Cascaded H‐Bridge Multilevel Inverters

This chapter reviews the single‐phase H‐bridge power cell, which is the building block for the cascaded H‐bridge (CHB) inverter and introduces various inverter topologies. The inverter DC bus voltage is usually fixed while its AC output voltage can be adjusted by either bipolar or unipolar modulation schemes. The chapter analyses two carrier‐based pulse‐width‐modulated (PWM) schemes, phase‐shifted and compares level‐shifted modulations and their performance. It presents a staircase modulation with selective harmonic elimination. Similar to the phase‐shifted modulation, a CHB inverter using level‐shifted multicarrier modulation scheme requires triangular carriers, all having the same frequency and amplitude. The chapter presents some of the figures that show three schemes for the level‐shifted multicarrier modulation: in‐phase disposition (IPD), alternative phase opposite disposition (APOD) and phase opposite disposition (POD). It discusses only IPD modulation scheme and provides the best harmonic profile of all three modulation schemes.