Page 33 - IJEEE-2023-Vol19-ISSUE-1

Received: 20 August 2022 Revised: 27 September 2022 Accepted: 27 September 2022
DOI: 10.37917/ijeee.19.1.4
Vol. 19| Issue 1| June 2023

Ð Open Access

Iraqi Journal for Electrical and Electronic Engineering

Original Article

Using a Reduced Order Robust Control Approach to

Damp Subsynchronous Resonance in Power Systems

Basim T. Kadhem
Electrical Engineering Department, University of Basrah, Basrah, Iraq

Correspondence
* Basim T. Kadhem
Electrical Engineering Department

University of Basrah, Basrah, Iraq.
Email: basim.kadhem@uobasrah.edu.iq

Abstract
This work focuses on the use of the Linear Quadratic Gaussian (LQG) technique to construct a reliable Static VAr
Compensator (SVC), Thyristor Controlled Series Compensator (TCSC), and Excitation System controller for damping
Subsynchronous Resonance ( SSR ) in a power system. There is only one quantifiable feedback signal used by the controller
(generator speed deviation). It is also possible to purchase this controller in a reduced-order form. The findings of the robust
control are contrasted with those of the "idealistic" full state optimal control. The LQG damping controller's regulator
robustness is then strengthened by the application of Loop Transfer Recovery (LTR). Nonlinear power system simulation is
used to confirm the resilience of the planned controller and demonstrates how well the regulator dampens power system
oscillations. The approach dampens all torsional oscillatory modes quickly while maintaining appropriate control actions,
according to simulation results.
KEYWORDS: Flexible AC Transmission Systems, FACTS, Linear Quadratic Gaussian, LQG Control, Loop Transfer
Recovery, LTR method, Power System Oscillation Damping.

I. INTRODUCTION (static VAr compensation) and excitation systems, H.R. Liang;
A.V. Prokhorov and H. Mokhlis, [3] developed an analytical
Three factors, namely voltage, impedance, and phase model of the TCSC. However, data revealed that die interarea
difference, affect the amount of power that is transmitted over mode is less damped when uncertain load factors are present.
a power system network. Flexible AC transmission systems are H. Ghorbani; D. E. Moghadam; A. L.and J. I. Candela [4]
the result of high voltage and high current power proposed the resilient adjustment of SVC. There are no
semiconductor device development (FACTS). FACTS devices controllers or schemes that can successfully dampen all SSR
are power electronics-based systems and other stationary modes at various levels of series compensation, over extremely
machinery that regulate one or more AC transmission system light load to overload conditions, for various types of severe
parameters [1]. In order to adapt changes in operating faults, according to a thorough review of the literature (without
circumstances of an electric transmission system while considering the natural damping of the system) [5–9].
maintaining enough steady-state and transient stability
margins, series compensator and static VAr systems (SVC) are In order to dampen the inertial and torsional modes of T-G
utilized as the FACTS devices in power systems. The issue of sets, a reliable control method is presented in this study.
subsynchronous resonance (SSR), which has two unique Generator speed deviation is the controller's input, and three
impacts, namely the induction generator effect and torsional control signals are its outputs. The Linear Quadratic Gaussian
interactions effect, is caused by the series compensation of a with Loop Transfer Recovery (LQG/LTR) is the foundation of
transmission line. The Turbine-Generator (T-G) set's shaft is the controller. This technique's primary benefit is its ability to
susceptible to breaking due to torsional vibrations, which could deliver strong performance with just one output feedback.
have disastrous effects [2]. In order to investigate the Additionally, the designed controller is reduced. For
subsynchronous torsional interaction between the thyristor evaluation purposes, the LQG/performance LTR's is
controlled series compensation (TCSC) and the turbine contrasted with that of the full state feedback optimum control.
generator shaft and to assess the control interactions between The system depicted in Fig. 1 is the subject of the
the TCSC and other power system components like the SVC investigation.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and

reproduction in any medium, provided the original work is properly cited.

© 2022 The Authors. Published by Iraqi Journal for Electrical and Electronic Engineering by College of Engineering, University of Basrah.

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