Applied Soft Computing Journal 79 (2019) 341–353 Contents lists available at ScienceDirect Applied Soft Computing Journal journal homepage: www.elsevier.com/locate/asoc High-speed fault detection and location in DC microgrids systems using Multi-Criterion System and neural network ✩ Ali Abdali, Kazem Mazlumi * , Reza Noroozian Department of Electrical Engineering, Faculty of Engineering, University of Zanjan, P.O. Box: 45371-38791, Zanjan, Iran highlights • Protection of DC microgrid is highly challenging, unlike conventional AC system. • A novel protection scheme based on MCS is proposed for DC microgrids. • An accurate fault location scheme based on NN is presented for DC microgrids. • The MCS, NN schemes and simulated network is implemented in laboratory-scale. • MCS implementation leads to the reduction of the protective system cost. article info Article history: Received 18 February 2018 Received in revised form 12 February 2019 Accepted 30 March 2019 Available online 8 April 2019 Keywords: Fault detection Fault location Multi-Criterion System (MCS) Neural network (NN) LVDC microgrids Circuit breaker abstract This paper presents a new protection method for LVDC ring-bus microgrid systems based on Multi- Criterion System (MCS) and Neural Network (NN). The proposed method aimed at high-speed detecting line-to-ground (LG) and line-to-line (LL) low impedance faults without using a definite threshold of differential current by using specific rules and multi-criterion system. MCS protection showed speed and accuracy compared to differential protection. Also, NN estimated fault location in percent of line length acceptably as a secondary controller. In order to evaluate the reliability and the enforceability of fault detection and location schemes, simulated network and protection algorithms are implemented and tested in laboratory-scale. The implementation results indicate that the MCS and NN protection scheme can consistently detect and estimate fault locations in the order of a few milliseconds. To reach this goal, a loop type LVDC microgrid with proper power electronic equipment like solid-state bidirectional breakers and the multi-level inverter is fulfilled. © 2019 Elsevier B.V. All rights reserved. 1. Introduction DC microgrids are effective structure and solution to attain a reliable power with higher yield via the use of distributed generations (DGs) units, power electronics converters, and energy storage devices. As well as, DC microgrid is a practical solu- tion for electric power distribution in various equipment like telecommunication systems, ships, spacecraft and distribution systems, which incorporate a considerable quantity of electronic demands. [1–4]. However, there are widespread concerns re- garding the protection system against the occurrence of faults, particularly in poly-source distribution networks [5–7]. The advantage of the DC systems is high efficiency [6], power flow optimization [7,8] reduction of equipment size and weight ✩ This work was supported by the University of Zanjan, Iran. * Corresponding author. E-mail addresses: ali_abdali@znu.ac.ir (A. Abdali), kmazlumi@znu.ac.ir (K. Mazlumi), noroozian@znu.ac.ir (R. Noroozian). [7], fewer converters requirements [6,7,9] and more power trans- fer capacity [8,9]. Ring-bus microgrids are one of the common structures of microgrids. It was shown that ring-bus microgrids are more efficient than, particularly when the distribution line is not long [10]. Fig. 1 demonstrates a perceptual scheme of a ring-bus LVDC microgrids systems. Notwithstanding its remarkable merits, the protection of LVDC microgrids faces plenty of challenges, as well as there is no existence of a published standard, solution, or experience with this regard [7]. In the distribution network, the ability of accurate fault detection and location brings merits like quick repair, main- tenance, and safety, which can decrease the power outages [6,11]. Load flow optimization, the increment of power quality, and the reductions in size and weight of equipment are the other merits of DC networks. The attendance of power electronic equipment controls current to a specified value in fault situations, which significantly makes it tough to detect faults and estimate its locations [11–13]. https://doi.org/10.1016/j.asoc.2019.03.051 1568-4946/© 2019 Elsevier B.V. All rights reserved.