الفهرس 
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Abstract
In this thesis, grid-connected and islanded microgrids power quality issues are addressed. A new Unified Power Quality Conditioner (UPQC) control system is proposed based on fuzzy logic control system. The proposed UPQC system is activated if Total Harmonic Distortion (THD) percentage exceeds a certain limit. During normal operation “accepted harmonic and voltage levels”, the proposed UPQC system is deactivated. The new UPQC is applied on grid connected microgrid system with variable load and renewable generation. The new UPQC system is simulated to validate the proposed method. This thesis introduces a new approach for AC/DC Power System (PS) configuration of islanded microgrid electric ships. A new control system for the load sharing system of the main three different ratings Active Front End Rectifiers (AFER) is proposed, which increases the AFERs lifetime and consequence reducing the rectifiers maintenance cost. The proposed AC/DC system has two main buses AC bus and DC bus. It has the capability to supply different AC loads directly from the AC bus. It supplies the DC loads and variable speed inverted loads from the DC bus. Using the proposed AFERs control system, the generators currents become sinusoidal respecting the standards of Institute of Electrical and Electronics Engineers (IEEE) and the international marine classification societies’ limitations for harmonics. The proposed PS can be applied in All Electrical Ships (AES), especially naval ships that need multiple frequency drives. The dissertation proposes a new Power Management System (PMS) for the new proposed ship PS configuration. The research proposes also a method for Fault Detection System (FDS) for the proposed AC/DC system. This work investigates a harmonic mitigation technique for a modern Electrical Propulsion Ships (EPS) microgrids using Multi-Pulse Rectifier (MPR) and Multi-Level Inverter (MLI) based Variable Frequency Drive (VFD). In this work, the proposed MPR-MLI-VFD system is studied using rectifier and inverter with different pulse levels to get the proper solution that reduces the harmonics in the main generating power system of the ships. So that, they are within the marine classification society’s limitations for harmonics. This is achieved using accepted harmonics multi-pulse rectifiers. Moreover, the voltage harmonic distortions at propulsion motor feeder buses are minimized. Fuzzy logic control is the proposed system for speed control of VFD. Matlab / Simulink is used for simulation and validation process. The results are compared with those obtained by conventional methods.