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  • Journal article
    Xiong S, Huang Y, Tan SC, Hui SYRet al., 2016,

    Morphing Switched-Capacitor Converters with Variable Conversion Ratio

    , IEEE Transactions on Power Electronics, Vol: 31, Pages: 5680-5693, ISSN: 0885-8993

    High-voltage-gain and wide-input-range dc-dc converters are widely used in various electronics and industrial products such as portable devices, telecommunication, automotive, and aerospace systems. The two-stage converter is a widely adopted architecture for such applications, and it is proven to have a higher efficiency as compared with that of the single-stage converter. This paper presents a modular-cell-based morphing switched-capacitor (SC) converter for application as a front-end converter of the two-stage converter. The conversion ratio of this converter is flexible and variable and can be freely extended by increasing more SC modules. The varying conversion ratio is achieved through the morphing of the converter's structure corresponding to the amplitude of the input voltage. This converter is light and compact, and is highly efficient over a very wide range of input voltage and load conditions. Experimental work on a 25-W, 6-30-V input, 3.5-8.5-V output prototype, is performed. For a single SC module, the efficiency over the entire input voltage range is higher than 98%. Applied into the two-stage converter, the overall efficiency achievable over the entire operating range is 80% including the driver's loss.

  • Journal article
    Pereda Torres J, green T, 2016,

    Direct Modular Multilevel Converter With Six Branches for Flexible Distribution Networks

    , IEEE Transactions on Power Delivery, Vol: 31, Pages: 1728-1737, ISSN: 0885-8977

    This paper presents a complete analysis of a direct ac-to-ac modular multilevel converter (direct MMC) applied in medium voltage distribution networks through the soft-openpoint concept. The direct MMC is capable of bidirectional power flow between two feeders at any power factor, even when the feeders have different nominal voltages and operate with a phase shift angle or unbalanced voltages. The converter has six branches, each one composed of full H-bridges cells connected in series to generate a multilevel voltage waveform, to share the blocking voltage of the power switches and to have fault tolerant operation.This paper presents a suitable control scheme and provides a discussion about the capabilities and limitations of the converter, the capacitor voltage balance control, the efficiency and the power loss mitigation at various operation points. Simulation results and power loss calculations are presented for a threephase 11 kV 16 MVA direct MMC with 10 H-bridge cells per branch. The direct MMC is simulated in a distribution network to demonstrate the features of the converter and control under various operation conditions, including grid faults.

  • Journal article
    Hui SYR, 2016,

    Magnetic resonance for wireless power transfer

    , IEEE Power Electronics Magazine, Vol: 3, Pages: 14-31, ISSN: 2329-9207

    Magnetic resonance has been a cornerstone of nonradiative wireless power transfer (WPT) since the late 19th century. However, some researchers have the misconception that magnetic resonance for WPT was developed recently. This article traces some early work of Tesla and other researchers related to the use of magnetic resonance in WPT. Included are some examples of magnetic resonance-based WPT projects conducted by researchers in the biomedical and power electronics communities over the last few decades. Two principles used in WPT are reiterated in this article, and their advantages and disadvantages are addressed. Some issues that may affect future trends of short- and midrange applications are discussed.

  • Journal article
    Guo Y, Li S, Lee ATL, Tan S-C, Lee CK, Hui SYRet al., 2016,

    Single-Stage AC/DC Single-Inductor Multiple-Output LED Drivers

    , IEEE Transactions on Power Electronics, Vol: 31, Pages: 5837-5850, ISSN: 1941-0107

    Various ac/dc LED driver topologies have been proposed to meet the challenges of achieving a compact, efficient, low-cost, and robust multistring LED lighting system. These LED drivers typically employ a two-stage topology to realize the functions of ac/dc rectification and independent current control of each LED string. The choice of having two stage conversions involves additional hardware components and a more complicated controller design process. Such two-stage topologies suffer from a higher system cost, increased power loss, and large form factor. In this paper, a single-stage ac/dc single-inductor multiple-output LED driver is proposed. It uses only one single inductor and N + 1 active power switches (N being the number of LED strings) with reduced component count and smaller form factor. The proposed driver can achieve both functions of ac/dc rectification with a high power factor and precise independent current control of each individual LED string simultaneously. A prototype of an ac/dc single-inductor triple-output LED driver is constructed for verification. Experimental results corroborate that precise and independent current regulation of each individual LED string is achievable with the proposed driver. A power factor of above 0.99 and a peak efficiency of 89% at 30-W rated output power are attainable.

  • Journal article
    Teng F, Trovato V, Strbac G, 2016,

    Stochastic scheduling with inertia-dependent fast frequency response requirements

    , IEEE Transactions on Power Systems, Vol: 31, Pages: 1557-1566, ISSN: 0885-8950

    High penetration of wind generation will increase the requirement for fast frequency response services as currently wind plants do not provide inertial response. Although the importance of inertia reduction has been widely recognized, its impact on the system scheduling has not been fully investigated. In this context, this paper proposes a novel mixed integer linear programming (MILP) formulation for stochastic unit commitment that optimizes system operation by simultaneously scheduling energy production, standing/spinning reserves and inertia-dependent fast frequency response in light of uncertainties associated with wind production and generation outages. Post-fault dynamic frequency requirements, rate of change of frequency, frequency nadir and quasi-steady-state frequency are formulated as MILP constraints by using the simplified model of system dynamics. Moreover the proposed methodology enables the impact of wind uncertainty on system inertia to be considered. Case studies are carried out on the 2030 Great Britain system to demonstrate the importance of incorporating inertia-dependent fast frequency response in the stochastic scheduling and to indicate the potential for the proposed model to inform reviews of grid codes associated with fast frequency response and future development of inertia-related market.

  • Journal article
    Parisini T, 2016,



    This editorial aims to share with our readership the status and a few figures about our TRANSACTIONS.

  • Conference paper
    Jiang J, Astolfi A, 2016,

    Shared-Control for Typical Driving Scenarios

    , European Control Conference
  • Conference paper
    Kerrigan EC, Khusainov B, Constantinides GA, 2016,

    What Is Different about Embedded Optimization?

    , European Control Conference (ECC), Publisher: IEEE, Pages: 600-600
  • Journal article
    Cooper SJG, Hammond GP, McManus MC, Pudjianto Det al., 2016,

    Detailed simulation of electrical demands due to nationwide adoption of heat pumps, taking account of renewable generation and mitigation

    , IET Renewable Power Generation, Vol: 10, Pages: 380-387, ISSN: 1752-1416

    This study quantifies the increase in the peak power demand, net of non-dispatchable generation, that may be required by widespread adoption of heat pumps. Electrification of heating could reduce emissions but also cause a challenging increase in peak power demand. This study expands on previous studies by quantifying the increase in greater detail; considering a wider range of scenarios, the characteristics of heat pumps and the interaction between wind generation and demand side management (DSM). A model was developed with dynamic simulations of individual heat pumps and dwellings. The increase in peak net-demand is highly sensitive to assumptions regarding the heat pumps, their installation, building fabric and the characteristics of the grid. If 80% of dwellings in the UK use heat pumps, peak net-demand could increase by around 100% (54 GW) but this increase could be mitigated to 30% (16 GW) by favourable conditions. DSM could reduce this increase to 20%, or 15% if used with extensive thermal storage. If 60% of dwellings use heat pumps, the increase in peak net-demand could be as low as 5.5 GW. High-performance heat pumps, appropriate installation and better insulated dwellings could make the increase in peak net-demand due to the electrification of heating more manageable.

  • Journal article
    Trovato V, Tindemans SH, Strbac G, 2016,

    The leaky storage model for optimal multi-service allocation of thermostatic loads

    , IET Generation Transmission & Distribution, Vol: 10, Pages: 585-593, ISSN: 1751-8687

    Collectively, thermostatically controlled loads (TCLs) offer significant potential for short-term demand response. This intrinsic flexibility can be used to provide various ancillary services or to carry out energy arbitrage. This paper introduces an aggregate description of the flexibility of a heterogeneous TCLs as a leaky storage unit, with associated constraints that are derived from the TCL device parameters and quality of service requirements. In association with a suitable TCL control strategy this enables a straightforward embedding of TCL dynamics in optimisation frameworks. The tools developed are applied to the problem of determining an optimal multi-service portfolio for TCLs. A linear optimisation model is constructed for the optimal simultaneous allocation of frequency services and energy arbitrage. In a case study, optimal service allocations are computed for eight representative classes of cold appliances and the results are validated using simulations of individual refrigerators. Finally, it is demonstrated that clustering of appliances with similar capabilities can significantly enhance the flexibility available to the system.

  • Journal article
    Shabbir W, Evangelou S, 2016,

    Exclusive Operation Strategy for the Supervisory Control of Series Hybrid Electric Vehicles

    , IEEE Transactions on Control Systems Technology, Vol: 24, Pages: 2190-2198, ISSN: 1558-0865

    Supervisory control systems (SCSs) are used to managethe powertrain of hybrid electric vehicles (HEV). This paperpresents a novel SCS called Exclusive operation strategy (XOS)that applies simple rules based on the idea that batteries areefficient at lower loads while engines and generators are efficientat higher loads. The XOS is developed based on insights gainedfrom three conventional SCSs for series HEVs: Thermostat controlstrategy (TCS), Power follower control strategy (PFCS) andGlobal equivalent consumption minimization strategy (GECMS).Also, recent technological developments have been considered tomake the XOS more suited to modern HEVs than conventionalSCSs. The resulting control decisions are shown to emulatethe operation of approximate global optimal solutions and thusachieve significant improvement in fuel economy as comparedto TCS and PFCS. In addition, the generally linear relationshipbetween required power and engine power for the XOS providesauditory cues to the driver that are comparable to conventionalvehicles, thus reducing barriers to adopting HEVs. The simplicityand effectiveness of the XOS makes it a practical SCS.

  • Conference paper
    De Paola A, Angeli D, Strbac G, 2016,

    Analysis of Nash equilibria in energy markets with large populations of price-responsive flexible appliances

    , 2015 54th IEEE Conference on Decision and Control (CDC), Publisher: IEEE, Pages: 5587-5592, ISSN: 0743-1546

    This paper deals with flexible electrical devices that, on the basis of a broadcast price signal, schedule their individual power consumption in order to minimize their energy cost. If the devices population is sufficiently large to be described as a continuum, it is possible to provide necessary and sufficient conditions for the existence of a Nash equilibrium in the energy market. This is done by comparing two functions which characterize, respectively, the valley capacity of the inflexible demand and the global properties of the appliances population. The equilibrium conditions, which do not require any iterative procedure to be applied, are finally tested in simulations.

  • Journal article
    Keliris C, Polycarpou MM, Parisini T, 2016,

    An integrated learning and filtering approach for fault diagnosis of a class of nonlinear dynamical systems

    , IEEE Transactions on Neural Networks and Learning Systems, Vol: 28, Pages: 988-1004, ISSN: 2162-237X

    This paper develops an integrated filtering and adaptive approximation-based approach for fault diagnosis of process and sensor faults in a class of continuous-time nonlinear systems with modeling uncertainties and measurement noise. The proposed approach integrates learning with filtering techniques to derive tight detection thresholds, which is accomplished in two ways: 1) by learning the modeling uncertainty through adaptive approximation methods and 2) by using filtering for dampening measurement noise. Upon the detection of a fault, two estimation models, one for process and the other for sensor faults, are initiated in order to identify the type of fault. Each estimation model utilizes learning to estimate the potential fault that has occurred, and adaptive isolation thresholds for each estimation model are designed. The fault type is deduced based on an exclusion-based logic, and fault detectability and identification conditions are rigorously derived, characterizing quantitatively the class of faults that can be detected and identified by the proposed scheme. Finally, simulation results are used to demonstrate the effectiveness of the proposed approach.

  • Journal article
    Ariff MAM, Pal BC, 2016,

    Adaptive Protection and Control in Power Systemfor Wide-Area Blackout Prevention

    , IEEE Transactions on Power Delivery, Vol: 31, Pages: 1815-1825, ISSN: 0885-8977

    This paper presents a new approach in adaptive outof-step(OOS) protection settings in power system in real-time.The proposed method uses extended equal area criterion (EEAC)to determine the critical clearing time (CCT) and critical clearingangle (CCA) of the system, which are vital information for OOSprotection setting calculation. The dynamic model parametersand the coherency groups of the system for EEAC analysis aredetermined in real time to ensure that the newly calculatedsettings suit with the prevalent system operating condition. Theeffectiveness of the method is demonstrated in a simulated datafrom 16-machine 68-bus system model.

  • Journal article
    Pin G, Assalone A, Lovera M, Parisini Tet al., 2016,

    Non-asymptotic kernel-based parametric estimation of continuous-time linear systems

    , IEEE Transactions on Automatic Control, Vol: 61, Pages: 360-373, ISSN: 0018-9286

    In this paper, a novel framework to address the problem of parametric estimation for continuous-time linear time-invariant dynamic systems is dealt with. The proposed methodology entails the design of suitable kernels of non-anticipative linear integral operators thus obtaining estimators showing, in the ideal case, “non-asymptotic” (i.e., “finite-time”) convergence. The analysis of the properties of the kernels guaranteeing such a convergence behaviour is addressed and a novel class of admissible kernel functions is introduced. The operators induced by the proposed kernels admit implementable (i.e., finite-dimensional and internally stable) state-space realizations. Extensive numerical results are reported to show the effectiveness of the proposed methodology. Comparisons with some existing continuous-time estimators are addressed as well and insights on the possible bias affecting the estimates are provided.

  • Journal article
    Li S, Tan S-C, Lee CK, Waffenschmidt E, Hui SYR, Tse CKet al., 2016,

    A Survey, Classification, and Critical Review of Light-Emitting Diode Drivers

    , IEEE TRANSACTIONS ON POWER ELECTRONICS, Vol: 31, Pages: 1503-1516, ISSN: 0885-8993
  • Journal article
    Bettiol P, Khalil N, Vinter RB, 2016,

    Normality of Generalized Euler-Lagrange Conditions for State Constrained Optimal Control Problems

    , Journal of Convex Analysis, Vol: 23, Pages: 291-311, ISSN: 0944-6532

    We consider state constrained optimal control problems in which the cost to minimize comprises both integral and end-point terms, establishing normality of the generalized Euler-Lagrange condition. Simple examples illustrate that the validity of the Euler-Lagrange condition (and related necessary conditions), in normal form, depends crucially on the interplay between velocity sets, the left end-point constraint set and the state constraint set. We show that this is actually a common feature for general state constrained optimal control problems, in which the state constraint is represented by closed convex sets and the left end-point constraint is a closed set. In these circumstances classical constraint qualifications involving the state constraints and the velocity sets cannot be used alone to guarantee normality of the necessary conditions. A key feature of this paper is to prove that the additional information involving tangent vectors to the left end-point and the state constraint sets can be used to establish normality.

  • Journal article
    Lin D, Zhang C, Hui SYR, 2016,

    Mathematical Analysis of Omnidirectional Wireless Power Transfer-Part-I: Two-Dimensional Systems

    , IEEE TRANSACTIONS ON POWER ELECTRONICS, Vol: 32, Pages: 625-633, ISSN: 0885-8993
  • Journal article
    Lin D, Zhang C, Hui SYR, 2016,

    Mathematic Analysis of Omnidirectional Wireless Power Transfer-Part-II Three-Dimensional Systems

    , IEEE TRANSACTIONS ON POWER ELECTRONICS, Vol: 32, Pages: 613-624, ISSN: 0885-8993
  • Journal article
    De Paola A, Angeli D, Strbac G, 2016,

    Scheduling of Wind Farms for Optimal Frequency Response and Energy Recovery

    , IEEE Transactions on Control Systems Technology, Vol: 24, Pages: 1764-1778, ISSN: 1063-6536

    This paper deals with control of variable speed wind turbines, which provide frequency support through temporary overproduction. In particular, it determines the optimal profile of power extraction among multiple generators in order to minimize the total loss of efficiency, while allowing for a prescribed increase in generation. Starting with the simplifying assumption of unconstrained generated/supplied power for the single turbine, the scheduling is characterized as the solution of an optimal control problem. On the basis of this result, a heuristic control strategy is proposed for the case of turbines with limited power output, investigating under which conditions this choice achieves optimality. Using a similar approach, the problem of energy recovery is also considered, calculating the optimal power profiles that bring back the turbines to their working point of maximum efficiency after having provided frequency response.

  • Conference paper
    Sun M, Konstantelos I, Strbac G, 2016,

    Analysis of diversified residential demand in London using smart meter and demographic data

    , 2016 IEEE PES General Meeting, Publisher: IEEE

    In the interest of economic efficiency, design of distribution networks should be taillored to the demonstrated needs of its consumers. However, in the absence of detailed knowledge related to the characteristics of electricity consumption, planning has traditionally been carried out on the basis of empirical metrics; conservative estimates of individual peak consumption levels and of demand diversification across multiple consumers. Although such practices have served the industry well, the advent of smart metering opens up the possibility for gaining valuable insights on demand patterns, resulting in enhanced planning capabilities. This paper is motivated by the collection of demand measurements across 2,639 households in London, as part of Low Carbon London project’s smart-metering trial. Demand diversity and other metrics of interest are quantified for the entire dataset as well as across different customer classes, investigating the degree to which occupancy level and wealth can be used to infer peak demand behavior.

  • Journal article
    Luo X, Lee CK, Ng WM, Yan S, Chaudhuri B, Hui SYRet al., 2016,

    Use of adaptive thermal storage system as smart load for voltage control and demand response

    , IEEE Transactions on Smart Grid, Vol: 8, Pages: 1231-1241, ISSN: 1949-3053

    This paper describes how a large-scale ice-thermal storage can be turned into a smart load for fast voltage control and demand-side management in power systems with intermittent renewable power, while maintaining its existing function of load shaving. The possibility of modifying a conventional thermal load has been practically demonstrated in a refrigerator using power electronics technology. With the help of an electric spring, the modified thermal load can reduce power imbalance in buildings while providing active and reactive power compensation for the power grid. Based on practical data, a building energy model incorporating a large-scale ice-thermal storage system has been successfully used to demonstrate the advantageous demand-response features using computer simulation of both grid connected and isolated power systems. The results indicate the potential of using ice-thermal storage in tall buildings in reducing voltage and frequency fluctuations in weak power grids.

  • Conference paper
    Majumdar A, Pal BC, 2016,

    A three-phase state estimation in unbalanced distribution networks with switch modelling

    , 1st IEEE International Conference on Control, Measurement and Instrumentation (CMI), Publisher: IEEE, Pages: 474-478

    State estimation has become an important task in modern energy/distribution management systems. However, the state estimation is not very popular in modern unbalanced three-phase distribution systems. This paper proposes a method for three-phase state estimation with detailed three-phase modelling of system components including switches and star and delta connected loads. This method is then tested on a standard IEEE 13-bus system and the results are compared with load flow results.

  • Conference paper
    Singh A, Pal B, 2016,

    An extended linear quadratic regulator and its application for control of power system dynamics

    , IEEE First International Conference on Control, Measurement and Instrumentation (CMI), Publisher: IEEE, Pages: 110-114

    This paper presents a generalized solution to the problem of optimal control of systems having an extra set of exogenous inputs besides control inputs. The solution is derived in the framework of linear quadratic control and it is termed `extended linear quadratic regulator (ELQR)'. The ELQR is applied for control of unstable or poorly damped oscillatory dynamics occurring in a power system and is shown to be significantly more cost effective than the classical power system stabilizer (PSS) based approach.

  • Conference paper
    Ye Y, Papadaskalopoulos D, Strbac G, 2016,

    Factoring Flexible Demand Non-Convexities in Electricity Markets

    , IEEE-Power-and-Energy-Society General Meeting (PESGM), Publisher: IEEE, ISSN: 1944-9925
  • Conference paper
    Sanz IM, Chaudhuri B, Strbac G, 2016,

    Inertial Response From Offshore Wind Farms Connected Through DC Grids

    , IEEE-Power-and-Energy-Society General Meeting (PESGM), Publisher: IEEE, ISSN: 1944-9925
  • Conference paper
    Teng F, Trovato V, Strbac G, 2016,

    Stochastic Scheduling with Inertia-dependent Fast Frequency Response Requirements

    , IEEE-Power-and-Energy-Society General Meeting (PESGM), Publisher: IEEE, ISSN: 1944-9925
  • Conference paper
    Chen Y, Teng F, Moreno R, Strbac Get al., 2016,

    Impact of Dynamic Line Rating with Forecast Error on the Scheduling of Reserve Service

    , IEEE-Power-and-Energy-Society General Meeting (PESGM), Publisher: IEEE, ISSN: 1944-9925
  • Conference paper
    Goharrizi AY, Muthumuni D, Pipelzadeh Y, 2016,

    Modeling of Type-3 Wind Farm and Investigation of Fault Contribution in Power System

    , IEEE-Power-and-Energy-Society General Meeting (PESGM), Publisher: IEEE, ISSN: 1944-9925
  • Conference paper
    Huang Y, Xiong S, Tan S-C, Hui S-YRet al., 2016,

    Compact Modular Switched-Capacitor DC/DC Converters with Exponential Voltage Gain

    , 31st Annual IEEE Applied Power Electronics Specialists Conference and Exposition (APEC), Publisher: IEEE, Pages: 1894-1899, ISSN: 1048-2334

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