基于MMC的多端柔性直流线路超高速保护关键技术研究

为了满足多端柔性直流电网输电线路超高速保护动作快速需求,在传统直流线路保护的基础上,介绍了柔性直流线路的保护配置和动作策略,根据故障行波的特征,提出了一种行波保护方法。该方法将电压信号经过S变换提取故障行波的特定频带特性,通过对不同时刻故障行波幅值的变化识别接地短路故障,进而构成行波保护出口的判据。最后基于实际工程参数,在RTDS搭建的多端柔性直流仿真模型与控制保护系统构成的闭环系统上进行试验验证,试验结果表明该方法有效、可靠。

Research on Key Technology of Ultra-high Speed Protection of Multi-terminal Flexible DC Line Based on MMC

In order to meet the requirements of ultra-high-speed protection action of multi-terminal flexible DC grid transmission lines, based on the traditional DC engineering line protection, the protection configuration and action strategy of flexible DC line are introduced.According to the characteristics of fault traveling wave, a traveling wave protection method is proposed.The method extracts the specific frequency band characteristics of the fault wave by S-transformation, and identify the ground short circuit fault by changing the amplitude of the fault traveling wave at different times, thereby forming a criterion for the traveling wave protection exit.Finally, based on the actual engineering parameters, the multi-terminal flexible DC simulation model built by RTDS and the closed-loop system composed of control and protection system are tested.The test results show that the method is effective and reliable.