Performance verification of a new cascaded transformer based multilevel inverter using modified carrier SPWM strategy

Abstract

In this article, a novel cascaded transformer based multilevel inverter is presented for single phase systems. The proposed topology can produce a 19-level output waveform with fewer count parts. It consists of two bridges with individual low-frequency transformers. The bridges can generate quasi-square waveform and pulse width modulated (PWM) waveform independently and energized the two transformers whose secondary terminals are cascaded to attain the maximum number of levels in the output voltage waveform. Presence of the transformer in the configuration mainly provides the inbuilt isolation between the supply and load, higher order harmonics are filtered out due to the leakage inductance of the transformers and ratings of the power electronic switches are reduced since the transformers are boosted up the voltages. As per switching concerns, this paper presents the most common LS-SPWM technique with a new carrier to improves the fundamental magnitude and shifts the dominant harmonics into three times of the traditional strategy for the same modulation indices. The detailed loss analysis of the converter is also presented. The performance of the proposed topology is validated with MATLAB-Simulink software.