Abstract: A device for converting a DC voltage into an AC voltage and vice versa comprises at least one phase leg with a first voltage source and a first inductor connected in series between a first DC terminal and a first AC terminal and with a second inductor and a second voltage source connected in series between the first AC terminal and a second DC terminal, where each of the voltage sources comprises at least a first and a second submodule in series-connection, each submodule comprising at least one power electronic switch connected in parallel with at least one capacitor. In the device, a passive electronic filter is arranged between the first and the second inductor as well as the first AC terminal for reducing harmonics in a circulating current.

Abstract: A Voltage Source Converter having at least one phase leg connected to opposite poles of a direct voltage side of the converter and comprising a series connection of switching cells has inductance means comprising a plurality of inductors (23) built in in said series connection of switching cells (7?) and connected in series with these cells by being connected to terminals (14, 15) thereof.

Abstract: A plant for transmitting electric power through HVDC comprises two converter stations interconnected by a bipolar direct voltage network and each connected to an alternating voltage network. Each converter station has a Voltage Source Converter with switching cells each including at least one energy storing capacitor. The Voltage Source Converters are configured to utilize a direct voltage having a higher magnitude for a first of the poles than for a second thereof with respect to ground.

Abstract: A Voltage Source Converter having at least one phase leg connected to opposite poles of a direct voltage side of the converter and comprising a series connection of switching elements including at least one energy storing capacitor and configured to obtain two switching states, namely a first switching state and a second switching state, in which the voltage across said at least one energy storing capacitor and a zero voltage, respectively, is applied across the terminals of the switching element, has semiconductor chips of said switching elements arranged in stacks comprising each at least two semiconductor chips. The converter comprises an arrangement configured to apply a pressure to opposite ends of each stack.

Abstract: A high voltage dry-type reactor is series-connected via a first terminal to an AC supply voltage and via a second terminal to the AC phase terminal of a high voltage converter and includes a cylindrical coil of insulated wire. In order to protect the reactor from a damaging DC field, the reactor further includes a metallic or resistive electrostatic shield which is connected to a same DC potential as the converter.

Abstract: An air-core reactor with natural-air cooling of a winding includes first open spaces to let air flow through the winding in parallel with an axis of symmetry of the reactor and second open spaces crossing the first open spaces to let air flow through the winding angular to the axis of symmetry. A ventilation unit to produce a forced-air flow is arranged in such a way to the air-core reactor that a first part of the forced-air flow enters one of the first or second open spaces and at least one guiding element is arranged with respect to the crossing of the first and the second open spaces in such a way that the first part of the forced-air flow leaves and a second part of the forced-air flow enters the one of the first or second open spaces. A shielding element is arranged at another crossing of the first and the second open spaces so that substantially no air can leave or enter the one of the first or second open spaces.

Abstract: A converter for converting alternating voltage into direct voltage and vice versa in a converter station of a high voltage transmission system. A series connection of converter valves includes power semiconductor devices connected in series and arranged in superimposed layers. The valves are arranged on top of each other in a column. Coolant liquid conducting tubes are in an extension over at least one part of the circumference of the column having no connections to cooling blocks for cooling the devices made of metal. Such metal tubes are arranged in the part for over this part of the column circumference forming an electric field shielding screen. The coolant liquid conducting tubes are when extending over parts of a circumference of the column where connections are made to cooling blocks made of an electrically insulating material. An electric field shield is arranged outside the column over these parts.

Abstract: In a VSC-converter for converting direct voltage to alternating voltage and conversely at least one phase leg (2) is arranged according to a NPC-connection. At least two of the four current valves (3-6) and the clamping rectifying members (10, 11) thereof are arranged close to each other and so that commutation currents generated on commutation of the converter therein will flow in substantially opposite directions.