Now showing 1 - 9 of 9
  • Publication
    Stability Analysis of Power Systems with Inclusion of Realistic-Modeling of WAMS Delays
    The paper studies the impact of realistic WideArea Measurement System (WAMS) time-varying delays on the dynamic behaviour of power systems. A detailed model of WAMS delays including pseudo-periodic, stochastic and constant components is presented. Then, the paper discusses numerical methods to evaluate the small-signal stability as well as the timedomain simulation of power systems with inclusion of such delays. The small-signal stability analysis is shown to be able to capture the dominant modes through the combination of a characteristic matrix approximation and a Newton correction technique. A case study based on the IEEE 14-bus system compares the accuracy of the small-signal stability analysis with Monte-Carlo time-domain simulations. Finally, the numerical efficiency of the proposed technique is tested through a real-world dynamic model of the all-island Irish system.
      473Scopus© Citations 68
  • Publication
    Impact of Current Transients on the Synchronization Stability Assessment of Grid-Feeding Converters
    The synchronization instability in the presence of a fault is a main issue for the dynamic behavior and control of grid-feeding converters. In the literature, the synchronization stability assessment is carried out considering the dynamics of Phase-Locked Loops (PLL) but the transients of converter currents are neglected. The letter shows that such a simplification leads to inaccuracies and, thus, the current transients cannot be neglected. The letter proposes a model that captures the effect of such current transients on the converter synchronization. This model allows assessing the transient behavior and, hence, the stability, of power electronics converters with high accuracy, comparable, in fact, to EMT models. The fidelity of the proposed model is duly discussed in the case study.
      113Scopus© Citations 19
  • Publication
    Modelling, Simulation and Hardware-in-the-Loop Validation of Virtual Synchronous Generator Control in Low Inertia Power System
    In recent literature, virtual synchronous generator control (VSG) has been proposed as a means to provide virtual inertia from non-synchronous generation in low inertia power systems. In this work we compare the power system support performance of VSG control to conventional droop when applied to electrical energy storage. A differential-algebraic equations (DAEs) model of VSG control is developed. This model is validated against measurement from a hardware in the loop implementation of the VSG. VSG and droop controlled storage is then incorporated into the IEEE 39 bus system model also incorporating different levels of generation from windfarms. The performance of both controls is compared in terms of their effect on the power system dynamics in the event of a contingency. The results show that VSG control in high wind penetration cases, improves the frequency nadir, reduces oscillations, and provide faster frequency and voltage stabilization.
      640Scopus© Citations 18
  • 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.
      256Scopus© Citations 5
  • Publication
    A novel approach to model a gas network
    The continuous uninterrupted supply of Natural Gas (NG) is crucial to today's economy, with issues in key infrastructure, e.g., Baumgarten hub in Austria in 2017, highlighting the importance of the NG infrastructure for the supply of primary energy. The balancing of gas supply from a wide range of sources with various end users can be challenging due to the unique and different behaviours of the end users, which in some cases span across a continent. Further complicating the management of the NG network is its role in supporting the electrical network. The fast response times of NG power plants and the potential to store energy in the network play a key role in adding flexibility across other energy systems. Traditionally, modelling the NG network relies on nonlinear pipe flow equations that incorporate the demand (load), flow rate, and physical network parameters including topography and NG properties. It is crucial that the simulations produce accurate results quickly. This paper seeks to provide a novel method to solve gas flow equations through a network under steady-state conditions. Firstly, the model is reformulated into non-linear matrix equations, then the equations separated into their linear and nonlinear components, and thirdly, the non-linear system is solved approximately by providing a linear system with similar solutions to the non-linear one. The non-linear equations of the NG transport system include the main variables and characteristics of a gas network, focusing on pressure drop in the gas network. Two simplified models, both of the Irish gas network (1. A gas network with 13 nodes, 2. A gas network with 109 nodes) are used as a case study for comparison of the solutions. Results are generated by using the novel method, and they are compared to the outputs of two numerical methods, the Newton-Raphson solution using MATLAB and SAINT, a commercial software that is used for the simulation of the gas network and electrical grids.
      340Scopus© Citations 18
  • Publication
    Placement of Virtual Synchronous Generator Controlled Electric Storage combined with Renewable Generation
    The virtual synchronous generator (VSG) control of power converters has been proposed to improve the system inertia. The commonly used VSG requires an energy storage (ESS) to provide the emulated inertia power and the frequency droop power. The placement of the ESS can be either in the DC port of the power electronics generation or co-located with the power electronics generation on the AC side. In the former case, the VSG control makes the total generator behave like a synchronous generator, while in the latter one, the VSG control only regulates the ESS in response to the grid frequency. The different placement of the ESS gives rise to different performance. This paper analyzes this performance firstly by means of simple transfer function analysis and secondly by comparing their effects on the grid frequency at the system level in the IEEE 39 bus test system. The results show that the placement of the ESS has no impact on the system transient stability while it has a significant impact on the frequency dynamics especially in the low inertia situation.
      151Scopus© Citations 8
  • Publication
    Smart Transformer for the Provision of Coordinated Voltage and Frequency Support in the Grid
    Considering the increase in renewable generation and the consequent reduction in power system inertia, the Virtual Synchronous Machine (VSM) control method has been proposed to control power converters to emulate the inertia and other the characteristics of the synchronous machine. However, to achieve the function of VSM control, an extra energy base, typically storage, is required to connect to the controlled converter. In this work we investigate the application of the VSM control to the distribution system demand through the use of a VSM controlled smart transformer. Through control of the demand in this way, the demand itself can be used to emulate inertia and provide frequency support. This paper presents the details of the flexible demand control applied to a smart transformer supplying a low voltage distribution grid. The operation of the control is validated on scaled hardware using real time simulation with hardware in the loop. Simulations on a 400 kVA, 400 V distribution network are used to quantify the demand flexible. IEEE 39 bus is used to verify the benefit of the proposed control in terms of voltage and frequency in the power system.
      315Scopus© Citations 14
  • 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.
      67Scopus© Citations 16
  • 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.
      383Scopus© Citations 37