基于巴氏距离算法的风电场交直流并网系统送出线纵联保护

Longitudinal Protection of Outgoing Line in AC/DC System of Wind Farm Based on Bhat-tacharyya Distance Algorithm

风电场常见的并网方式有交流并网和柔性直流并网,交流并网送出线和柔性直流并网交流侧送出线发生短路故障时,线路保护都会受到风机故障特征的影响,且在柔性直流送出系统中,电气量还受到换流侧电子元件的非线性调节和谐波的影响,导致传统继电保护在两种送出系统中的动作性能较差。因此,根据送出线发生区内外故障的电流波形特征,将基于时域量的巴氏距离算法与纵联保护结合,计算两端电流波形相似程度,以此判断线路是否发生故障,并考虑过渡电阻、噪声干扰、混叠频率、CT饱和等对保护方案的影响。最后,基于MATLAB/Simulink和PSCAD/EMTDC平台搭建双馈风机分别经交流送出的系统电磁暂态仿真模型,仿真验证保护方案在双馈风电场送出线上的适应性。结果表明,保护方案在以上因素影响下仍能正确动作,保护的动作性能较好。

The common grid connection modes of wind farms include AC grid connection and flexible DC grid connection.In case of short-circuit fault of AC grid connected outgoing line and flexible DC grid connected AC side outgoing line,the line protection is affected by the fault characteristics of the fan.In the flexible DC outgoing system,the electrical quantity is also affected by the nonlinear regulation and harmonic of the electronic components at the converter side.As a result,the action performance of traditional relay protection in the two transmission systems is poor.Therefore,according to the current waveform characteristics of faults inside and outside the outgoing line,the Babbitt distance algorithm based on time domain quantity is combined with pilot protection to calculate the similarity of current waveforms at both ends,so as to judge whether the line has faults.The influence of transition resistance,noise interference,aliasing frequency,CT saturation,etc.on the protection scheme is considered.Finally,based on MATLAB/Simulink and PSCAD/EMTDC platform,the system electromagnetic transient simulation model of doubly fed fan sent out by AC is built to verify the adaptability of the protection scheme on the outgoing line of doubly fed wind farm.The results show that the protection scheme can still operate correctly under the influence of the above factors,and the action performance of the protection is good.