青藏直流输电工程系统试验研究

Research of System Test for HVDC Transmission Project From Qinghai to Tibet

对世界上海拔最高的青藏直流输电工程系统试验内容进行了研究分析,包括系统试验方案编制,直流系统解锁/闭锁方式,以及安全稳定措施等。提出了青藏直流系统试验期间的开机方式;对直流单极和双极降压起停方式进行了分析,通过研究提出了本阶段系统试验直流输送功率水平,并进行了试验验证。针对藏中电网"大直流、小电网和弱受端"电网系统的频率和电压稳定问题进行了分析,编制了系统试验方案和现场试验实施计划,对每项试验都落实了安全措施。对现场系统试验进行了分析,结果满足工程技术规范要求。对无站间通信极间功率转带控制策略进行了分析,提出了在站间通信故障后,立即将直流功率降至受端(拉萨侧)用电负荷的百分之八以下。系统试验期间发现的问题解决保证了青藏直流输电工程系统调试的顺利进行和按期投入试运行。

The content of system commissioning for HVDC power transmission project from Qinghai to Tibet, which is located at the region with the highest altitude in the world, is researched and analyzed, including the drafting of system commissioning scheme, blocking/deblocking control modes of HVDC system and measures for system security and stability, and so on. The start-up mode of generators in Central Tibet power system during the system commissioning of the project is put forward; the monopole and bipolar voltage-reducing start/stop control modes are analyzed, and through the research the HVDC transmission power during the system commissioning in present stage is proposed and corresponding experimental verification is performed. In view of such feature of Central Tibet power system as high HVDC transmission capacity, small power system and weak receiving end, the stability of both frequency and voltage of Central Tibet power system are analyzed and the system commissioning scheme and the implementation of on-site testing are drafted, besides, the safety precautions for each test item are implemented. The conditions of on-site system commissioning are analyzed to ensure them satisfying the demands specified in technical specifications. The power transfer control strategy between poles without communication between converter stations is analyzed and it is pointed out that after the occurrence of communication failure between converter stations the transmitted DC power should be immediately reduced to below the 8% of current load at the receiving end, namely the load in Lhasa. The solution of technical problems found during the system commissioning ensures the successful implementation of the commissioning and putting into operation of HVDC power transmission project form Qinghai to Tibet on time.