This webinar will present the best paper selected from the IEEE Trans. Power Delivery special section "Frontiers of DC technology". The webinar will also provide an overview the papers published in the special section The paper to be presented introduces a new thyristor-augmented multilevel structure called a Power-Group (PG), which replaces the stacks of SMs in modular converters. Each PG is formed out of a series stack of SMs with a parallel force-commutated thyristor branch, which is used during normal operation as a low loss bypass path in order to achieve a significant reduction in overall losses. The PG also offers negative voltage capability and so can be used to construct high-efficiency DC fault tolerant converters. Estimates indicate that this concept could result in converter topologies with power losses as low as 0.3% rated power while retaining high-quality current waveforms and achieving tolerance to both AC and DC faults.