MULTI LEVEL INVERTER USING SQUARE PULSE WIDTH MODULATION SWITCHING STRATEGY

This Paper presents a single-phase cascaded trans- former based multilevel inverter with a modified carrier-based level shift sinusoidal pulse width modulation (LS-SPWM) tech- nique. The developed topology has two bridges with individual low frequency transformers. The bridges can generate quasi-square waveform and pulse width modulated waveform independently and energized the two transformers whose secondary terminals are cascaded to attain 19-level output voltage waveform across the load. The anticipated configuration has the least number of components to reduce the cost and enhance the reliability of the converter for medium power applications with inbuilt isolation. Furthermore, this letter presents the most common LS-SPWM technique with a new carrier to enhance the fundamental magnitude and shifts the dominant harmonics into three times of the traditional strategy for the same modulation indices. The performance of the proposed topology is validated with experimental results.