一种新型的高压直流输电技术——MMC-HVDC

介绍了模块化多电平换流器型高压直流输电(MMC-HVDC)的基本结构、工作原理和技术特点,比较了MMC-HVDC相对于电压源换流器型高压直流输电(VSC-HVDC)的优势;对MMC-HVDC目前在国内外的研究进展和工程应用情况进行了回顾,分析了MMC-HVDC技术的不足之处和未来发展中可能的重点方向,包括主电路拓扑的相关问题研究、系统设计、故障保护、接地、谐波和损耗等,指出目前研究所采用的MMC-HVDC分析模型精度较低;因自身拓扑限制,目前成熟的VSC-HVDC控制方法无法直接用于MMC-HVDC;MMC-HVDC拥有较强的故障保护能力,当前研究着重于故障仿真分析,亟待探讨适合工程应用的保护策略;由于直流侧无需安装高压电容器组,MMC-HVDC接地实现困难;由于MMC-HVDC子模块数较多,采用较低的开关频率可得到较好的输出电压波形,使得系统损耗大幅降低;最后探讨了适合我国国情的MMC-HVDC工程实践。

New HVDC power transmission technology:MMC-HVDC

The structure,operational principle and technical features of MMC-HVDC are described and the differences between MMC-HVDC and VSC-HVDC are compared.A brief survey is made on the present research statuses and engineering applications of MMC-HVDC.The drawbackes and some possible important trends of MMC-HVDC are analyzed,including:MMC-topology-related research,system design,fault protection,grounding,harmonics,loss,and so on.It is pointed out that the MMC-HVDC model for current research has low precision.For the limit of MMC topology,the mature control methods of VSC-HVDC can not be directly applied to MMC-HVDC.MMC-HVDC system has a strong ability of fault protection.Since current research emphasizes on the simulative analysis of fault protection,further research of MMC-HVDC protection strategy suitable for engineering applications is urgently needed.The implementation of grounding is difficult for high voltage capacitor banks are removed.For the large number of MMC sub-module,the better output voltage waveform is obtained when low switching frequency is used,and the system loss is low.The engineering practice of MMC-HVDC fit for China is discussed.