Abstract: In the field of high voltage direct current (HVDC) power transmission, a converter comprises three converter limbs, each corresponding to a respective phase of the converter, each extending between first and second DC terminals and each including first and second limb portions separated by an AC terminal. Each limb portion includes a chain-link converter that is operable to provide a stepped variable voltage source, and a primary switching element to selectively switch the respective limb portion into and out of circuit. The converter also includes a first controller that is programmed to selectively operate for one converter limb at a time the primary switching element in each limb portion thereof to simultaneously switch both the first and second limb portions into circuit and thereby define a fully-conducting converter limb to sequentially route via each said fully-conducting converter limb a DC current demand (IDC) between the first and second DC terminals.

Abstract: A voltage source converter includes DC terminals, a plurality of single-phase limbs, and a controller. Each single-phase limb includes a phase element and switching elements. Each limb is connected between the DC terminals and is controllable to generate an AC voltage at the AC side of the corresponding phase element so as to draw a respective phase current from a multi-phase AC electrical network. The controller is configured to selectively generate a modified AC voltage demand for at least one limb in response to an imbalance in the phase currents and/or a change in electrical rating of at least one limb. The controller is configured to selectively control, in accordance with the or the respective modified AC voltage demand, the or each corresponding limb independently of the or each other limb to modify the voltage at the AC side of its phase element and thereby modify the corresponding phase current.

Abstract: A voltage source converter includes at least one limb connected between DC terminals, the or each limb including: a phase element including switching elements to interconnect a DC electrical network and an AC electrical network; an auxiliary sub-converter configured to be controllable to act as a waveform synthesizer to modify a first DC voltage presented to the DC electrical network; and a tertiary sub-converter connected in parallel with the electrical block and controllable to act as a waveform synthesizer to modify a second DC voltage presented to a DC side of the phase element, the tertiary sub-converter (39) including at least one energy storage device. The voltage source converter includes a controller configured to selectively control the or each tertiary sub-converter to synthesize at least one tertiary voltage component so as to transfer energy to or from that tertiary sub-converter and thereby regulate an energy level of that tertiary sub-converter.

Abstract: A voltage source converter includes three branches connected at a first end to a junction to form a star configuration, the second end of each branch defining a DC terminal, the second ends of the second and third branches being connectable to a first DC voltage, and the second ends of the first and second branches being connectable to a second DC voltage. The first and second branches include primary switching elements, and the third branch includes a primary inductive element. The converter includes a converter limb connected in parallel with one of the first and second branches, the converter limb including a chain-link auxiliary converter including multiple series-connected modules controllable to selectively provide a voltage source to modify a branch voltage across the branch connected in parallel with the converter limb, each module including at least one secondary switching element and at least one energy storage device.

Abstract: The present disclosure relates to control circuits. One circuit includes first and second primary terminals for connection to first and second power transmission lines and a current transmission path extending between the primary terminals and having current transmission path portions separated by a third primary terminal. A first current transmission path portion includes at least one primary switching element connected in series between the first and third primary terminals, the second current transmission path portion includes an energy conversion block connected between the second and third primary terminals, and the energy conversion block includes at least one primary energy conversion element for removing energy from the power transmission lines. The control circuit further includes a converter limb connected across the second and third primary terminals that includes an auxiliary converter.

Abstract: Described is an electrical machine, including: a rotor having a magnetic flux source mounted thereto; a stator winding arrangement having a first set of electrical connections to provide a first output channel, and a second set of electrical connections to provide a second output channel, the first and second channels being electrically out of phase, wherein the stator winding arrangement is constructed from a plurality of winding portions which are connected in electrical series.