Study on the Transmission Capability of Dianxibei UHVDC Project and the Method to Enhance It in Early Stage of the Project’s Operation

In early stage of Dianxibei UHVDC project’s operation, the production progress of the accessory power plants at the sending-end lags far behind the original schedule, which causes a lack of generation problem in sending-end grid. The effects on transmission capability of Dianxibei UHVDC project from diverse aspects, such as the stability of the islanding system after the sending-end converter station switching into islanding mode, the overvoltage of the islanding system and the harmonic resonance risks of the islanding system are analyzed in this paper. The analysis result shows that the transmission capability of Dianxibei HVDC project is limited and unable to meet the demand of system commission tests. For the purpose of enhancing transmission capability of Dianxibei UHVDC project, a stopgap according to which the UHVDC system will block itself following a preset strategy if the converter station switches into islanding mode is presented, and the transmission capability of Dianxibei UHVDC project after adopting the stopgap is also analyzed. Finally, the quitting conditions of the stopgap, under which Dianxibei UHVDC project can reach it’s rated transmission capacity safely without any stopgap, is researched. The study results of this paper guarantees the security and adequacy of Dianxibei UHVDC project’s power transmission in early stage of it’s operation, and also provide significant guidance on experiments conducting in system commissioning test periods of the project.