Abstract: An electronic valve apparatus for a high voltage direct current, HVDC, power transmission system. The electronic valve apparatus includes a first device chain including a number of first devices connected in series between an input node and an output node. Each of the first devices has an asymmetric transfer function configured substantially to block current flow through the device in a first direction, and the first devices are connected such that they all block current flow in the same direction. The electronic valve apparatus also includes a second device chain including a number of second devices connected in series between the input node and the output node. Each of the second devices has an asymmetric transfer function configured substantially to block current flow through the device in a first direction, and the second devices are connected such that they all block current flow in the same direction.

Abstract: The present disclosure relates to a voltage source converter (VSC) (300) comprising: a first MOSFET switching element (302) including a first body diode (306); a second MOSFET switching element (304) including a second body diode (308), the second MOSFET switching element (304) being connected in series with the first MOSFET switching element (302); a protection device (318) connected in parallel with the second MOSFET switching element (304); and a controller (312), wherein the controller (312) is configured, on detection of an overcurrent event, to: switch off the first MOSFET switching element (302); and switch off the second MOSFET switching element (304), thereby forcing current flowing in the VSC (300) following the overcurrent event to flow through the second body diode (308) rather than through conducting channels of the first and second MOSFET switching elements (302, 304).

Abstract: A switching apparatus (20) comprises first and second current paths, each current path configured to be capable of conducting an electrical current, the first current path including a first switching element (28) connected in parallel with a first passive current check element (30), the switching apparatus (20) further including a switching controller configured to selectively control the switching of the first switching element (28), wherein the switching controller is configured to selectively switch the first switching element (28) at a first intra-current path switching speed to commutate the electrical current between the first switching element (30) and the first passive current check element (32), the switching controller is configured to selectively switch the first switching element (28) at a first inter-current path switching speed to commutate the electrical current between the first and second current paths, and the first intra-current path switching speed is faster or slower than the first inter-

Abstract: This application relates to a cell (1200) or sub-module for a voltage source converter (1201). The cell includes an energy storage apparatus (101; 101a, 101b) and a plurality of dual-switch semiconductor packages (201), each having first and second semiconductor switches (202, 203) connected in series. The cell is operable in an active state in which an energy storage apparatus (101; 101a, 101b) is electrically connected in series between cell terminals (102a, 102b) and a bypass state in the cell terminals (102a, 102b) are electrically connected via a path that bypasses the first energy storage apparatus.

Abstract: A switching apparatus (20) comprises first and second current paths, each current path configured to be capable of conducting an electrical current, the first current path including a first switching element (28) connected in parallel with a first passive current check element (30), the switching apparatus (20) further including a switching controller configured to selectively control the switching of the first switching element (28), wherein the switching controller is configured to selectively switch the first switching element (28) at a first intra-current path switching speed to commutate the electrical current between the first switching element (30) and the first passive current check element (32), the switching controller is configured to selectively switch the first switching element (28) at a first inter-current path switching speed to commutate the electrical current between the first and second current paths, and the first intra-current path switching speed is faster or slower than the first inter-

Abstract: The present disclosure relates to an electronic valve apparatus for a high voltage direct current, HVDC, power transmission system. The electronic valve apparatus comprises a first device chain (301) including a plurality of first devices (302, 303) connected in series between an input node (330) and an output node (332) of the electronic valve apparatus (300, 400, 500). Each of the plurality of first devices (302, 303) has an asymmetric transfer function configured substantially to block current flow through the device in a first direction, and the plurality of first devices (302, 303) are connected such that they all block current flow in the same direction. The electronic valve apparatus also includes a second device chain (311) including a plurality of second devices (312, 313) connected in series between the input node (330) and the output node (332).

Abstract: A method of controlling a voltage source converter including at least one converter limb, each converter limb including limb portions, at least one limb portion including a chain-link converter having modules, each module including at least one switching element and at least one energy storage device, which combine to selectively provide a voltage source, comprising the steps of: establishing during an operating cycle of the chain-link converter a utilization peak based on the actual peak number of modules providing a voltage source; establishing a target utilization based on a desired number of modules providing a voltage source during the operating cycle; and determining a control function based on a difference between the established utilization peak and the target utilization which alters the peak number of modules providing a voltage source during a subsequent operating cycle of the chain-link converter so as to drive the utilization peak towards the target utilization.

Abstract: A method of controlling a voltage source converter (10) including at least one converter limb (16A, 16B, 16C), the or each converter limb (16A, 16B, 16C) extending between first and second DC terminals (12, 14) and including first and second limb portions (18A, 18B, 18C, 20A, 20B, 20C) separated by an AC terminal (22A, 22B, 22C), at least one limb portion (18A, 18B, 18C, 20A, 20B, 20C) including a chain-link converter (28) having a plurality of series-connected modules (30), each module (30) including at least one switching element (32) and at least one energy storage device (34), the or each switching element (32) and the or each energy storage device (34) of each module (30) combining to selectively provide a voltage source (VIND) whereby the corresponding chain-link converter (128) is operable to provide a stepped variable voltage source (VA+, VB+, VC+, VA?, VB?, VC?), comprises with respect to at least one chain-link converter (28) the steps of: (a) establishing during an operating cycle of the chain-link

Abstract: This application relates to a cell (1200) or sub-module for a voltage source converter (1201). The cell includes an energy storage apparatus (101; 101a, 101b) and a plurality of dual-switch semiconductor packages (201), each having first and second semiconductor switches (202, 203) connected in series. The cell is operable in an active state in which an energy storage apparatus (101; 101a, 101b) is electrically connected in series between cell terminals (102a, 102b) and a bypass state in the cell terminals (102a, 102b) are electrically connected via a path that bypasses the first energy storage apparatus.

Abstract: The present disclosure relates to a voltage source converter (VSC) (300) comprising: a first MOSFET switching element (302) including a first body diode (306); a second MOSFET switching element (304) including a second body diode (308), the second MOSFET switching element (304) being connected in series with the first MOSFET switching element (302); a protection device (318) connected in parallel with the second MOSFET switching element (304); and a controller (312), wherein the controller (312) is configured, on detection of an overcurrent event, to: switch off the first MOSFET switching element (302); and switch off the second MOSFET switching element (304), thereby forcing current flowing in the VSC (300) following the overcurrent event to flow through the second body diode (308) rather than through conducting channels of the first and second MOSFET switching elements (302, 304).

Abstract: In the field of voltage assemblies with a charge storage capability for use in high voltage direct current converters there is provided a corona shield. The corona shield includes a peripheral frame which is formed from one or more frame members and within which lies a frame aperture. The corona shield also includes a barrier member that is fixedly secured to the peripheral frame. The barrier member extends across and occludes the frame aperture to inhibit bodily ingress through the frame aperture.

Abstract: A power semiconductor module including a housing within which lies at least one semiconductor switching element. The housing includes a vent aperture that is selectively openable and closeable by a cooperating vent cover. The vent cover is held in an open position during normal operation of the power semiconductor module to open the vent aperture and provide ventilation for the or each semiconductor switching element within the housing.

Abstract: Fault protection of a voltage source converter is provided. An apparatus has a chain-link circuit in series with a director switch. The chain-link circuit includes cells including an energy storage element and cell switching elements connected with anti-parallel diodes. Each cell switching element has a cell switching element controller. The director switch includes director switch units, each having a director switching element and a director switch unit controller. Each cell switching element controller monitors for a fault current and turns-off its associated cell switching element and reports a fault event to a fault controller. Each director switch unit controller monitors for a fault current and reports a fault event to the fault controller but the director switch unit control keeps its associated director switching element turned-on. The fault controller monitors for reports of fault events to order the cell switching elements of at least some of the cells to turn-off.

Abstract: An electrical bypass apparatus is provided, which comprises first and second terminals for connection across an electrical component; an electrically-triggered bypass switch being switchable to form a short circuit across the first and second terminals; and a first control circuit connected between the first and second terminals. The first control circuit includes mutually coupled first and second windings, the first winding being isolated from the second winding. The first control circuit is configured to inhibit a current flowing between the first and second terminals from flowing through the first winding when a normal operating voltage is present across the first and second terminals; and to permit a current to flow between the first and second terminals and through the first winding when an overvoltage is present across the first and second terminals and thereby induce a current pulse in the second winding.

Abstract: This application describes methods and apparatus for achieving voltage balancing of clamp capacitors of director switch units of a voltage source converter (VSC). An arm or director switch may be formed from a number of director switch units connected in series, each director switch unit having a semiconductor switching element such as an IGBT. Typically a clamp capacitor may be connected across the IGBT. In some arrangements a floating power supply may draw power from the clamp capacitor to provide power for the director switch unit. In the present application the director switch unit is operable in a voltage balancing mode such that the power drawn from the clamp capacitor varies based on the voltage across the clamp capacitor. In this way the power demand for power drawn from the clamp capacitor may have the characteristic of a resistive load.

Abstract: Fault protection of a voltage source converter is provided. An apparatus has a chain-link circuit in series with a director switch. The chain-link circuit includes cells including an energy storage element and cell switching elements connected with anti-parallel diodes. Each cell switching element has a cell switching element controller. The director switch includes director switch units, each having a director switching element and a director switch unit controller. Each cell switching element controller monitors for a fault current and turns-off its associated cell switching element and reports a fault event to a fault controller. Each director switch unit controller monitors for a fault current and reports a fault event to the fault controller but the director switch unit control keeps its associated director switching element turned-on. The fault controller monitors for reports of fault events to order the cell switching elements of at least some of the cells to turn-off.

Abstract: In the field of voltage assemblies with a charge storage capability for use in high voltage direct current converters there is provided a corona shield. The corona shield includes a peripheral frame which is formed from one or more frame members and within which lies a frame aperture. The corona shield also includes a barrier member that is fixedly secured to the peripheral frame. The barrier member extends across and occludes the frame aperture to inhibit bodily ingress through the frame aperture.

Abstract: A power semiconductor module including a housing within which lies at least one semiconductor switching element. The housing includes a vent aperture that is selectively openable and closeable by a cooperating vent cover. The vent cover is held in an open position during normal operation of the power semiconductor module to open the vent aperture and provide ventilation for the or each semiconductor switching element within the housing.

Abstract: Circuits comprising at least one energy storage device, a resistor and switch arranged in series with the resistor are described. The energy storage device is arranged in parallel with the series connection of the switch and the resistor, and the switch is arranged to selectively switch the resistor into a parallel connection to the energy storage device. In some examples, the switch comprises a series connection of semiconductor switching elements. In some examples, the circuit may comprise a sub-module for use in a multilevel modular converter.

Abstract: There is provided a capacitor unit, for use as a high voltage device, comprising: a capacitor element; a housing (including a plurality of walls arranged to contain the capacitor element within the housing, the plurality of walls including first and second end walls, the plurality of walls further including a side wall extending between the end walls, the outer surface of the side wall being larger than the outer surface of each end wall; and at least one capacitor terminal electrically connected to the capacitor element, wherein the or each capacitor terminal is mounted on or extends through the side wall.