适用于MMC-MTDC的母线侧故障分析及保护策略

Bus-side Fault Analysis and Protection Strategy for MMC-MTDC

柔性直流输电系统中,直流故障的分析与判别是柔直系统中亟待解决的重要问题。为了更好地分析故障特征,推导出一种多端柔性直流输电网(modular multilevel converter-high voltage direct current,MMC-MTDC)的母线侧简化电路故障计算方法,并分析了母线侧单极接地故障和极间短路故障的故障特征,在此基础上设计了一种适用于多端柔性直流输电网的故障判别方案和保护措施。该判别方案通过故障启动判据、故障区域判别和故障类型判别3个模块进行故障判定,采用了故障电压瞬时跌落值与系统电压之差及故障线路电流值作故障特征量,整套判别方案不受其他元件参数、故障位置等因素的影响,将Spearman相关性分析与传统电气故障区域判别相结合,准确判定系统区内外故障的同时,解决了故障区域判别中受线路各参数干扰导致误判的问题,仿真测试验证了本保护方案的可行性。

The analysis and discrimination of DC faults is an important problem that needs to be solved in the flexible DC system.This paper derives a bus-side simplified circuit fault calculation method for MMC-MTDC and analyzes the fault characteristics of bus-side pole-to-ground fault and pole-to-pole short circuit fault.Based on the results above,a fault discrimination scheme for multi-terminated flexible DC transmission networks are designed.The discriminative scheme uses three modules for fault discrimination,and adopts the post-fault voltage dip peak and post-fault line current value as the fault characteristic quantity,and the whole discriminative scheme is not affected by other component parameters,fault location and other factors.The combination of Spearman correlation analysis and traditional electrical fault area discrimination accurately determines faults within and outside the system area,while solving the problem of misjudgment caused by interference of line parameters in fault area discrimination,and the simulation test verifies the feasibility of this protection scheme.