الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 125 |  |  |
| | | from | 125 | | |
Abstract
Integration of distributed energy resources (DERs), renewables and non-renewables, forming what is called ‘Microgrids (MGs)’ has been widely deployed to benefit both utilities and consumers. MGs are continuously developed along with the progress in information and communication technologies (ICTs). Technologies of MGs help power grid evolve into one that is more efficient, lesspolluting, reduced losses, and more flexible to provide energy consumers’ want and need. However, because of thenature of various renewable energy sources (RESs) integrated into the MGs such as variability and inabilityto accurately predict and control, different technical problems have been created. Power quality (PQ) is one of the mostimportant issues to be addressed, especially harmonic distortion and voltage stabilization. These two aspects may result from loads nonlinearity due to the presenceof electronic devices and drives in consumers’ premises, andsources uncertainty due to both of generation intermittencyof renewable sources and the electronic interface devices.To improve the quality of power, several distributed flexible AC transmission systems (D-FACTS) topologies have been employed dealing with all DERs condition variations.
Three modes of operation MGs can operate in; utility grid-connected, islanded and isolated.Several isolated MGs may exist in remote areas because of the geographical and/or utility investment limitations. The isolated MG has its own advantages and challenges depending on its configuration, energy sources and nature of loads. Clustering these MGs based on their relative locations to constitute a number of clusters and interconnecting the MGs of each cluster for providing regional power supply may add more advantages such as enriching the reliability, improving the stability and economic operation. This entails the capability of energy sharing between the energy sources within individual MGs and the power exchange among MGs through designing an effective energy management system (EMS).
The objective of this work is topay attention forimproving the performance of individual isolated MGs by studying two important issues;PQ issue that arises due to nature of various RESs integrated into the MGs andan EMS which is essential for optimal use of the DERs in intelligent, secure, reliable, and coordinated ways. First,an adaptive switched filter compensator (ASFC) with developed proportional-integral-derivative (PID) controller is proposed to improve the overall dynamic performance of the MGs. The PID’s controller gains are optimally tuned via the application of grasshopper’s optimization algorithm (GOA) to act adaptively with self-tuning as the
operating conditions may subject to change during MG operation. Different case studies are proposed to reveal the robustness of the presented ASFC on harmonic mitigation, dynamic voltage stabilization, reactive power compensation and power factor improvement considering the features of RESs such as variations of wind speed, solar photovoltaic (PV) irradiation and temporary fault conditions. A distribution synchronous static compensator (D-STATCOM), as one of the most popular D-FACTS, with optimal tuned PID controller by using the GOA is also proposed. To validate both the proposed ASFC topology and the modified D-STATCOM, comparative studies including what has been published in literature are examined by using MATLAB/Simulink platform.
Second, with clustering the MGs, this thesis presents a proposed EMS, whose design is based on hierarchical decentralized strategy for a cluster of interconnected MGs. The criterion of the proposed EMS design encompasses two key steps. First, developing a MG central controller (MGCC) in each MG. It is connected to local controllers (LCs) associated with MG components, one for each, to optimally manage the utilization of power among a large-scale hybrid distributed renewable and nonrenewable energy resources and energy storage systems (ESSs). An optimization technique, e.g., GOA is applied with an objective function formulated as costs minimization of both maintenance and emission of the fossil fuel generators. This should ensure the power balance between supply and loadsand identifying the events at which load shedding is allowed, especially when handling the intermittency of renewable sources. Second, defining the function of the MG operator (MGO) that helps achieve the power exchange among the cluster-MGs with a goal of surmounting any probable unbalance between generations and demand overall the area covered by the cluster. Different cases are studied using the MATLAB/Simulink platform. The results confirm the effectiveness and robustness of the proposed strategy.