Now showing 1 - 10 of 35
  • Publication
    Validating Two Novel Equivalent Impedance Estimators
    Certain approaches to appraising voltage stability use an equivalent impedance to characterise the wider power system. This letter proposes two newways of inferring an appropriate equivalent impedance from a powersystem's admittance matrix. Continuation power flow simulations are used to validate the quality of the new estimators, and to benchmark them against some extant approaches.
  • Publication
    Hardware-in-the-Loop Validation of the Frequency Divider Formula
    This paper validates a theoretical approach, namely, the frequency divider formula, recently proposed by the first and fourth authors to estimate local frequency variations based on the synchronous machine rotor speeds and on signals from phasor measurement units (PMUs). The validation is based on simulations performed in a Real-Time Digital Simulator with physical PMUs connected in the loop. The case study considers the well-known WSCC 3-machine, 9-bus test system. Simulation results show the high accuracy of the frequency divider formula to estimate the frequency at every bus of the network. Results also show that the frequency divider prevents the numerical issues due to fast variations of the voltage when measured by the PMU and indicate that such a formula can be utilized to test the fidelity of PMU implementations.
  • Publication
    100% Converter-Interfaced generation using virtual synchronous generator control: A case study based on the irish system
    The increase in the use of Converter-Interfaced Generation (CIG) in the power system will require these generators to not only feed the power but also establish the voltage and maintain the grid stability. Virtual Synchronous Generator (VSG) control of the CIG is proposed to fulfill this requirement since it mimics the dynamics of synchronous generation. This paper takes the all-Island Irish transmission system as an example to investigate the frequency stability of the system as it migrates towards 100% CIG under VSG control and quantifies the minimum conditions for frequency support to sustain the system under 100% CIG. Simulations are carried out considering the worst contingency in the Irish grid which is the loss of largest infeed, namely, the disconnection of the HVDC interconnector to the UK. The results are compared and discussed considering other scenarios that include primary frequency control of conventional power plants.
      69Scopus© Citations 19
  • Publication
    Assessment of Grid-Feeding Converter Voltage Stability
    This letter applies voltage stability analysis to grid feeding converters in the presence of the converter stability versus the grid state and its operation. By applying this analysis, it is shown that the converter may become unstable if the converter reference power or current exceeds the line capacity. This letter proposes to use a conventional PV curve to determine the stability of the dynamic response of grid-feeding converters considering both power and current limits.
      330Scopus© Citations 24
  • Publication
    Simplified Model to Study the Induction Generator Effect of the Subsynchronous Resonance Phenomenon
    This letter presents a simple model of induction machines able to appraise the induction generator effect of the subsynchronous resonance phenomenon. The proposed model is general and can be applied to induction machines utilized in wind power applications, such as doubly-fed induction generators. A rigorous stability analysis is carried out based on the proposed model. This analysis shows that the induction generator effect leads to a Neimark–Sacker bifurcation.
      523Scopus© Citations 19
  • Publication
    MPC based AGC for AC/DC grids with delays and voltage constraints
    Multi-terminal HVDC (MTDC) grids have been cited as a means of efficiently sharing renewables over wide areas, such as the European grid. As these grids proliferate it is of interest to include these grids in frequency regulation. Here Model Predictive Control is presented as a means of using MTDC grids to aid in Automatic Generation Control (AGC) while considering delays and regulating DC voltages within bounds.
      256Scopus© Citations 1
  • Publication
    Primal and Dual Generalized Eigenvalue Problems for Power Systems Small-Signal Stability Analysis
    (Institute of Electrical and Electronics Engineers (IEEE), 2017-03-07) ;
    The paper presents a comprehensive study of small-signal stability analysis of power systems based on matrix pencils and the generalized eigenvalue problem. Both primal and dual formulations of the generalized eigenvalue problem are considered and solved through a variety of state-of-the-art solvers. The paper also discusses the impact on the performance of the solvers of two formulations of the equations modelling the power systems, namely, the explicit and semi-implicit form of differential-algebraic equations. The case study illustrates the theoretical aspects and numerical features of these formulations and solvers through two real-world systems, namely, a 1,479-bus model of the all-island Irish system, and a 21,177-bus model of the ENTSO-E network.
      323Scopus© Citations 23
  • Publication
    Model Predictive Control-Based AGC for Multi-Terminal HVDC-Connected AC grids
    Multi-terminal high-voltage direct current (MTDC) grids are seen as the enabling technology in the development of massive scale international grids such as the European supergrid. It is expected that these grids can play a significant role in regulating ac system frequencies. To date, many proportional-integral (PI) controller-based techniques have been proposed for frequency regulation in ac MTDC-connected grids. In this paper, model predictive control (MPC) is proposed as a means of implementing automatic generation control, while minimizing dc grid power losses. The advantages of using MPC versus PI are highlighted with regard to improvements in both frequency and dc grid regulation, while explicitly considering both delays and dc voltage constraints.
  • Publication
    Stochastic Transient Stability Analysis of Transmission Systems With Inclusion of Energy Storage Devices
    The letter provides a thorough stochastic analysis of the impact of energy storage systems on the transient stability of transmission grids. This impact is evaluated considering the combined effect of different energy storage technologies, fault clearing times, and network topologies. The latter concerns the relative positions of faults, storage devices, and synchronous machines. The case study consists of stochastic time-domain simulations carried out for the all-island, 1479-bus model of the Irish transmission system that includes a real-world hybrid storage device. Results lead to some nonintuitive conclusions.
      409Scopus© Citations 27
  • Publication
    Small-Signal Stability Analysis for Non-Index 1 Hessenberg Form Systems of Delay Differential-Algebraic Equations
    (Institute of Electrical and Electronics Engineers (IEEE), 2016-07-11) ;
    This paper focuses on the small-signal stability analysis of systems modelled as differential-algebraic equations and with inclusions of delays in both differential equations and algebraic constraints. The paper considers the general case for which the characteristic equation of the system is a series of infinite terms corresponding to an infinite number of delays. The expression of such a series and the conditions for its convergence are first derived analytically. Then, the effect on small-signal stability analysis is evaluated numerically through a Chebyshev discretization of the characteristic equations. Numerical appraisals focus on hybrid control systems recast into delay algebraic-differential equations as well as a benchmark dynamic power system model with inclusion of long transmission lines.
      256Scopus© Citations 43