An arrangement for exchanging power

摘要

An arrangement for exchanging power with a three-phase electric power network (1 ) comprises a Voltage Source Converter (6) having three phase legs (7-9) with each a series connection of switching cells (10). The three phase legs are interconnected in a neutral point (22) by forming a wye-connection. The arrangement also comprises a device (27) connected to the neutral point (22) of the converter and configured to provide a current path for a zero-sequence current. A control unit (25) is configured to calculate a value for amplitude and phase position for a zero-sequence current for which, when added to said three phase legs upon generation of a negative-sequence current, the resulting energy stored in energy storing capacitors (19) in each phase leg will be constant and to control semiconductor devices of said switching cells to add such a zero-sequence current to the currents of each phase leg of the converter.