Page 34 - IJEEE-2023-Vol19-ISSUE-1

30 | Basim T. Kadhem

II. SYSTEM MODELS C. Static VAr Compensator (SVC)

A. Power System The studies employ a thyristor-controlled reactor (TCR) as
the SVC. The corresponding model of the SVC and its control
The system under discussion consists of a 200MVA steam system is shown in Fig. 3. A controllable voltage source
turbine synchronous generator (type TVV-200) connected to concealed behind a set reactance is how the controlled reactor
the infinite bus through a long transmission line with TCSC is depicted [10-19]. According to Fig. 1, the SVC unit is
and SVC fixed capacitors and an inductor whose inductance is attached to the capacitor terminal. Reactive power control and
variable by modifying the conduction angle of the thyristor in system voltage stabilization are the SVC's two main tasks. To
response to terminal voltage change, as illustrated in Fig.1. reduce the inertial and torsional modes, the auxiliary
The high-pressure turbine (HP), mid-pressure turbine (MP), stabilizing signal (Usr) is supplied to the main input of the
low-pressure turbine (LP), generator rotor (Gen), and exciter SVC controller.
are the five masses that make up the T-G set's shaft system
(EXC). At frequencies of 125 rad/sec, 174 rad/sec, 191 rad/sec, V Kour Ure B B
and 407 rad/sec, the shaft system has four torsional modes. For Tour s + 1
systems lacking TCSC and SVC, the first torsional mode is V - S +V f 1 B
unstable at 60% level compensation while the second and third K1ur s Trp s +1 S
modes are just slightly stable. The mathematical depiction of T1ur s + 1 -
the shaft system makes use of a spring-mass concept. The
electrical system for generators is represented using the Park's S
two axes model. One damper winding, one field winding, and
one damper winding on the d-axis and q-axis, respectively, are +
used to represent the rotor circuits. The comparable lumped
parameters of the transmission lines and step-up transformer Usr
serve as representations. In appendix I, the system's
electro-mechanical data are listed. B

Fig.3. Modeling for Static VAr Compensator (SVC).

Turbine D. Thyristor Controlled Series Compensation TCSC

Exc. Gen LP MP HP The TCSC, which enables quick and continuous changes
to the transmission line impedance, is one crucial FACTS
Synchronous (TCSC) component. Under a variety of operating conditions, active
Generator ?VV-200 power flows over the compensated transmission line can be
T RL ?L ?? kept at a given value. A TCSC module is shown schematically
?? in Fig. 4 and consists of a series capacitor bank parallel to a
Thyristor-controlled reactor (TCR). Fig. 4 illustrates the
equivalent TCSC model. The primary input to the TCSC is the
terminal voltage across the fixed capacitor error. In order to
reduce the inertial and torsional oscillation modes of (Vec), the
auxiliary stabilizing signal (Usc) is applied.

Vc Uref BCmax BCo

Vcref + Vce K ou? - 1
Tou? s + 1 Trp s + 1
SVC -S S S BC

+

?s Usc BCmin

Fig.4 Modeling for TCSC.

Fig.1. Schematic diagram of the system under study.

B. Excitation System III. THE ROBUST THE LQG/LTR CONTROLS

The excitation system utilized for the investigations is Typically, a notional model of the plant to be controlled
depicted in Fig. 2. The terminal voltage error (Ve) serves as the serves as the foundation for a control system's design. The
primary input to the excitation system. (Ve) is supplemented design process frequently involves the typical simplifications,
by the supplementary stabilizing signal (Usf) to reduce the such as linearization around an operating point or lumped
inertial and torsional oscillation modes. parameter approximation, and it frequently ignores the effects
of unmolded dynamics, sensor/actuator noise, and undesirable
Vg K 0u Ure Efmax Efo E external disturbances on various system components. The end
Vre + Ve T0u s + 1 result is an approximation plant, or uncertain plant as it is
f -S f 1 S sometimes referred as. Therefore, the controller's effectiveness
K1u s Tps +1 in assisting the real plant in achieving the intended goals must
T1u s + 1 - be a concern for the controller's designer, as well as the
viability of designing a controller that addresses more than just
S the aforementioned concerns. This results in the development
of robust control, as it is known today. When presented with
+ models that have large uncertainties, the robust control

Usf Efmin

Fig. 2. Excitation system used in the study.