SYNCHRONIZING GRID SIDE HARMONIC FILTER AND PRE-CHARGING CELL CAPACITORS IN MODULAR MULTILEVEL CONVERTERS

Synchronizing a grid side harmonic filter and pre-charging cell capacitors in modular multilevel converters can be achieved by: opening a transmission circuit breaker disposed on a first path between a power grid and a converter system; closing a pre-charging contactor disposed on a second path between the power grid and the converter system that includes a set of pre-charge resistors; connecting the power grid to the converter system and the harmonic filter over the second path; selectively charging cell capacitors in the converter system until a charge threshold is reached, wherein a smaller subset of the cell capacitors is charged at a given time than in an earlier time, and each cell capacitor is charged to a higher cell voltage than in the earlier time; and closing the transmission circuit breaker and connecting a generator to the converter system via a generator circuit breaker while leaving the pre-charging contactor closed.