A novel five-level neutral-point-clamped inverter with an auxiliary DC source

Abstract

Multi-level inverters have drawn much intention from researchers and industry, in which 3-level inverters have been widely used in practice. One of the most interesting issues is to increase the number of levels to achieve higher performances such as large power, high voltage and low harmonic distortion. Basic multilevel inverter configurations such as neutral point clamping diodes, flying capacitor clamping, and cascaded inverters have their own disadvantages when increasing the number of levels. To overcome these problems, different hybrid multilevel inverters have been proposed. As results, there are a lot of five-level hybrid inverters designed for practical applications. This paper proposes a new hybrid 5-level neutral point clamped inverter by adding auxiliary DC source. The novel hybrid inverter shows its performances comparable to the ideal NPC inverter fed by 4 ideal DC sources, and requires hardware simpler than cascaded and flying multilevel inverters. It has a good ability of self-balancing of the voltages across the DC capacitors. Consequently, simple and effective PWM control strategies can be utilized that enables achieving high working performances. The paper content consists of analyzing of the proposed hybrid inverter configuration, investigating the voltage balance on the DC capacitors, validating control characteristics and studying output performance when applying the carrier based pulse width modulation control. The analysis and characteristics of the proposed configuration are verified through simulation results using MATLAB/SIMULINK.