The Concept and Technical Analysis on Cryogenic VSC-HVDC System

Cryogenic operation of power converter will result in improved control speed and power handling capability, so a concept and layout of cryogenic VSC-HVDC is proposed to link AC networks. The bipolar coaxial HTS DC cable is described in details. The PWM control strategy based on the change of DC voltages is analyzed. In the system, SMES provides necessary power channel to protect the cable under the faults. HTS self-limiting-current smoothing reactor not only can be regarded as a regulator to reduce the fault current / voltage, but also may provide a damping for the oscillations. The transient stability assessment indicates high rotor angle stability. Some problems of the cable are emphasized, which are related to the stability of the cable, cryogenic dielectric and the losses of the system, etc.