SST-Based 25-Level T-Type MLI for Integration of Microgrids

Abstract

The demand for independent dc sources and switching components is increasing and turned to be the primary challenge with multilevel inverters (MLIs) for integrating renewable energy sources. As a result, the component reduction is crucial in these systems. The introduction of cascaded MLIs based on solid-state transformers (SSTs) has significantly reduced the requirement for dc sources. This article proposes a novel SST-based MLI with a single dc source and two capacitors to generate 25 levels at the output. Two medium-frequency isolation transformers with different rated voltages make up the proposed MLI. A cascaded H-bridge (CHB) connects the primary windings of each transformer, and the secondary windings are connected in series with the load. The proposed SST-based MLI uses a simple nearest level control switching methodology to generate the nearest level. A laboratory prototype was built to assess the proposed SST-based MLI performance. The power loss analysis of the system is also discussed. The proposed SST topology is also compared with other recent topologies of similar type.