Transient analysis method using high pass filter circuit in VSC interfaced multi-terminal DC system

Due to the lack of zero-crossing in dc current and the rapid discharging of the dc-link capacitor, a typical fast-growing transient current will be generated after the dc fault inception in VSC interfaced dc power system, which may affect the dc grid operation and damage power electronics equipment. Therefore, a novel fault detection method with fast response speed and high robustness is urgently-needed. In this paper, a high pass filter (HPF) circuit based transient analysis method is proposed, detecting faults within 1 ms. Since dc faults have high frequency components when passing through a HPF, the high-frequency components are retained while low pass components are suppressed. This theoretical background of the HPF circuit based transient analysis method is presented in detail. In this regard, the HPF circuit is designed; the validity of the proposed method is tested on a seven bus multi-terminal dc (MTDC) system in the simulation and a four bus MTDC system in the experiment. A comparative analysis of the proposed method with some popular methods for fault identification, which includes wavelet transform (WT), the short-time Fourier Transform (STFT), the S transform (ST), and the Hilbert-Huang transform (HHT), emphasizes the comprehensive performance of the proposed method.