Improved PWM Approach for Cascaded Five-Level NPC H-Bridge Configurations in Multilevel Inverter

Abstract

Multilevel inverter (MLI) design for high voltage and high power applications faces challenges such as unequal power losses and junction temperatures. To address the issues of decreased efficiency and reliability, this paper introduces two innovative pulse width modulation (PWM) approaches, such as Enhanced Level Shifted PWM (ELS-PWM) and Enhanced Phase Shifted PWM (EPS-PWM). They are designed for five-level neutral point clamped (NPC) H-Bridge Configurations (FLNPCHC), which are further cascaded to form MLIs. These methods leverage modified modulating waves and restructured triangular waves to improve power quality, balance power distribution, and ensure uniform power allocation across the inverter legs. The result is identical switch utilization rates, reduced switching times, lower junction temperatures, and enhanced overall efficiency of the FLNPCHC-MLI. These approaches are validated through MATLAB simulations and tested using a 1 kVA laboratory prototype. The outcomes demonstrate significant improvements in total harmonic distortion (reduced to approximately 2.3%) and efficiency (increased to approximately 97.8%), offering a promising solution for high-voltage applications.