Full SiC Three-Level T-Type Quasi-Z Source Inverter as Grid-Forming Unit in Islanded Nanogrid

Abstract

As the electricity landscape evolves towards greater penetration of renewable energy, voltage source inverters (VSIs) have established themselves as the key power electronics interface between distributed energy resources and the electrical power distribution in modern nanogrids (nGs), capable of working as grid-following (GFL) converters during grid-connected operation and as grid-forming (GFM) converters when islanded. As a relatively recent advanced inverter topology, the three-level T-type quasi-impedance source inverter (3L T-Type qZSI) offers the improved harmonic distortion and lower switching losses characteristic of the three-level T-type topology, combined with the boosting capability of the quasi-impedance source network, all within a single power stage. Despite the many benefits of this topology, neither the use of wide bandgap semiconductors for the power converter design nor the study of its feasibility in an islanded ac nG has been conducted. In this paper, a full silicon carbide (SiC) 3L T-Type qZSI experimental prototype was designed, assembled and tested in the context of an islanded nG with a hierarchical GFM control structure operating at a high switching frequency of 50 kHz. The performance of the 3L T-Type qZSI prototype and the overall nG system was verified by simulation and experimentally.