Enhanced Kullback-Leibler divergence based pilot protection for lines connecting battery energy storage stations

In light of the challenges faced by existing protection methods when battery energy storage station (BESS) and various nonideal conditions emerge, enhanced Kullback-Leibler divergence-based time-domain pilot protection is put forward in this article. Given the discrepancy in current waveforms between internal and external faults, KLD is employed to quantify the degree of similarity between two current waveforms, enabling the accurate distinction between internal and external faults. To eliminate the asymmetry of KLD, improved KLD(IKLD) is introduced. Whereafter, a technique is proposed to convert the current sampling sequence into a probability distribution that can be utilized by IKLD. To counteract the negative influence of current transformer(CT) saturation on IKLD-based protection, the time-domain waveform features of summation current are adequately employed to develop an enhanced KLD(EKLD). Further, high and low thresholds are legitimately designed to ensure both dependability and security. The flowchart of EKLD-based pilot protection is described, and its effectiveness is extensively validated by variation in fault resistance, location, type and operating mode of BESS using PSCAD and a hardware-in-the-loop(HIL) testing platform. Additionally, proposed protection outclasses power frequency component-based current differential protection and some up-to-date presented time-domain protection methods.