Abstract:
This paper designs the configuration scheme of the control and protection system in different converter stations at the sending-terminal for the cascade multi-terminal ultra high voltage direct current (CMT-UHVDC), according to the characteristics of the topology and operation mode of Jinsha river upstream CMT-UHVDC project. The DC voltage balance control method for the high-voltage converter and the low-voltage converter in different stations at the sending-terminal is proposed. The method include two control strategies: one is the fire-angle coordination with additional voltage balance control strategy, the other is one converter runs in constant voltage control mode and the other converter runs in constant current control mode. According to the communication states between the stations at sending terminal, one of the two control strategies will be selected as active. The protection function configuration scheme for the sending-terminal of CMT-UHVDC is studied, and a clearing method for the fault which occurs in pole/converter zone in Station 1 or the DC line between Stations at sending terminal is proposed. The RTDS closed-loop simulation results show the control and protection prototype for CMT-UHVDC can adapt the requirements of practical project.