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Abstract
In recent years, interests on the microgrid have been growing because it is a small-scale power system including clean energy sources, such as solar power, wind power, and fuel cells, as its major energy sources. To meet the rating frequency, 50 or 60 Hz, is an important requirement for microgrid operation. The frequency is closely related to a balance between power supply and power demand. Especially, load shedding, which is an intentional load reduction, is used in order to maintain the frequency in the case of supply shortage in the islanded operation mode. For this reason, the fairness for load shedding is an important topic for the load-shedding problem. Recently, the load-shedding scheme using the bankruptcy rule has been proposed as a reasonable method. In this paper, the load-shedding schemes using four well-known bankruptcy rules are compared and discussed in the viewpoint of fairness. For this, the fairness index is customized to evaluate fairness of load-shedding schemes for islanded microgrid operation in a multiagent system.
Key Words: Microgrid, Microgrid operation, Multiagent-based microgrid operation, Load-shedding scheme using bankruptcy rule, Fairness index
1. Introduction
The microgrid, which was proposed by R. H. Lasseter in 2001 [1], is a small-scale power system composed of distributed generation systems (DGs), such as solar power, wind power, and fuel cells, distributed storage systems (DSs), and loads. The microgrid provides electricity and/or heat to customers such as residential buildings, commercial buildings, public offices, and industrial compounds. The microgrid is considered as a clean energy system because of its renewable energy sources. Recently, research and demonstration projects for the microgrid have been undergoing in many countries [2, 3].
For operating the microgrid it is a very important requirement to meet the rating frequency, 50 or 60 Hz. That is, the microgrid should maintain a balance between power supply and demand because the rating frequency is very closely related to maintaining balance. In the grid-connected microgrid mode, the microgrid can trade power with the upstream power grid to maintain the balance. That is, the microgrid sells surplus power to the power grid and buys short power from the power grid for maintain the balance. In the case of fault occurrence in the power grid, the microgrid is disconnected to protect its components....