Now showing 1 - 5 of 5
  • Publication
    Modeling and Stability Analysis of Power Systems with Discontinuous Right Hand Side Differential, Algebraic Equations
    (University College Dublin. School of Electrical and Electronic Engineering, 2021) ;
    Power systems are one of the most complex dynamic systems due to their multi-time scale and non-linear nature. This work focuses in particular on the electromechanical dynamics of power systems which are hybrid (discrete-continuous) and are therefore studied using a set of Hybrid Differential-Algebraic Equations (HDAEs) or Discontinuous Right-Hand Side DAEs (DRHS DAEs). Traditional HDAEs possess several challenges during modeling, implementation, and numerical simulation stages, depending on the nature of the discontinuities arising from different applications. This thesis studies the impact of discontinuities on power system physical stability as well as on the numerical stability of a solver considering two specific discontinuous models. The first model is an under load tap changing transformer, which introduces a discrete variable in the DRHS DAEs due to the physical operation of the transformer. The second model is a proportional-integral controller used in different components of power systems, e.g. voltage source converter and automatic voltage regulators which introduces a discontinuity in the state and algebraic variables of DRHS DAEs. In particular, a thorough discussion of the deadlock and chattering issues during time-domain simulation arise from the latter model is provided. This discussion is based on two time domain simulation techniques widely used in power system tools, namely, time-stepping and event-driven method. To solve the deadlock and chattering issues in both of these simulation techniques, a theoretical approach given by Filippov is proposed. Case studies with small to large sizes, e.g., single machine infinite bus, WSCC 9-bus, IEEE 14-bus, 74-bus Nordic system and all-island Irish system with 1479-buses connected to a simplified 63-bus Great Britain system through a high-voltage direct current link are considered and tested in the thesis. Simulation results indicate the importance of accurate modeling and implementation of discontinuous models for dynamic analysis.
  • Publication
    Power system modelling as stochastic functional hybrid differential-algebraic equations
    This paper presents the software tools developed for the research project Advanced Modelling for Power System Analysis and Simulation (AMPSAS) funded by Science Foundation Ireland from 2016 to 2021. The main objective of AMPSAS was the development of novel analytical and computational tools to understand, efficiently design, and optimise ever-changing modern power systems and smart grids, through model-based approaches. In particular, the paper discusses (i) stochastic differential equations for modelling power systems, which are subject to large stochastic perturbations (e.g. wind and solar generation); (ii) the effect of controller and modelling imperfections, for example, delays, discontinuities, and digital signals, on both local and area-wide regulators in power systems; and (iii) the stability analysis and dynamic performance of power systems modelled through stochastic, delay and hybrid implicit differential-algebraic equations. The software tool developed during the execution of AMPSAS integrates areas of applied mathematics, automatic control, and computer science. Several implementation features and open challenges of this software tool are also discussed in the paper. A variety of examples that illustrates the features of this software tool are based on a dynamic model of the all-island Irish transmission system.
    Scopus© Citations 1  13
  • Publication
    Stability Analysis of Wide Area Damping Controllers with Multiple Time Delays
    The paper discusses the impact of multiple time delays on the stability of centralized wide area damping controllers (WADCs). These controllers are utilized in electric power systems to damp the interarea oscillations. With this aim, an ideal WADC is first designed based on the well-known H∞ control scheme. Then delays are included for all remote signals of the WADC and different delay models, namely, constant, stochastic and periodic delays with dropout, are considered and compared. Both nonlinear time domain simulations and closed-loop eigenvalue analysis based on the 2-area test system are carried out. Finally, a probabilistic method to evaluate the impact of stochastic communication delays on small-signal stability is discussed.
    Scopus© Citations 4  11
  • Publication
    Theory and Implementation of Fractional Order Controllers for Power System Applications
    (Institute of Electrical and Electronics Engineers, 2020-11) ; ; ;
    The paper presents the theoretical foundation and practical implementation aspects of Fractional Order Controllers (FOCs) for power system applications. With this aim, the paper provides a comprehensive mathematical background on the stability analysis of dynamic systems with inclusion of fractional order derivatives and discusses their software implementation based on the Oustaloup's Recursive Approximation (ORA) method. Then the paper illustrates a variety of examples of ORA-based FOCs, namely, automatic generation control of synchronous machines; frequency control of a converter-interfaced energy storage system; and voltage control through a static synchronous compensator. The WSCC 9-bus test system and a realistic 1,479-bus model of the Irish transmission system are employed to test and compare the examined FOCs with their integer-order versions.
    Scopus© Citations 42  21
  • Publication
    Using Differential Geometry to Revisit the Paradoxes of the Instantaneous Frequency
    (Institute of Electrical and Electronics Engineers, 2022-06-28) ; ; ; ;
    This paper proposes a general framework to interpret the concept of Instantaneous Frequency (IF) in three-phase systems. The paper first recalls the conventional frequency-domain analysis based on the Fourier transform as well as the definition of IF which is based on the concept of analytic signals. The link between analytic signals and Clarke transform of three-phase voltages of an ac power system is also shown. Then the well-known five paradoxes of the IF are stated. In the second part of the paper, an approach based on a geometric interpretation of the frequency is proposed. This approach serves to revisit the five IF paradoxes and explain them through a common framework. The case study illustrates the features of the proposed framework based on a variety of examples and on a detailed model of the IEEE 39-bus system.
    Scopus© Citations 2  10