基于开–闭滤波和多分辨形态梯度的直流线路纵联保护新原理

A Novel Pilot Protection Based on Open-close Filtering and Multi-resolution Morphological Gradient Operators for HVDC Transmission Line

在传统的高压直流输电线路保护中,行波保护动作速度快,但反映过渡电阻的能力较弱。纵差保护虽具有良好的反映高阻接地故障的能力,但为防止电容电流造成保护误动,其动作时间较长。为了解决现阶段传统保护存在的问题,提出基于开–闭滤波(open-closefiltering)和多分辨形态梯度(multi-resolutionmorphologicalgradient,MMG)的纵联保护新原理。该原理根据内、外部故障时,整流侧与逆变侧短路电流波形变化特征差异,先利用数学形态学中的开–闭滤波滤除电流中的高频谐波和噪声,再利用多分辨形态梯度进行波形特征辨识,通过纵联通道,获取两侧波形特征辨识结果,进行综合判断,以区分内外部故障。仿真结果表明,所提出的纵联保护新原理动作速度快、反映接地电阻能力强,具备很强的抗噪能力,无需电容电流补偿。

In the traditional protection of HVDC transmission line,the traveling wave protection is fast,but the ability to react to transition resistance is weak.Although the differential protection has a good ability to reflect high-resistance ground faults,it has a long operating time to prevent the capacitor current from causing protection misoperation.In order to solve the problems of traditional protection at this stage,this paper proposed a novel pilot protection based on open-close filtering and multi-resolution morphological gradient(MMG).According to the difference between the rectification side and the inverter side short-circuit current waveform characteristics,use the open-close filter in mathematical morphology to filter out high-frequency harmonics and noise in the current,and then use multiresolution morphological gradient to identify the waveform features.The waveform identification results of both sides were obtained through the longitudinal channel,and comprehensive judgment was made to distinguish internal and external faults.The simulation results show that the proposed novel pilot protection has fast action speed,strong reaction grounding resistance,strong anti-noise capability,and it does not require capacitive current compensation.