SWITCHING CONTROL METHOD OF MODULAR MULTILEVEL CONVERTER FOR VOLTAGE BALANCING OF SUB-MODULE GROUP

摘要

The present invention relates to a switching method for a module type multilevel converter and, more specifically, to a switching method for a module type multilevel converter, capable of remarkably reducing time for sorting a voltage value of each sub module by allocating the number of modules to be switched for each group by grouping the sub modules, and maintaining voltage balance between the groups by additionally allocating the module to be switched to a sub module group having a maximum or minimum voltage. The switching method for the module type multilevel converter includes: a step of dividing multiple sub modules into the multiple sub module groups comprising the same number of the different sub modules; a step of receiving a command value voltage level by a switching controller and comparing a current voltage level to the command value voltage level; a step of maintaining a current switch state of each sub module by the switching controller in case the current voltage level and the command value voltage level are identical and calculating the number of the modules to be switched in each sub module group by dividing the command value voltage level by the number of the sub module group in case the current voltage level and the command value voltage level are different; and a step of switching on a switch in each sub module group as many as the number of the switching modules by the switching controller.