A New Approach to AC Microgrids Protection Using a Bi-Level Multi-Agent System

Nowadays, microgrids are expanding due to their numerous benefits. However, the control and protection of microgrids is a serious challenge. All the implemented plans for the protection of microgrids have drawbacks. This study presents a bi-level multi-agent system (MAS) approach to microgrids protection. The first level is responsible for microgrid lines protection. Firstly, it calculates the pilot impedance of each line. For line’s internal faults, pilot impedance is a limited number, but for line’s external faults, it will be infinite. so, the line’s internal fault is detected by evaluation of pilot impedance with a predetermined value. The second level is responsible for Distributed Generation (DGs) protection. Firstly, it decomposes the DGs output signals by Discrete Wavelet Transform (DWT). Then, it multiplies the summations of the first and second level’s details of each signal together as CC index. CC is zero in normal grid conditions and has a negative peak with a sharp negative rate in external faults, and will experience a positive peak with a sharp positive rate for internal faults and changes with a very slow rate in case of grid’s natural transitions. So, the agent detects the fault by evaluating the CC. The simulation results in a ۵-bus microgrid indicate the proposed scheme protects the microgrid with a reliability of ۱۰۰% with considering all microgrid’s uncertainties.