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  • Journal article
    Falugi P, 2014,

    Model predictive control for tracking randomly varying references

    , International Journal of Control, Vol: 88, Pages: 745-753, ISSN: 1366-5820

    This paper proposes a model predictive control scheme for tracking a-priori unknown references varying in a wide range and analyses its performance. It is usual to assume that the reference eventually converges to a constant in which case convergence to zero of the tracking error can be established. In this note we remove this simplifying assumption and characterise the set to which the tracking error converges and the associated region of convergence.
  • Journal article
    Trutnevyte E, Barton J, O'Grady A, Ogunkunle D, Pudjianto D, Robertson Eet al., 2014,

    Linking a storyline with multiple models: A cross-scale study of the UK power system transition

    , TECHNOLOGICAL FORECASTING AND SOCIAL CHANGE, Vol: 89, Pages: 26-42, ISSN: 0040-1625
  • Journal article
    Linash PK, Pal BC, 2014,

    Selection of Feedback Signals for ControllingDynamics in Future Power Transmission Networks

    , IEEE Transactions on Smart Grid, Vol: PP, Pages: 1-10, ISSN: 1949-3053

    This paper deals with the selection of feedbacksignal(s) that retain the modal behaviour of power system electromechanicaldynamics under varying operating circumstances.The approach seeks signal that has relatively large magnitude ofresidue, less variation of the magnitude and phase angle, sufficientgap between the critical pole-zeros and least sensitive to othermodes. The methodology is tested in a 16-machine interconnectedpower system model with multiple wind farms.
  • Journal article
    Mueller MA, Angeli D, Allgoewer F, 2014,

    Transient average constraints in economic model predictive control

    , Automatica, Vol: 50, Pages: 2943-2950, ISSN: 1873-2836

    In this paper, an economic model predictive control algorithm is proposed which ensures satisfaction of transient average constraints, i.e., constraints on input and state variables averaged over some finite time period. We believe that this stricter form of average constraints (compared to previously proposed asymptotic average constraints) is of independent interest in various applications such as the operation of a chemical reactor, where e.g. the amount of inflow or the heat flux during some fixed period of time must not exceed a certain value. Besides guaranteeing fulfillment of transient average constraints for the closed-loop system, we show that closed-loop average performance bounds and convergence results established in the setting of asymptotic average constraints also hold in case of transient average constraints. Furthermore, we illustrate our results with a chemical reactor example.
  • Conference paper
    Trovato V, Tindemans SH, Strbac G, 2014,

    Security constrained economic dispatch with flexible thermostatically controlled loads

    , IEEE PES ISGT Europe 2014

    Thermostatically controlled loads (TCLs) such as refrigerators and air conditioners are natural candidates for short term demand response. In this paper we quantify the value associated with the TCLs' ability to provide system security and transmission constraint management services. The analysis builds on recent results that enable the aggregate control of TCLs as a leaky storage unit. We incorporate this model in a security constrained economic dispatch (SCED) that minimizes the system operational cost of a two bus-bar system, subject to frequency response and transmission constraints. Further sensitivity studies assess the impact of different penetration levels of controllable loads and transmission flow constraints.
  • Journal article
    Strbac G, Pollitt M, Konstantinidis CV, Konstantelos I, Moreno R, Newbery D, Green Ret al., 2014,

    Electricity transmission arrangements in Great Britain: Time for change?

    , Energy Policy, Vol: 73, Pages: 298-311, ISSN: 0301-4215

    In Great Britain (GB) and across Europe significant investment in electricity transmission is expected over the coming years as decarbonisation and market integration efforts are intensified. However, there is also significant uncertainty with the amount, location and timing of new generation connection, which in turn will drive the transmission investment needs. Given the absence of efficient market design, we identify three key areas of concern with the current transmission investment arrangements: (i) a mis-aligned incentives framework for transmission investment and operation; (ii) lack of coordination of investment and operation; and (iii) conflicts of interest. We then propose three options for future evolution of transmission regimes, which cover the full spectrum of institutional arrangements with respect to transmission planning and delivery, i.e. how and who plans, owns, builds and operates the transmission system. For each option we present: key characteristics; evolution of the current regimes; the ability of the option to address the concerns; and key strengths and weaknesses. Overall, we conclude in the case of GB (this conclusion could be extended to other European countries) that the most appropriate option would be that of an Independent System Operator (ISO) who would be responsible for planning and operating the transmission system.
  • Journal article
    Schiffer J, Ortega R, Astolfi A, Raisch J, Sezi Tet al., 2014,

    Conditions for stability of droop-controlled inverter-based microgrids

    , Automatica, Vol: 50, Pages: 2457-2469, ISSN: 0005-1098

    We consider the problem of stability analysis for droop-controlled inverter-based microgrids with meshed topologies. The inverter models include variable frequencies as well as voltage amplitudes. Conditions on the tuning gains and setpoints for frequency and voltage stability, together with desired active power sharing, are derived in the paper. First, we prove that for all practical choices of these parameters global boundedness of trajectories is ensured. Subsequently, assuming the microgrid is lossless, a port-Hamiltonian description is derived, from which sufficient conditions for stability are given. Finally, we propose for generic lossy microgrids a design criterion for the controller gains and setpoints such that a desired steady-state active power distribution is achieved. The analysis is validated via simulation on a microgrid based on the CIGRE (Conseil International des Grands Réseaux Electriques) benchmark medium voltage distribution network.
  • Journal article
    Papadaskalopoulos D, Pudjianto D, Strbac G, 2014,

    Decentralized Coordination of Microgrids With Flexible Demand and Energy Storage

    , IEEE TRANSACTIONS ON SUSTAINABLE ENERGY, Vol: 5, Pages: 1406-1414, ISSN: 1949-3029
  • Journal article
    Egea-Alvarez A, Junyent-Ferre A, Bergas-Jane J, Bianchi FD, Gomis-Bellmunt Oet al., 2014,

    Control of a wind turbine cluster based on squirrel cage induction generators connected to a single VSC power converter

    , INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS, Vol: 61, Pages: 523-530, ISSN: 0142-0615
  • Journal article
    Li S, Hui SYR, 2014,

    Self-Configurable Current-Mirror Circuit With Short-Circuit and Open-Circuit Fault Tolerance for Balancing Parallel Light-Emitting Diode (LED) String Currents

    , IEEE TRANSACTIONS ON POWER ELECTRONICS, Vol: 29, Pages: 5498-5507, ISSN: 0885-8993
  • Journal article
    Chang H, Krieger A, Astolfi A, Pistikopoulos ENet al., 2014,

    Robust multi-parametric model predictive control for LPV systems with application to anaesthesia

    , JOURNAL OF PROCESS CONTROL, Vol: 24, Pages: 1538-1547, ISSN: 0959-1524
  • Conference paper
    Carmichael R, Schofield J, Bilton M, Ozaki R, Strbac Get al., 2014,

    Dynamic pricing of electricity for wind-following?: Understanding demand-response and consumer engagement on the UK’s first trial of a dynamic time-of-use tariff for residential electricity

    , BEHAVE 2014 Conference
  • Book
    Chaudhuri N, Chaudhuri B, Majumder R, Yazdani Aet al., 2014,

    Multi-terminal Direct-Current Grids

    , Publisher: Wiley IEEE, ISBN: 9781118729106

    Commercial unavailability of efficient DC side fault current interruption technology for conventional voltage sourced converter systems This book addresses the first issue in details by presenting a comprehensive modeling, analysis and ...
  • Report
    Konstantelos I, Sun M, Strbac G, 2014,

    Quantifying demand diversity of households

    , Quantifying demand diversity of households, Publisher: Imperial College London
  • Journal article
    Hui SYR, Zhong W, Lee CK, 2014,

    A Critical Review of Recent Progress in Mid-Range Wireless Power Transfer

    , IEEE TRANSACTIONS ON POWER ELECTRONICS, Vol: 29, Pages: 4500-4511, ISSN: 0885-8993
  • Journal article
    Ng WM, Zhang C, Lin D, Hui SYRet al., 2014,

    Two- and Three-Dimensional Omnidirectional Wireless Power Transfer

    , IEEE TRANSACTIONS ON POWER ELECTRONICS, Vol: 29, Pages: 4470-4474, ISSN: 0885-8993
  • Journal article
    Chaillet A, Angeli D, Ito H, 2014,

    Strong iISS is preserved under cascade interconnection

    , AUTOMATICA, Vol: 50, Pages: 2424-2427, ISSN: 0005-1098
  • Journal article
    Chang HJ, Moog CH, Astolfi A, Rivadeneira PSet al., 2014,

    A control systems analysis of HIV prevention model using impulsive input

    , BIOMEDICAL SIGNAL PROCESSING AND CONTROL, Vol: 13, Pages: 123-131, ISSN: 1746-8094
  • Journal article
    Chaillet A, Angeli D, Ito H, 2014,

    Combining iISS and ISS With Respect to Small Inputs: The Strong iISS Property

    , IEEE TRANSACTIONS ON AUTOMATIC CONTROL, Vol: 59, Pages: 2518-2524, ISSN: 0018-9286
  • Report
    Carmichael R, Schofield J, Woolf M, Bilton M, Ozaki R, Strbac Get al., 2014,

    Residential consumer attitudes to time-varying pricing

    , Report A2 for the 'Low Carbon London' LCNF project, London, Publisher: Imperial College, A2
  • Journal article
    Chaudhuri NR, Lee CK, Chaudhuri B, Hui SYRet al., 2014,

    Dynamic Modeling of Electric Springs

    , IEEE TRANSACTIONS ON SMART GRID, Vol: 5, Pages: 2450-2458, ISSN: 1949-3053
  • Report
    Bilton M, Carmichael R, Whitney A, Dragovic J, Schofield J, Woolf M, Strbacet al., 2014,

    Accessiblity and validity of smart meter data

    , Report C5 for the “Low Carbon London” LCNF project: Imperial College London, C5
  • Journal article
    Sanz IM, Chaudhuri B, Strbac G, 2014,

    Inertial Response From Offshore Wind Farms Connected Through DC Grids

    , IEEE Transactions on Power Systems, Vol: 30, Pages: 1518-1527, ISSN: 0885-8950
  • Conference paper
    Falugi P, 2014,

    Model predictive Control: a passive scheme

    , 19th IFAC World Congress, Publisher: International Federation of Automatic Control, Pages: 1017-1022

    This note studies the formulation of model predictive control exploiting passivity properties. The introduction of passive constraints in model predictive control schemes is particularly appealing since robustness against model uncertainty is inherently guaranteed. The potential of the discussed control scheme is shown on the regulation problem of a robot manipulator.
  • Journal article
    Yan S, Tan S-C, Lee C-K, Chaudhuri B, Hui SYRet al., 2014,

    Electric Springs for Reducing Power Imbalance in Three-Phase Power Systems

    , IEEE Transactions on Power Electronics, Vol: 30, Pages: 3601-3609, ISSN: 0885-8993
  • Conference paper
    Ye Y, Papadaskalopoulos D, Strbac G, 2014,

    Pricing Flexible Demand Non-Convexities in Electricity Markets

    , 18th Power Systems Computation Conference (PSCC), Publisher: IEEE, Pages: 1-7, ISSN: 1944-9933

    Uniform marginal prices cannot generally support competitive equilibrium solutions in markets with non-convexities and yield schedules' inconsistency and surplus sub-optimality effects. Previous work has identified non-convexities associated with the generation side of electricity markets and proposed a generalized uplift approach to eliminate these effects. This paper examines the above issues from the perspective of the flexible demand (FD) side. FD non-convexities are identified, including its ability to forgo demand activities and minimum power levels, and resulting inconsistency and surplus sub-optimality effects are demonstrated through simple examples. Generalized uplift functions for FD participants are proposed, including quadratic pricing terms to limit their tendency to concentrate at the lowest-priced periods, and binary terms associated with their ability to forgo activities. Finally, a new rule is proposed for the equitable distribution of the total surplus loss among the market participants. These contributions are supported by case studies on a market with a day-ahead horizon and hourly resolution.
  • Journal article
    Tortelli OL, Laurenco EM, Garcia AV, Pal BCet al., 2014,

    Fast Decoupled Power Flow to Emerging Distribution Systems via Complex pu Normalization

    , IEEE Transactions on Power Systems, Vol: PP, Pages: 1-8, ISSN: 0885-8950

    This paper proposes a generalized approach of the per unit normalization, named complex per unit normalization (cpu), to improve the performance of fast decoupled power flow methods applied to emerging distribution networks. The proposed approach takes into account the changes envisaged and also already faced by distribution systems, such as high penetration of generation sources and more interconnection between feeders, while considering the typical characteristics of distribution systems, as the high R/ X ratios. These characteristics impose difficulties on the performance of both backward-forward sweep and decoupled-based power flow methods. The cpu concept is centred on the use of a complex volt-ampere base, which overcomes the numerical problems raised by the high R/ X ratios of distribution feeders. As a consequence, decoupled power flow methods can be efficiently applied to distribution system analysis. The performance of the proposed technique and the simplicity of adapting it to existing power flow programs are addressed in the paper. Different distribution network configurations and load conditions have been used to illustrate and evaluate the use of cpu.
  • Journal article
    Chen HT, Lin DY, Tan SC, Hui SYRet al., 2014,

    Chromatic, photometric and thermal modeling of LED systems with nonidentical LED devices

    , IEEE Transactions on Power Electronics, Vol: 29, Pages: 6636-6647, ISSN: 0885-8993

    With the emergence of new color-mixing LED systems based on LED devices of different color temperatures, the need for a new modeling technique for LED systems with nonidentical LED devices becomes imminent. This paper presents a modeling technique for LED systems with LED arrays comprising nonidentical LED devices that have nonidentical optical-thermal-electrical properties. Based on a general 3-D photo-electro-thermal LED node model, LED devices of different kinds can be arranged in various array forms according to their system construction and design. By linking the system matrix to the correlated-colorerature prediction, the proposed modeling technique provides an accurate prediction of the temperature distribution, luminous flux, and correlated color temperature of the LED systems. The temperature distribution and light output of the LED systems have been measured using an infrared imaging system and a spectrophotocolorimeter with an integrating sphere. The modeling technique has been successfully demonstrated and experimentally verified on several LED systems comprising nonidentical LED devices. It is particularly useful as a modeling tool to study new color-mixing LED systems based on different types of LED devices. © 2014 IEEE.
  • Journal article
    Lueth T, Merlin MMC, Green TC, Hassan F, Barker CDet al., 2014,

    High-frequency operation of a DC/AC/DC system for HVDC applications

    , IEEE Transactions on Power Electronics, Vol: 29, Pages: 4107-4115, ISSN: 0885-8993

    Voltage ratings for HVdc point-to-point connections are not standardized and tend to depend on the latest available cable technology. DC/DC conversion at HV is required for interconnection of such HVdc schemes as well as to interface dc wind farms. Modular multilevel voltage source converters (VSCs), such as the modular multilevel converter (MMC) or the alternate arm converter (AAC), have been shown to incur significantly lower switching losses than previous two- or three-level VSCs. This paper presents a dc/ac/dc system using a transformer coupling two modular multilevel VSCs. In such a system, the capacitors occupy a large fraction of the volume of the cells but a significant reduction in volume can be achieved by raising the ac frequency. Using high frequency can also bring benefits to other passive components such as the transformer but also results in higher switching losses due to the higher number of waveform steps per second. This leads to a tradeoff between volume and losses which has been explored in this study and verified by simulation results with a transistor level model of 30-MW case study. The outcome of the study shows that a frequency of 350 Hz provides a significant improvement in volume but also a penalty in losses compared to 50 Hz.
  • Journal article
    Casagrande D, Astolfi A, Langarica D, Ortega Ret al., 2014,

    Solution to the multi-machine transient stability problem and simulated validation in realistic scenarios

    , IET GENERATION TRANSMISSION & DISTRIBUTION, Vol: 8, Pages: 1392-1405, ISSN: 1751-8687

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