Study on Control Strategies for UHVDC System with 500kV/1000kV AC Hierarchical Connection at Receiving End

摘要

With the upgrading of UHVDC system capacity, State Grid of China (SGCC) employs the 500kV/1000kV AC hierarchical connection mode in receiving end with double series 12-pulse converters in Ximeng-Taizhou ± 800 KV UHVDC Project for the first time, in order to improve the accommodation capacity, security and stability of the receiving end AC systems. This paper analyzes the specific requirements of this novel connection to DC control system, differences of DC control strategy between reversed operation and normal operation, and proposes the DC control strategies applicable to reversed operation and normal operation. An analysis and study is made for the key functions of the control system for hierarchical connection, covering voltage balance control for series converters, tap control, reactive power control, etc. and suggests the principles of the functions and their realization methods. A simulation research is made on Ximeng-Taizhou ± 800 kV UHVDC Project with the assistance of PSCAD/EMTDC. The simulation results show that the proposed strategies are feasible and can be used in other planned receiving end hierarchical connection projects.