Voltage profile improvement in islanded DC microgrid using load shedding method based on DC bus voltage estimation

DC microgrid is a leading technology that enables the integration of distributed generation (DG) units and avoids extreme complexity within the power system. One of the main challenges associated with islanded microgrids is the limited primary resources and variation of DGs' output power. For this reason, in some cases, the microgrid may face an imbalance in the amount of power generation and consumption, which, if it exceeds the standard limit, would lead to severe voltage collapse and power system failure. In fact, when demand surpasses the available power generation, in cases where the imbalance is not too extreme, it results in a decrease in voltage; in more severe instances, it can cause a breakdown in the system's stability. In such scenarios, the emergency control and protective unit of the microgrid becomes active and initiates a process of disconnecting non-essential loads, known as load shedding process. Hence, a load shedding strategy is necessary for such circumstances. In this paper, by sampling the bus voltage to which the sensitive loads are connected and calculating the voltage curve fitting, the emergency control system can estimate the maximum voltage drop caused by the imbalance and optimally shed the non-critical loads. Three different scenarios are defined. The simulation results verify the accurate performance of the proposed load shedding method.