Active Power Shifting Strategy for the Bipolar VSC-MTDC

Abstract

Currently, the bipolar VSC-MTDC has become increasingly popular in practical projects. With the traditional wiring mode, line overload, generator tripping or load shedding may occur if a DC line or converter quits operation. While with a more flexible bipolar wiring mode, power shifting from the faulty network to the healthy one is permitted under same conditions. This paper proposes an active power shifting strategy based on bipolar VSC-MTDC. Since the positive-pole and negative-pole networks can be controlled independently, the transmitted power of the healthy pole network can be increased and that of the faulty pole network can be decreased, which is to avoid power surplus under abnormal operation conditions. This strategy has improved the reliability and transmission capacity of VSC-MTDC system. Then a 4-terminal MTDC simulation is established in PSCAD/EMTDC. The validity of the proposed strategy has been proved by the simulation results.