Publications
556 results found
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
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
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
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.
Giannelos S, Konstantelos I, Strbac G, 2015, Option value of Soft Open Points in distribution networks, IEEE Powertech, Publisher: IEEE
We propose a novel stochastic planning model thatconsiders investment in conventional assets as well as in SoftOpen Points, as a means of treating voltage and thermalconstraints caused by the increased penetration of renewabledistributed generation (DG) sources. Soft Open Points areshown to hold significant option value under uncertainty;however, their multiple value streams remain undetected undertraditional deterministic planning approaches, potentiallyundervaluing this technology and leading to a higher risk ofstranded assets.
Ye Y, Papadaskalopoulos D, Strbac G, 2015, Factoring Flexible Demand Non-Convexities in Electricity Markets, IEEE TRANSACTIONS ON POWER SYSTEMS, Vol: 30, Pages: 2090-2099, ISSN: 0885-8950
Strbac G, Konstantinidis CV, Moreno R, et al., 2015, It's All About Grids, IEEE POWER & ENERGY MAGAZINE, Vol: 13, Pages: 61-75, ISSN: 1540-7977
Tindemans SH, Trovato V, Strbac G, 2015, Frequency control using thermal loads under the proposed ENTSO-E Demand Connection Code, PowerTech 2015, Publisher: IEEE, Pages: 1-6
Thermal loads such as refrigerators and electric space heaters use temperature hysteresis controllers that are insensitive to small temperature fluctuations. This results in an ability to modulate their power consumption, thus providing cost-effective frequency support, balancing services and energy arbitrage. In order to partially realise these benefits, ENTSO-E has proposed a mandatory frequency support service for thermal loads in its Network Code on Demand Connection. This is to be implemented as a proportional shift of the setpoint temperature in accordance with frequency deviations. In this paper we argue that this implementation choice results in an unpredictable response that depends strongly on controller details. Furthermore, it restricts the flexibility to implement advanced controllers that deliver multiple services simultaneously. We present a case study that demonstrates very different frequency response patterns from three controllers that are each compatible with the proposed Code. Alternative implementations of the code and controllers are presented to illustrate the scope for improvement.
Calvo JL, Ramirez Torrealba PJ, Tindemans S, et al., 2015, Cost-Benefit Analysis of Unreliable System Protection Scheme Operation, IEEE PowerTech 2015, Publisher: IEEE
System Protection Schemes (SPS) have the potential to greatly enhance the utilization of the network, often by automatically disconnecting generators in response to contingency events. However, malfunctions of such systems may expose the system to harmful blackouts. The operation of unreliable SPS is therefore subject to a cost-benefit balance between the benefits of increased system utilization and the risk of outages. This paper studies this trade-off in a year-round basis. The problem is firstly stated from a centralized perspective to probabilistically minimize the operational costs for a whole operating year. A case study based on a basic simple representation of the Great Britain system is considered. The results show great annual benefits from equipping the SPS with multiple generation disconnection systems, which are mainly associated with critical operating conditions. However, it is demonstrated that redundant SPS configurations do not necessarily reduce the levels of operational risk exposure.
Strbac G, Vasilakos Konstantinidis C, Moreno Vieyra R, et al., 2015, It’s All About Grids: The Importance of Transmission Pricing and Investment Coordination in Integrating Renewables, IEEE Power and Energy Magazine, ISSN: 1540-7977
Schofield J, Carmichael R, Tindemans S, et al., 2015, Experimental validation of residential consumer responsiveness to dynamic time-of-use pricing, 23rd International Conference on Electricity Distribution (CIRED)
This paper describes the first analysis from the LowCarbon London (LCL), residential dynamic time-of-use(dToU) pricing trial that took place in the London areaduring 2013. High price induced peak reductions fornetwork constraint management are investigatedalongside the temporal availability of demand responsefor supply balancing. By examining both these use caseswe identify potential conflicts between network andsystem objectives. Demand response results are stratifiedby a ranking metric for engagement with the dToU tariffas well as household occupancy and socio-economicclassification.
Ustinova T, Woolf M, Ortega Calderon JE, et al., 2015, Analysis of Customers' Performance in Industrial & Commercial Demand Side Response Trials, 23rd International Conference on Electricity Distribution (CIRED 2015)
Papadaskalopoulos D, Strbac G, 2015, Nonlinear and Randomized Pricing for Distributed Management of Flexible Loads, IEEE Transactions on Smart Grid, Vol: 7, Pages: 1137-1146, ISSN: 1949-3061
Price-based management of distributed energy resources within microgrids is continuously gaining ground due to scalability and privacy limitations of centralized architectures. However, the concentration of flexible loads' response to the lowest-priced periods yields inefficient solutions. A previously proposed measure imposing a flexibility restriction on flexible loads might raise acceptability and feasibility concerns by the users. This paper develops a novel fully price-based approach where this hard restriction is replaced by a soft nonlinear price signal. This signal is customized to the operating properties of the different flexible load types by penalizing the square of the demand and the duration of cycle delay of loads with continuously adjustable power levels and deferrable cycles, respectively. This approach is shown to produce more efficient solutions than the flexibility restriction measure for both types of loads. For the latter type, randomization of the nonlinear prices brings additional benefits, especially in low operating diversity cases. These contributions are supported by case studies on a microgrid test system with electric vehicles and wet appliances used as representative examples of the above flexible load types.
Trutnevyte E, Strachan N, Dodds PE, et al., 2015, Synergies and trade-offs between governance and costs in electricity system transition, Energy Policy, Vol: 85, Pages: 170-181, ISSN: 1873-6777
Affordability and costs of an energy transition are often viewed as the most influential drivers. Conversely, multi-level transitions theory argues that governance and the choices of key actors, such as energy companies, government and civil society, drive the transition, not only on the basis of costs. This paper combines the two approaches and presents a cost appraisal of the UK transition to a low-carbon electricity system under alternate governance logics. A novel approach is used that links qualitative governance narratives with quantitative transition pathways (electricity system scenarios) and their appraisal. The results contrast the dominant market-led transition pathway (Market Rules) with alternate pathways that have either stronger governmental control elements (Central Co-ordination), or bottom-up proactive engagement of civil society (Thousand Flowers). Market Rules has the lowest investment costs by 2050. Central Co-ordination is more likely to deliver the energy policy goals and possibly even a synergistic reduction in the total system costs, if policies can be enacted and maintained. Thousand Flowers, which envisions wider participation of the society, comes at the expense of higher investment and total system costs. The paper closes with a discussion of the policy implications from cost drivers and the roles of market, government and society.
Trovato V, Tindemans SH, Strbac G, 2015, Designing effective frequency response patterns for flexible thermostatic loads, 2015 IEEE 15th International Conference on Environment and Electrical Engineering (EEEIC), Publisher: IEEE, Pages: 1003-1008
Future power systems will have to integrate large amounts of wind and solar generation to drastically reduce CO2 emissions. Achieving this goal comes at the cost of a reduced level of the system inertia and an increased need for fast response services. Previous research has shown the effectiveness of thermostatically controlled loads (TCLs) providing frequency response, and the ability to accurately control the aggregate power consumption of TCLs. In this paper, we explore the design space of frequency response patterns of flexible TCLs. Two distinct frequency response implementations are presented. The first makes the TCLs' power consumption a linear function of system frequency and/or its rate of change; in the second, TCLs respond to a frequency event tracking a pre-programmed reference power profile. Computer simulations illustrate strengths and weaknesses of the proposed implementations in the context of the GB 2020 Gone Green scenario.
Pipelzadeh Y, Moreno Vieyra R, Chaudhuri B, et al., 2015, Role of Smart Grid Technology and Corrective Control in Enhancing Network Capacity Utilisation in Great Britain with HVDC links, CIGRE SYMPOSIUM, Publisher: CIGRE
A range of advanced, technically effective and economically efficient corrective (or postfault) actions has been proposed to release latent transmission network capacity of the existing system and thus reduce network congestion and accommodate increased connection of low-carbon generation. Although the increased use of corrective control that can manage post-fault transmission overloads has proven to be clearly beneficial from an economic perspective, there are concerns related to the consequent stability (angular and voltage) of transmission systems. In this context, this paper demonstrates various corrective control measures (that can be undertaken by Special Protection Schemes –SPS–) including rapid response of generation and demand against double line outages (N-2) under extremely high power transfer conditions. To demonstrate these benefits, case studies are carried out on a detailed (full) dynamic system model of the Great Britain (GB) transmission network in DIgSILENT, which includes the Western Line-Commutated Converter based High Voltage Direct Current (LCC-HVDC). The value of corrective control measures, based on generationand demand response accompanied by Transient Assistive Measures (TAM) such as rapid changes in DC power order to improve system stability is demonstrated. It is shown that such measures can significantly increase the power transfers through the England-Scotland inter-connector while maintaining N-2 security. Moreover, it is demonstrated that although a generation ramp up/down response is naturally slower than a step-change tripping action over generation and demand (tripping actions are preferred in SPS) and therefore more prone to transient instability problems, generation-only operational measures can be deployed to deal with double circuit (N-2) outages under extremely high power transfers, given that the right portfolio of TAM is deployed. Thus TAM can effectively enhance the set of correctivecontrol measures considered b
Strbac G, Hatziargyriou N, Lopes JP, et al., 2015, Microgrids, IEEE Power & Energy Magazine, Vol: 13, Pages: 35-43, ISSN: 1540-7977
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Teng F, Pudjianto D, Strbac G, et al., 2015, Potential value of energy storage in the UK electricity system, Proceedings of the ICE - Energy, Vol: 168, Pages: 107-117, ISSN: 1751-4223
This paper assesses the value of distributed energy storage and informs the business case for its multiple applications in the UK electricity system. In contrast to earlier studies that focus on the benefits of energy storage for system operation and development, this work analyses the value that it may deliver to the owner. For this purpose, three models are proposed and applied to analyse the benefit of energy storage with applications in energy and ancillary service markets, revenue maximisation in the context of feed-in tariffs and reduction of carbon dioxide emissions. A large set of studies is carried out to quantify the commercial and emissions benefits of energy storage for those applications. Sensitivity analysis across various scenarios is performed to understand the key drivers for the value of energy storage and how it is affected by energy storage parameters and other factors such as network constraints, prices of energy and ancillary services, and inherent energy system characteristics. A review of current and near-term storage technology costs and functionality is also presented.
Welsch M, Howells M, Hesamzadeh MR, et al., 2015, Supporting security and adequacy in future energy systems: The need to enhance long-term energy system models to better treat issues related to variability, INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Vol: 39, Pages: 377-396, ISSN: 0363-907X
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- Citations: 46
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