Publications
541 results found
Moreira 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: 1751-8687
Energy 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.
De 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: 1474-6670
This 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.
Newbery D, Strbac G, Viehoff I, 2016, The benefits of integrating European electricity markets, Energy Policy, Vol: 94, Pages: 253-263, ISSN: 1873-6777
The 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.
Giannelos 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: IEEE
Under 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.
Teng F, Strbac G, 2016, Assessment of the role and value of frequency response support from wind plants, IEEE Transactions on Sustainable Energy, Vol: 7, Pages: 586-595, ISSN: 1949-3029
High penetration of wind generation causes concerns over frequency stability, as currently wind plants do not provide frequency response support. Extensive research has been conducted to investigate alternative designs of controllers to facilitate the provision of synthetic inertia and primary frequency response from wind plants. However, frequency response support from wind plants differs from that provided by conventional plants and its impact on the system's economic performance is not yet fully understood. In this context, this paper develops a novel methodology to incorporate the frequency response support from wind plants into generation scheduling, thus enabling the benefits of alternative control strategies to be quantified. Studies are carried out on the future Great Britain power system with different wind energy penetration levels and frequency response requirements. The impact of the uncertainty associated with the quantity of wind plants being online and the energy recovery effect are also analyzed. The results demonstrate that the benefits of frequency response support from wind plants may be significant, although these are system specific. The proposed model could also inform the development of grid codes, market mechanisms, and business cases associated with the frequency response support from wind plants.
Mohtashami S, Pudjianto D, Strbac G, 2016, Strategic distribution network planning with smart grid technologies, IEEE Transactions on Smart Grid, Vol: 8, Pages: 2656-2664, ISSN: 1949-3061
This paper presents a multiyear distribution network planning optimization model for managing the operation and capacity of distribution systems with significant penetration of distributed generation (DG). The model considers investment in both traditional network and smart grid technologies, including dynamic line rating, quadrature-booster, and active network management, while optimizing the settings of network control devices and, if necessary, the curtailment of DG output taking into account its network access arrangement (firm or non-firm). A set of studies on a 33 kV real distribution network in the U.K. has been carried out to test the model. The main objective of the studies is to evaluate and compare the performance of different investment approaches, i.e., incremental and strategic investment. The studies also demonstrate the ability of the model to determine the optimal DG connection points to reduce the overall system cost. The results of the studies are discussed in this paper.
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.
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.
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.
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.
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.
Teng F, Strbac G, 2016, Primary frequency control in future GB power system with high penetration of wind generation
The system inertia reduction, driven by the integration of renewables, imposes significant challenges on the primary frequency control to maintain the post-fault frequency evolution within the security boundary. Dynamic simulations through a simplified GB power system dynamic model are carried out in this paper to illustrate the impact of declining system inertia on the primary frequency control. This paper also demonstrates the increased requirement on primary frequency response driven by larger online plants and higher penetration of wind generation. Furthermore, an advanced stochastic system scheduling tool is applied to quantify the amount of primary frequency response provision as well as the associated cost and carbon emission under two representative GB 2030 system scenarios.
Karimi H, Papadaskalopoulos D, Strbac G, 2016, Integrating Customers' Differentiated Supply Valuation in Distribution Network Planning and Charging, 13th International Conference on the European Energy Market (EEM), Publisher: IEEE, ISSN: 2165-4077
Fan Y, Papadaskalopoulos D, Strbac G, 2016, A Game Theoretic Modeling Framework for Decentralized Transmission Planning, 19th Power Systems Computation Conference (PSCC), Publisher: IEEE
Teng F, Strbac G, 2016, Commercial strategy for operating energy storage in supporting integration of renewable generation, 8th IEEE International Power Electronics and Motion Control Conference (IPEMC-ECCE Asia), Publisher: IEEE, Pages: 519-523
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Strbac G, Hatziargyriou N, 2016, The need for a fundamental review of electricity networks reliability standards, Publisher: European Union
The EU electricity system faces challenges of unprecedented proportions. Although the electricity transmission and distribution networks have historically delivered secure and reliable supplies to customers, the key issue regarding the future evolution of the network reliability standards is associated with the question of efficiency of the use of existing assets and the role that advanced smart grid technologies could play in facilitating cost effective and secure evolution to lower carbon futures.The historical network reliability standards and practices require that network security is provided through network asset redundancy, i.e. historical asset based paradigm may contradict the Smart Grid paradigm that focuses on novel, non-network asset solutions to network problems. The historical network reliability standards may impose barriers for innovation in network operation and design and prevent implementation of technically effective and economically efficient solutions that enhance the utilisation of the existing network assets and maximise network users’ benefits.In this context, this paper sets out the case for a fundamental review of the philosophy of transmission and distribution network operation and design may be needed to inform the industry, consumers, regulators, policy makers, in order to facilitate a cost effective delivery of the EU energy policy objectives.
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
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
Papadaskalopoulos D, Strbac G, 2016, Nonlinear and Randomized Pricing for Distributed Management of Flexible Loads, IEEE-Power-and-Energy-Society General Meeting (PESGM), Publisher: IEEE, ISSN: 1944-9925
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
Chen Y, Teng F, Moreno R, et 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
Ramirez PJ, Papadaskalopoulos D, Strbac G, 2015, Co-Optimization of Generation Expansion Planning and Electric Vehicles Flexibility, IEEE Transactions on Smart Grid, Vol: 7, Pages: 1609-1619, ISSN: 1949-3061
The envisaged de-carbonization of power systems poses unprecedented challenges enhancing the potential of flexible demand. However, the incorporation of the latter in system planning has yet to be comprehensively investigated. This paper proposes a novel planning model that allows co-optimizing the investment and operating costs of conventional generation assets and demand flexibility, in the form of smart-charging/discharging electric vehicles (EV). The model includes a detailed representation of EV operational constraints along with the generation technical characteristics, and accounts for the costs required to enable demand flexibility. Computational tractability is achieved through clustering generation units and EV, which allows massively reducing the number of decision variables and constraints, and avoiding non-linearities. Case studies in the context of the U.K. demonstrate the economic value of EV flexibility in reducing peak demand levels and absorbing wind generation variability, and the dependence of this value on the required enabling cost and users' traveling patterns.
Pipelzadeh Y, Chaudhuri B, Green T, 2015, Modelling and Dynamic Operation of the Zhoushan DC Grid: Worlds First Five-Terminal VSC-HVDC Project, International High Voltage Direct Current 2015 Conference, Publisher: IET, Pages: 87-95
This paper highlights the world’s first operational MTDC grid, namely the 5-terminal Zhoushan DC grid. The scheme went under operation in 2014. The topology and operation of the Zhoushan DC grid are demonstrated with recorded measurements obtained from the converter station, after being subjected to system disturbances. A generic modeling framework for the Zhoushan DC grid is developed inPSCAD/EMTDC. One particular concern is how the Zhoushan DC grid would react to DC side faults and the resulting power imbalance. Despite the completion of the Zhoushan MTDC grid, technological barriers such as the unavailability of fast protection systems, DC circuit breakers and highly efficient VSCs with DC side fault-clearing capabilities have all been bottlenecks at the time of commissioning, but are now under extensive research and development. The challenges and importance of DC grid protection are highlighted through case studies performed on the DC grid model in PSCAD/EMTDC.
Teng F, Aunedi M, Strbac G, 2015, Benefits of flexibility from smart electrified transportation and heating in the future UK electricity system, Applied Energy, Vol: 167, Pages: 420-431, ISSN: 1872-9118
This paper presents an advanced stochastic analytical framework to quantify the benefits of smart electric vehicles (EVs) and heat pumps (HPs) on the carbon emission and the integration cost of renewable energy sources (RES) in the future UK electricity system. The typical operating patterns of EVs/HPs as well as the potential flexibility to perform demand shifting and frequency response are sourced from recent UK trials. A comprehensive range of case studies across several future UK scenarios suggest that smart EVs/HPs could deliver measurable carbon reductions by enabling a more efficient operation of the electricity system, while at the same time making the integration of electrified transport and heating demand significantly less carbon intensive. The second set of case studies establish that smart EVs/HPs have significant potential to support cost-efficient RES integration by reducing: (a) RES balancing cost, (b) cost of required back-up generation capacity, and (c) cost of additional low-carbon capacity required to offset lower fuel efficiency and curtailed RES output while achieving the same emission target. Frequency response provision from EVs/HPs could significantly enhance both the carbon benefit and the RES integration benefit of smart EVs/HPs.
Newbery D, Strbac G, 2015, What is needed for battery electric vehicles to become socially cost competitive?, Economics of Transportation, Vol: 5, Pages: 1-11, ISSN: 2212-0122
Battery electric vehicles (BEVs) could be key to decarbonizing transport, but are heavily subsidized. Most assessments of BEVs use highly taxed road fuel prices and ignore efficient pricing of electricity. We use efficient prices for transport fuels and electricity, to judge what battery costs would make BEVs cost competitive. High mileage, low discount rates and high oil prices could make BEVs cost competitive by 2020, and by 2030 fuel costs are comparable over a wider range. Its contribution lies in careful derivation of efficient fuel and electricity prices and the concept of a target battery cost.
Djapic P, Tindemans S, Strbac G, 2015, Comparison of Approaches for Quantifying Demand Side Response Capacity Credit for the Use in Distribution Network Planning, IET International Conference on Resilience of Transmission and Distribution Networks (RTDN 2015), Publisher: IET
The present UK distribution network planning standard,Engineering Recommendation P.2/6 (P2/6), defines theacceptable durations of supply outages following first andsecond circuit outage conditions as function of group demand.In addition, P2/6 specifies a capacity value for distributedgeneration (DG) to be used in future circuit capacity planning.The approach does not consider other elements of thedistribution network. This paper analyses the reliabilityperformance of distribution system when DSR is used todefer network upgrades driven by load growth. The analysisuses actual DSR performance data from trials that wereexecuted as part of the Low Carbon London project. The DSRcontribution to security of supply is assessed using aprobabilistic risk modelling framework to further inform anumber of topics (i) reliability contribution of DSRtechnologies in a network context, (ii) strengths andweaknesses of P2/6 in estimating contribution to security ofsupply, (iii) benefits of contractual redundancy, (iv) impact ofDSR coincidence in delivery (common mode failures) oncontribution to security, and (v) impact of DSR scale andmagnitude on contribution to security of supply.
Calvo JL, Tindemans S, Strbac G, 2015, Managing Risks from Reverse Flows under Distribution Network Outage Scenarios, IET International Conference on Resilience of Transmission and Distribution Networks (RTDN 2015), Publisher: IET
Distribution networks have been traditionally conceived fortransporting electricity downstream into low voltage demandnodes. However, the connection of significant amounts ofdistributed generation may reverse this condition, resulting indistribution nodes exporting power to other parts of thenetwork. The current planning standard of the UK distributionnetworks (Engineering recommendation P2/6) requires makingavailable sufficient capacity and redundancy for downstreamflows under peak demand levels. However, it does notexplicitly consider the implications of DG-mediated flowreversals that may cause flow constraints under circuit outageconditions. Relying on a Monte Carlo approach to sample windand demand with adjustable correlations, this paper providesinsights into the risks associated with an increase of variabledistributed generation to the point where reverse flows mayexceed the connection capacity under circuit outage conditions.Remote tripping schemes that disconnect distributedgenerators upon occurrence of a fault are explored to mitigateoutage related costs. The latter strategy carries benefits but alsonovel risks in the form of a reliance on real-timecommunication and control, which may malfunction. It isshown that even unreliable corrective actions conveysignificant benefits to system reliability.
Tindemans SH, Trovato V, Strbac G, 2015, Decentralized control of thermostatic loads for flexible demand response, IEEE Transactions on Control Systems Technology, Vol: 23, Pages: 1685-1700, ISSN: 1063-6536
Thermostatically controlled loads (TCLs), such as refrigerators, air-conditioners and space heaters, offer significant potential for short-term modulation of their aggregate power consumption. This ability can be used in principle to provide frequency response services, but controlling a multitude of devices to provide a measured collective response has proven to be challenging. Many controller implementations struggle to manage simultaneously the short-term response and the long-term payback, whereas others rely on a real-time command-and-control infrastructure to resolve this issue. In this paper, we propose a novel approach to the control of TCLs that allows for accurate modulation of the aggregate power consumption of a large collection of appliances through stochastic control. By construction, the control scheme is well suited for decentralized implementation, and allows each appliance to enforce strict temperature limits. We also present a particular implementation that results in analytically tractable solutions both for the global response and for the device-level control actions. Computer simulations demonstrate the ability of the controller to modulate the power consumption of a population of heterogeneous appliances according to a reference power profile. Finally, envelope constraints are established for the collective demand response flexibility of a heterogeneous set of TCLs.
Teng F, Aunedi M, Pudjianto D, et al., 2015, Benefits of demand-side response in providing frequency response service in the future GB power system, Frontiers in Energy Research, Vol: 3, ISSN: 2296-598X
The demand for ancillary service is expected to increase significantly in the future Great Britain (GB) electricity system due to high penetration of wind. In particular, the need for frequency response, required to deal with sudden frequency drops following a loss of generator, will increase because of the limited inertia capability of wind plants. This paper quantifies the requirements for primary frequency response and analyses the benefits of frequency response provision from demand-side response (DSR). The results show dramatic changes in frequency response requirements driven by high penetration of wind. Case studies carried out by using an advanced stochastic generation scheduling model suggest that the provision of frequency response from DSR could greatly reduce the system operation cost, wind curtailment, and carbon emissions in the future GB system characterized by high penetration of wind. Furthermore, the results demonstrate that the benefit of DSR shows significant diurnal and seasonal variation, whereas an even more rapid (instant) delivery of frequency response from DSR could provide significant additional value. Our studies also indicate that the competing technologies to DSR, namely battery storage, and more flexible generation could potentially reduce its value by up to 35%, still leaving significant room to deploy DSR as frequency response provider.
Tindemans SH, Strbac G, 2015, Visualising risk in generating capacity adequacy studies using clustering and prototypes, IEEE Power and Energy Society General Meeting, 2015, Publisher: IEEE
Generating capacity adequacy studies play a significantrole in long term capacity planning. Risks of capacitydeficits are usually reported in the form of one or more averagequantities, which cannot fully convey the nature of the risksbeing faced. Chronological Monte Carlo simulations may be usedto construct comprehensive multi-dimensional risk profiles, butsuch profiles tend to be difficult to interpret. This paper proposesthe use of a clustering method to partition the risk profile intoclusters of similar outcomes with associated probabilities. Theresults are presented in accessible tabular form, and prototypicalscenarios can be analysed in detail to provide further insight.
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