Fault Location Method for MMC-HVDC Systems Based on Numerical Laplace Transform

Fault location plays a pivotal role in expediting the restoration of systems after faults. However, the necessity for rapid fault isolation in multi-terminal direct current (MTDC) systems dictates that only a few milliseconds of data are available for fault location. Therefore, accurately determining the fault location using an extreme short data window presents a challenge. To address this challenge, a frequency domain fault location method that utilizes data from both ends of lines is proposed. This method accurately considers frequency-dependent and distributed characteristics of line parameters and relies on data collected within 3 ms following a fault occurrence. Initially, the fault location equation is derived. Then, the numerical Laplace transform (NLT) method is introduced to solve this equation, from which the explicit expression for fault distance is obtained. Lastly, the comprehensive fault location scheme is outlined. Numerical simulations demonstrate that this method can accurately locate faults and exhibit good robustness against fault impedance. Additionally, the method features a reduced computational burden, higher accuracy, and stronger noise immunity compared to existing methods.