A MODULAR MULTILEVEL CONVERTER FOR HANDLING AC SIDE FAULTS

摘要

A modular multilevel converter comprises a number of phase legs comprising cells (C1p1, … C5p1, C1n1, … C5n1) having a bipolar voltage contribution capability. The modular multilevel converter (14) also comprises a control unit (22) configured to enter a first protective control mode upon the detection of an operational disturbance of the converter, the first protective control mode comprising controlling all the bipolar voltage contribution cells to operate as unipolar voltage contribution cells, and if the operational disturbance is identified as a fault on a phase of a connected AC link, to block the cells of the phase leg connected to the phase for the remainder of the first protective control mode and control the cells of the phase legs connected to the healthy phases of the AC link to handle effects of the fault.