On the Control of Time Delay Power Systems (original) (raw)
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Wide-range reliable stabilization of time-delayed power systems
TURKISH JOURNAL OF ELECTRICAL ENGINEERING & COMPUTER SCIENCES, 2016
Steam valve control is usually discarded in power system stability due to belief in its slow response. The present manuscript makes use of it as a backup control in the case of failure of the main fast excitation control. The model describing system dynamics as a function of the two controllers, with wide range loading conditions, is derived in a norm-bounded format. Linear matrix inequalities are derived as a sufficient condition to obtain reliable controllers that provide good oscillation damping when both controllers are sound or even in the case of failure of either one. The design scheme is robust in the sense that it keeps reliable stability against wide load changes as well. A single machine infinite bus system is presented to illustrate the proposed design procedure and exhibit its performance. Results of excitation and governor controller testing show that the desired performance could be fulfilled from light load to heavy load conditions. System performance shows a remarkable improvement of dynamic stability by obtaining a well-damped oscillation time response even in the case of failure of either controller. Extension of the proposed controller to multiarea load-frequency control with time delay is also presented.
Hinfin;controllers for linearised time-delay power systems
Three H,-control schcmcs arc developed for the stabilisation of power-system models with state delays. Two control schemes which consist of one gain term representing pure statc feedback are proposed first. Then, a controllcr consisting of two gain terms comprising pure plus delayed slate feedback is developed. The proposed controllcrs guarantee the asymptotic stability of the controlled system and the Ifm-norm bound of the closed-loop transfer function of the system. The associated gains are determined in each case from the solution of a litiear-matrix-ineqluality feasibility problem. Simulation results of the proposed schemes are presented and discussed.
Robust stabilizing controller for an interconnected power system: a time delay approach
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This paper focuses on the problem of robust stabilization of power systems. The power system model contains input delays due to the synchronization of the measurements. Sufficient conditions for the closed loop stability of the linearized power system model are given in terms of the existence of symmetric and positive-definite solutions of linear matrix inequality contraints. A controller that robustly stabilizes the power system is designed, in the presence of this time-delay. The proposed controller was tested on two standard 4-machine power system model. The robustness of the controller with respect to the increasing of tie-line power flow as well as the inter-area oscillations present in the test systems is also assessed.
Research on the Low-order Control Strategy of the Power System With Time Delay
In this paper, the design problem of the low-order controller is considered for the power system with a fixed time delay. A linear model of the power system with time delay is firstly established. Then the proportional-integral-differential (PID) controller, which is the typical low-order controller, is designed to improve the stability of the power system. The stabilizing region of the PID controller is obtained. The control parameters chosen arbitrarily in the resultant region can ensure the stability of the power system. Finally, based on the stabilizing result, the PID controller satisfying the H∞ performance index is designed, which improves the robustness of the whole power system. The main advantage of the proposed method lies in that there is no need to approximate the model of the power system. The method can be further extended to the power system which is more complex.
Impact of Time Delays on Power System Stability
IEEE Transactions on Circuits and Systems I: Regular Papers, 2000
The paper describes the impact of time-delays on small-signal angle stability of power systems. With this aim, the paper presents a power system model based on delay differential algebraic equations (DDAE) and describes a general technique for computing the spectrum of DDAE. The paper focuses in particular on delays due to the terminal voltage measurements and transducers of automatic voltage regulators and power system stabilizers of synchronous machines. The proposed technique is applied to a benchmark system, namely the IEEE 14-bus test system, as well as to a real-world system. Time domain simulations are also presented to confirm the results of the DDAE spectral analysis.
Small-Signal Stability Analysis of Delayed Power System Stabilizers
This paper presents a stability analysis of power system stabilizers (PSS) for synchronous generators with inclusion of time delays. The paper shows that a time delay in the PSS feedback loop can improve the small-signal stability of a power system if the regulator gain is properly tuned. The paper provides a proof-of-principle analysis based on the classical model of the synchronous machine as well as a case study based on a detailed transient model of the IEEE 14-bus test system. The paper also provides a discussion on the practical implications that the properties of delayed PSS can have on the control of synchronous machines and of the whole power system.
Time-delay power systems control and stability with Discretized Lyapunov Functional method
Proceedings of the 33rd Chinese Control Conference, 2014
Control design and stability analysis are developed for time-delay power systems. The coupled differential-difference equations are used to model the practical power system dynamics. A robust state feedback controller design stabilizing the unstable power plant is proposed first. Then, the stability analysis with Discretized Lyapunov Functional method is conducted. The overall system stability is determined from the solution of a linear matrix inequality feasibility problem. Numerical simulation results of the proposed schemes are presented and discussed to illustrate the effectiveness and robustness in power systems control and stability applications.
H∞-controllers for linearised time-delay power systems
IEE Proceedings - Generation, Transmission and Distribution, 2000
Three H,-control schcmcs arc developed for the stabilisation of power-system models with state delays. Two control schemes which consist of one gain term representing pure statc feedback are proposed first. Then, a controllcr consisting of two gain terms comprising pure plus delayed slate feedback is developed. The proposed controllcrs guarantee the asymptotic stability of the controlled system and the Ifm-norm bound of the closed-loop transfer function of the system. The associated gains are determined in each case from the solution of a litiear-matrix-ineqluality feasibility problem. Simulation results of the proposed schemes are presented and discussed.
TURKISH JOURNAL OF ELECTRICAL ENGINEERING & COMPUTER SCIENCES, 2016
This paper studies the impact of load increase and a power system stabilizer (PSS) on the stability delay margin of a single-machine-infinite-bus system including an automatic voltage regulator. An analytical method is proposed to determine the stability delay margin of the excitation control system. The proposed method first eliminates transcendental terms in the characteristic equation of the excitation system without making any approximation and transforms the transcendental characteristic equation into a regular polynomial. The key result of the elimination process is that the real roots of the new polynomial correspond to the imaginary roots of the transcendental characteristic equation. With the help of the new polynomial, it is also possible to determine the delay dependency of system stability and the root tendency with respect to the time delay. Delay margins are computed for various loading conditions and PSS gains. It is observed that the delay margin generally decreases as the PSS gain and load demand increase, resulting in a less stable system.
Delayed Feedback Controller for stabilizing subsynchronous oscillations in power systems
2009
This paper presents a novel controller based on the delayed feedback control theory for stabilizing unstable torsional oscillations caused by Subsynchronous Resonance (SSR) in power systems. The first system of the IEEE Second Benchmark Model, which consists of a synchronous generator connected to an infinite busbar through two parallel transmission lines, one of which is equipped with a series capacitor, is used to evaluate the controller's effectiveness. Dynamics of the generator damper windings and the Automatic Voltage Regulator (AVR) are included in the nonlinear model. The controller uses the synchronous generator rotor angular speed as the only input. The difference between the input signal's value ¿-time in the past and its current value is multiplied with a gain to obtain the controller output, which is then combined into the AVR as the stabilizing signal. The effectiveness of the proposed controller in damping the torsional oscillations is demonstrated via time-dom...