A DC Distribution Network Protection Method Based on Improved VMD and Abrupt Energy

In this paper, a line longitudinal protection method based on improved variational mode decomposition (VMD) and abrupt energy is proposed to effectively identify faults in ring-shaped DC distribution network, improve the protection reliability, selectivity, speed and sensitivity, and ensure the stable operation of the system. To use the VMD algorithm, the number of modes that matters to the decomposition effect needs to be set first. Hence the Sparrow search algorithm (SSA) is used to find a better number of modes for the VMD algorithm so as to ensure optimal decomposition effect under this parameter. Then a protection scheme is devised according to the difference of abrupt energy at the head and tail of the line. The voltage and current fault components collected are decomposed by SSA-VMD to obtain several modal components and calculate their abrupt energy. The internal and external fault criteria are developed according to the difference of abrupt energy in the areas separated by the direct current reactor. The fault pole criteria are developed according to the difference of the abrupt energy ratio between positive and negative poles at the time of failure. A circular DC distribution network model is built in PSCAD/EMT-DC, and the protection method is validated by MATLAB. The results show that the proposed method works quickly (within 3 ms) and reliably for different types of faults. It can identify both internal and external faults, realize fault pole selection and protect the full length of the line. It can also well withstand transition resistance (up to 20 CI). Under a noise level of 40 dB, it can still identify faults and resist jamming to a certain extent. © 2023 Xi'an Jiaotong University. All rights reserved.