Now showing 1 - 10 of 35
  • Publication
    On the Stability Analysis of Systems of Neutral Delay Differential Equations
    This paper focuses on the stability analysis of systems modeled as neutral delay differential equations (NDDEs). These systems include delays in both the state variables and their time derivatives. The proposed approach consists of a descriptor model transformation that constructs an equivalent set of delay differential algebraic equations (DDAEs) of the original NDDEs. We first rigorously prove the equivalency between the original set of NDDEs and the transformed set of DDAEs. Then, the effect on stability analysis is evaluated numerically through a delay-independent stability criterion and the Chebyshev discretization of the characteristic equations.
    Scopus© Citations 46  602
  • Publication
    Comparison of the Dynamic Response of Wind Turbine Primary Frequency Controllers
    This paper presents a comparison of a variety of control strategies for the primary frequency control of wind power plants. These strategies include inertial as well as pitch angle regulators. The inertial control is sensitive to both the frequency variation through a standard droop control, and the rate of change of frequency. Since these controllers tend to counteract the operation of the Maximum Power Point Tracking (MPPT), the paper also investigates the effect of blocking the MPPT whenever the inertial control is enabled. The pitch angle control allows for a power reserve and prevents the rotor speed from exceeding the nominal value. A modified version of the WSCC 9-bus, 3-machine system with a 30% of wind penetration and a type 3 wind turbine model is considered in the case study. The behavior of these controllers are first analyzed separately. Then a compound controller, which merges together all strategies above, is proposed and discussed.
    Scopus© Citations 7  393
  • 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.
      340Scopus© Citations 48
  • Publication
    Comparison of different control strategies for energy storage devices
    This paper compares three control strategies for energy storage devices. Detailed formulations and implementation procedures of PI, sliding mode, and H-infinity controllers are presented and discussed. The dynamic performance of each control technique is also studied and compared. With this aim, the paper duly discusses a comprehensive case study based on the IEEE 14-bus test system with inclusion of a wind power plant and an energy storage device.
    Scopus© Citations 10  432
  • Publication
    On the Impact of Microgrid Energy Management Systems on Power System Dynamics
    This paper compares the impact of microgrids on the transient response of the transmission system, and, more specifically, on its frequency variations, when different control strategies and different storage capacities are employed. Extensive Monte Carlo simulations are performed based on the IEEE 39-bus system, and show that the dynamic behavior of the transmission system is affected in a non-trivial way by the control strategy of the microgrids energy management system and their storage capacity.
    Scopus© Citations 3  301
  • 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.
      319Scopus© Citations 1
  • Publication
    Efficient implementation of MPC-based AGC for real-world systems with low inertia
    (Elsevier, 2018-05) ;
    The paper discusses practical implementation and computational aspects of an AGC scheme based on model predictive control (MPC) for a real-world power system, namely the all-island Irish transmission system. This system is particularly interesting from the frequency regulation point of view due to the high penetration of wind power generation. This leads to a significant reduction in system inertia, which in turn impacts on the ability of the system operator to regulate the system frequency. The paper compares the performance of the MPC-based AGC with a conventional AGC based on PI controllers and draws relevant conclusions. The case study is a high-resolution simulation of a 1479-bus model of the Irish electrical grid with significant wind penetration, stochastic loads, and controller delays.
    Scopus© Citations 14  455
  • Publication
    Small-signal stability analysis of neutral delay differential equations
    This paper focuses on the small-signal stability analysis of systems modeled as Neutral Delay Differential Equations (NDDEs). These systems include delays in both the state variables and their first time derivatives. The proposed approach consists in descriptor model transformation that constructs an equivalent set of Delay Differential Algebraic Equations (DDAEs) of the original NDDE. The resulting DDAE is a non-index-1 Hessenberg form, whose characteristic equation consists of a series of infinite terms corresponding to infinitely many delays. Then, the effect on small-signal stability analysis is evaluated numerically through a Chebyshev discretization of the characteristic equations. Numerical appraisals focus on a variety of physical systems, including a population-growth model, a partial element equivalent circuit and a neutral delayed neural network.
    Scopus© Citations 6  406
  • Publication
    Frequency Participation Factors
    This paper discusses two quantitative and complementary approaches to evaluate the participation of synchronous generators and interconnection buses on local bus frequency variations during electromechanical transients. Both approaches are based on the concept of frequency divider formula recently proposed by the authors on these transactions. A thorough comparison of the two approaches is provided considering several scenarios and three networks, namely the New England 39-bus test system, the all-island 1,479-bus Irish transmission system, and the ENTSO-E 21,177-bus transmission system.
      507Scopus© Citations 6
  • 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.
      485