Conventional H-bridge and recent multilevel inverter topologies

Abstract

Traditional H-bridge inverters are composed of four switches controlled with any SPWM strategy, such as bipolar, unipolar, or hybrid. Among these methods, the bipolar SPWM reduces the leakage current by providing constant CMV. Researchers have proposed some alternative multilevel inverter topologies to overcome drawbacks seen in isolated and nonisolated inverters. The H5 and H6 topologies are constructed to manage a DC side bypass operation, while the HERIC inverter topologies use an AC side bypass operation. The H5 inverter topology uses an extra switch at the positive terminal of the DC link. On the other hand, the H6 topology is improved by using a similar topology to the H5 inverter but with an additional switch connected to the negative terminal of the H5 inverter topology. These topologies reduce the leakage current and THD. In addition to this, HERIC ensures higher efficiency, due to using extra switches only in the freewheeling mode. This chapter deals with conventional and recent multilevel inverter topologies that are mostly derived from H4 topology.