Abstract: A method and apparatus for detecting a fault close to a grounding circuit in a high voltage direct current (HVDC) power transmission system. The HVDC power transmission system includes a first converter device having a first terminal and a second terminal, a second converter device having a third terminal and a fourth terminal, a transmission cable connecting the first terminal with the third terminal, and a neutral line connecting the second terminal with the fourth terminal. The method includes generating an alternating current signal by a source converter device, such that a major portion of the generated alternating current signal flows through a direct current circuit (DC, circuit) including a stray capacitance associated with the transmission cable and a return path. The method further includes measuring current at a number of points in the power transmission system and detecting a fault electrically close to the grounding circuit.

Abstract: A voltage source converter includes first and second DC terminals which have at least one converter limb extending therebetween. Each limb portion includes a chain-link converter that extends between an associated AC terminal and a corresponding one of the first or the second DC terminal. Each chain-link converter also includes a chain-link converter controller which is programmed to control a series of connected chain-link modules. The voltage source converter additionally includes a voltage source converter controller which is arranged in operative communication with each chain-link converter controller to coordinate operation of the chain-link converters. Each chain-link converter controller is further programmed to reconstruct from a received modulation index demand the chain-link converter voltage reference, which the chain-link converter it is controlling is required to produce, by multiplying the received modulation index demand by a total voltage sum established at a first time instant.

Abstract: A bipole power transmission network includes a first upstream power converter which has a first DC terminal that is connected with a first transmission conduit which extends, in-use, to a first downstream power converter. The first upstream power converter has a second DC terminal that is connected with a return conduit which extends, in-use, to the first downstream power converter and a second downstream power converter. The first upstream power converter has at least one first AC terminal electrically connected with a first AC power source. The bipole power transmission network includes a second upstream power converter which has a third DC terminal that is connected with the return conduit, and a fourth DC terminal which is connected with a second transmission conduit that extends, in-use, to the second downstream power converter, and at least one second AC terminal electrically connected with a second AC power source.

Abstract: A method of controlling a power converter in a power transmission network. The method includes determining a first AC voltage at the point of connection and regulating a second AC voltage, output from the power converter for counteracting the first AC voltage. The step of regulating the second AC voltage includes comparing a first amplitude value of a first negative phase sequence voltage component of the first AC voltage to a first limit value; and then outputting a second negative phase sequence voltage component of the second AC voltage to include a second amplitude value that is substantially equal to zero, when the comparing determines the first amplitude value is less than or equal to the first limit value, and, substantially equal to the difference between the first amplitude value and the first limit value, when the comparing determines the first amplitude value is greater than the first limit value.

Abstract: A method of controlling a power converter in a power transmission network. A first amplitude limit value for a first AC current output from an AC side of the power converter is received. A second amplitude limit value for a negative phase sequence component of the first AC current is received. The negative phase sequence component is measured to provide a measured second amplitude. The negative phase sequence component is regulated to flow with a second amplitude that is the lesser of the measured second amplitude and second amplitude limit value. A positive phase sequence component of the first AC current is regulated to flow with an amplitude not exceeding a regulated third amplitude. The third amplitude is set using a function such that the second amplitude and the third amplitude provide a first amplitude for the first AC current that is substantially equal to the first amplitude limit value.

Abstract: An electrical assembly including a voltage sourced converter for connection to an AC network, a controller programmed so that, responsive to detection of a fault in the AC network, the controller obtains a first set of voltage and current measurements taken at an interface connection point, change operation of the voltage sourced converter to inject a modified fault current, and then obtain a second set of voltage and current measurements, determine operating parameters of the voltage sourced converter for injecting a target fault current having a target phase angle that is substantially the same as a phase angle of a reference fault current that would have resulted from operation of the voltage sourced converter in accordance with pre-fault steady-state voltage phase and magnitude values, and operate the voltage sourced converter in accordance with the determined operating parameters so as to inject the target fault current at the target phase angle.

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: A circuit interruption device including first and second terminals for connection, to a respective electrical circuit or network, a current-conductive branch including first, second, and third current-conductive branch portions successively connected in series between the first and second terminals, the first current-conductive branch portion including a first switching element, the second current-conductive branch portion including a second switching element, the third current-conductive branch portion including a third switching element, each switching element configured to be switchable to selectively permit and block a flow of current in the respective current-conductive branch portion, first and second current bypass paths, the first current bypass path connected across the first and second current-conductive branch portions, the second current bypass path connected across the second and third current-conductive branch portions, and a controller configured to selectively control the switching of the swit

Abstract: A voltage source converter includes first and second DC terminals which have at least one converter limb extending therebetween. Each limb portion includes a chain-link converter that extends between an associated AC terminal and a corresponding one of the first or the second DC terminal. Each chain-link converter also includes a chain-link converter controller which is programmed to control a series of connected chain-link modules. The voltage source converter additionally includes a voltage source converter controller which is arranged in operative communication with each chain-link converter controller to coordinate operation of the chain-link converters. Each chain-link converter controller is further programmed to reconstruct from a received modulation index demand the chain-link converter voltage reference, which the chain-link converter it is controlling is required to produce, by multiplying the received modulation index demand by a total voltage sum established at a first time instant.

Abstract: A DC energy storage system may include first and second DC terminals for connection to a DC link, a DC energy storage converter including a number of modules connected in series between the first and second DC terminals, 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 being combinable to selectively provide a voltage source, and at least one circuit interruption device connected in series with the DC energy storage converter between the first and second DC terminals, the or each circuit interruption device operable to electrically separate the DC energy storage converter from the DC link.

Abstract: A bipole power transmission network includes a first upstream power converter which has a first DC terminal that is connected with a first transmission conduit which extends, in-use, to a first downstream power converter. The first upstream power converter has a second DC terminal that is connected with a return conduit which extends, in-use, to the first downstream power converter and a second downstream power converter. The first upstream power converter has at least one first AC terminal electrically connected with a first AC power source. The bipole power transmission network includes a second upstream power converter which has a third DC terminal that is connected with the return conduit, and a fourth DC terminal which is connected with a second transmission conduit that extends, in-use, to the second downstream power converter, and at least one second AC terminal electrically connected with a second AC power source.

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: A circuit interruption device including first and second terminals for connection, to a respective electrical circuit or network, a current-conductive branch including first, second, and third current-conductive branch portions successively connected in series between the first and second terminals, the first current-conductive branch portion including a first switching element, the second current-conductive branch portion including a second switching element, the third current-conductive branch portion including a third switching element, each switching element configured to be switchable to selectively permit and block a flow of current in the respective current-conductive branch portion, first and second current bypass paths, the first current bypass path connected across the first and second current-conductive branch portions, the second current bypass path connected across the second and third current-conductive branch portions, and a controller configured to selectively control the switching of the swit

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: This application relates to methods and apparatus for control of voltage source converters. The control apparatus has a reference voltage generator that generates a voltage control signal as part of a voltage control loop. The reference voltage generator may be a DC voltage/power controller operated to regulate DC voltage or power and may generate the voltage control signal based on a feedback DC voltage/power signal and a defined set-point. An overcurrent controller generates a current control signal for modulating the voltage control signal to prevent an overcurrent. The overcurrent controller generates the current control signal as part of a control path that is independent from the voltage control loop. The DC voltage/power controller may thus directly generate a voltage reference and may act to keep the DC voltage substantially constant over the time scale of short term transients, with the overcurrent controller providing current limiting only when required.

Abstract: There is disclosed a controller (112) for a power electronic network element (110) of a power transmission network (100), wherein the controller (112) is configured to vary a control parameter of the network element (110) which at least partly determines a ripple profile in a transmission line of the network. The controller (112) is configured to vary the control parameter between at least a first value and second value to cause the ripple profile in the transmission line to change; and the controller is configured to vary the control parameter periodically or in response to a signal indicating a threshold temperature at a hotspot location along the transmission line. A method of optimising control parameters for a power transmission network (100) is also disclosed.

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: This application relates to methods and apparatus for control of voltage source converters. The control apparatus has a reference voltage generator that generates a voltage control signal as part of a voltage control loop. The reference voltage generator may be a DC voltage/power controller operated to regulate DC voltage or power and may generate the voltage control signal based on a feedback DC voltage/power signal and a defined set-point. An overcurrent controller generates a current control signal for modulating the voltage control signal to prevent an overcurrent. The overcurrent controller generates the current control signal as part of a control path that is independent from the voltage control loop. The DC voltage/power controller may thus directly generate a voltage reference and may act to keep the DC voltage substantially constant over the time scale of short term transients, with the overcurrent controller providing current limiting only when required.

Abstract: A bipolar DC power transmission scheme including first and second DC poles, each including a respective DC power transmission medium extending between first and second ends; a plurality of converters wherein each end of the transmission medium of each of the poles is operatively connected to at least one of the converters to form a rectifier and an inverter at opposite ends of the DC power transmission media; and a controller to operate at least one converter of one of the rectifier and inverter in a control mode and at least one converter of the other of the rectifier and inverter in a second control mode in response to a fault occurring on either of the poles. Additionally, the first control mode decreases and the second control mode increases the operating DC voltage of the or each corresponding converter from a normal operating voltage value.

Abstract: A power transmission network including: a variable power source; an AC transmission link for AC power transmission from the variable power source to at least one source side converter; at least one source side converter including: an AC connecting point operably connected to the AC transmission link; and a DC connecting point for connection to a DC transmission link; and a control system configured to operate the source side converter or at least one of the source side converters in a frequency damping mode to control an AC voltage at its AC connecting point and thereby damp at least one frequency component at its AC connecting point and/or in the AC transmission link.