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: 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 computer-implemented method of controlling a power converter in a power transmission network, including: measuring a first AC voltage and/or a first AC current at a point of connection, determining whether a fault condition is present in the AC network, setting a current limit for a second AC current output, by: if a fault condition is determined not to be present, setting the current limit to be equal to a first current limit value, and if a fault condition is determined to be present in the AC network, setting the current limit to be equal to a second current limit value, wherein the second current limit value is less than the first current limit value, and regulating, based on the current limit, a second AC voltage that is output from the AC side of the power converter, such that the second AC current does not exceed the current limit.

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: In the field of high voltage direct current (HVDC) power transmission networks, there is a need for improvements to allow a single power converter to control individual AC network voltages carried by multiple AC transmission conduits to multiple AC network elements, such as respective wind parks.

Abstract: A control apparatus is described for controlling a frequency set-point for a first AC network electrically connected to a first HVDC station to regulate active power. The controller has a frequency controller operable in a first mode of operation to determine a frequency set-point for the first AC network based on a measured DC voltage at the first HVDC station. A disturbance detector is configured to monitor the measured value of DC voltage at the first HVDC station for a predetermined characteristic indicative that a variation in measured DC voltage does correspond to a known modulation applied to the DC voltage by a second HVDC station. The frequency controller is configured to determine the frequency set-point for the first AC network based on a measured value of DC voltage if said predetermined characteristic is detected, and to control the frequency set-point to a predetermined default frequency if not detected.

Abstract: A bipole power transmission scheme with two independent converts, two power feed and one return conduit. During operation of the bipole power transmission scheme under abnormal conditions, when a return conduit is faulty and unable to provide a return current path, each converter controller is programmed to monitor the first power feed in the first transmission conduit and the second power feed in the second transmission conduit and, if the first power feed in the first transmission conduit and the second power feed in the second transmission conduit differ from one another, at least one converter controller modifies the power infeed from its corresponding power source to reduce the difference between the first power feed and the second power feed.

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 voltage source converter having first and second DC terminals for connection to a DC network is provided. The voltage source converter includes at least one converter limb that extends between the first and second DC terminals and first and second limb portions that are separated by a respective AC terminal for connection to a corresponding phase of an AC network. Each limb portion includes a chain-link converter which is defined by a plurality of series-connected switching modules which operate in combination to provide a stepped variable voltage source. The voltage source converter includes a control apparatus configured to coordinate operation of the chain-link converters to cause an exchange of power between the DC and AC networks, evaluate the performance of one of the pluralities of series-connected switching modules, and modify the operation of the respective chain-link converter when the performance becomes degraded to a predetermined amount.

Abstract: There is provided a switching valve for a voltage source converter, the switching valve comprising a plurality of modules, each module including at least one switching element and at least one energy storage device, each switching element and each energy storage device in each module arranged to be combinable to selectively provide a voltage source, the switching valve including a regulator programmed to selectively control the switching of the switching elements to select one or more of the modules to contribute a respective voltage to a switching valve voltage, wherein the regulator is programmed to selectively regulate an energy stored in each energy storage device by controlling the switching of the switching elements to regulate a voltage of each energy storage device towards a target voltage, and the regulator is programmed to vary the target voltage of each energy storage device as a function of a number of healthy modules.

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: A bipole power transmission scheme with two independent converts, two power feed and one return conduit. During operation of the bipole power transmission scheme under abnormal conditions, when a return conduit is faulty and unable to provide a return current path, each converter controller is programmed to monitor the first power feed in the first transmission conduit and the second power feed in the second transmission conduit and, if the first power feed in the first transmission conduit and the second power feed in the second transmission conduit differ from one another, at least one converter controller modifies the power infeed from its corresponding power source to reduce the difference between the first power feed and the second power feed.

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: The present disclosure includes methods and apparatus for HVDC power distribution. A control apparatus is described for controlling a frequency set-point for a first AC network electrically connected to a first HVDC station to regulate active power. The controller has a frequency controller operable in a first mode of operation to determine a frequency set-point (Fref) for the first AC network based on a measured DC voltage at the first HVDC station. A disturbance detector is configured to monitor the measured value of DC voltage at the first HVDC station (VDC1) for a predetermined characteristic indicative that a variation in measured DC voltage does correspond to a known modulation applied to the DC voltage by a second HVDC station.

Abstract: In the field of high voltage direct current (HVDC) power transmission networks, there is a need for improvements to allow a single power converter to control individual AC network voltages carried by multiple AC transmission conduits to multiple AC network elements, such as respective wind parks. A power transmission network (10; 100) comprises a power converter (12) which has first and second DC converter terminals (14, 16) that are for connection, in use, to a DC network. The power converter (12) also includes an AC converter terminal (22) which is electrically connected to a plurality of AC transmission conduits (241, 242, 24n), each of which is for connection, in use, to a respective AC network element (261, 262, 26n) that is configured to operate at a respective individual AC network voltage.

Abstract: In the field of high voltage direct current (HVDC) transmission, a voltage source converter comprises first and second DC terminals that are for connection to a DC network. The voltage source converter also includes at least one converter limb. The or each converter limb extends between the first and second DC terminals and includes first and second limb portions that are separated by a respective AC terminal for connection to a corresponding phase of an AC network. Each first limb portion extends between the first DC terminal and a corresponding AC terminal, and each second limb portion extends between the second DC terminal and the corresponding AC terminal. Each limb portion includes a respective chain-link converter which is defined by a plurality of series-connected switching modules which are operable in combination to provide a stepped variable voltage source.

Abstract: This invention relates to a multiple phase electrical system, including: a first and a second electrical lane, each lane having a generator and a load connected by a bus system, and a rectifier between the generator and load; and, a transformer connected between the two lanes, the transformer having a plurality of power windings across each of which corresponding phases of the first and second lanes are connected, and a plurality of phase shift windings.

Abstract: This invention relates to a multiple phase electrical system, including: a first and a second electrical lane, each lane having a generator and a load connected by a bus system, and a rectifier between the generator and load; and, a transformer connected between the two lanes, the transformer having a plurality of power windings across each of which corresponding phases of the first and second lanes are connected, and a plurality of phase shift windings.