±800kV特高压直流输电控制保护系统分析

Discussion of ±800 kV UHVDC Transmission Control and Protection System

为探讨特高压直流(UHVDC)控制保护与常规高压直流(HVDC)控制保护的异同点,深入分析了特高压直流控制保护系统的独有特点。以向上特高压直流输电工程为例,介绍了特高压直流控制保护系统的框架、配置特点以及与常规高压直流控制保护系统的异同,分析了特高压直流在功率补偿、阀组控制、换流单元的在线投退策略、融冰运行模式等方面控制算法的变化,最后阐述了基于常规高压直流保护改进的换流变压器压器饱和保护和最后断路器保护原理以及特高压直流特有的保护功能。分析结果表明,特高压直流采用双12脉动阀串联结构,并增加了旁路开关等阀连接母线区,其一次系统接线的独有特点及更高可靠性的要求是特高压直流控制保护系统与常规高压直流控制保护系统有所区别的主要原因。DCC800特高压直流控制保护系统拥有控制UHVDC串联阀组的能力,增加了阀组之间的协调控制和保护,使特高压运行方式更具灵活性和多样性;特高压直流采用"三取二"保护原理和冗余的增强型时分多路复用(eTDM)总线,并较好地解决了主机死机的问题,整体可靠性更高。

To explore the similarities and differences between the control and protections of ultra-high voltage direct current systems （UHVDC） and conventional high voltage direct current systems （HVDC}, the characteristics of UHVDC control and protection system is analyzed in detail. Firstly, taking the Xiangjiaba-Shanghai UHVDC project as an example, we introduced its control and protection framework, configuration features, and its similarities and differences compared with that of HVDC. Then, we analyzed the control algorithm changes in UHVDC, such as changes in the control algorithms of power compensation, valve control, online input and withdrawal strategy of converters, de-icing operation mode and so on. Finally, we discussed the converter transformer saturation protection and the final breaker protection principles which were developed based on HVDC protection, and described the specific protection functions of UHVDC. According to the analysis, the dual 12-pulse valve in series adopted in the UHVDC projects, and the bypass breakers added in the bus area of valve connecting in which UHVDC is different from HVDC in primary connections, as well as the higher protection standard for UHVDC, are the main reasons that cause the difference of UHVDC protection systems from HVI）C. A protection system DCCS00 is capable of controlling valves in series, enhancing the coordination of control and protection among valves, which will result in more flexibility and diversity of UHVDC operations. In the presented UHVDC protection system, a ＂Two out of three＂ protection principle and redundant eTDM buses are adopted in UHVDC, and the problem of main computer stalling is solved well, ensuring that the system has more overall reiiability.