54 results found
Perez A, Quintero V, Jaramillo F, et al., 2018, Characterization of the degradation process of lithium-ion batteries when discharged at different current rates, Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering, Vol: 232, Pages: 1075-1089, ISSN: 0959-6518
The use of energy storage devices, such as lithium-ion batteries, has become popular in many different domains and applications. Hence, it is relatively easy to find literature associated with problems of battery state-of-charge estimation and energy autonomy prognostics. Despite this fact, the characterization of battery degradation processes is still a matter of ongoing research. Indeed, most battery degradation models solely consider operation under nominal (or strictly controlled) conditions, although actual operating profiles (including discharge current) may differ significantly from those. In this context, this article proposes a lithium-ion battery degradation model that incorporates the impact of arbitrary discharge currents. Also, the proposed model, initially calibrated through data reported for a specific lithium-ion battery type, can characterize degradation curves for other lithium-ion batteries. Two case studies have been carried out to validate the proposed model, initially calibrated by using data from a Sony battery. The first case study uses our own experimental data obtained for a Panasonic lithium-ion cell, which was cycled and degraded at high current rates. The second case study considers the analysis of two public data sets available at the Prognostics Center of Excellence of NASA Ames Research Center website, for batteries cycled using nominal and 2-C (twice the nominal) discharge currents. Results show that the proposed model can characterize degradation processes properly, even when cycles are subject to different discharge currents and for batteries not manufactured by Sony (whose data were used for the initial calibration).
Moreno Vieyra R, 2018, Coordination Strategies for Securing AC/DC FlexibleTransmission Networks With Renewables, IEEE Transactions on Power Systems, ISSN: 0885-8950
Reus L, Munoz F, Moreno Vieyra R, 2018, Retail consumers and risk in centralized energy auctions for indexed long-term contracts in Chile, Energy Policy, Vol: 114, Pages: 566-577, ISSN: 0301-4215
Centralized energy auctions for long-term contracts are commonly-used mechanisms to ensure supply adequacy, to promote competition, and to protect retail customers from price spikes in Latin America. In Chile, the law mandates that all distribution companies must hold long-term contracts—which are awarded on a competitive centralized auction—to cover 100% of the projected demand from three to fifteen years into the future. These contracts can be indexed to a series of financial parameters, including fossil fuel prices at reference locations. Drawing from portfolio theory, we use a simple example to illustrate the difficulties of selecting, through the current clearing mechanism that focuses on average costs and individual characteristics of the offers, a portfolio of long-term energy contracts that could simultaneously minimize the expected future cost of energy and limit the risk exposure of retail customers. In particular, we show that if the objective of the regulator is to limit the risk to regulated consumers, it could be optimal to include contracts that would not be selected based on individual characteristics of the offers and a least-cost auction objective, but that could significantly reduce the price variance of the overall portfolio due to diversification effects between indexing parameters.
Moreno R, Ferreira R, Barroso L, et al., 2017, Facilitating the Integration of Renewables in Latin America: The Role of Hydropower Generation and Other Energy Storage Technologies, IEEE Power and Energy Magazine, Vol: 15, Pages: 68-80, ISSN: 1540-7977
Strbac G, Aunedi M, Konstantelos I, et al., 2017, Opportunities for Energy Storage: Assessing Whole-System Economic Benefits of Energy Storage in Future Electricity Systems, IEEE Power and Energy Magazine, ISSN: 1540-7977
Moreno R, Street A, Arroyo JM, et al., 2017, Planning low-carbon electricity systems under uncertainty considering operational flexibility and smart grid technologies, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol: 375, Pages: 20160305-20160305, ISSN: 1364-503X
Moreira A, strbac G, Moreno R, et al., 2017, A Five-Level MILP Model for Flexible Transmission Network Planning under Uncertainty: A Min-Max Regret Approach, IEEE Transactions on Power Systems, Vol: 33, Pages: 486-501, ISSN: 0885-8950
The benefits of new transmission investment significantly depend on deployment patterns of renewable electricity generation that are characterized by severe uncertainty. In this context, this paper presents a novel methodology to solve the transmission expansion planning (TEP) problem under generation expansion uncertainty in a min-max regret fashion, when considering flexible network options and n 1 security criterion. To do so, we propose a five-level mixed integer linear programming (MILP) based model that comprises: (i) the optimal network investment plan (including phase shifters), (ii) the realization of generation expansion, (iii) the co-optimization of energy and reserves given transmission and generation expansions, (iv) the realization of system outages, and (v) the decision on optimal post-contingency corrective control. In order to solve the fivelevel model, we present a cutting plane algorithm that ultimately identifies the optimal min-max regret flexible transmission plan in a finite number of steps. The numerical studies carried out demonstrate: (a) the significant benefits associated with flexible network investment options to hedge transmission expansion plans against generation expansion uncertainty and system outages, (b) strategic planning-under-uncertainty uncovers the full benefit of flexible options which may remain undetected under deterministic, perfect information, methods and (c) the computational scalability of the proposed approach.
Konstantelos I, Moreno R, Strbac G, 2017, Coordination and uncertainty in strategic network investment: Case on the North Seas Grid, ENERGY ECONOMICS, Vol: 64, Pages: 131-148, ISSN: 0140-9883
The notion of developing a transnational offshore grid in the North Sea has attracted considerable attention in the past years due to its potential for substantial capital savings and increased scope for cross-border trade, sparking a European-wide policy debate on incentivizing integrated transmission solutions. However, one important aspect that has so far received limited attention is that benefits will largely depend on the eventual deployment pattern of electricity infrastructure which is currently characterized by severe locational, sizing and timing uncertainty. Given the lack of coordination between generation and network developments across Europe, there is a real risk for over-investment or a premature lock-in to options that exhibit limited adaptability. In the near future, important choices that have to be made concerning the network topology and amount of investment. In this paper we identify the optimal, in terms of reduced cost, network investment (including topology) in the North Seas countries under four deployment scenarios and five distinct policy choices differing in the level of offshore coordination and international market integration. By drawing comparisons between the study results, we quantify the net benefit of enabling different types of coordination under each scenario. Furthermore, we showcase a novel min–max regret optimization model and identify minimum regret first-stage commitments which could be deployed in the near future in order to enhance strategic optionality, increase adaptability to different future conditions and hence reduce any potential sub-optimality of the initial network design. In view of the above, we put forward specific policy recommendations regarding the adoption of a flexible anticipatory expansion framework for the identification of attractive investment opportunities under uncertainty.
PIpelzadeh Y, Moreno R, Chaudhuri B, et al., 2017, Corrective control with transient assistive measures: value assessment for Great Britain transmission system, IEEE Transactions on Power Systems, Vol: 32, Pages: 1638-1650, ISSN: 0885-8950
In this paper, the efficacy and value of using corrective control supported by transient assistive measures (TAM) is quantified in terms of the cost savings due to less constrained operation of the system. The example TAM is a rapid modulation of the power order of the high-voltage direct current (HVDC) links in the system so as to improve transient stability during corrective control. A sequential approach is used for the offline value assessment: a security constrained economic dispatch (SCED) module (master problem) determines the optimal generation dispatch, HVDC settings, and the corrective control actions to be used post-fault (generation and demand curtailed) so as to minimize the operational costs while ensuring static security. The transient stability module (slave problem) assesses the dynamic stability for the operating condition set by the SCED and, if needed, applies appropriate TAM to maintain the system transiently stable. If this is not possible, the master module uses a tighter set of security constraints to update the dispatch and other settings until the system can be stabilized. A case-study on the Great Britain system is used to demonstrate that corrective control actions supported by TAM facilitate significantly higher pre-fault power transfers whilst maintaining N-2 security.
Strbac G, Kirschen D, Moreno R, 2016, Reliability Standards for the Operation and Planning of Future Electricity Networks, Foundations and Trends® in Electric Energy Systems, Vol: 1, Pages: 143-219, ISSN: 2332-6557
Electricity networks, designed and operated in accordance with the historic deterministic standards, have broadly delivered secure and reliable supplies to customers. A key issue regarding their evolution is how the operation and planning standards should evolve to make efficient use of the existing assets while taking advantage of emerging, non-network (or non-wires) technologies. Deployment of the smart grid will require fundamental changes in the historical principles used for network security in order to ensure that integration of low-carbon generation is undertaken as efficiently as possible through the use of new information and communication technology (ICT), and new flexible network technologies that can maximize utilization of existing electricity infrastructure. These new technologies could reduce network redundancy in providing security of supply by enabling the application of a range of advanced, technically effective, and economically efficient corrective (or post-fault) actions that can release latent network capacity of the existing system. In this context, this paper demonstrates that historical deterministic practices and standards, mostly developed in the 1950s, should be reviewed in order to take full advantage of new emerging technologies and facilitate transition to a smart grid paradigm. This paper also demonstrates that a probabilistic approach to developing future efficient operating and design strategies enabled by new technologies, will appropriately balance network investment against non-network solutions while truly recognizing effects of adverse weather, common-mode failures, high-impact low-probability events, changing market prices for pre- and post-contingency actions, equipment malfunctioning, etc. This clearly requires explicit consideration of the likelihood of various outages (beyond those considered in deterministic studies) and quantification of their impacts on alternative network operation and investment decisions, which canno
Inzunza A, Moreno R, Bernales A, et al., 2016, CVaR constrained planning of renewable generation with consideration of system inertial response, reserve services and demand participation, Energy Economics, Vol: 59, Pages: 104-117, ISSN: 0140-9883
Moreira R, Moreno R, Strbac G, 2016, Synergies and conflicts among energy storage services, IEEE - Energycon 2016, Publisher: IEEE
Energy storage can provide services to several sectors in electricity industry, including generation, transmission and distribution and support a cost-effective transition to a low carbon electricity industry. Sharing storage plant’s energy and power capacity for multiple services portfolios leads to conflicting or synergic interactions among services. In this context, the proposed methodology determines interactions among services for distributed energy storage plants, including energy arbitrage, peak demand shaving and various balancing services, and assesses the impact that such interactions have on storage plant remunerability in a multiple service business model framework for distributed energy storage. We demonstrate that services interact differently depending on markets and system operating conditions. We also find that correlation between energy market and local system conditions is important to determine whether energy arbitrage conflicts with further services.
Perez A, Moreno R, Moreira R, et al., 2016, Effect of Battery Degradation on Multi-Service Portfolios of Energy Storage, IEEE Transactions on Sustainable Energy, Vol: 7, Pages: 1718-1729, ISSN: 1949-3029
In an electricity market environment, energy storage plant owners are remunerated for the provision of services to multiple electricity sectors. Some of these services, however, may accelerate battery aging and degradation and hence this needs to be properly balanced against associated services remunerations. In this framework, we propose a combined economic-degradation model to quantify effects of operational policies (mainly focused on constraining State of Charge –SOC– to prescribed levels in order to reduce effects of aging) on gross revenue, multi-service portfolios, degradation and lifespan of distributed energy storage plants that can provide multiple services to energy and balancing market participants and Distribution Network Operators (DNO). Through various case studies based on the Great Britain (GB) system, we demonstrate that although operational policies focused on battery damage reduction will lead to a revenue loss in the shortterm, such loss can be more than compensated by long-term revenues due to a lengthier battery lifespan. We also demonstrate that operational policies to reduce battery degradation mainly affect services related to the energy (rather than balancing) market, which represents a smaller proportion of the overall revenue streams of a distributed storage plant. The model is also used to study effects of ambient temperature fluctuations.
Flores-Quiroz A, Palma-Behnke R, Zakeri G, et al., 2016, A column generation approach for solving generation expansion planning problems with high renewable energy penetration, Electric Power Systems Research, Vol: 136, Pages: 232-241, ISSN: 0378-7796
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.
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.
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
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, Konstantelos I, Moreno Vieyra R, 2015, Emerging Modelling Capabilities for System Operations, Emerging Modelling Capabilities for System Operations, Publisher: Institute of Engineering and Technology (IET)
The Institution of Engineering and Technology was commissioned by the Council of Science and Technology(CST) to research the emerging challenges for modelling electricity systems and how Britain’s capabilitieswould need to be adapted to assess electricity system resilience as GB makes the transition to a low carbonelectricity system.
Moreno R, Moreira R, Strbac G, 2015, A MILP model for optimising multi-service portfolios of distributed energy storage, Applied Energy, Vol: 137, Pages: 554-566, ISSN: 0306-2619
Energy storage has the potential to provide multiple services to several sectors in electricity industry and thus support activities related to generation, network and system operation. Hence aggregating the value delivered by storage to these sectors is paramount for promoting its efficient deployment in the near future, which will provide the level of flexibility needed to deal with the envisaged high renewables share and the increase in peak demand driven by transport and heating electrification. In this context, we develop a Mixed Integer Linear Programming (MILP) model to schedule operation of distributed storage by coordinating provision of a range of system services which are rewarded at different market prices. The model maximises distributed storage’s net profit while providing distribution network congestion management, energy price arbitrage and various reserve and frequency regulation services through both active and reactive power control. We demonstrate benefits associated with the coordination of these services and its impacts on commercial strategies to determine optimal multi-service portfolios in the long term. We also demonstrate the value of reactive power control to support not only distribution network congestion management, but also efficient trading of energy and balancing services which are usually treated through active power-only control. In addition, we use the model to price the service of distribution network congestion management and propose an efficient investment policy to upgrade distribution network capacity in the presence of distributed storage. Finally, several case studies under current market conditions in Great Britain (GB) demonstrate that distributed storage revenues associated with frequency control services are significantly more profitable.
Strbac G, Pollitt M, Konstantinidis CV, et al., 2014, Electricity transmission arrangements in Great Britain: Time for change?, Energy Policy, Vol: 73, Pages: 298-311, ISSN: 0301-4215
In Great Britain (GB) and across Europe significant investment in electricity transmission is expected over the coming years as decarbonisation and market integration efforts are intensified. However, there is also significant uncertainty with the amount, location and timing of new generation connection, which in turn will drive the transmission investment needs. Given the absence of efficient market design, we identify three key areas of concern with the current transmission investment arrangements: (i) a mis-aligned incentives framework for transmission investment and operation; (ii) lack of coordination of investment and operation; and (iii) conflicts of interest. We then propose three options for future evolution of transmission regimes, which cover the full spectrum of institutional arrangements with respect to transmission planning and delivery, i.e. how and who plans, owns, builds and operates the transmission system. For each option we present: key characteristics; evolution of the current regimes; the ability of the option to address the concerns; and key strengths and weaknesses. Overall, we conclude in the case of GB (this conclusion could be extended to other European countries) that the most appropriate option would be that of an Independent System Operator (ISO) who would be responsible for planning and operating the transmission system.
Strbac G, Moreno Vieyra R, Konstantelos I, et al., 2014, Strategic Development of North Sea Grid Infrastructure to Facilitate Least-Cost Decarbonisation, Strategic Development of North Sea Grid Infrastructure to Facilitate Least-Cost Decarbonisation, Publisher: E3G
Offshore wind power is expected to make a significant contribution towards de-carbonisingthe European energy system. It is envisaged that today’s installed capacity levels of about 5GW of offshore wind generation may reach 150GW by 2030, with approximately half of thiscapacity located in the North Seas. Given Europe’s goal of increased integration of the powermarkets by expanding cross-border interconnectors, there is a significant opportunity tointegrate offshore wind generation and interconnector projects in the North Seas in order totake advantage of potentially significant economies of scale and thus reduce network costs.
Moreno R, Pudjianto D, Strbac G, 2013, Transmission Network Investment with Probabilistic Security and Corrective Control, IEEE Transactions on Power Systems
Moreno R, 2013, Operacion y Diseno Eficiente de Redes Electricas de Transmision Mediante el Uso de Nuevas Tecnologias Inteligentes [Efficient Operation and Design of Transmission Networks through New Smart Technologies], Electricidad, Vol: 155, Pages: 23-25
Moreno J, Moreno R, Rudnick H, et al., 2012, Licitaciones para el Abastecimiento Electrico de Clientes Regulados en Chile: Dificultades y Oportunidades [Auctions for Electricity Supply to Regulated Customers in Chile: Challenges and Opportunities], Revista del Centro de Estudios Publicos de Chile, Vol: 125, Pages: 139-168
Vasilakos C, Strbac G, Pudjianto D, et al., 2012, European Transmission Tariff Harmonization: A Modeling Analysis, 9th International Conference on the European Energy Market EEM12
Moreno R, Pudjianto D, Strbac G, 2012, Integrated reliability and cost-benefit-based standards for transmission network operation, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART O-JOURNAL OF RISK AND RELIABILITY, Vol: 226, Pages: 75-87, ISSN: 1748-006X
Moreno R, Pudjianto D, Strbac G, 2012, Integrated Reliability and Cost-Benefit-Based Standards for Transmission Network Operation, Proceedings of the Institution of Mechanical Engineers Part O-Journal of Risk and Reliability, Vol: 226, Pages: 75-87
Strbac G, Moreno R, Pudjianto D, et al., 2011, Towards a Risk-Based Network Operation and Design Standards, IEEE Power Engineering Society 2011 General Meeting
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