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  • Report
    Tindemans S, Djapic P, Schofield J, Ustinova T, Strbac Get al., 2014,

    Resilience performance of smart distribution networks

    , Report D4 for the “Low Carbon London” LCNF project
  • Journal article
    Lourenço EM, Coelho EPR, Pal BC, 2014,

    Topology Error and Bad Data Processingin Generalized State Estimation

    , IEEE Transactions on Power Systems, Vol: 30, Pages: 3190-3200, ISSN: 1558-0679

    This paper presents a method for processing real-timedata error in generalized state estimation (GSE). Attention is focusedon the two main types of error: network topology errorsand bad data on analog measurements. The proposed approach isable to handle both errors without making any previous assumptionregarding the nature of those errors. The degrading effectsof topology errors over bad data processing when both topologyand measurement errors occur at the same time are evaluated andnew strategy is proposed to overcome it. GSE is treated as a constrainedoptimization problem where measurements and circuitbreakerstatus are modeled as equality constraints.Geometric testsbased on the geometric interpretation of the Lagrange multipliervector are then utilized to determine the source of the error. Theproposed strategy is tested on two model power networks representedat the bus-section level which is derived from the IEEE30-bus and 118-bus systems.
  • Journal article
    Chen B, Pin G, Ng WM, Lee CK, Hui SYR, Parisini Tet al., 2014,

    An adaptive observer-based switched methodology for the identification of a perturbed sinusoidal signal: theory and experiments

    , IEEE Transactions on Signal Processing, Vol: 62, Pages: 6355-6365, ISSN: 1053-587X

    This paper deals with a novel adaptive observer-based technique for estimating the amplitude, frequency, and phase of a single sinusoidal signal from a measurement affected by structured and unstructured disturbances. The structured disturbances are modeled as a time-polynomial so as to represent bias and drift phenomena typically present in applications, whereas the unstructured disturbances are modelled as bounded noise signals. The proposed estimation technique exploits a specific adaptive observer scheme equipped with a switching criterion allowing to properly address in a stable way poor excitation scenarios. The estimator's stability properties are analyzed by input-to-state stability arguments. The practical characteristics of the proposed estimation approach are evaluated and compared with other existing tools by extensive simulation trials. Real experimental results are provided as well.
  • Journal article
    Shabbir W, Evangelou SA, 2014,

    Real-time control strategy to maximize hybrid electric vehicle powertrain efficiency

    , Applied Energy, Vol: 135, Pages: 512-522, ISSN: 0306-2619

    The proposed supervisory control system (SCS) uses a control map to maximize the powertrain efficiency of a hybrid electric vehicle (HEV) in real-time. The paper presents the methodology and structure of the control, including a novel, comprehensive and unified expression for the overall powertrain efficiency that considers the engine-generator set and the battery in depth as well as the power electronics. A control map is then produced with instructions for the optimal power share between the engine branch and battery branch of the vehicle such that the powertrain efficiency is maximized. This map is computed off-line and can thereafter be operated in real-time at very low computational cost. A charge sustaining factor is also developed and introduced to ensure the SCS operates the vehicle within desired SOC bounds. This SCS is then tested and benchmarked against two conventional control strategies in a high-fidelity vehicle model, representing a series HEV. Extensive simulation results are presented for repeated cycles of a diverse range of standard driving cycles, showing significant improvements in fuel economy (up to 20%) and less aggressive use of the battery.
  • Journal article
    Mueller MA, Angeli D, Allgoewer F, Amrit R, Rawlings JBet al., 2014,

    Convergence in economic model predictive control with average constraints

    , Automatica, Vol: 50, Pages: 3100-3111, ISSN: 0005-1098

    In this paper, we thoroughly investigate various aspects of economic model predictive control with average constraints, i.e., constraints on average values of state and input variables. In particular, we first show that a certain time-varying output constraint has to be included into the MPC problem formulation in order to ensure fulfillment of these average constraints. Optimizing a general (possibly economic) performance criterion may result in a non-converging behavior of the corresponding closed-loop system. While such a behavior might be acceptable in some cases, it may be undesirable for other types of applications. Hence as a second contribution, we provide a Lyapunov-like analysis to conclude that indeed asymptotic convergence to the optimal steady-state follows if the system satisfies a certain dissipativity condition. Finally, for the case that this dissipativity property is not satisfied but still a convergent behavior of the closed-loop is required, we examine two different methods how convergence can be enforced within an economic MPC setup by imposing additional average constraints on the system. In the first method, an additional average constraint is defined which results in the system being dissipative, while the second consists of imposing an additional even zero-moment average constraint. We illustrate our results with various examples.
  • Conference paper
    Scarciotti G, Astolfi A, 2014,

    Model reduction by moment matching for nonlinear time-delay systems

    , Pages: 3642-3647
  • Journal article
    Jerez JL, Goulart PJ, Richter S, Constantinides GA, Kerrigan EC, Morari Met al., 2014,

    Embedded Online Optimization for Model Predictive Control at Megahertz Rates

    , IEEE TRANSACTIONS ON AUTOMATIC CONTROL, Vol: 59, Pages: 3238-3251, ISSN: 0018-9286
  • 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
    • Cite
    • Citations: 14
  • 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
    • Cite
    • Citations: 18
  • 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
    • Cite
    • Citations: 1147
  • 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
    • Cite
    • Citations: 36
  • 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
    • Cite
    • Citations: 20
  • 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

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