Multilevel voltage source converter and method for balancing capacitors

摘要

A control apparatus for use with a voltage source converter includes legs, each of which is configured by a plurality of converter modules each having a capacitor. Each of the legs has a first terminal on a positive side and a second terminal on a negative side. The control apparatus is configured to create command pulses for operating the converter modules. The command pulses have a frequency that is a non-integer multiple of a frequency of a system voltage. The non-integer multiple may be, for example, 3.5.

主权项

1. A control apparatus for use with a voltage source converter, comprising:
legs each of which is configured by a plurality of converter modules each having a capacitor, wherein
each of said legs has a first terminal on a positive side and a second terminal on a negative side,said control apparatus is configured to create command pulses for operating the converter modules,the at least one of the plurality of converter modules has a switching device,controlling of the switching device causes electrical energy to travel into and out of the capacitor via the first and second terminals,connecting of the first and second terminals causes at least some of the plurality of converter modules to be connected in series,a frequency of the command pulses is a non-integer multiple of a frequency of a system voltage so as to reduce a respective difference, for respective converter modules, of voltages charged in the capacitor of the plurality of converter modules, andtwice of the frequency of the command pulses is an integer multiple of the frequency of the system voltage.