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  • Conference paper
    Khusainov B, Kerrigan EC, Constantinides GA, 2017,

    Multi-objective Co-design for Model Predictive Control with an FPGA

    , European Control Conference 16, Publisher: IEEE, Pages: 110-115

    In order to achieve the best possible performanceof a model predictive controller (MPC) for a given set ofresources, the software algorithm and computational platformhave to be designed simultaneously. Moreover, in practicalapplications the controller design problem has a multi-objectivenature: performance is traded off against computational hardwareresource usage, namely time, energy and space. Thispaper proposes formulating an MPC design problem as a multiobjectiveoptimization (MOO) problem in order to explore thedesign trade-offs in a systematic way.Since the design objectives in the resulting MOO problem areexpensive to evaluate, i.e. evaluation requires time consumingsimulations, most of the classical and evolutionary MOOalgorithms cannot be employed for this class of design problems.For this reason a practical MOO algorithm that can deal withexpensive-to-evaluate functions is presented. The algorithm isbased on Kriging and the hypervolume criterion that wasrecently proposed in the expensive optimization literature. Anumerical example for a fast gradient-based controller designshows that the proposed approach can efficiently exploreoptimal performance-resource trade-offs.

  • Journal article
    Qadrdan M, Ameli H, Strbac G, Jenkins Net al., 2017,

    Efficacy of options to address balancing challenges: integrated gas and electricity perspectives

    , Applied Energy, Vol: 190, Pages: 181-190, ISSN: 1872-9118

    Integration of a large capacity of wind generation in the Great Britain(GB)electricity network is expected to pose a number of operational challenges. The variable nature of wind generation necessitates introduction of technologies that can provide flexibility to generation portfolios and therefore compensate for intermittency of wind generation. In this paper, the efficacy of three options to address electricity balancing challenges was evaluated: flexible gas-fired plants, electricity storage andPower-to-Gas system. The combined gas and electricity network model (CGEN) was enhanced and through adopting a rolling optimisation approach the model aims at minimising the operational cost of an integrated gas and electricity networks that represents a GBsystem in 2030. The potential impacts of employing each of the flexibility options on the operation of the integrated electricity and gas networks were investigated. The analysis showed that amongst all the flexibility options, the deployment of grid-scale electricity storage will achieve the highest reduction in the operational cost of the integrated system (£12 million reduction in a typical winter week, and £3 million reduction in a typical summerweek). The results of this study provide insights on the system-wide benefits offered by each of the flexibility options and role of the gas network in the energy system with large capacity of wind generation.

  • Journal article
    Wang XM, Hui SYR, 2017,

    Graphical modelling of pinched hysteresis loops of memristors

    , IET Science Measurement and Technology, Vol: 11, Pages: 86-96, ISSN: 1751-8822

    In this study, a graphical modelling approach of the pinched hysteresis loops exhibited by memristors is presented. This method provides a tool to emulate the hysteresis loop pinched at the origin, with the lobe area varying with the excitation frequency. The direction of the pinched hysteresis loop can be controlled. This graphical modelling method provides an alternative to describe the behaviour of memristors without deriving the coupled non-linear differential equations typically required for physical memristors. The method has been successfully applied to model the Hewlett–Packard memristor device.

  • Journal article
    Boem F, Ferrari RMG, Keliris C, Parisini T, Polycarpou MMet al., 2017,

    A distributed networked approach for fault detection of large-scale systems

    , IEEE Transactions on Automatic Control, Vol: 62, Pages: 18-33, ISSN: 0018-9286

    Networked systems present some key new challenges in the development of fault diagnosis architectures. This paper proposes a novel distributed networked fault detection methodology for large-scale interconnected systems. The proposed formulation incorporates a synchronization methodology with a filtering approach in order to reduce the effect of measurement noise and time delays on the fault detection performance. The proposed approach allows the monitoring of multi-rate systems, where asynchronous and delayed measurements are available. This is achieved through the development of a virtual sensor scheme with a model-based re-synchronization algorithm and a delay compensation strategy for distributed fault diagnostic units. The monitoring architecture exploits an adaptive approximator with learning capabilities for handling uncertainties in the interconnection dynamics. A consensus-based estimator with timevarying weights is introduced, for improving fault detectability in the case of variables shared among more than one subsystem. Furthermore, time-varying threshold functions are designed to prevent false-positive alarms. Analytical fault detectability sufficient conditions are derived and extensive simulation results are presented to illustrate the effectiveness of the distributed fault detection technique.

  • Journal article
    Green RJ, Pudjianto D, Staffell I, Strbac Get al., 2016,

    Market Design for Long-Distance Trade in Renewable Electricity

    , Energy Journal, Vol: 37, Pages: 5-22, ISSN: 0195-6574

    While the 2009 EU Renewables Directive allows countries to purchase some of their obligation fromanother member state, no country has yet done so, preferring to invest locally even where load factors arevery low. If countries specialised in renewables most suited to their own endowments and expandedinternational trade, we estimate that system costs in 2030 could be reduced by 5%, or €15 billion a year,after allowing for the costs of extra transmission capacity, peaking generation and balancing operationsneeded to maintain electrical feasibility.Significant barriers must be overcome to unlock these savings. Countries that produce more renewablepower should be compensated for the extra cost through tradable certificates, while those that buy fromabroad will want to know that the power can be imported when needed. Financial Transmission Rightscould offer companies investing abroad confidence that the power can be delivered to their consumers.They would hedge short-term fluctuations in prices and operate much more flexibly than the existingsystem of physical point-to-point rights on interconnectors. Using FTRs to generate revenue fortransmission expansion could produce perverse incentives to under-invest and raise their prices, sorevenues from FTRs should instead be offset against payments under the existing ENTSO-Ecompensation scheme for transit flows. FTRs could also facilitate cross-border participation in capacitymarkets, which are likely to be needed to reduce risks for the extra peaking plants required.

  • Conference paper
    Raimondo DM, Boem F, Gallo A, Parisini Tet al., 2016,

    A decentralized fault-tolerant control scheme based on Active Fault Diagnosis

    , 2016 IEEE 55th Conference on Decision and Control, Publisher: IEEE

    This paper deals with a decentralized fault-tolerant control methodology based on an Active Fault Diagnosis approach. The proposed technique addresses the important problem of monitoring interconnected Large-Scale Systems (LSS). The fault diagnosis approach is made of a passive set-based fault detection method and an active fault isolation technique, able to guarantee isolability subject to local input and state constraints. The proposed scheme can be implemented locally in a decentralized way. A significant feature is the decentralized design constructed on tube-based Model Predictive Control to possibly allow the disconnection of faulty subsystems or the reconfiguration of local controllers. The Active Fault Diagnosis tool is designed to support the decision-making process for the control and monitoring of the LSS.

  • Conference paper
    Boem F, Carli R, Farina M, Ferrari-Trecate G, Parisini Tet al., 2016,

    Scalable monitoring of interconnected stochastic systems

    , 2016 IEEE 55th Conference on Decision and Control, Publisher: IEEE

    In this paper, we propose a novel distributed faultdetection method to monitor the state of a linear system, par-titioned into interconnected subsystems. The approach hingeson the definition of a partition-based distributed Luenbergerestimator, based on the local model of the subsystems andthat takes into account the dynamic coupling terms betweenthe subsystems. The proposed methodology computes –in adistributed way– a bound on the variance of a properly definedresidual signal, considering the uncertainty related to thestate estimates performed by the neighboring subsystems. Thisbound allows the computation of suitable local thresholds withguaranteed maximum false-alarms rate. The implementationof the proposed estimation and fault detection method isscalable, allowingPlug & Playoperations and the possibilityto disconnect the faulty subsystem after fault detection. Theo-retical conditions guaranteeing the convergence of the estimatesand of the bounds are provided. Simulation results show theeffectiveness of the proposed method.

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

    Decentralized coordination of large populations of flexible electrical appliances through demand saturation

    , 2016 IEEE 55th Conference on Decision and Control, CDC 2016, Publisher: Institute of Electrical and Electronics Engineers (IEEE), Pages: 4937-4943

    This paper presents a novel decentralized control strategy for integration of price-responsive loads in the electricity market. Previous work has shown that, by approximating the devices population as a continuum, it is possible to provide necessary and sufficient conditions for the existence of a Nash equilibrium (no device has unilateral interest in changing its scheduling when considering the resulting profile of aggregate demand). These results are now extended by introducing a time varying proportional constraint on the maximum power consumption of the appliances. This allows to saturate the flexible demand and obtain a Nash equilibrium for a much wider range of scenarios. The performance of the proposed control technique, which also minimizes the task time of all appliances, is tested in simulation.

  • Conference paper
    Forni P, Angeli D, 2016,

    Cascades of iISS and Strong iISS systems with multiple invariant sets

    , 2016 IEEE 55th Conference on Decision and Control, CDC 2016, Publisher: Institute of Electrical and Electronics Engineers (IEEE), Pages: 459-464

    In recent papers, the notions of Input-to-State Stability (ISS) and Integral ISS (iISS) have been generalized for systems evolving on manifolds and having multiple invariant sets, i.e. multistable systems. The well-known property of conservation of ISS under cascade interconnection has also been proven true for multistable systems in different scenarios [3]. Unfortunately, multistability hampers a straightforward extension of analogous conservation properties for integral ISS systems. By means of counterexamples, this work highlights the necessity of the additional assumptions which yield the conservation of the iISS and Strong iISS properties in cascades of multistable systems. In particular, a characterization of the invariant set of the cascade is provided in terms of its finest possible decomposition.

  • Conference paper
    Manfredi S, Angeli D, 2016,

    Consensus for nonlinear monotone networks with unilateral interactions

    , 2016 IEEE 55th Conference on Decision and Control, CDC 2016, Publisher: Institute of Electrical and Electronics Engineers (IEEE), Pages: 2609-2614

    This paper deals with an extended framework of the distributed asymptotic agreement problem by allowing the presence of unilateral interactions (optimistic or pessimistic) in place of bilateral ones, for a large class of nonlinear monotone time-varying networks. In this original setup we firstly introduce notions of unilateral optimistic and/or pessimistic interaction, of associated bicolored edge in the interaction graph and a suitable graph-theoretical connectedness property. Secondly, we formulate a new assumption of integral connectivity and show that it is sufficient to guarantee exponential convergence towards the agreement subspace. Finally, we remark that the proposed conditions are also necessary for consensuability. Theoretical advances are emphasized through illustrative examples given both to support the discussion and to highlight how the proposed framework extends all existing conditions for consensus of monotone networks.

  • Conference paper
    Forni P, Angeli D, 2016,

    Output-to-State Stability for systems on manifolds with multiple invariant sets

    , 2016 IEEE 55th Conference on Decision and Control, CDC 2016, Publisher: Institute of Electrical and Electronics Engineers (IEEE), Pages: 453-458

    Output-to-State Stability (OSS) is a notion of detectability for nonlinear systems that is formulated in the ISS framework. We generalize the notion of OSS for systems evolving on manifolds and having multiple invariant sets. Building upon a recent extension of the Input-to-State Stability (ISS) theory for this very class of systems [1], the paper provides equivalent characterizations of the OSS property in terms of asymptotic estimates of the state trajectories and, in particular, in terms of existence of Lyapunov-like functions.

  • Conference paper
    Thammawichai M, Kerrigan EC, 2016,

    Feedback Scheduling for Energy-Efficient Real-Time Homogeneous Multiprocessor Systems

    , 55th IEEE Conference on Decision and Control, Publisher: IEEE

    Real-time scheduling algorithms proposed in theliterature are often based on worst-case estimates of taskparameters and the performance of an open-loop scheme cantherefore be poor. To improve on such a situation, one caninstead apply a closed-loop scheme, where feedback is exploitedto dynamically adjust the system parameters at run-time. Wepropose an optimal control framework that takes advantageof feeding back information of finished tasks to solve a realtimemultiprocessor scheduling problem with uncertainty intask execution times, with the objective of minimizing thetotal energy consumption. Specifically, we propose a linearprogramming-based algorithm to solve a workload partitioningproblem and adopt McNaughton’s wrap around algorithmto find the task execution order. Simulation results for aPowerPC 405LP and an XScale processor illustrate that ourfeedback scheduling algorithm can result in an energy savingof approximately 40% compared to an open-loop method.

  • Journal article
    Strbac G, Kirschen D, Moreno R, Strbac G, Kirschen D, Moreno Ret al., 2016,

    Reliability Standards for the Operation and Planning of Future Electricity Networks

    , Foundations and Trends® in Electric Energy Systems, Vol: 1, Pages: 143-219, ISSN: 2332-6557

    Electricity networks, designed and operated in accordance with the historic deterministic standards, have broadly delivered secure and reliable supplies to customers. A key issue regarding their evolution is how the operation and planning standards should evolve to make efficient use of the existing assets while taking advantage of emerging, non-network (or non-wires) technologies. Deployment of the smart grid will require fundamental changes in the historical principles used for network security in order to ensure that integration of low-carbon generation is undertaken as efficiently as possible through the use of new information and communication technology (ICT), and new flexible network technologies that can maximize utilization of existing electricity infrastructure. These new technologies could reduce network redundancy in providing security of supply by enabling the application of a range of advanced, technically effective, and economically efficient corrective (or post-fault) actions that can release latent network capacity of the existing system. In this context, this paper demonstrates that historical deterministic practices and standards, mostly developed in the 1950s, should be reviewed in order to take full advantage of new emerging technologies and facilitate transition to a smart grid paradigm. This paper also demonstrates that a probabilistic approach to developing future efficient operating and design strategies enabled by new technologies, will appropriately balance network investment against non-network solutions while truly recognizing effects of adverse weather, common-mode failures, high-impact low-probability events, changing market prices for pre- and post-contingency actions, equipment malfunctioning, etc. This clearly requires explicit consideration of the likelihood of various outages (beyond those considered in deterministic studies) and quantification of their impacts on alternative network operation and investment decisions, which canno

  • Conference paper
    Ascencio P, Astolfi A, Parisini T, 2016,

    Backstepping PDE-based adaptive observer for a single particle model of lithium-ion batteries

    , 55th IEEE Conference on Decision and Control (CDC), Publisher: IEEE, Pages: 5623-5628, ISSN: 0743-1546

    This article deals with the observer design problem for the simultaneous estimation of the solid Lithium concentration and of the diffusion parameter for a Single Particle Model of Lithium-Ion Batteries. The design is based on the Backstepping PDE methodology, including a modified Volterra transformation to compensate for the diffusivity uncertainty. The resulting coupled/uncoupled Kernel-PDE and Ordinary Differential Equation (ODE) are recast, via a Sum-of-Squares decomposition, in terms of a convex optimization problem and solved by semidefinite programming, allowing, at each fixed time, an efficient computation of the state and parameter observer gains. In addition, based on the Moment approach, a novel scheme of inversion of the nonlinear output mapping of the Single Particle Model is presented. The effectiveness of this approach is illustrated by numerical simulations.

  • Conference paper
    Scarciotti G, 2016,

    Moment matching for nonlinear differential-algebraic equations

    , IEEE 55th Annual Conference on Decision and Control (CDC), Publisher: IEEE

    The problem of model reduction by momentmatching for nonlinear singular systems is considered. Thenotion of moment is extended to this class of systems bymeans of the center manifold theory. The characterization ofthe moments at infinity and of the moments for nonlinearparametric singular systems is discussed. The problem of modelreduction for singular perturbation systems is analyzed. Afamily of singular reduced order models achieving momentmatching is presented. Throughout the paper the results areillustrated by means of examples.

  • Conference paper
    Scarciotti G, Astolfi A, Jiang Z-P, 2016,

    Constrained optimal reduced-order models from input/output data

    , IEEE 55th Annual Conference on Decision and Control (CDC), Publisher: IEEE

    Model reduction by moment matching does notpreserve, in a systematic way, the transient response of thesystem to be reduced, thus limiting the use of this modelreduction technique in control problems. With the final goalof designing reduced-order models which can effectively beused (not just for analysis but also) for control purposes, wedetermine, using a data-driven approach, an estimate of themoments and of the transient response of an unknown system.We compute the unique, up to a change of coordinates, reducedordermodel which possesses the estimated transient and,simultaneously, achieves moment matching at the prescribedinterpolation points. The error between the output of the systemand the output of the reduced-order model is minimized andwe show that the resulting system is a constrained optimal (ina sense to be specified) reduced-order model. The results of thepaper are illustrated by means of a simple numerical example.

  • Conference paper
    Padoan A, Scarciotti G, Astolfi A, 2016,

    A geometric characterisation of the persistence of excitation condition for sequences generated by discrete-time autonomous systems

    , IEEE 55th Annual Conference on Decision and Control (CDC), Publisher: IEEE

    The persistence of excitation condition for sequencesgenerated by time-invariant, discrete-time, autonomouslinear and nonlinear systems is studied. A rank conditionis shown to be equivalent to the persistence of excitationof sequences generated by the class of systems considered,consistently with the results established by the authors for thecontinuous-time case. The condition is geometric in nature andcan be checked a priori for a Poisson stable system, that is,without knowing explicitly the state trajectories of the system.The significance of the ideas and tools presented is illustratedby means of simple examples.

  • Conference paper
    Mylvaganam T, Astolfi A, 2016,

    Dynamic Algorithms for Solving Coupled Algebraic Riccati Equations Arising in Mixed H2/H∞ Control for Scalar Linear Systems

    , IEEE Conference on Decision & Control, Publisher: IEEE, ISSN: 0743-1546

    The problem of mixed H2/H∞ control canbe formulated as a two-player nonzero-sum differentialgame as done by Limebeer et al. in the 1990s. For linearsystems the problem is characterised by two coupled algebraicRiccati equations. Solutions for such algebraic Riccatiequations are not straight-forward to obtain, particularly forinfinite-horizon problems. In this paper two algorithms forobtaining solutions for the coupled algebraic Riccati equationsassociated with the mixed H2/H∞ control problemfor scalar, linear systems is provided along with illustrativenumerical examples.

  • Conference paper
    Ge M, Kerrigan EC, 2016,

    Relations between Full Information and Kalman-Based Estimation

    , 55th IEEE Conference on Decision and Control, Publisher: IEEE

    For nonlinear state space systems with additivenoises, sometimes the number of process noise signals couldbe less than the dimension of the state space. In order toimprove the accuracy and stability of nonlinear state estimation,this paper provides for the first time the derivation of thefull information estimator (FIE) for such nonlinear systems.We verify our derivation of the FIE by firstly proving theunbiasedness and minimum-variance of the FIE for linear timevarying (LTV) systems, then showing the equivalence betweenthe Kalman filter/smoother and the FIE for LTV systems.Finally, we prove that the FIE will provide more accurate stateestimates than the extended Kalman filter (EKF) and smoother(EKS) for nonlinear systems.

  • Conference paper
    Mylvaganam T, Astolfi A, 2016,

    A Nash Game Approach to Mixed H2/H∞ Control for Input-Affine Nonlinear Systems

    , Nonlinear Control System Symposium (NOLCOS), Publisher: Elsevier, Pages: 1024-1029, ISSN: 1474-6670

    With the aim of designing controllers to simultaneously ensure robustness and optimality properties, the mixed H2/H∞ control problem is considered. A class of input-affine nonlinear systems is considered and the problem is formulated as a nonzero-sum differential game, similar to what has been done in the 1990s by Limebeer et al. for linear systems. A heuristic algorithm for obtaining solutions for the coupled algebraic Riccati equations which are characteristic of the linear quadratic problem is provided together with a systematic method for constructing approximate solutions for the general, nonlinear problem. A few numerical examples are provided.

  • Conference paper
    Scarciotti G, Astolfi A, 2016,

    Model reduction for hybrid systems with state-dependent jumps

    , 10th IFAC Symposium on Nonlinear Control Systems, Publisher: Elsevier, Pages: 850-855, ISSN: 1474-6670

    In this paper we present a model reduction technique based on moment matchingfor a class of hybrid systems with state-dependent jumps. The problem of characterizing thesteady-state for this class of systems is studied and a result which allows to described the steadystateresponse of hybrid systems through the use of a hybrid mapping is given. Then a familyof hybrid reduced order models which achieve moment matching and are easily parameterizableis provided. The special case of periodic input signals is analyzed and conditions for applyingthe technique are given for this class. A numerical simulation illustrates the results.

  • Conference paper
    Padoan A, Scarciotti G, Astolfi A, 2016,

    A geometric characterisation of persistently exciting signals generated byautonomous systems

    , 10th IFAC Symposium on Nonlinear Control Systems, Publisher: Elsevier, Pages: 826-831, ISSN: 1474-6670

    The persistence of excitation of signals generated by time-invariant, continuous-time,autonomous linear and nonlinear systems is studied. The notion of persistence of excitation ischaracterised as a rank condition which is reminiscent of a geometric condition used to study thecontrollability properties of a control system. The notions and tools introduced are illustratedby means of simple examples and of an application in system identification.

  • Conference paper
    Xiang X, Merlin MMC, Green TC, 2016,

    Cost Analysis and Comparison of HVAC, LFAC and HVDC for Offshore Wind Power Connection

    , IET 12th International Conference on AC andDC Transmission, Publisher: IET

    Low frequency AC (LFAC) has been proposed as a means toavoid some of the large converter station costs of high voltageDC (HVDC) while delivering some of the benefits in terms ofbetter line or cable utilization and its technical feasibility hasbeen established. It is said to offer a lower costs than HVDC orconventional high voltage AC (HVAC) for a range ofintermediate distances, with HVDC becoming cheaper overlong distances. However, the basis for identifying the distancerange and extent of cost saving has not been established. Here,cost estimate methodologies are extended for LFAC. Adifficulty is the absence of commercial schemes that canprovide practical examples of costs. In this paper, costs arebroken down into constituent terms and estimates are madefrom the most similar equipment from other schemes. Thecapacity limits and power losses associated with subsea cablesare analyzed for low frequency cases. For a given powertransfer and for each distance, a choice of operating voltage,cable size and number of parallel circuits is made in order tofind the lowest route cost. This yields cost as a function ofdistance that is a non-linear and discontinuous function. Thecost curves for LFAC are compared with HVDC and HVACoptions. The results for current cost estimates show that LFAChas a range of route length over which it is the lowest costoption and but this range narrows and eventually ceases to existfor higher power transfer ratings.

  • Journal article
    Parisini T, 2016,

    Editorial

    , IEEE Transactions on Control Systems Technology, Vol: 25, Pages: 1-2, ISSN: 1558-0865

    With this last Editorial, I’m very pleased to welcome the new Editor in Chief of the IEEE Transactions on Control Systems Technology, Prof. Andrea Serrani, effective January 1, 2017. Prof. Serrani received the Laurea (B.Eng.) degree in electrical engineering (summa cum laude) and the Ph.D. degree in artificial intelligence systems from the University of Ancona, Italy, in 1993 and 1997, respectively, and the M.S. and D.Sc. degrees in systems science and mathematics from Washinton University in St. Louis, MI, USA, in 1996 and 2000, respectively. From 1994 to 1999, he was a Fulbright Fellow at Washington University in St. Louis. Since 2002, he has been with the Department of Electrical and Computer Engineering at The Ohio State University, where he is currently a Professor and Chair of Graduate Studies. Between 2004 and 2007, he served as the technical leader for the Reusable Launch Vehicle area of the AFOSR/AFRL Collaborative Center for Control Sciences at The Ohio State University. He has held visiting positions at the Center for Research on Complex Automated Systems of the University of Bologna and at the University of Padua, Italy, and multiple summer faculty positions at the Air Force Research Laboratory, including two AF-ASEE Fellowships. Among other editorial positions, Andrea served as Associate Editor of these Transactions since 2010. Prof. Serrani has an outstanding research track record both on theory and applications. He is simply a perfect choice for this position.

  • Journal article
    Yan S, Tan SC, Lee CK, Chaudhuri B, Hui SYRet al., 2016,

    Use of Smart Loads for Power Quality Improvement

    , IEEE Journal of Emerging and Selected Topics in Power Electronics, Vol: 5, Pages: 504-512, ISSN: 2168-6777

    Electric spring (ES) was originally proposed as a distributed demand-side management technology for making noncritical loads adaptive to the availability of intermittent renewable power generation. The second generation of ES, fed with batteries (ES-2) and associated with a noncritical load, can form a new kind of combined smart load and distributed energy storage technology for smart grids. With its four-quadrant operation, ES-2 is able to offer ancillary grid services in addition to its major functions of voltage and frequency regulation. This paper presents the operating principles and the input current control of ES-2 for power quality improvement such as power factor correction and harmonics reduction. The operating principles and the proposed input current control have been verified with the experimental results obtained from a small-scale power grid. Another weak single-phase power system fed by intermittent wind power is set up to prove the combined operation of ES-2 for power quality improvement and ES-1 (ES with capacitor storage) for voltage stabilization. The experimental results show that ES-2 with input current control can carry out power quality improvement as its ancillary function.

  • Journal article
    Singh A, Pal B, 2016,

    An extended linear quadratic regulator for LTI systems with exogenous inputs

    , Automatica, Vol: 76, Pages: 10-16, ISSN: 0005-1098

    This paper proposes a cost effective control law for a linear time invariant (LTI) system having an extra set of exogenousinputs (or external disturbances) besides the traditional set of control inputs. No assumption is made with regard to a-prioriknowledge of the modeling equations for the exogenous inputs. The problem of optimal control for such a system is definedin the standard framework of linear quadratic control and an extended linear quadratic regulator (ELQR) is proposed as thesolution to the problem. The ELQR approach is demonstrated through an example and is shown to be significantly more costeffective than currently available approaches for linear quadratic control.

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

    Transmission network expansion planning with stochastic multivariate load and wind modeling

    , PMAPS 2016, Publisher: IEEE

    The increasing penetration of intermittent energy sources along with the introduction of shiftable load elements renders transmission network expansion planning (TNEP) a challenging task. In particular, the ever-expanding spectrum of possible operating points necessitates the consideration of a very large number of scenarios within a cost-benefit framework, leading to computational issues. On the other hand, failure to adequately capture the behavior of stochastic parameters can lead to inefficient expansion plans. This paper proposes a novel TNEP framework that accommodates multiple sources of operational stochasticity. Inter-spatial dependencies between loads in various locations and intermittent generation units' output are captured by using a multivariate Gaussian copula. This statistical model forms the basis of a Monte Carlo analysis framework for exploring the uncertainty state-space. Benders decomposition is applied to efficiently split the investment and operation problems. The advantages of the proposed model are demonstrated through a case study on the IEEE 118-bus system. By evaluating the confidence interval of the optimality gap, the advantages of the proposed approach over conventional techniques are clearly demonstrated.

  • Conference paper
    Vasconcelos MH, Carvalho LM, Meirinhos J, Omont N, Gambier-Morel P, Jamgotchian G, Cirio D, Ciapessoni E, Pitto A, Konstantelos I, Strbac G, Ferraro C, Biasuzzi Cet al., 2016,

    Online security assessment with load and renewable generation uncertainty: The iTesla project approach

    , 2016 International Conference on Probabilistic Methods Applied to Power Systems (PMAPS), Publisher: IEEE

    The secure integration of renewable generation into modern power systems requires an appropriate assessment of the security of the system in real-time. The uncertainty associated with renewable power makes it impossible to tackle this problem via a brute-force approach, i.e. it is not possible to run detailed online static or dynamic simulations for all possible security problems and realizations of load and renewable power. Intelligent approaches for online security assessment with forecast uncertainty modeling are being sought to better handle contingency events. This paper reports the platform developed within the iTesla project for online static and dynamic security assessment. This innovative and open-source computational platform is composed of several modules such as detailed static and dynamic simulation, machine learning, forecast uncertainty representation and optimization tools to not only filter contingencies but also to provide the best control actions to avoid possible unsecure situations. Based on High Performance Computing (HPC), the iTesla platform was tested in the French network for a specific security problem: overload of transmission circuits. The results obtained show that forecast uncertainty representation is of the utmost importance, since from apparently secure forecast network states, it is possible to obtain unsecure situations that need to be tackled in advance by the system operator.

  • Journal article
    Riverso S, Boem F, Ferrari-Trecate G, Parisini Tet al., 2016,

    Plug-and-Play Fault Detection and control-reconfiguration for a class of nonlinear large-scale constrained systems

    , IEEE Transactions on Automatic Control, Vol: 61, Pages: 3963-3978, ISSN: 0018-9286

    This paper deals with a novel Plug-and-Play (PnP) architecture for the control and monitoring of Large-Scale Systems (LSSs). The proposed approach integrates a distributed Model Predictive Control (MPC) strategy with a distributed Fault Detection (FD) architecture and methodology in a PnP framework. The basic concept is to use the FD scheme as an autonomous decision support system: once a fault is detected, the faulty subsystem can be unplugged to avoid the propagation of the fault in the interconnected LSS. Analogously, once the issue has been solved, the disconnected subsystem can be re-plugged-in. PnP design of local controllers and detectors allow these operations to be performed safely, i.e. without spoiling stability and constraint satisfaction for the whole LSS. The PnP distributed MPC is derived for a class of nonlinear LSSs and an integrated PnP distributed FD architecture is proposed. Simulation results in two paradigmatic examples show the effectiveness and the potential of the general methodology.

  • Journal article
    Arana C, Evangelou SA, Dini D, 2016,

    Series active variable geometry suspension application to comfort enhancement

    , Control Engineering Practice, Vol: 59, Pages: 111-126, ISSN: 1873-6939

    This paper explores the potential of the Series Active Variable Geometry Suspension (SAVGS) for comfort and road holding enhancement. The SAVGS concept introduces significant nonlinearities associated with the rotation of the mechanical link that connects the chassis to the spring-damper unit. Although conventional linearization procedures implemented in multi-body software packages can deal with this configuration, they produce linear models of reduced applicability. To overcome this limitation, an alternative linearization approach based on energy conservation principles is proposed and successfully applied to one corner of the car, thus enabling the use of linear robust control techniques. An H∞ controller is synthesized for this simplified quarter-car linear model and tuned based on the singular value decomposition of the system's transfer matrix. The proposed control is thoroughly tested with one-corner and full-vehicle nonlinear multi-body models. In the SAVGS setup, the actuator appears in series with the passive spring-damper and therefore it would typically be categorized as a low bandwidth or slow active suspension. However, results presented in this paper for an SAVGS-retrofitted Grand Tourer show that this technology has the potential to also improve the high frequency suspension functions such as comfort and road holding.

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