Method And Apparatus For Calculating Insertion Indeces For A Modular Multilevel Converter

摘要

A method for calculating insertion indices for a phase leg of a DC to AC modular multilevel converter. Each phase leg includes two serially connected arms, wherein each arm includes a number of submodules, wherein each submodule can be in a bypass state or a voltage insert mode. The insertion index includes data representing the portion of available submodules that should be in the voltage insert mode. The method includes the steps of: calculating a desired arm voltage for an upper arm connected to the upper DC source common bar and a lower arm connected to the lower DC source common bar, obtaining values representing actual total arm voltages in the upper arm and lower arm, respectively, and calculating modulation indices for the upper and lower arm, respectively, using the respective desired arm voltage and the respective value representing the total actual arm voltage. A corresponding apparatus is also presented.