Abstract: An interface arrangement is configured to couple an alternating current, AC, power system with a direct current, DC, power system, or vice versa. The interface arrangement includes a plurality of series-connected converter modules. Each converter module includes at least one multi-level converter cell configured to provide a voltage contribution to at least a portion of an AC waveform for example based on voltage of the DC power system. Each converter module includes at least one converter valve, electrically connected to the multi-level converter cells and including at least two anti-parallel thyristors. The converter valves are switchable between conducting states with a selected current conduction direction and a non-conducting state so as to selectively control polarity of any voltage contribution provided by the at least one multi-level converter cell. The converter valves can also serve as fault protection, e.g. to divert overcurrents.

Abstract: A voltage source converter includes a number of converter modules, one for each of a number of phases, connected in-series between two DC terminals. Each converter module includes an upper director valve in series with a lower director valve, where a junction between the two provides a primary AC terminal, an upper wayshaper section, a common waveshaper block and a lower waveshaper section in parallel with the valves, where the upper and lower waveshaper sections include multilevel cells and the common waveshaper block include at least one common waveshaper connected between the upper and lower waveshaper sections, a first switching element connected between a secondary AC terminal and the upper waveshaper section and a second switching element connected between the secondary AC terminal and the lower waveshaper section.

Abstract: A voltage source converter includes a number of converter modules, one for each of a number of phases, connected in-series between two DC terminals. Each converter module includes an upper director valve in series with a lower director valve, where a junction between the two provides a primary AC terminal, an upper waveshaper section, a common waveshaper block and a lower waveshaper section in parallel with the valves, where the upper and lower waveshaper sections include multilevel cells and the common waveshaper block include at least one common waveshaper connected between the upper and lower waveshaper sections, a first switching element connected between a secondary AC terminal and the upper waveshaper section and a second switching element connected between the secondary AC terminal and the lower waveshaper section.

Abstract: A voltage source converter has director valve phase legs in parallel with waveshaper phase legs between two DC terminals. The director valve and waveshaper phase legs include upper and lower phase arms alternately operated to form waveshapes on AC terminals of the converter, thereby allowing a number of waveshaper phase arms to be available for use for other purposes. At least one of the available phase arms is controlled to contribute to other aspects of converter operation than waveshaping.

Abstract: A voltage source converter has director valve phase legs in parallel with waveshaper phase legs between two DC terminals. The director valve and waveshaper phase legs include upper and lower phase arms alternately operated to form waveshapes on AC terminals of the converter, thereby allowing a number of waveshaper phase arms to be available for use for other purposes. At least one of the available phase arms is controlled to contribute to other aspects of converter operation than waveshaping.

Abstract: An interface arrangement is configured to couple an alternating current, AC, power system with a direct current, DC, power system, or vice versa. The interface arrangement includes a plurality of series-connected converter modules. Each converter module includes at least one multi-level converter cell configured to provide a voltage contribution to at least a portion of an AC waveform for example based on voltage of the DC power system. Each converter module includes at least one converter valve, electrically connected to the multi-level converter cells and including at least two anti-parallel thyristors. The converter valves are switchable between conducting states with a selected current conduction direction and a non-conducting state so as to selectively control polarity of any voltage contribution provided by the at least one multi-level converter cell. The converter valves can also serve as fault protection, e.g. to divert overcurrents.

Abstract: A voltage source converter includes a number of valves, the valves including switching elements with anti-parallel diodes provided in a bridge for switching between two states. The bridge is provided in at least one phase leg that stretches between two direct current poles and has at least one midpoint, which is connected to an alternating current terminal. The switching element of at least one valve is a thyristor. The converter further includes a commutation cell associated with the valve, where the commutation cell is controllable to reverse-bias the valve if it is to stop conducting current.

Abstract: An arrangement for tapping power from a DC power line to an AC power line includes power transfer modules between two DC potentials, each including a first branch with a string of converter cells in parallel with a second branch including a capacitor and being connected to an AC phase. There is at least one control unit that controls the arrangement considering one or more of a) distributing appropriate AC and DC voltages in converter output voltages of all series connected modules, b) maintaining/setting cell capacitor voltages in specific range and allowing boost mode operation, c) performing possible balancing of the introduced capacitor and d) employing an alternate approach of using passive filters to mitigate low order harmonics.

Abstract: An arrangement for tapping power from a DC power line to an AC power line includes power transfer modules between two DC potentials, each including a first branch with a string of converter cells in parallel with a second branch including a capacitor and being connected to an AC phase. There is at least one control unit that controls the arrangement considering one or more of a) distributing appropriate AC and DC voltages in converter output voltages of all series connected modules, b) maintaining/setting cell capacitor voltages in specific range and allowing boost mode operation, c) performing possible balancing of the introduced capacitor and d) employing an alternate approach of using passive filters to mitigate low order harmonics.

Abstract: A voltage source converter includes a number of valves, the valves including switching elements with anti-parallel diodes provided in a bridge for switching between two states. The bridge is provided in at least one phase leg that stretches between two direct current poles and has at least one midpoint, which is connected to an alternating current terminal. The switching element of at least one valve is a thyristor. The converter further includes a commutation cell associated with the valve, where the commutation cell is controllable to reverse-bias the valve if it is to stop conducting current.

Abstract: It is presented a high voltage DC/DC converter for converting between a first DC connection and a second DC connection. The high voltage DC/DC converter comprises: a first set of DC terminals; a second set of DC terminals); a multiphase transformer device comprising a plurality of primary windings and a corresponding plurality of secondary windings; a first converter arranged to convert DC to AC, comprising a plurality of phase legs serially connected between the first set of DC terminals, wherein each phase leg is connected to an AC connection of a respective primary winding; and a second converter arranged to convert AC from the secondary windings to DC on the second set of DC terminals.

Abstract: An arrangement transmits power between a DC power line and an AC power line carrying a voltage having a number of phases. The arrangement includes a number of transformers, one for each phase and a number of power transfer modules, one for each phase, connected in series between the DC power line and ground, where each module includes a first branch including series connected converter cells and a second branch including series connected switching elements. The primary winding of a transformer is connected to a corresponding AC phase conductor of the AC power line and the secondary winding is connected between a midpoint of the first branch and a midpoint of the second branch of a corresponding power transfer module.

Abstract: It is presented a high voltage DC/DC converter for converting between a first DC connection and a second DC connection. The high voltage DC/DC converter comprises: a first set of DC terminals; a second set of DC terminals); a multiphase transformer device comprising a plurality of primary windings and a corresponding plurality of secondary windings; a first converter arranged to convert DC to AC, comprising a plurality of phase legs serially connected between the first set of DC terminals, wherein each phase leg is connected to an AC connection of a respective primary winding; and a second converter arranged to convert AC from the secondary windings to DC on the second set of DC terminals.

Abstract: The present invention relates to an AC/DC converter comprising at least two phase legs connected in series between first and second DC connection terminals of the AC/DC converter, wherein each phase leg comprises: an AC connection having first and second terminals arranged to connect the phase leg to a phase of an AC system; a phase branch comprising at least one converter cell and having first and second branch end terminals; and a capacitor. The capacitor is connected the between the first branch end terminal and the first AC connection terminal, so that the capacitor forms a DC blocking capacitor. The second AC terminal is connected to the second branch end terminal. The series connection of the phase legs between first and second DC connection terminal is such that a first series connection point in a phase leg is located between the first branch end terminal and the capacitor, while a second series connection point is located between the second branch end terminal and the second AC connection.

Abstract: An arrangement transmits power between a DC power line and an AC power line carrying a voltage having a number of phases. The arrangement includes a number of transformers, one for each phase and a number of power transfer modules, one for each phase, connected in series between the DC power line and ground, where each module includes a first branch including series connected converter cells and a second branch including series connected switching elements. The primary winding of a transformer is connected to a corresponding AC phase conductor of the AC power line and the secondary winding is connected between a midpoint of the first branch and a midpoint of the second branch of a corresponding power transfer module.

Abstract: An apparatus for controlling the electric power transmission in a high voltage direct current, HVDC, power transmission system includes at least one HVDC transmission line for carrying direct current, DC. The apparatus includes a first converter for converting alternating current, AC, to direct current and/or direct current to alternating current, and a second converter for converting direct current to alternating current and/or alternating current to direct current, each of the first and second converters having an AC side for output and/or input of alternating current and a DC side for output and/or input of direct current. The first converter is connectable via its DC side to the HVDC transmission line, the AC side of the second converter is connected to the AC side of the first converter, and the second converter is connectable via its DC side to a DC source.

Abstract: The present invention relates to an AC/DC converter comprising at least two phase legs connected in series between first and second DC connection terminals of the AC/DC converter, wherein each phase leg comprises: an AC connection having first and second terminals arranged to connect the phase leg to a phase of an AC system; a phase branch comprising at least one converter cell and having first and second branch end terminals; and a capacitor. The capacitor is connected the between the first branch end terminal and the first AC connection terminal, so that the capacitor forms a DC blocking capacitor. The second AC terminal is connected to the second branch end terminal. The series connection of the phase legs between first and second DC connection terminal is such that a first series connection point in a phase leg is located between the first branch end terminal and the capacitor, while a second series connection point is located between the second branch end terminal and the second AC connection.