الفهرس 
Chapter 1 IntroductionOnly 14 pages are availabe for public view
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Abstract
The basic responsibility of the independent system operator (ISO) in electrical power systems is to achieve the system reliability and security. Voltage control and reactive power support are essential services for enabling the delivery of power in the transmission grid, and providing adequate reserves. Sufficient reactive power sources are needed to maintain the power flow limits on transmission lines, and the voltage at bus-bars within their permissible limits.
The goal of this thesis is to find a methodology for optimal planning of reactive power sources (OPRPS) in electrical power systems in order to achieve maximum technical benefits and economical investment. It plans suitable location and size of new reactive power sources, and also optimally uses the available reactive power sources.
The formulation of the OPRPS considers several objective functions such as the installation and maintenance cost of the newly installed reactive power sources, the overall system losses, voltage deviation and voltage stability margin with maintaining the equality and inequality constraints. It is considered as a complex nonlinear constrained multi- objective optimization problem.
In this thesis, an iterative heuristic method based on the updated weak buses is proposed to determine the optimal placements and the most suitable sizes for installing additional reactive power sources. Moreover, a comparative study between the various integrated strategies of differential evolution algorithms, genetic algorithm, and particle swarm optimization are proposed to assess the OPRPS to minimize both the system operational cost of power losses and the investment cost in different power systems. All the algorithms are implemented in MATLAB 7.13 (R2011b) and run on a PC with Intel® core I7 CPU, 2.4 GHz, and 8 GB RAM.
Likewise, different modifications to this problem are proposed that reveal a lot of practical aspects of installing and operating the additional reactive power sources into the power system. Firstly, the operational cost of power losses is counted regarding to the fuel cost function of the active power generation at slack bus. Secondly, the investment cost of new VAR sources is modeled considering the
loss in value of its utilization during the lifetime. Thirdly, maximizing the savings due to MVA capacities release of transformer through the transmission network are incorporated, which is highly benefited on transmission and distribution systems especially in very loaded systems nowadays. Fourthly, the OPRPS problem is handled as multi-objective optimization problem and mixed discrete with practical steps of VAR sources and tap changers.
Furthermore, the differential evolution algorithm is developed based on search space concentration to handle the proposed single and multi-objective OPRPS optimization problems. Various objective functions are treated, which are minimization of investment and operational costs, maximization of MVA capacities release of transformers, voltage profile improvement, and voltage stability enhancement.
Last but not least, the developed multi-objective differential evolution is examined to solve the optimal power flow problem and comprehensively compared with various evolutionary methods reported in the literature.