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The precision with which directional overcurrent relays (DOCRs) are set up establishes the microgrid customers' access to reliable and uninterrupted electricity. In order to avoid failure in DOCRs operation, it is critical to consider a single contingency (N-1 event) on the protection optimization setting problem (POSP). However, power systems may face cascading outages or simultaneous contingencies (N-K events), which greatly expand the problem's complexity and scale. The effect of cascading events on this problem is an open research gap. Initially, this paper proposes a novel approach to reducing the scale of simultaneous events called the N-K events scale reduction technique (N-K-ESRT). Moreover, an innovative method named fuzzy zero-violation clustering is utilized to group these contingencies. Ultimately, the DOCRs' decision parameters are generated by three optimization algorithms, namely interior point (IPA), simulated annealing, and pattern search. In all case studies (including a real industrial network called TESKO2 feeder, the IEEE Std. 399-1997, and the IEEE 14 bus systems), the capabilities of the proposed method are effectively validated based on the DOCR's tripping time and the algorithm's execution time. [ABSTRACT FROM AUTHOR]

Photovoltaic is one of the renewable energies in generating electricity. The MPPT as effective technique can improve the performance of photovoltaic cells. Key problem in photovoltaic systems is that it does not achieve much power since the various weather conditions effects on photovoltaic power cells in working such as solar radiation or rainy and cloudy weather. Therefore, the MPPT in PV cells runs and leads to change during the day and seasons. On the other hand, providing an appropriate controller for the MPPT is too important. Here, main purpose is applying the robust controller, which is tuned by firefly algorithm to optimize MPPT in photovoltaic systems. The main reason to propose this method is some defects in previous controllers such as low stability, low battery lifetime, inability to combine AC/DC and low efficiency. The suggested model is performed by MATLAB/Simulink software. Finally, the FLFA model has higher efficiency and best dynamic response than other methods. [ABSTRACT FROM AUTHOR]

Power system is getting complex due to a boost in the number of new power plants and the expansion of the transmission system in order to meet the growing for electricity. This scenario results in a large number of short circuits in the system, which may exceed the rating of existing circuit breakers (CBs) and may severely destroy system equipment. Installing fault current limiters (FCLs) into the power system is one of the most cost-effective ways to degrade fault current levels. This paper presents a method to specify the optimal numbers and locations for FCLs placement in terms of installing the smallest FCL parameters to restrain short-circuit currents below the interrupting currents of circuit breakers, to minimize transmission loss. Due to a lack of genetic, PSO and other optimization algorithms, an Elitist Gravitational Search Algorithm (EGSA) for more accurate and better results is used. This algorithm is employed to search for the location and parameter of FCLs to meet the specific requirements. The proposed method is applied to the IEEE 30-bus test system. Simulation results indicated the adequacy and precision of the proposed method [ABSTRACT FROM AUTHOR]