| Περίληψη: | The continuous growth of demand and the dispersed nature of most new generation create a number of
challenges for modern Power Systems like dynamic stability, line limit utilization, power sharing
between different areas and reliability. Bus voltage magnitude is an important parameter for the quality
of a power system and it is related to the flow of reactive power across the lines. Bus voltage
magnitude is in direct relationship with the demand of reactive power. Decrease in bus voltages below
the minimum threshold of nominal voltage range may cause voltage collapse and increase in bus
voltage beyond the maximum threshold may lead to black out. The smaller the deviation of bus
voltages from nominal, the more stable the power system will be.
This research has been carried out with the goals of improving voltage profile of the system buses,
decreasing system losses and limiting line fault currents. Distributed Flexible AC Transmission System
Controllers (D-FACTS) are among those devices that can provide series compensation to the power
system. To achieve the goals, Distributed Thyristor Controlled Series Capacitor Device (D-TCSC) has
been utilized to provide series compensation to the network because of their simple structure, low cost,
quick response and communication capability. Mathematical model of the device has been
incorporated in the power flow equations by introducing new variables having lower and upper bounds
based on the levels of capacitive and inductive compensations those can be provided by these series controllers. The Matpower/Matlab platform has been used for formulation of power flow equations and
to calculate the gradients of equality and inequality nonlinear constraints. Objective function is
formulated considering the total cost of power generation and the cost of these devices. Knitro
optimizer has been utilized to find the optimal power flow solution. Further to this work, Fault Limit
Constraint on a transmission line has also been incorporated in power flow as a new nonlinear
constraint to find the optimal values for inductive compensation those satisfy the set fault constraint.
The methodology has been tested on IEEE 06-Bus and 30-Bus power systems. In both cases,
improvement in voltage profile has been observed. Reactive power line losses are reduced significantly
whereas active power dissipation across the lines remained same causing decrease in total MVA
generation of generating units. Some increase in line limit utilization of few lines has been observed;
however, in general the average line utilization of the network has been reduced. Moreover, the set
fault limit constraint has been respected with successful convergence to the optimal solution.
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