Keywords: multilevel inverters, MLIs, modular structured multilevel inverter, MSMI, pulse width modulation, unipolar PWM, sub-harmonic PWM, inverted sine PWM, carrier overlapping PWM, phase shift PWM, dSPACE, simulation, cascaded inverters
Comparative study on various unipolar PWM strategies for single phase five-level cascaded inverter
A single phase cascaded inverter consisting of two full bridges creates a five-level AC output voltage. Due to switch combination redundancies, there are certain degrees of freedom to generate the five-level AC output voltage. This paper presents the different types of unipolar pulse width modulation (PWM) strategies for the chosen inverter. The effectiveness of the developed strategies are demonstrated by simulation and experimentation. The results indicate that the multilevel inverter triggered by the developed unipolar PWM strategies exhibits reduced harmonics and higher DC bus utilisation. PWM strategies developed are implemented in real time using dSPACE/real time interface (RTI). The simulation and experimental results closely match with each other validating the strategies presented.