Coordinated Load Shedding Strategy to Restore Voltage and Frequency of Microgrid to Secure Region

To elide malicious consequences of failures and drastic variations in microgrids, load shedding (LSH) protective schemes are presented to enhance voltage and frequency (v&f) stability margin or prevent v&f collapse. Nonetheless, conventional/off-line LSH algorithms which are devised based on one of v&f stability indicators, do not result in good performance. Under severe circumstances, restoring both v&f by removing optimal load values from appropriate buses is very vital. This paper proposes a four variable/dimensional voltage-frequency LSH strategy as a secondary control plan to expurgate the deviations of v&f in microgrids, independent of the primary control plan. In this, 4-D piecewise linear curves are proposed to determine the proper LSH location and amount of load rejection (ALR). Furthermore, LSH speed, duration of the v&f deviation, and the secure region border can be manipulated. Also, a solution is provided to prevent the over-voltage and over-frequency following LSH. This strategy is successfully applied on a 5-bus microgrid and the standard IEEE 37-bus system. The outcomes confirm the achievement of all aspects considered as the goal of the LSH strategy along with the decent dynamic responses of v&f. Eventually, a comparison proves that the ALR is optimized more than 20 percent using the proposed strategy.