Abstract: An electrical assembly includes a converter-based electrical device and a transformer for connecting the converter-based electrical device to an AC electrical network, a first transformer side of the transformer connected to the converter-based electrical device, a second transformer side of the transformer for connection to the AC electrical network, the transformer including a number of taps, the transformer including a tap changer operable to selectively connect to the or each tap to modify a turn ratio of the transformer. The transformer includes a controller configured to selectively operate the tap changer in an AC voltage modification mode, responsive to an abnormal operating state of the electrical assembly, to modify the turn ratio of the transformer so as to modify an AC voltage at the first transformer side.

Abstract: In the field of chain-link converters operable to provide a stepped variable voltage source, there is a need for an improved method of operating such a chain-link converter. A method of operating a chain-link converter, the chain-link converter including a number of series connected chain-link modules, each chain-link module including at least one switching element and an energy storage device which together are selectively operable to provide a voltage source whereby the chain-link converter is able to provide a stepped variable voltage source, including the steps of: (i) identifying one or more unhealthy chain-link modules having a reduced performance characteristic compared to one or more healthy chain-link modules having a normal performance characteristic, (ii) utilizing the healthy chain-link modules normally in the operation of the chain-link converter, and (iii) reducing the utilization of the or each unhealthy chain-link module.

Abstract: A voltage source converter comprises a converter arm extending between two terminals each terminal being connectable to a or a respective electrical network, the converter arm including a valve that includes at least one module, the or each module being operable to selectively provide a voltage source; and a controller programmed to selectively operate the valve to clamp a voltage at either or both of the two terminals and thereby operate the valve as a current limiter to limit a selected current flowing in the converter arm at or below a fixed or variable current threshold.

Abstract: In the field of high voltage direct current power transmission and distribution there is provided a converter which includes first and second DC terminals for connection to a DC electrical network and between which extends converter limbs. Each converter limb includes first and second limb portions that are separated by an AC terminal for connection to a respective phase of a multi-phase AC electrical network. Each limb portion includes a current sensor to measure current flowing in the corresponding limb portion. The converter also includes further current sensors, located elsewhere in the converter, and a current sensor management unit. The current sensor management unit is programmed to: receive a measured current value from each current sensor; identify at least one faulty current sensor from the received measured current values; and replace the measured current value of the or each identified faulty current sensor with a calculated current value.

Abstract: In the field of high voltage direct current power transmission and distribution there is provided a converter which includes first and second DC terminals for connection to a DC electrical network and between which extends converter limbs. Each converter limb includes first and second limb portions that are separated by an AC terminal for connection to a respective phase of a multi-phase AC electrical network. Each limb portion includes a current sensor to measure current flowing in the corresponding limb portion. The converter also includes further current sensors, located elsewhere in the converter, and a current sensor management unit. The current sensor management unit is programmed to: receive a measured current value from each current sensor; identify at least one faulty current sensor from the received measured current values; and replace the measured current value of the or each identified faulty current sensor with a calculated current value.

Abstract: A voltage source converter comprises a converter arm extending between two terminals each terminal being connectable to a or a respective electrical network, the converter arm including a valve that includes at least one module, the or each module being operable to selectively provide a voltage source; and a controller programmed to selectively operate the valve to clamp a voltage at either or both of the two terminals and thereby operate the valve as a current limiter to limit a selected current flowing in the converter arm at or below a fixed or variable current threshold.