الفهرس 
Voltage Instability Problem StatementOnly 14 pages are availabe for public view
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Abstract
This thesis proposed an integrated method to deal with the voltage
instability problem in radial distribution networks (RDNs). This problem
arises due to the ever-increasing load demand which pushing the power
systems to their stability boundaries and increases the risk of widespread
of partial blackouts. The central core of this strategy is based initially on
finding a method to define voltage stability boundaries and index, then
the requirements of this analysis are determined. Accordingly, the
appropriate solution for voltage instability can be finally found.
The proposed method implies the following main tasks ; load flow
analysis for computing the bus voltage and power flow required for
computing voltage stability index (SI), voltage stability analysis to
evaluate the SI for each bus (node) of the system, voltage stability
enhancement to mitigate voltage stability problem by applying the
proposed solutions and finally economic study is implemented to choose
the best solution.
The developed load flow method which based on the
Forward/Backward (F/B) sweep process which is based on the ladder
system theory will be capable of handling the unique properties of RDN
with any number of buses and different loads to find the voltage at each
bus, power flow on each branch and the total system power losses more
accurately among with less time of calculation.
The SI is taken from the bi-quadratic equation which is commonly
used for the voltage stability calculation of distribution load flow
algorithms. A developed formula for computing the SI of all nodes of any
distribution network is proposed in this thesis work. Accordingly, the
weakly node having the minimum value of SI is the most sensitive node
to voltage instability which may result in a voltage collapse.
Installation of DGs in non-optimal places, sizes and without
selecting power factors may result in an increase in system losses; voltage problems cause more voltage instability. Optimal DG‟s
location and size affect the voltage stability improvement resulting
an increase in system power loss and others for minimizing the
system power loss resulting voltage instability trouble. Therefore,
an optimization algorithm is needed so that it can find the optimal
location, size, and power factor to enhance the voltage profile and
minimize system power losses.
Therefore, DGs sizes and locations must be selected optimally.
Optimally placement of DGs can be achieved via maximize SI or
minimize the system power loses or both depending on the system
characteristics and required performance, which gives the maximum
reduction in system power losses and improves the voltage profile. Two
new algorithms (Ant Lion optimizer and Whale Optimizer algorithm)
compared with particle swarm optimization (PSO) are used for optimal
locations, sizing and power factor of different DG types.
An economic analysis is implemented on the three tested systems
after VS enhancement to find the most economical solution.
The proposed strategy is implemented in three tested systems, two
standard systems the IEEE 33-bus, 69-bus, and also a practical system of
34-bus in Kafr Elsheikh City to evaluate its effectiveness. All the required
software is developed using MATLAB as a platform. The results denote
the effectiveness of the presented methodology in minimizing the system
losses and improving the voltage profile.
Keywords: Voltage stability enhancement; forward/backward sweep;
distributed generation; ant lion optimizer; whale optimize algorithm;
particle swarm optimization; economic analysis.