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Journal articleKonstantelos I, Giannelos S, Strbac G, 2016,
Strategic valuation of smart grid technology options in distribution networks
, IEEE Transactions on Power Systems, Vol: 32, Pages: 1293-1303, ISSN: 0885-8950The increasing penetration of renewabledistributed generation (DG) sources in distribution networks canlead to violations of network constraints. Thus, significantnetwork reinforcements may be required to ensure that DGoutput is not constrained. However, the uncertainty around themagnitude, location and timing of future DG capacity rendersplanners unable to take fully-informed decisions and integrateDG at a minimum cost. In this paper we propose a novelstochastic planning model that considers investment inconventional assets as well as smart grid assets such as demandsideresponse, coordinated voltage control and soft open points(SOPs). The model also considers the possibility of active powergeneration curtailment of the DG units. A node-variableformulation has been adopted to relieve the substantialcomputational burden of the resulting mixed integer non-linearprogramming (MINLP) problem. A case study shows that smarttechnologies can possess significant strategic value due to theirinherent flexibility in dealing with different system evolutiontrajectories. This latent benefit remains undetected undertraditional deterministic planning approaches which may hinderthe transition to the smart grid.
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Conference paperZhang C, Jaimoukha IM, Segundo Sevilla, 2016,
Fault-tolerant observer design with a tolerance measure for systems with sensor failure
, 2016 American Control Conference, Publisher: IEEE, Pages: 7523-7528, ISSN: 0743-1619A fault-tolerant switching observer design methodology is proposed. The aim is to maintain a desired level of closed-loop performance under a range of sensor fault scenarios while the fault-free nominal performance is optimized. The range of considered fault scenarios is determined by a minimum number p of assumed working sensors. Thus the smaller p is, the more fault tolerant is the observer. This is then used to define a fault tolerance measure for observer design. Due to the combinatorial nature of the problem, a semidefinite relaxation procedure is proposed to deal with the large number of fault scenarios for systems that have many vulnerable sensors. The procedure results in a significant reduction in the number of constraints needed to solve the problem. Two numerical examples are presented to illustrate the effectiveness of the fault-tolerant observer design.
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Conference paperScarciotti G, Astolfi A, 2016,
A note on the electrical equivalent of the moment theory
, 2016 American Control Conference (ACC), Publisher: IEEE, Pages: 7462-7465In this short note the relation between the moments of a linear system and the phasors of an electric circuit is discussed. We show that the phasors are a special case of moments and we prove that the components of the solution of a Sylvester equation are the phasors of the currents of the system. We point out several directions in which the phasor theory can be extended using recent generalizations of the moment theory, which can benefit the analysis of circuits and power electronics.
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Conference paperPadoan A, Astolfi A, 2016,
Nonlinear system identification for continuous-time autonomous systems via functional equations methods
, 2016 American Control Conference (ACC), Publisher: IEEE, Pages: 1814-1819The problem of identifying an autonomous nonlinear system, that is, the problem of finding a state-space description of a given sequence generated by sampling the output of an unknown autonomous nonlinear system, is studied. A theoretical framework which combines the use of the Schroder functional equation with realization-theoretic techniques is developed.
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Journal articleBauso D, Mylvaganam T, Astolfi A, 2016,
Crowd-averse robust mean-field games: approximation via state space extension
, IEEE Transactions on Automatic Control, Vol: 61, Pages: 1882-1894, ISSN: 0018-9286We consider a population of dynamic agents, also referred to as players. The state of each player evolves according to a linear stochastic differential equation driven by a Brownian motion and under the influence of a control and an adversarial disturbance. Every player minimizes a cost functional which involves quadratic terms on state and control plus a cross-coupling mean-field term measuring the congestion resulting from the collective behavior, which motivates the term “crowd-averse.” Motivations for this model are analyzed and discussed in three main contexts: a stock market application, a production engineering example, and a dynamic demand management problem in power systems. For the problem in its abstract formulation, we illustrate the paradigm of robust mean-field games. Main contributions involve first the formulation of the problem as a robust mean-field game; second, the development of a new approximate solution approach based on the extension of the state space; third, a relaxation method to minimize the approximation error. Further results are provided for the scalar case, for which we establish performance bounds, and analyze stochastic stability of both the microscopic and the macroscopic dynamics.
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Conference paperChaffey GP, Judge PD, Merlin MMC, et al., 2016,
DC Fault Ride Through of Multilevel Converters
, 2016 IEEE Energy Conversion Congress and Exposition (ECCE)Modular Multilevel Converters (MMC) can providesignificant advantages for power transmission applications, how-ever there are remaining challenges trading off DC fault response,losses and controllability. Alternative multilevel converter topolo-gies using combinations of full bridge and half bridge submodulesor series switches allow for competitive efficiency whilst retainingcontrol over the DC fault current. Several possible fault responsesare analysed to evaluate appropriate converter control actions.Experimental results from a 60 submodule 15 kW demonstratorare presented to validate the DC fault performance of the fullbridge MMC, the mixed stack MMC and the alternate armconverter. It is shown that each can control the current intoa low impedance DC fault, and there no requirement to blockthe semiconductor devices.
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Journal articleZhang C, Lin D, Hui SY, 2016,
Basic control principles of omnidirectional wireless power transfer
, IEEE Transactions on Power Electronics, Vol: 31, Pages: 5215-5227, ISSN: 0885-8993This paper presents the basic control principles of omnidirectional wireless power transfer (WPT) based on the current amplitude control. The principles involve 1) an “omnidirectional” scanning process for detecting the power requirements in a 3-D space and 2) a “directional” power flow control for focusing the wireless power toward the targeted areas. Such principles apply to any WPT system comprising three orthogonal transmitter coils and multiple receivers with coil resonators. A current amplitude control method capable of generating a magnetic vector at a set of points evenly distributed on a spherical surface is explained. Based on the voltage and the current information in the transmitter circuit, the power involved in each vector over the spherical surface can be obtained. By scanning the vector over the spherical surface, the collective power flow requirements for the targeted loads can be determined. Based on the power requirements for the vectors over the spherical surface, a weighted time-sharing scheme is adopted to focus the wireless power toward the targeted areas. This method has been successfully applied to a hardware prototype. Both theoretical and experimental results are included to confirm these principles.
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Conference paperYang Y, Tindemans S, Strbac G, 2016,
An implicit switching model for distribution network reliability assessment
, 19th Power Systems Computation Conference (PSCC)Modern active distribution networks make use of intelligent switching actions to restore supply to end users after faults. This complicates the reliability analysis of such networks, as the number of possible switching actions grows exponentially with network size. This paper proposes an approximate reliability analysis method where switching actions are modelled implicitly. It can be used graphically as a model reduction method, and simulated using time-sequential or state sampling Monte Carlo methods. The method is illustrated on a simple distribution network, and reliability indices are reported both as averages and distributions. Large speedups result from the use of biased non-sequential Monte Carlo sampling–a method that is hard to combine with explicit switching models.
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Conference paperSun M, Konstantelos I, Tindemans S, et al., 2016,
Evaluating composite approaches to modelling high-dimensional stochastic variables in power systems
, 19th Power Systems Computation ConferenceThe large-scale integration of intermittent energy sources, the introduction of shiftable load elements and the growing interconnection that characterizes electricity systems worldwide have led to a significant increase of operational uncertainty. The construction of suitable statistical models is a fundamental step towards building Monte Carlo analysis frameworks to be used for exploring the uncertainty state-space and supporting real-time decision-making. The main contribution of the present paper is the development of novel composite modelling approaches that employ dimensionality reduction, clustering and parametric modelling techniques with a particular focus on the use of pair copula construction schemes. Large power system datasets are modelled using different combinations of the aforementioned techniques, and detailed comparisons are drawn on the basis of Kolmogorov-Smirnov tests, multivariate two-sample energy tests and visual data comparisons. The proposed methods are shown to be superior to alternative high-dimensional modelling approaches.
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Journal articleTeng F, Mu Y, Jia H, et al., 2016,
Challenges of Primary Frequency Control and Benefits of Primary Frequency Response Support from Electric Vehicles
, Energy Procedia, Vol: 88, Pages: 985-990, ISSN: 1876-6102As the integration of wind generation displaces conventional plants, system inertia provided by rotating mass declines, causing concerns over system frequency stability. This paper implements an advanced stochastic scheduling model with inertia-dependent fast frequency response requirements to investigate the challenges on the primary frequency control in the future Great Britain electricity system. The results suggest that the required volume and the associated cost of primary frequency response increase significantly along with the increased capacity of wind plants. Alternative measures (e.g. electric vehicles) have been proposed to alleviate these concerns. Therefore, this paper also analyses the benefits of primary frequency response support from electric vehicles in reducing system operation cost, wind curtailment and carbon emissions.
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Journal articleChen HT, Tan SC, Lee ATL, et al., 2016,
Precise color control of red-green-blue light-emitting diode systems
, IEEE Transactions on Power Electronics, Vol: 32, Pages: 3063-3074, ISSN: 0885-8993© 1986-2012 IEEE. The complex nature and differences of the luminous and thermal characteristics of red, green, and blue (RGB) light-emitting diodes (LEDs) make precise color control of RGB LED systems a great technological challenge. This paper presents a nonlinear model that includes coupling effects among LED devices for predicting color in RGB LED systems. A control method is included to demonstrate that this model can be used for precise color control. The proposed model and control method have been successfully evaluated in practical tests. The measurements agree well with model predictions. They form a new design tool for precise color control of RGB LED systems.
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Journal articleMiller LM, Elliott ADT, Mitcheson PD, et al., 2016,
Maximum performance of piezoelectric energy harvesters when coupled to interface circuits
, IEEE Sensors Journal, Vol: 16, Pages: 4803-4815, ISSN: 1530-437XThis paper presents a complete optimization of a piezoelectric vibration energy harvesting system, including a piezoelectric transducer, a power conditioning circuit with full semiconductor device models, a battery and passive components. To the authors awareness, this is the first time and all of these elements have been integrated into one optimization. The optimization is done within a framework, which models the combined mechanical and electrical elements of a complete piezoelectric vibration energy harvesting system. To realize the optimization, an optimal electrical damping is achieved using a single-supply pre-biasing circuit with a buck converter to charge the battery. The model is implemented in MATLAB and verified in SPICE. The results of the full system model are used to find the mechanical and electrical system parameters required to maximize the power output. The model, therefore, yields the upper bound of the output power and the system effectiveness of complete piezoelectric energy harvesting systems and, hence, provides both a benchmark for assessing the effectiveness of existing harvesters and a framework to design the optimized harvesters. It is also shown that the increased acceleration does not always result in increased power generation as a larger damping force is required, forcing a geometry change of the harvester to avoid exceeding the piezoelectric breakdown voltage. Similarly, increasing available volume may not result in the increased power generation because of the difficulty of resonating the beam at certain frequencies whilst utilizing the entire volume. A maximum system effectiveness of 48% is shown to be achievable at 100 Hz for a 3.38-cm3 generator.
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Journal articleKunjumuhammed LP, Pal BC, Oates C, et al., 2016,
The adequacy of the present practice in dynamic aggregated modelling of wind farm systems
, IEEE Transactions on Sustainable Energy, Vol: 8, Pages: 23-32, ISSN: 1949-3037Large offshore wind farms are usually composed ofseveral hundred individual wind turbines, each turbine havingits own complex set of dynamics. The analysis of the dynamicinteraction between wind turbine generators (WTG), interconnectingac cables, and voltage source converter (VSC) based HighVoltage DC (HVDC) system is difficult because of the complexityand the scale of the entire system. The detailed modelling andmodal analysis of a representative wind farm system reveal thepresence of several critical resonant modes within the system.Several of these modes have frequencies close to harmonicsof the power system frequency with poor damping. From acomputational perspective the aggregation of the physical modelis necessary in order to reduce the degree of complexity to apractical level. This paper focuses on the present practices ofthe aggregation of the WTGs and the collection system, andtheir influence on the damping and frequency characteristics ofthe critical oscillatory modes. The effect of aggregation on thecritical modes are discussed using modal analysis and dynamicsimulation. The adequacy of aggregation method is discussed.
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Journal articleForni P, Angeli D, 2016,
The ISS approach to the stability and robustness properties of nonautonomous systems with decomposable invariant sets: an overview
, European Journal of Control, Vol: 30, Pages: 50-60, ISSN: 0947-3580This paper is an overview of recent developments in the Input-to-State Stability framework, dealing in particular with the extension of the classical concept to systems with multiple invariant sets and possibly evolving on Riemannian manifolds. Lyapunov-based characterizations of the properties are discussed as well as applications to the study of cascaded nonlinear systems.
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Journal articleGuo J, Liang J, Zhang X, et al., 2016,
Reliability Analysis of MMCs Considering Submodule Designs with Individual or Series-Operated IGBTs
, IEEE TRANSACTIONS ON POWER DELIVERY, Vol: 32, Pages: 666-677, ISSN: 0885-8977The half-bridge-based modular multilevel converter (MMC) has emerged as the favored converter topology for voltage-source HVDC applications. The submodules within the converter can be constructed with either individual insulated-gate bipolar transistor (IGBT) modules or with series-connected IGBTs, which allows for different redundancy strategies to be employed. The main contribution of this paper is that an analytical method was proposed to analyze the reliability of MMCs with the consideration of submodule arrangements and redundancy strategies. Based on the analytical method, the relative merits of two approaches to adding redundancy, and variants created by varying the submodule voltage, are assessed in terms of overall converter reliability. Case studies were conducted to compare the reliability characteristics of converters constructed using the two submodule topologies. It is found that reliability of the MMC with series-connected IGBTs is higher for the first few years but then decreases rapidly. By assigning a reduced nominal voltage to the series valve submodule upon IGBT module failure, the need to install redundant submodules is greatly reduced.
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Journal articleAngeli D, Casavola A, Tedesco F, 2016,
Theoretical advances on Economic Model Predictive Control with time-varying costs
, Annual Reviews in Control, Vol: 41, Pages: 218-224, ISSN: 1872-9088Economic Model Predictive Control is a technique for optimization of economic revenues arising from controlled dynamical processes that has established itself as a variant of standard Tracking Model Predictive Control. It departs from the latter in that arbitrary cost functions are allowed in the formulation of the stage cost. This paper takes a further step in expanding the applicability of Economic Model Predictive Control by illustrating how the paradigm can be adapted in order to accommodate time-varying or parameter-varying costs.
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Journal articleBettiol P, Vinter RB, 2016,
L∞ estimates on trajectories confined to a closed subset, for control systems with bounded time variation
, Mathematical Programming, Vol: 168, Pages: 201-228, ISSN: 1436-4646The term ‘distance estimate’ for state constrained control systems refers to an estimate on the distance of an arbitrary state trajectory from the subset of state trajectories that satisfy a given state constraint. Distance estimates have found widespread application in state constrained optimal control. They have been used to establish regularity properties of the value function, to establish the non-degeneracy of first order conditions of optimality, and to validate the characterization of the value function as a unique solution of the HJB equation. The most extensively applied estimates of this nature are so-called linear L∞L∞ distance estimates. The earliest estimates of this nature were derived under hypotheses that required the multifunctions, or controlled differential equations, describing the dynamic constraint, to be locally Lipschitz continuous w.r.t. the time variable. Recently, it has been shown that the Lipschitz continuity hypothesis can be weakened to a one-sided absolute continuity hypothesis. This paper provides new, less restrictive, hypotheses on the time-dependence of the dynamic constraint, under which linear L∞L∞ estimates are valid. Here, one-sided absolute continuity is replaced by the requirement of one-sided bounded variation. This refinement of hypotheses is significant because it makes possible the application of analytical techniques based on distance estimates to important, new classes of discontinuous systems including some hybrid control systems. A number of examples are investigated showing that, for control systems that do not have bounded variation w.r.t. time, the desired estimates are not in general valid, and thereby illustrating the important role of the bounded variation hypothesis in distance estimate analysis.
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Journal articleChen B, Pin G, Ng WM, et al., 2016,
A fast-convergent modulation integral observer for online detection of the fundamental and harmonics in grid-connected power electronics systems
, IEEE Transactions on Power Electronics, Vol: 32, Pages: 2596-2607, ISSN: 1941-0107Harmonics detection is a critical element of activepower filters. A previous review has shown that the RecursiveDiscrete Fourier Transform and the Instantaneous p-q Theory areeffective solutions to extracting power harmonics in single-phaseand three-phase power systems, respectively. This paper presentsthe operating principle of a new modulation function integralobserver algorithm that offers a fast solution for the extraction ofthe fundamental current and the total harmonic current whencompared with existing methods. The proposed method can beapplied to both single- and three-phase systems. The observerbasedalgorithm has an advantageous feature of being able to betuned offline for a specific application, having fast convergenceand producing estimated fundamental component with highcircularity. It has been tested with both simulations and practicalmeasurements for extracting the total harmonic current in ahighly efficient manner. The results have confirmed that theproposed tool offers a new and highly effective alternative to thesmart grid industry.
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Conference paperLi S, Lee ATL, Siew-Chong-Tan, et al., 2016,
A plug-and-play ripple mitigation approach for DC-links in hybrid systems
, APEC 2016, Publisher: IEEE, Pages: 169-176In this paper, a plug-and-play ripple mitigation technique is proposed. It requires only the sensing of the DC-link voltage and can operate fully independently to remove the low-frequency voltage ripple. The proposed technique is nonintrusive to the existing hardware and enables hot-swap operation without disrupting the normal functionality of the existing power system. It is user-friendly, modular and suitable for plug-and-play operation. The experimental results demonstrate the effectiveness of the ripple-mitigation capability of the proposed device. The DC-link voltage ripple in a 110 W miniature hybrid system comprising an AC/DC converter and two resistive loads is shown to be significantly reduced from 61 V to only 3.3 V. Moreover, it is shown that with the proposed device, the system reliability has been improved by alleviating the components' thermal stresses.
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Conference paperYang Y, Tan SC, Hui SY, 2016,
Adaptive reference model predictive control for power electronics
, APEC 2016, Publisher: IEEE, Pages: 1169-1175An adaptive reference model predictive control (ARMPC) approach is proposed as an alternative means of controlling power converters in response to the issue of steady-state residual errors presented in power converters under the conventional model predictive control (MPC). Differing from other methods of eliminating steady-state errors of MPC based control, such as MPC with integrator, the proposed ARMPC is designed to track the so-called virtual references instead of the actual references. Subsequently, additional tuning is not required for different operating conditions. In this paper, ARMPC is applied to a single-phase full-bridge voltage source inverter (VSI). It is experimentally validated that ARMPC exhibits strength in substantially eliminating the residual errors in environment of model mismatch, load change, and input voltage change, which would otherwise be present under MPC control. Moreover, it is experimentally demonstrated that the proposed ARMPC shows a consistent erasion of steady-state errors, while the MPC with integrator performs inconsistently for different cases of model mismatch after a fixed tuning of the weighting factor.
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Conference paperAldhaher S, Mitcheson PD, Yates DC, 2016,
Load-independent Class EF inverters for inductive wireless power transfer
, 2016 IEEE Wireless Power Transfer Conference (WPTC), Publisher: IEEEThis paper will present the modelling, analysis and design of a load-independent Class EF inverter. This inverter is able to maintain zero-voltage switching (ZVS) operation and produce a constant output current for any load value without the need for tuning or replacement of components. The load-independent feature of this inverter is beneficial when used as the primary coil driver in multi megahertz high power inductive wireless power transfer (WPT) applications where the distance between the coils and the load are variable. The work here begins with the traditional load-dependent Class EF topology for inversion and then specifies the criteria that are required to be met in order achieve load-independence. The design and development of a 240W load-independent Class EF inverter to drive the primary coil of a 6.78MHz WPT system will be discussed and experimental results will be presented to show the load-independence feature when the distance between the coils of the WPT system changes.
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Journal articleScarciotti G, 2016,
Low computational complexity model reduction of power systems with preservation of physical characteristics
, IEEE Transactions on Power Systems, Vol: 32, Pages: 743-752, ISSN: 1558-0679A data-driven algorithm recently proposed to solvethe problem of model reduction by moment matching is extendedto multi-input, multi-output systems. The algorithm isexploited for the model reduction of large-scale interconnectedpower systems and it offers, simultaneously, a low computationalcomplexity approximation of the moments and the possibilityto easily enforce constraints on the reduced order model. Thisadvantage is used to preserve selected slow and poorly dampedmodes. The preservation of these modes has been shown to beimportant from a physical point of view and in obtaining anoverall good approximation. The problem of the choice of the socalledtangential directions is also analyzed. The algorithm andthe resulting reduced order model are validated with the studyof the dynamic response of the NETS-NYPS benchmark system(68-Bus, 16-Machine, 5-Area) to multiple fault scenarios.
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Journal articleMoreira R, Moreno R, Strbac G, 2016,
Value of corrective network security for distributed energy storage applications
, IET Generation, Transmission & Distribution, Vol: 10, Pages: 1758-1767, ISSN: 1751-8687Energy storage can provide services to several sectors in electricity industry, including generation, transmission and distribution, where conflicts and synergies may arise when storage is used to manage network congestion and provide services in energy and balancing markets. In this context, this study proposes an optimisation model to coordinate multiple services delivered to various market participants that uses corrective actions to resolve conflicts between provision of distribution network services (e.g. congestion and security of supply) and other services. The model maximises storage profit by scheduling active and reactive power to provide portfolio of services including distribution network congestion management, energy price arbitrage, frequency response and reserve services remunerated at different prices. The authors demonstrate that adopting corrective security to provide network services and deal with network congestion in a post-fault fashion, is overall more beneficial despite the energy needed to be stored during pre-fault conditions for applying post-contingency actions right after a network fault occurs. Furthermore, the authors' analysis shows that application of corrective security can benefit both (i) storage owners through increased revenues in energy and balancing services markets and (ii) Distribution Network Operators through reduction in payments to storage owners and increased utilisation of network infrastructure.
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Journal articleBeddard A, sheridan CE, Barnes M, et al., 2016,
Improved Accuracy Average Value Models of Modular Multilevel Converters
, IEEE Transactions on Power Delivery, Vol: 31, Pages: 2260-2269, ISSN: 0885-8977Modular multilevel converters (MMCs) have become the converter topology of choice for voltage-source converter-high-voltage direct-current systems. Excellent work has previously been conducted to develop much needed average value models (AVM) for these complex converters; however, there a number of limitations as highlighted in this paper. This paper builds on the existing models, proposing numerous modifications and resulting in an enhanced MMC-AVM, which is significantly more accurate and which can be used for a wider range of studies, including DC faults.
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Journal articleCanizares C, Farnandes T, Gerladi E, et al., 2016,
Benchmark models for the analysis and control of small-signal oscillatory dynamics in power systems
, IEEE Transactions on Power Systems, Vol: 32, Pages: 715-722, ISSN: 1558-0679This paper summarizes a set of six benchmark systemsfor the analysis and control of electromechanical oscillationsin power systems recommended by the IEEE Task Force onBenchmark Systems for Stability Controls of the Power SystemDynamic Performance Committee. The benchmark systems werechosen for their tutorial value and particular characteristicsleading to control system design problems relevant to the researchcommunity. For each benchmark, the modelling guidelinesare provided, along with eigenvalues and time-domain resultsproduced with at least two simulation software, and onepossible control approach is provided for each system as well.Researchers and practicing engineers are encouraged to use thesebenchmark systems when assessing new oscillation dampingcontrol strategies.
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Conference paperDe Paola A, Angeli D, Strbac G, 2016,
Frequency support by scheduling of variable-speed wind turbines
, 19th IFAC World Congress, Publisher: Elsevier, Pages: 7904-7910, ISSN: 1474-6670This paper characterizes optimal control policies for wind farms operated as frequency response services in case of a fault of conventional generators. The frequency support is provided through temporary over-production: when frequency drops, the turbines move from the steady-state operating point and extra power is produced by slowing down the turbines and releasing part of their kinetic energy. The control task is formulated and solved as an optimal containment problem: the time during which an extra quantity of power can be produced, within the set speed constraints for each turbine, is maximized. The solutions are calculated and compared for different assumptions on the electric torque of the turbines.
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Journal articleNewbery D, Strbac G, Viehoff I, 2016,
The benefits of integrating European electricity markets
, Energy Policy, Vol: 94, Pages: 253-263, ISSN: 1873-6777The European Commission's Target Electricity Model (TEM) aims to integrate EU electricity markets. This paper estimates the potential benefit of coupling interconnectors to increase the efficiency of trading day-ahead, intra-day and balancing services across borders. Further gains are possible by eliminating unscheduled flows and avoiding the curtailment of renewables with better market design. In the short run the gains could be as high as €3.9 billion/yr, more than 100% of the current gains from trade. About one-quarter of this total comes from day-ahead coupling and another third from shared balancing. If shared balancing is so valuable, completing the TEM becomes more urgent, and regulators should ensure these gains are paid to interconnectors to make the needed investment in the cross-border links more commercially profitable.
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Conference paperGiannelos S, Konstantelos I, Strbac G, 2016,
Stochastic optimisation-based valuation of smart grid options under firm DG contracts
, 2016 IEEE International Energy Conference (ENERGYCON), Publisher: IEEEUnder the current EU legislation, Distribution NetworkOperators (DNOs) are expected to provide firm connections to newDG, whose penetration is set to increase worldwide creating theneed for significant investments to enhance network capacity.However, the uncertainty around the magnitude, location andtiming of future DG capacity renders planners unable to accuratelydetermine in advance where network violations may occur. Hence,conventional network reinforcements run the risk of assetstranding, leading to increased integration costs. A novel stochasticplanning model is proposed that includes generalized formulationsfor investment in conventional and smart grid assets such asDemand-Side Response (DSR), Coordinated Voltage Control (CVC)and Soft Open Point (SOP) allowing the quantification of theiroption value. We also show that deterministic planning approachesmay underestimate or completely ignore smart technologies.
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Journal articleChakravorty D, Chaudhuri B, Hui SYR, 2016,
Rapid Frequency Response from Smart Loads in Great Britain Power System
, IEEE Transactions on Smart Grid, Vol: 8, Pages: 2160-2169, ISSN: 1949-3053Flexibility in certain types of loads could be exploited to provide fast and controllable power reserve if the supply voltage/frequency is controlled using existing power electronic interfaces (e.g. motor drives) or additional ones like recently proposed Electric Springs. Such a load together with its power electronic interface forms a so called ‘smart load’. Effectiveness of static smart loads for primary frequency response provision has been shown in previous papers through case studies ona segment of the LV/MV distribution network. In this paper, collective contribution of both static and motor type smart loads to rapid frequency response provision is demonstrated through a case study on the Great Britain (GB) transmission system. The active power reserve available from such smart loads are quantified and aggregated at each node at the transmission level (275/400 kV). The study shows that the smart loads collectively offer a short-term power reserve which is comparable to the spinning reserve in the GB system and thus can ensure acceptable frequency deviation and its rate of change (RoCoF) following a large infeed loss.
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Conference paperspallarossa C, merlin M, Green TC, 2016,
Augmented inertial response of Multi-Level Converters using internal energy storage
, 2016 IEEE International Energy Conference (ENERGYCON), Publisher: IEEEDuring the recent years, the number of High Voltage Direct Current (HVDC) links, used for accommodating renewable energy sources and for interconnecting different power systems, has increased significantly. Apart from enhancing system stability, HVDC links can be used to provide ancillary services, such as frequency support. This paper investigates the potential of the energy storage capability of Modular Multi-level Converters (MMCs) to contribute to the frequency response. MMCs provide fast released energy through their cells capacitor that may be used to improve the system inertial response during the fault transient after a loss of generation event. To assess the effect of the converter energy storage capability, a mixed AC and DC transmission platform is developed in PowerFactory. It consists of a multi-machine system including a point-to-point MMC based HVDC link. A generation outage is applied to investigate the contribution of the MMC energy storage capability to the frequency recovery.
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