Simulator Study of Multiterminal HVDC System With Small Parallel Tap and Weak AC Systems

The paper describes a simulator study of a four-terminal HVdc system with a small parallel tap and interconnected to an AC network with weak AC systems at the four dc terminals. The small tap is rated at 25% of the rating of the HVdc system and the effective short-circuit ratios at the dc terminals are in the range of 2.1 to 3.0. The study includes the transient performance of the dc system for various types of system disturbances, such as AC system faults, dc line faults, and commutation failure at the small inverter.