An Investigation of THD in 5-level NPC Multilevel Inverter Based on Multicarrier PWM Techniques

Abstract

This paper presents an investigation of the Total Harmonic Distortion in 5-level neutral point clamped multilevel inverter using 4 strategies of multicarrier PWM techniques; Phase Disposition, Phase Opposition Disposition, Phase Opposition Disposition with different frequencies, and Alternative Phase Opposition Disposition. The signals of the controlled switches of the multilevel inverter based on 4 strategies of multicarrier PWM techniques created by a TMS320F28335 DSP controller are proposed in this paper. Experimental results by varying the modulation index (m a) in the range of 0.4 to 1, the lowest percentage of the THD of the system is produced when the multilevel inverter is controlled by the PD modulation technique. The %THDv and the %THDi are 9.3 and 9.6,respectively, when the prototype of the multilevel inverter with a resistive load 50 Ω and an inductive load 8 mH is controlled by the PD modulation technique using m a = 0.9.