Thyristor-Based T-Type Converter With Modular Multilevel DC-Link

This article proposes a thyristor-based T-type converter with modular multilevel dc-link (TTC-MMD), where the thyristor-based T-type converter provides the basic phase commutation capability and two arms of cascaded submodules in dc-link generate the multilevel switching line voltages. To guarantee the successful turn-
on
and turn-
off
of thyristors, one full-bridge submodule (FBSM) is embedded in each arm. In addition, the FBSM can also be employed to participate in the multilevel switching modulation. For real applications, the TTC-MMD can be employed as a medium-/high-voltage static synchronous compensator, which features triplen frequency fluctuation of capacitor voltages and easy balancing of capacitor voltage under various operation conditions due to the common dc-link shared for three phases. It can also be implemented in other medium-/high-voltage applications. Finally, simulation and experimental results verified the performance of the proposed converter.