Patent ID: 8867242

Claim:
A voltage source converter for use in high voltage direct current power transmission and reactive power compensation, the voltage source converter comprising: first and second DC terminals for connection in use to a DC network, three phase elements and three auxiliary converters connected between the first and second DC terminals, each phase element including two parallel connected strings of series connected primary switching elements, the each mid-points between each string of series-connected primary switching elements defining an AC terminals for connection in use to a respective phase of an AC network, each auxiliary converter being connected in parallel with a respective one of the phase elements to define a single-phase converter limb and the three single-phase converter limbs being mounted and connected in series to the first and second DC terminals to define a two-terminal DC network for three-phase power transmission; the primary switching elements being controllable in use to facilitate power conversion between the AC and DC networks, each auxiliary converter being operable in use to act as a waveform synthesizer to modify a first DC voltage presented to the DC network so as to minimise ripple in the DC voltage.