A Generalized Zero-Current-Transition Concept to Simplify Multilevel ZCT Converters

A concept of generic half-bridge zero-current-transition (ZCT) cell is developed, which employs one auxiliary switch and one LC resonant tank to assist switching transitions. Application of the concept leads to the discovery of a family of simplified multilevel multiphase soft-switching inverters, including two-level three-phase inverters using only three auxiliary switches and three-level three-phase inverters using six auxiliary switches. Unlike existing techniques, these inverters require no modification to normal space-vector modulation (SVM) schemes, and in the meantime achieve soft commutation for all main switches, diodes and auxiliary switches at all operation modes. Based on personal computer simulation program with integrated circuit emphasis (PSPICE) simulation using actual device models and including parasitic inductance, the simplified three-level ZCT inverters are analyzed in details, and its unique behaviors and limitations are investigated. Hardware implementation and experimental results are provided