Study on operation characteristics and stability evaluation method at sending-end of DC transmission system

Abstract

For the situation that many Ultra-HVDC projects can not reach the maximum transmission capacity in the beginning of operation. Considering more Ultra-HVDC projects put into operation recently, this paper analyzed key facts limiting transmission capability at the sending-end of Ultra-HVDC from static stability, voltage fluctuation and AC-DC coupling characteristics. Furthermore, based on short-circuit ratio which is usually in receiving-end of DC, analyzes the relationship between short-circuit ratio of sending-end of DC and maximum transmission capability, and the critical short-circuit ratio maintaining stable operation of system at sending-end of DC transmission is given. Considering these HVDC projects that have been put into operation recently and based on various operation modes in AC&DC system, this paper firstly studied on the mutual influence between AC systems and DC systems, and finally provides comprehensive analysis on the power angel, voltage and frequency problems that may threaten the operation of the power grid at DC sending-end and proposes not only the key factors affecting the stability of the power system at DC sending-end and transmission capability of the DC system but also the corresponding solutions. Meanwhile, based on the short circuit ratio that is often used to evaluate the stability of the power system at DC receiving-end, we also investigate the relationship between the short circuit ratio of the DC sending-end system and the maximum transmission capability of DC system and give the critical short circuit ratio of the stable operation of the DC sending-end power system. Finally, according to the above research, we propose the comprehensive indexes for evaluating the stability of the DC sending-end power system. Our research, considering both the theory and the reality, has great value on guarantying the stability of the DC sending-end power system.