Protection Scheme for Transient Impedance Dynamic-Time-Warping Distance of a Flexible DC Distribution System

Flexible DC power distribution systems have characteristics such as rapid fault occurrence and fragile power electronics. DC faults usually result in rapid converter blocking (2-5 ms). However, existing protection schemes are susceptible to distributed capacitance, cannot tolerate long communication delays, and require artificial boundaries, among other features that make it impossible to combine speediness, selectivity, and reliability. A technique based on normalized transient impedance dynamic-time-warping (DTW) distance is proposed to improve the performance of the protection scheme. First, the fault equivalent circuit of the flexible DC distribution system (& PLUSMN;10 kV) is established, and its transient impedance expression is derived accordingly. Subsequently, the expression components are split and their fault characteristics are resolved separately. Finally, the protection scheme for normalized DTW distance is proposed based on the transient impedance fault characteristics. A flexible DC distribution system (& PLUSMN;10 kV) is established to verify the performance of the scheme.