Analysis of Improved Phase Shift PWM With Delta Strategy for Single Phase Cascaded H-Bridge Multilevel Inverter

This paper analyzes the improved modulation techniques based on Phase Shift Pulse Width Modulation (PS-PWM) for single phase Cascaded H-Bridge (CHB) Multilevel inverter. Cascaded H-Bridge Multilevel topology is a good choice for high-power medium-voltage applications. The PS-PWM has greater advantages to ensure the quality of the waveforms and also ensures the power balance between modules. When PS-PWM is operated at high switching frequency which results increases the total harmonic distortion (THD) and reduces efficiency of the inverter. In order to solve this problem a new kind of improved carrier and reference waveform based modulation strategy is proposed. The proposed modulation strategy is a hybrid strategy, like the carrier wave is designed for PS-PWM but it appears as a Level Shift Pulse width modulation (LS-PWM) carrier with delta modulation strategy integration and also the modulating wave is a combination of sinusoidal and a square wave. This improved method can reduce the switching states and the THD and also improves the efficiency and also applicable to different power applications. The proposed strategy is validated and compared with basic PS-PWM using with Simulink.