Novel Change Detection and Fault Classification Scheme for AC Microgrids

A novel scheme is suggested for change detection and fault classification in ac microgrids (μGs) with different operating modes. The proposed method utilizes a Teager-Kaiser energy operator based approach for analyzing the current-based signal to detect changes in the μG. The current-based signal is a summation of squared three-phase currents (SSC), measured at one end of a line in the μG. Since μGs have different operating modes, a proper signal should be defined to have some valuable signatures of the changes in different conditions. The SSC signal is constant during normal conditions of the grid-connected and islanded μG, whereas in any possible change condition experiences considerable variation. After the detection, the faulty phase is determined using three similar indices, derived from the squared currents. These indices are the ratios of squared currents for each phase with half-cycle window length, before and after the change detection. The proposed protection scheme is able to handle both operation modes of the μG. The proposed technique is evaluated in a MATLAB/Simulink simulated network and laboratory small-scaled test bench. The results confirm high accuracy and quickness of the proposed approach. Furthermore, the performance of the proposed methodology is compared with some other similar methods.