Patent ID: 8665617

Claim:
A plant for transmitting electric power comprising a direct voltage network for High Voltage Direct Current and at least one three-phase alternating voltage network connected thereto through a station, in which the station is configured to perform transmitting of electric power between the direct voltage network and the alternating voltage network and comprises at least one Voltage Source converter configured to convert direct voltage into alternating voltage and conversely and a unit configured to control said converter according to a Pulse Width Modulation (PWM) pattern for generating an alternating voltage in each of three phase legs of the converter having a third harmonic voltage part added to a fundamental voltage part, where the fundamental voltage part has the same frequency as the alternating voltage on said alternating voltage network, wherein the direct voltage on the direct voltage network is adapted to a peak value of the alternating voltage of said alternating voltage network, the alternating voltage network is connected to phase outputs of each said phase leg without any intermediate full transformer, and the plant further comprises an arrangement connected to each said phase leg and configured to block said third harmonic voltage part and to prevent said third harmonic voltage part from reaching the alternating voltage network, wherein said arrangement comprises at least one third harmonic blocking filter with an inductor and a capacitor for each said phase leg, and the inductor and the capacitor are connected in parallel.