A converter station and a method for controlling a converter station

A converter station comprising at least two converters, including a first voltage source converter and a second voltage source converter,

• wherein the converter station is configured to be connected to a direct current (DC) system and to an alternating current (AC) system, wherein the DC system has two poles and the AC system has multiple phases, and
• wherein the first voltage source converter and the second voltage source converter are connectable to a respective one of the two poles and are connected to each other;
• the converter station further comprising a first converter control unit and a second converter control unit connected to the first voltage source converter and to the second voltage source converter, respectively,
• wherein the first converter control unit and the second converter control unit are configured to obtain phase currents of the first voltage source converter and phase currents of the second voltage source converter,
• wherein the first converter control unit and the second converter control unit further comprises a first damping controller and a second damping controller, respectively,
• wherein each one of the first damping controller and the second damping controller comprises a regulator,
• wherein the first damping controller is configured to determine first current differences between the phase currents of the first and second voltage source converters, and the second damping controller is configured to determine second current differences between the phase currents of the first and second voltage source converters, wherein the first damping controller is configured to determine the first current differences by subtracting the phase currents of the second voltage source converter from the phase currents of the first voltage source converter, and the second damping controller is configured to determine the second current differences by subtracting the phase currents of the first voltage source converter from the phase currents of the second voltage source converter,
• wherein the first and second damping controllers are configured to multiply the first current differences and the second current differences, respectively, with a respective gain for generating first damping control signals and second damping control signals, respectively, wherein the gain introduced by means of the regulator, and
• wherein the first converter control unit is further configured to combine the first damping control signals with a converter reference voltage of the first voltage source converter and the second converter control unit is further configured to combine the second damping control signals with a converter reference voltage of the second voltage source converter, in order to provide respective modified converter reference voltages for the first voltage source converter and the second voltage source converter.