Computation of Delay Margin in a Power System Having Open Channel Communication Based Automatic Generation Control using Pade´ Approximation
10 Jun 2019-
TL;DR: A new and simple method based on Pade approximation and Routh–Hurwitz criterion to calculate communication delay margin for time delayed automatic generation control (AGC) system is proposed.
Abstract: This paper proposes a new and simple method based on Pade approximation and Routh–Hurwitz criterion to calculate´ communication delay margin for time delayed automatic generation control (AGC) system. In modern power systems, due to extensive use of open and distributed channel communication the stability is a concern as these types of communication systems lead to instability. Although various complex algorithms can be used to compute the delay margin (critical delay), this paper proposes a simpler method which is based on Pade´ approximation. The accuracy of the method is presented in the results obtained with MATLAB / Simulink simulation.
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TL;DR: In this article , the authors investigated the impact of frequency sensitive loads on system dynamics, and the effect of variation in damping coefficient (D) is studied and it is shown how the D is influencing the dynamics.
Abstract: In liberalized power system, the distribution companies are free to choose the contracts with all available generating companies (GENCOs), while the independent system operator acting as regulatory authority. In this article, the liberalized automatic generation control problem is studied for a two-area interconnected power system. The studies are divided into two parts. In first part, the investigations are carried out with only thermal generations in each area. In second part, the multi-diverse sourced thermal-hydro-gas GENCOs are assumed in each control area. For damping out the system frequency and tie-line power dynamics, the popularly known PI and PID controllers are employed considering poolco, bilateral and contract violation transactions. In both the parts, the comparative performance between PI/PID controllers is made. Studies reveal that PID outperforms PI controller. A case study with introduction of time delay in the system is performed as the open communication infrastructure introduces inherent time delay in the smart grid scenario. To understand the impact of frequency sensitive loads on system dynamics, the effect of variation in damping coefficient (D) is studied and it is shown how the D is influencing the dynamics. The effect of double reheat turbines is also studied and found that they deteriorate the dynamics when compared to single reheat turbines. In all the above studies, the powerful nature inspired firefly algorithm is employed to optimize the parameters of controllers using the integral squared error method.
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Book•
26 Jun 2003
TL;DR: Preface, Notations 1.Introduction to Time-Delay Systems I.Robust Stability Analysis II.Input-output stability A.LMI and Quadratic Integral Inequalities Bibliography Index
Abstract: Preface, Notations 1.Introduction to Time-Delay Systems I.Frequency-Domain Approach 2.Systems with Commensurate Delays 3.Systems withIncommensurate Delays 4.Robust Stability Analysis II.Time Domain Approach 5.Systems with Single Delay 6.Robust Stability Analysis 7.Systems with Multiple and Distributed Delays III.Input-Output Approach 8.Input-output stability A.Matrix Facts B.LMI and Quadratic Integral Inequalities Bibliography Index
4,200 citations
TL;DR: In this article, a direct method for determining both local and regional stability of systems described by nonlinear differential-difference equations is presented, with respect to a general class of initial curves.
Abstract: A direct method is presented for determining both local and regional stability of systems described by nonlinear differential-difference equations. Prediction of stability is with respect to a general class of initial curves. The practical as well as the conservative nature of the procedure is demonstrated by a numerical example.
1,087 citations
"Computation of Delay Margin in a Po..." refers methods in this paper
...Examples of frequency domain method are Schur-Cohn method [4], [5], Rekasius substitution [6]–[8] etc....
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TL;DR: Some new delay-dependent stability criteria are devised by taking the relationship between the terms in the Leibniz-Newton formula into account, which are less conservative than existing ones.
1,069 citations
TL;DR: A novel method is proposed in this note for stability analysis of systems with a time-varying delay by considering the additional useful terms when estimating the upper bound of the derivative of Lyapunov functionals and introducing the new free-weighting matrices.
Abstract: A novel method is proposed in this note for stability analysis of systems with a time-varying delay. Appropriate Lyapunov functional and augmented Lyapunov functional are introduced to establish some improved delay-dependent stability criteria. Less conservative results are obtained by considering the additional useful terms (which are ignored in previous methods) when estimating the upper bound of the derivative of Lyapunov functionals and introducing the new free-weighting matrices. The resulting criteria are extended to the stability analysis for uncertain systems with time-varying structured uncertainties and polytopic-type uncertainties. Numerical examples are given to demonstrate the effectiveness and the benefits of the proposed method
737 citations
"Computation of Delay Margin in a Po..." refers methods in this paper
...Examples of time domain method are use of Lyapunov theory of stability and linear matrix inequalities techniques [9]–[11]....
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TL;DR: This study presents a unique explicit analytical expression in terms of the system parameters which not only reveals the stability regions (pockets) in the domain of time delay, but it also declares the number of unstable characteristic roots at any given pocket.
Abstract: A general class of linear time invariant systems with time delay is studied. Recently, they attracted considerable interest in the systems and control community. The complexity arises due to the exponential type transcendental terms in their characteristic equation. The transcendentality brings infinitely many characteristic roots, which are cumbersome to elaborate as evident from the literature. A number of methodologies have been suggested with limited ability to assess the stability in the parametric domain of time delay. This study offers an exact, structured and robust methodology to bring a closure to the question at hand. Ultimately we present a unique explicit analytical expression in terms of the system parameters which not only reveals the stability regions (pockets) in the domain of time delay, but it also declares the number of unstable characteristic roots at any given pocket. The method starts with the determination of all possible purely imaginary (resonant) characteristic roots for any positive time delay. To achieve this a simplifying substitution is used for the transcendental terms in the characteristic equation. It is proven that the number of such resonant roots for a given dynamics is finite. Each one of these roots is created by infinitely many time delays, which are periodically distributed. An interesting property is also claimed next, that the root crossing directions at these locations are invariant with respect to the delay and dependent only on the crossing frequency. These two unique findings facilitate a simple and practical stability method, which is the highlight of the work.
582 citations