheme. Because of the improved
THD content, improvement in the other inverter parameters such as rms voltage,
rms current and increased output power is also observed.

Keywords

Cascaded H-bridge inverter, Inverter modulation scheme, Multilevel inverter, Nearest level modulation, Total harmonics distortion

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