SERIES-PARALLEL MODULAR MULTI-LEVEL CONVERTER WITH CUT-OFF CAPABILITY AND CONTROL METHOD THEREOF

摘要

Disclosed are a series-parallel modular multi-level converter with cut-off capability and a control method thereof. The multi-level converter is of an ABC three-phase structure, each phase comprises an identical upper bridge arm (1.1) and lower bridge arm (1.2), each of the upper bridge arm (1.1) and the lower bridge arm (1.2) is composed of N sub-modules comprising M single-polarity full-bridge sub-modules (1.3) that are connected in series and N-M half-bridge sub-modules (1.4), and two identical bridge arm inductors (1.5, 1.6) are connected in series between the lower end of the upper bridge arm (1.1) and the upper end of the lower bridge arm (1.2) in the same phase; and the upper bridge arms (1.1) and the lower bridge arms (1.2) of different phases are connected in a staggered manner by means of six thyristor branches (1.7), the upper ends of the upper bridge arms (1.1) of the three phases are in short circuit and then are connected to the direct current side by means of a first isolation switch (1.8), and the lower ends of the lower bridge arms of the three phases are in short circuit and then are connected to the direct current side via a second isolation switch (1.9). According to the technical solution, the same output characteristic as a traditional three-phase modular multi-level converter can be realized, and meanwhile, the short-circuit current can be quickly extinguished when a short-circuit fault occurs on the direct-current side, such that short-circuit fault protection is realized.