ABSTRACT
Power system stabilizers and other controllers are employed to damp oscillations in
power systems, thereby guaranteeing satisfactory dynamic performance following major
network disturbances. However, the parameters of these controllers are often tuned based
on the power system linearized model which generally is a function of the system
operating point or state. These controllers suffer from poor performance when the system
state changes. The aim of the research work reported in this Thesis is to develop
nonlinear synchronous generator excitation control schemes with control laws for
providing improved transient stability when the system is subjected to wide parameter
variations due to network disturbances. The study employed fourth-and third-order
models of a single-machine-connected-to-an-infinite-bus system to design two nonlinear
sliding mode control laws (CLs) and one finite-time homogeneous control law (CL),
which were constructed based on a well-chosen output function of the system. The
parameters of the control laws were properly selected and/or tuned to give desirable
dynamic characteristics using well established linear control methods. Justifications for
the selection of the fourth-and third-order synchronous generator models to design the
aforesaid controllers are presented. Dynamic simulations of the system under the action
of the control laws were carried out using MATLAB®/SIMULINK. In order to test the
performance of the laws, several simulation studies were performed when the voltage
magnitude (V) of the infinite bus and the transmission line reactance (XE) of the system
changed due to an applied three-phase symmetrical fault at the infinite bus and generator
terminals. Results obtained from these studies show that the dynamic characteristics of
the system being investigated have improved significantly, in terms of the rotor angle and
rotor speed first peak, damping of low-frequency mechanical oscillations in rotor angle
following fault clearance, and settling times of key stability indicators (rotor angle and
rotor speed). For instance, for application of each of 5-cycle, 7-cycle, and 9-cycle fault at
the infinite bus, the system rotor angle settled to its stable steady values within 1 - 2.2s
with minimal control effort that varied between -5pu and 5pu before settling at the prefault
value of 1.5603pu in 4.32s (CL1), in 1.92s (CL2), and in 3.32s (CL3). Whereas,
CL3, which is a contribution to the improvement of the existing general higher-order
sliding mode control structure for synchronous excitation control, was able to make the
system withstand greater fault duration than CL1, CL2, which has a new positive
parameter (called the dilation gain) incorporated into it, furnished the system with the
greatest fault-retaining capability. In practice, the implementation of the three control
laws can be carried out in a static exciter configuration with a very fast response.
AWELEWA, A (2021). Development Of Nonlinear Control Schemes For Electric Power System Stabilization. Afribary. Retrieved from https://track.afribary.com/works/development-of-nonlinear-control-schemes-for-electric-power-system-stabilization-1
AWELEWA, AYOKUNLE "Development Of Nonlinear Control Schemes For Electric Power System Stabilization" Afribary. Afribary, 20 May. 2021, https://track.afribary.com/works/development-of-nonlinear-control-schemes-for-electric-power-system-stabilization-1. Accessed 24 Nov. 2024.
AWELEWA, AYOKUNLE . "Development Of Nonlinear Control Schemes For Electric Power System Stabilization". Afribary, Afribary, 20 May. 2021. Web. 24 Nov. 2024. < https://track.afribary.com/works/development-of-nonlinear-control-schemes-for-electric-power-system-stabilization-1 >.
AWELEWA, AYOKUNLE . "Development Of Nonlinear Control Schemes For Electric Power System Stabilization" Afribary (2021). Accessed November 24, 2024. https://track.afribary.com/works/development-of-nonlinear-control-schemes-for-electric-power-system-stabilization-1