الفهرس 
صفحة العنوانOnly 14 pages are availabe for public view
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Abstract
A smart grid aims to modernizing the electric power delivery system so that it can effectively monitor, protect and automatically optimize the operation of its interconnected elements. Smart grid provides higher quality power supply in terms of voltage and frequency under different operating conditions.
Reactive power and voltage magnitude are tightly coupled. Many blackouts and brownouts throughout the world have been directly associated
to the phenomena of voltage instability, e.g. in Egypt, France, Italy, Japan, Great Britain, USA, etc. The study of this problem shows that the major reason is the system inability to draw enough reactive power to meet the demands at different operating conditions. The voltage control hierarchy consists of three levels: primary voltage control, secondary voltage control and tertiary voltage control. The primary voltage control is directed to control the voltage at the generator terminals while the secondary voltage control is
directed to control the load bus voltage and the tertiary voltage control is directed to calculate the optimal voltage values to optimally operate the power system.
The main objective of this work is to assure the security and optimal
operation of the system in terms of voltage control at different conditions through applying secondary and tertiary control levels. The secondary voltage control is implemented by controlling pilot bus voltage of each region. The pilot bus is a load bus with the highest sensitivity to reactive power variations in the region. Hierarchical automatic voltage regulation is
implemented in several power systems using the reactive power capabilities
of controlled alternators in transmission networks. With the introduction of power plants based on renewable energy sources, in the transmission network there are new possible participants to the voltage regulation which replace in part the traditional large alternators.
This research applies smart grid technologies to optimally control the load voltages under several conditions in different grids. The applied techniques will be demonstrated to control the voltage and the reactive power of the following grids
1.IEEE 14 bus system as a single region power system.
2.100% penetration level of renewables 14 bus grid
3.IEEE 39 bus system as a multi-region power system.
4.The Egyptian 500/220 kV grid
In the IEEE 14 bus system which is considered a single region power
system, the voltage control is applied to a load bus by using a genetic PID
controller, neural network and Phasor Measurement Units (PMUs). In addition, a 100% renewable grid model (based on the IEEE 14 bus system) is established to apply voltage and reactive power control considering grid codes of countries which have high penetration level of renewables. In the IEEE 39 bus system which is considered to be a multi-region system, secondary voltage control is applied to control the voltage at selected load buses (pilot buses). This is based on the graph theory method for system partitioning, PMUs, genetic PID controllers and neural network.
A digital model of the Egyptian grid was developed based on available
actual data of the power stations, transmission lines, transformers, reactors, capacitors and loads. Renewable energy parks/farms are integrated into the Egyptian grid considering the Egyptian grid codes.
In order to apply voltage and reactive power on the Egyptian grid, an
optimal wide area measurement system configuration based on total cost
minimization is presented. Also, a novel technique is presented to select the optimal pilot buses and is checked by short circuit analysis results. Optimal power flow is applied to achieve maximum reactive power reserve based at different operating conditions. The secondary voltage controller parameters are calculated to minimize the error between optimal voltage values resulted from optimal power flow and the measured voltage values of pilot buses.
The results have shown that artificial intelligence mainly neural network
based genetic algorithm and fuzzy logic can be used to achieve optimal
secondary voltage control based on power system optimization at different
operating conditions. Also, it is proved through results that wind farms and photovoltaic parks can support voltage control and reactive power control considering the renewable energy grid code integration limitations. The results recommend applying secondary voltage control in the Egyptian grid with an objective to maximize the reactive power reserve.
Two software applications the IgSILENT powerfactory 14.1.3 and MATLAB / Simulink 2017a were used to perform optimization and simulation studies.