Abstract: A static synchronous compensator for use in reactive power compensation, the static synchronous compensator comprising at least one primary compensator limb including first and second DC terminals, and an AC terminal for connection in use to an AC network, the or each primary compensator limb defining first and second limb portions, each limb portion—including at least one switching element connected in series with a chain-link converter—between a respective one of the first and second DC terminals and the AC terminal, the switching elements of the first and second limb portions being operable to switch the respective chain-link converters in and out of circuit between the respective DC terminal and the AC terminal and the chain-link converters being operable to generate a voltage waveform at the AC terminal; and a secondary compensator limb including at least one DC link capacitor connected between the first and second DC terminals, the secondary compensator limb being connected in parallel with the or each

Abstract: A hybrid on-load tap changer, for use in high voltage alternating current power transmission, including a selector and a diverter having two legs defining respective current paths. Each leg includes a pair of opposed first and second semiconductor switches. The hybrid on-load tap changer also includes a controller configured to switch on one of the first or second semiconductor switches of a given leg at a predetermined point within the alternating current cycle so as to commutate off a desired semiconductor switch in the other leg.

Abstract: A hybrid on-load tap changer, for use in high voltage alternating current power transmission, including a selector and a diverter having two legs defining respective current paths. Each leg includes a pair of opposed first and second semiconductor switches. The hybrid on-load tap changer also includes a controller configured to switch on one of the first or second semiconductor switches of a given leg at a predetermined point within the alternating current cycle so as to commutate off a desired semiconductor switch in the other leg.

Abstract: A converter for high voltages includes a bridge circuit having serially arranged switching assemblies so connected as to define at least two input notes and two output nodes. The input nodes are adapted to receive an input voltage across the input nodes, and the output nodes are adapted to provide a take-off point for the output waveform. A control circuit supplies a respective control signal to each switching assembly in the bridge circuit. A resonant circuit is connected across the output nodes. The devices are switched at the resonant frequency of the resonant circuit. Thus, by switching as the current crosses zero in the resonant circuit, sudden rises in voltage across the devices are avoided.

Abstract: A substation is disclosed for use in a power transmission and distribution network. The substation comprises a single phase isolating high frequency transformer having at least one input winding and at least one output winding with corresponding input and output solid state switching networks. Each input solid state switching network comprises a plurality of semiconductor switching devices which receive an input waveform from the transmission network and output a high frequency waveform to the primary winding of the transformer. Likewise, each output solid state switching network comprises a plurality of semiconductor switching devices receiving a high frequency waveform from the secondary winding of the transformer and outputting an output frequency waveform from the substation. A control circuit is adapted to control the operation of the switching devices of the input and output switching networks to generate the output waveform from the input waveform.

Abstract: A converter for high voltages is disclosed. The apparatus comprises a bridge circuit having serially arranged switching assemblies (1, 2, 3, 4) so connected as to define at least two input nodes (50, 60) and two output nodes (70, 80), the input nodes being adapted to receive the input voltage across the nodes, and the output nodes being adapted to provide a take-off point for the output waveform. A control circuit is provided to supply a respective control signal to each switching assembly in the bridge circuit. The apparatus also includes a resonant circuit (100) connected across the output nodes (70, 80). The devices are switched at the resonant frequency of the resonant circuit. Thus, by switching as the current crosses zero in the resonant circuit sudden rises in voltage across the devices can be avoided.

Abstract: A substation (100) is disclosed for use in a power transmission and distribution network. The substation comprises a single phase isolating high frequency transformer (101) having at least one input winding (112, 113) and at least one output winding (114-117) with corresponding input (104) and output (105) solid state switching networks. Each input solid state switching network (104) comprises a plurality of semiconductor switching devices which receive an input waveform from the transmission network and output a high frequency waveform to the primary winding of the transformer. Likewise, each output solid state switching network (105a-105d) comprises a plurality of semiconductor switching devices receiving a high frequency waveform from the secondary winding (114-117) of the transformer and outputting an output frequency waveform from the substation.