基于电流波形畸变特征的高比例光伏配电网故障方向判别原理

New Fault Direction Identification Based on Current Distortion Characteristics in High Proportion PV Distribution System

随着配电网中分布式光伏渗透率的提高,原有单向故障潮流网络变为多向潮流网络,现有三段式过流保护面临误动风险。该文提出基于电流畸变特征的故障方向判别原理。首先,挖掘了光伏与同步发电机的故障电流特征差异,考虑光伏控制特性探究了光伏故障电流畸变特征和谐波分量产生机理。其次,对故障电流求导以放大故障波形特征差异,在此基础上提出了基于故障电流波形畸变特征的方向闭锁判据。最后,仿真表明所提故障方向判别原理在不同逆变器控制策略和电网不同运行状态下均能可靠判别正、反向故障,并具备一定的耐受过渡电阻和抗噪能力。该思想将分布式电源非线性特征对保护的干扰转化为故障方向判据,无需电压信息和双端通信设备,能有效降低现场施工难度。

With the increase of distributed PV penetration,the existing three-staged overcurrent protection faces the risk of malfunction.This paper presents a new fault direction identification based on the distortion characteristics of fault current waveforms.Firstly,the difference is explored between the fault current waveforms supplied by the distributed PV and by the traditional synchronous power.The characteristics of PV fault current distortion and the generation mechanism of harmonic components are studied.Secondly,the method of fault feature extraction is studied,and the direction blocking criterion based on fault current waveform distortion is proposed.The simulation results validate that the proposed method is able to reliably decide the forward and the reverse fault directions under different inverter control strategies with the abilities to withstand the fault resistance and the noise of signal sampling.This idea converts the interference of nonlinear characteristics to the fault direction criteria with no voltage measurement information and communication equipment,which will effectively reduce the technical difficulty of the distribution system construction.