الفهرس 
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Abstract
Small-scale renewable energy resources (RERs) have been installed to distribution networks along the years, forming the concept of distributed generation/generators (DG/DGs). After that, these DGs in addition to other sources such as diesel generators introduced as a small-scale grid, named microgrids (MG). MGs have given high attention due to their ability to increase the operational efficiency of DGs and the whole power systems reliability and controllability. MG are categorized into AC microgrids (AC-MG), DC microgrid (DC-MG), and hybrid (i.e. contains both AC and DC buses) microgrid (H-MG). H-MGs are more beneficial due to the fact that they combine the merits of both AC-MG and DC-MG. In this thesis, a H-MG is proposed, which includes AC and DC buses, two voltage levels, linear and nonlinear loads, and different distributed generators such as diesel, wind, and PV besides storage units. Modified angle droop control is utilized in the coupling inverters between DC-MG and AC-MG because it leads to a much smaller standard frequency deviation than conventional droop control. Also, to enhance the intermitted sources of energy sharing and the system characteristics of damping, an additional control loop is introduced. Where, both the voltage angle and the voltage magnitude are corrected by adjusting the output of the droop controller. Moreover, due to the high R/X ratio of the study system as in rural area, the proposed angle droop control is enhanced by using some transformation to amend both the feedback gains and the droop equations to account for the high coupling between active and reactive power and enhance power-sharing in such case. Various simulation studies are executed to validate the proposed controller for H-MG operation and control. The studied system is based on a modified IEEE 14-bus and IEEE-33 bus test systems. Real wind speed and solar irradiance data, taken at Mansoura University-Egypt, are used in this study to show the accuracy of the proposed controller with actual operating conditions. Moreover, all studies in this system are made in form of comparison with conventional droop control to show the efficiency and quality of the proposed MG operation technique. Both controllers (i.e. droop control and proposed control) are applied to the system under study and system behavior in both cases is recorded. Voltage profile, power losses in all lines, power factor at all buses, and total harmonic distortion (THD) along the system are measured as metrics of controller efficiency and energy quality. Results show that the proposed controller results in better operating conditions in terms of lower losses and distortion in the system and higher power transmission efficiency.