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

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

References

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