An underfrequency load shedding scheme for islanded microgrids

• In this paper an UFLS scheme for implementing in MG was proposed.
• This load shedding method estimates the power deficit based on the frequency first derivative.
• It considers power generation variations during the load shedding process.
• The proposed load shedding scheme is independent from MG parameters.
• A microgrid with several DER is adopted to demonstrate the effectiveness of the proposed method.

The underfrequency load shedding scheme is an important protective schemes, responsible for maintaining frequency of power systems within permissible limits in case of severe power deficits and as such, its proper performance is of great interest. In microgirds, disconnecting/connecting power generation sources and loads result in variations in the system parameters. Moreover, the output power of some distributed energy resources such as photovoltaic/wind turbine generators, might change during load shedding process and consequently affect the performance. Hence, an underfrequency load shedding scheme is proposed here which is not only independent of the microgrid parameters, but also considers power generation variations during the process. A microgrid power system with several distributed energy resources is adopted to demonstrate the effectiveness of the proposed method.