An arrangement for exchanging power with a three-phase electric power network comprises a Voltage Source Converter having three phase legs with each a series connection of switching cells. The three phase legs are interconnected by forming a delta-connection. The arrangement also includes a control unit configured to calculate a value for amplitude and phase position for a zero-sequence current for which, when circulated in the delta-connection circuit of the three phase legs, the balance of the total direct voltage of each of the three phase legs with respect to the other two phase legs is restored will there be an unbalance and control the semiconductor devices of switching cells of the phase legs to add such a zero-sequence current to the currents of each phase leg of the converter.