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Ensuring the secure operation of power systems has become an important and critical matter during the present time, along with the development of large, complex and load-increasing systems. Security constraints such as the thermal limits of transmission lines and bus-voltage limits must be satisfied under all of a system's operational conditions. An alternative solution to improve the security of a power system is the employment of Flexible Alternating-Current Transmission Systems (FACTS). FACTS devices can reduce the flows of heavily loaded lines, maintain the bus voltages at desired levels, and improve the stability of a power network. The Unified Power Flow Controller (UPFC) is a versatile FACTS device that can independently or simultaneously control the active power, the reactive power and the bus voltage; however, to achieve such functionality, it is very important to determine the optimal location of the UPFC device, with the appropriate parameter setting, in the power system. In this paper, a genetic algorithm (GA) method is applied to determine the optimal location of the UPFC device in a network for the enhancement of the power-system loadability and the minimization of the active power loss in the transmission line. To verify our approach, simulations were performed on the IEEE 14 Bus, 30 Bus, and 57 Bus test systems. The proposed work was implemented in the MATLAB platform.

This paper present the speed controller based on fuzzy logic applied to photovoltaic water pumping systems driving by a brushless permanent magnet motor. The study proposed model consists essentially of photovoltaic generator associated to chopper converter controlled by fuzzy logic to ensure the maximum power point tracking. However, in order to have the desired performances, a robust controller is necessary. Through simulation results using MatLab/Simulink show that the performance of speed control then obtained by fuzzy logic depends variation of speed and load.

In this paper a stand-alone Photovoltaic systems is presented for water pumping. It based pumping systems without battery can provide a cost-effective use of solar energy. For this work of improving efficiency of the system controlled by fuzzy logic to ensure maximum power. This system and to show how to achieve an effective photovoltaic pumping system without battery storage. Results are presented based on different cases of irrigation pumping application and availability of solar irradiance are studied. Simulation results using MATLAB/SIMULINK show that the performance of the controllers both in transient as well as in steady state is quite satisfactory.

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