In the last few years, microgrids have become a potential solution to improve reliability and security in the supply of electricity to power systems. When a microgrid changes its operation mode from grid-connected to islanded, particular attention must be paid by the operation services. In the islanded mode, the microgrids' frequency and voltage may reach undesirable values, harming the security and quality of the operation. This paper aims to propose global and local strategies of load shedding to preserve the energy supply to high priority loads within quality standards. The focus of this paper is to consider a microgrid operating only with primary control. In this sense, a proper microgrid time-continuous load flow is applied, considering the constant verification of the frequency and the voltage of all buses. Finally, a Monte Carlo Simulation is used to validate the proposal presented and to give some indices that quantify the load shed in each period. The results show the superior performance of the proposed strategy compared to a state-of-the-art load shedding solution that does not consider the priority of loads.
This paper presents a new methodology based on the incremental transmission loss concept for allocating electric losses to generators and loads, participating in multiple interconnected energy markets. The main objective is to generalize the formulation proposed in the companion paper, Part I, in order to identify through a decomposition technique, the amount of losses that each participant in the market causes on all system areas. The concept of interchange losses is introduced: the total amount of losses that occurs outside a given market whose agents are responsible for causing them. Some criteria to share these losses among the market agents are presented and discussed. The IEEE Reliability Test System is used to illustrate the proposed methodology.
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