Synchronization Strategies in Cascaded H-Bridge Multi Level Inverters for Phase Shifted Carrier Based Sinusoidal PWM Techniques

This paper analyses synchronization strategies for cascaded H-Bridge multi level inverter topologies with carrier based sinusoidal phase shifted pulse width modulation technique. In phase shifted pulse width modulation technique, a separate carrier is used for each H-Bridge. The carriers are generally phase shifted from each other by π/n Rad (n=No. of HBs). Hence, the positions of carriers w.r.t. voltage references play an important role for maintaining 3-Ф, half wave and quarter wave symmetries among multi level inverter pole voltages. This paper analytically shows the conditions for half wave and quarter wave symmetry and experimentally verifies those conditions for phase shifted pulse width modulation technique with a 5 level cascaded H-Bridge multi level inverter laboratory prototype. Keywords—cascaded H-Bridge multilevel inverter, phase shifted PWM, synchronous carrier, symmetry.