Abstract: There is provided an electrical assembly including at least one power converter and at least one dynamic reactive power source, the or each power converter and the or each dynamic reactive power source connectable to an AC network, the or each power converter and the or each dynamic reactive power source operable to exchange reactive power with the AC network, wherein the or each dynamic reactive power source is configured to selectively adjust its exchange of reactive power with the AC network in response to a characteristic of a reactive current demand of the or each power converter crossing a or a respective reactive current characteristic threshold.

Abstract: A bipole power transmission scheme includes a first converter station positioned in-use remote from a second converter station, and first and second transmission conduits to in-use interconnect the first converter station with the second converter station and thereby permit the first converter station to transmit power to the second converter station. The first converter station includes a first power converter, a second power converter, and a converter station controller which is programmed to selectively transition the bipole power transmission scheme into an asymmetrical monopole configuration, while maintaining the transfer of power from both the first and second power sources.

Abstract: In the field of high voltage direct current (HVDC) power transmission networks there is a need for an improved power converter. A power converter, for use in a HVDC power transmission network, comprises first and second DC terminals, for connection in use to a DC network and between which extends at least one converter limb. The or each converter limb includes first and second limb portions which are separated by an AC terminal, for connection in use to an AC network. Each limb portion includes a switching valve, and the power converter including a controller programmed to control switching of the switching valves to control the flow of a converter current (Imax) through the power converter and thereby in-use transfer power between the power converter and the AC network. The power transferred between the power converter and the AC network has an active component and a reactive component.

Abstract: A bipole power transmission scheme includes a first converter station that is positioned, in-use, remote from a second converter station. First and second transmission conduits and a return conduit interconnect, in-use, the first converter station with the second converter station and thereby permit the transfer of power between the first and second converter stations. The first converter station includes a first power converter, a second power converter, and a converter station controller.

Abstract: There is provided a switching valve for a voltage source converter, the switching valve including a number of modules, each module including at least one switching element and at least one energy storage device, the or each switching element and the or each energy storage device in each module arranged to be combinable to selectively provide a voltage source, the switching valve including a controller programmed to selectively control the switching of the switching elements to select one or more of the modules to contribute a or a respective voltage to a switching valve voltage.

Abstract: Embodiments of the disclosure include an electrical assembly. The electrical assembly can include a converter including a DC side and an AC side, the DC side configured for connection to a DC network, the AC side configured for connection to an AC network, the converter including at least one switching element; a circuit interruption device operably connected to the AC side of the converter; a DC voltage modification device operably connected to the DC side of the converter, the DC voltage modification device including a DC chopper; and a controller configured to selectively control the or each switching element, the circuit interruption device and the DC voltage modification device, wherein the controller is configured to be responsive to a converter internal fault by carrying out a fault operating mode.

Abstract: The present disclosure an include an electrical assembly comprising a power converter having an AC side and a DC side, the AC side for connection to an AC network; at least one power transmission medium connected to the DC side of the power converter; a dynamic braking system operably connected to the or each power transmission medium, the dynamic braking system including a dynamic braking control unit programmed to selectively control activation of the dynamic braking system to carry out a dynamic braking operation; a monitoring unit for monitoring an electrical parameter of the AC network; and a processing unit programmed to determine an operating state of the AC network from the monitored electrical parameter, wherein the dynamic braking control unit is programmed to be responsive to the determined operating state of the AC network by configuring the dynamic braking system to be activatable.

Abstract: In the field of high voltage direct current (HVDC) power transmission networks there is a need for an improved power converter. A power converter, for use in a HVDC power transmission network, comprises first and second DC terminals, for connection in use to a DC network and between which extends at least one converter limb. The or each converter limb includes first and second limb portions which are separated by an AC terminal, for connection in use to an AC network. Each limb portion includes a switching valve, and the power converter including a controller programmed to control switching of the switching valves to control the flow of a converter current (Imax) through the power converter and thereby in-use transfer power between the power converter and the AC network. The power transferred between the power converter and the AC network has an active component and a reactive component.

Abstract: A method and apparatus for controlling a fault blocking voltage source converter apparatus which is, in use, connected to an AC system and a DC system for power transmission, in the event of a DC side interruption operating the voltage source converter apparatus after identification of a need for a DC side interruption based on a voltage order, so as to extract at least some electrical energy stored in the connected DC system to the voltage source converter apparatus.

Abstract: A method and apparatus for start-up of a voltage source converter (VSC) which is connected to an energized DC link (DC+, DC?). The VSC is connected to a first AC network via a first transformer and an AC isolation switch, the AC isolation switch being coupled between the first transformer and the AC network. The method involves using an auxiliary AC power supply to generate an AC supply to energize the first transformer with the AC isolation switch open. The VSC is then started, with a VSC controller using the AC supply generated by the auxiliary AC power supply as a reference for controlling the VSC. The auxiliary AC power supply may also be used to supply power to at least one VSC load, such as the controller and/or an auxiliary load such as a cooling system. Once the VSC is started the isolation switch 204 can be closed.

Abstract: A converter apparatus and methods of operation thereof are disclosed. In an example, a converter unit of a bipole converter apparatus comprising a neutral connection having a breaker switch is disclosed. In the event of a DC fault, the fault condition may be monitored and it is determined whether a breaker switch operation condition is met. The breaker switch is opened when the breaker switch operation condition is met. In one example, the breaker switch operation condition may comprise a current level.

Abstract: A power transmission network includes converters interconnected via electrical elements, at least one power flow router, and a controller. Each power flow router being operatively connected to the electrical elements, each power flow router configured to selectively control current flow in the electrical elements so as to direct power between two or more of the plurality of converters.

Abstract: This application relates to methods and apparatus for fault protection in a DC power transmission network or grid that aid in determining the location of a fault in the network. The method involves, in the event of a fault, controlling at least one current limiting element of the network so as to limit a fault current flowing to below a first current level which is within the expected current operating range of the network in normal operation, i.e. a safe level. The fault current is then controlled to maintain a non-zero level of fault current flow and the characteristics of the fault current flow at different parts of the network are determined by fault current detection modules. The location of the fault is then determined based on the determined characteristics.

Abstract: A method and apparatus for controlling a voltage source converter to energize a DC link. A voltage order generating module generates a voltage order for controlling the voltage source converter to generate a DC voltage on the DC link. An oscillation damping module monitors the DC current flow to determine an indication of current oscillation and the voltage order is based on a voltage reference signal which is modulated by the indication of current oscillation to provide oscillation damping.

Abstract: Methods and apparatus for controlling a voltage source converter to energize a DC link. A voltage order generating module generates a voltage order for controlling the voltage source converter to generate a DC voltage on the DC link. the voltage order is based on a time varying voltage reference signal. A voltage reference module, which may include a ramp generator generates the time varying voltage reference signal such that the rate of change of the voltage reference signal changes over time. The rate of change of the voltage reference signal may decrease over time, to become more gradual as the nominal operating voltage is reached to avoid over-voltages.

Abstract: A converter apparatus and methods of operation thereof are disclosed. In an example, a converter unit of a bipole converter apparatus comprising a neutral connection having a breaker switch is disclosed. In the event of a DC fault, the fault condition may be monitored and it is determined whether a breaker switch operation condition is met. The breaker switch is opened when the breaker switch operation condition is met. In one example, the breaker switch operation condition may comprise a current level.

Abstract: A DC to DC converter for converting voltage between two voltage levels is described. The converter comprises a plurality of capacitors and switch units and is controllable between a first and second commutation state. In the first commutation state, the converter is configured for connection to higher voltage terminals and the capacitors are connected in series. In the second commutation state, the converter is configured for connection to lower voltage terminals, and the capacitors are connected to form at least two branches connected in parallel, the branches comprising a series connection of at least two capacitors. In some embodiments, one or more intermediate commutation states may also be provided.

Abstract: Methods and apparatus for controlling a voltage source converter to energise a DC link. A voltage order generating module generates a voltage order for controlling the voltage source converter to generate a DC voltage on the DC link. the voltage order is based on a time varying voltage reference signal. A voltage reference module, which may include a ramp generator generates the time varying voltage reference signal such that the rate of change of the voltage reference signal changes over time. The rate of change of the voltage reference signal may decrease over time, to become more gradual as the nominal operating voltage is reached to avoid over-voltages.

Abstract: A method and apparatus for controlling a voltage source converter to energise a DC link. A voltage order generating module generates a voltage order for controlling the voltage source converter to generate a DC voltage on the DC link. An oscillation damping module monitors the DC current flow to determine an indication of current oscillation and the voltage order is based on a voltage reference signal which is modulated by the indication of current oscillation to provide oscillation damping.

Abstract: A method and apparatus for controlling a fault blocking voltage source converter apparatus which is, in use, connected to an AC system and a DC system for power transmission, in the event of a DC side interruption operating the voltage source converter apparatus after identification of a need for a DC side interruption based on a voltage order, so as to extract at least some electrical energy stored in the connected DC system to the voltage source converter apparatus.