基于自定义差分电流的MMC-HVDC输电线路纵联保护

Pilot Protection for MMC-HVDC Transmission Line Based on Custom Difference Current

为可靠检测模块化多电平换流器型高压直流(MMC-HVDC)输电线路故障并实现故障选极,提出一种纵联保护新原理。基于MMC-HVDC系统自身特点,综合使用两端换流站不同极线路电压量和电流量构造保护特征量——自定义差分电流。分析研究表明,直流侧故障时的自定义差分电流绝对值明显大于系统正常运行和交流侧故障时的自定义差分电流绝对值;直流侧正极接地故障、负极接地故障和双极短路故障时自定义差分电流正负性不同。根据此特征,构造纵联保护判据来识别直流侧故障并完成故障选极。仿真结果表明,该原理在一定故障条件下可快速可靠地识别直流线路故障并实现故障选极。

In order to improve the reliability of fault detection and fault line selection for modular multilevel converter based high voltage direct current（MMC-HVDC）transmission line,a novel pilot protection principle is proposed.Based on the characteristics of the MMC-HVDC system,custom difference current（named CDC-BPN）between the positive pole at one terminal and the negative pole at the other is constructed and used for voltage and current protection.The analysis shows that the absolute value of CDC-BPN for DC line faults is obviously higher than that of normal operation condition and AC system faults.In addition,the sign（positive or negative）of CDC-BPN for positive pole-to-ground fault,negative pole-to-ground fault and pole-to-pole fault is obviously different.According to these characteristics,apilot protection criterion is constructed to recognize DC line faults and fault line.Simulation results show that the proposed protection is able to detect DC line fault under different fault conditions and select the fault line quickly and reliably.