基于暂态电流相关系数的环状直流配电网保护方法

Protection Scheme of Ring-shaped DC Distribution Network Based on Transient Current Correlation Coefficient

基于模块化多电平换流器(modular multilevel converter,MMC)的环状直流配电网因其供电可靠性优势而备受瞩目,MMC环状直流配电网的稳定运行与快速而又可靠的线路保护方法息息相关。为了保证环状直流配电网系统的安全运行,提出了基于故障暂态电流的Pearson相关系数保护方法。首先,提取环状直流配电网中线路首末两端电流的线模分量,利用其线模电流的差异完成区内、外故障的识别;根据单极接地和双极短路故障时的特征,利用线路正负极暂态电流相关系数数值差异进行单双极故障判定,并完成故障选极;最后,在PSCAD/EMTDC(power systems computer aided design/electromagnetic transients including DC)中搭建环状直流配电网模型进行验证,结果表明:所提方法在2 ms内可以快速可靠动作,可以保护线路全长,耐过渡电阻能力强,在40 dB噪声情况下,依旧可以识别故障,有一定的抗干扰能力,并且不严格要求同步通信。

The ring-shaped DC distribution network based on modular multilevel converter(MMC)has attracted much attention because of its power supply reliability advantage.The stable operation of MMC ring-shaped DC distribution network is closely related to the fast and reliable line protection method.To meet this requirement,a Pearson correlation coefficient protection method based on fault transient current was proposed.First,the line mode components of the current at the beginning and end of the line in the ring-shaped DC distribution network were extracted,and the difference of the line mode current was used to complete the identification of internal and external faults.According to the characteristics of single-pole grounding and double-pole short-circuit faults,using the numerical difference of the correlation coefficient between the positive and negative transient currents of the line,the single and bipolar faults were judged,and the fault pole selection was completed.Finally,a ring-shaped DC distribution network model was built in power systems computer aided design/electromagnetic transients including DC(PSCAD/EMTDC)for verification.It can operate quickly and reliably within 2 ms,can protect the full length of the line,and has strong resistance to transition resistance.In the case of 40 dB noise,it can still identify faults,has a certain anti-interference ability,and does not strictly require synchronous communication.