Imperial College London

Professor Goran Strbac

Faculty of EngineeringDepartment of Electrical and Electronic Engineering

Chair in Electrical Energy Systems
 
 
 
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Contact

 

+44 (0)20 7594 6169g.strbac

 
 
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Assistant

 

Miss Guler Eroglu +44 (0)20 7594 6170

 
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Location

 

1101Electrical EngineeringSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

389 results found

Cremer JL, Strbac G, 2021, A machine-learning based probabilistic perspective on dynamic security assessment, International Journal of Electrical Power and Energy Systems, Vol: 128, ISSN: 0142-0615

Probabilistic security assessment and real-time dynamic security assessments(DSA) are promising to better handle the risks of system operations. Thecurrent methodologies of security assessments may require many time-domainsimulations for some stability phenomena that are unpractical in real-time.Supervised machine learning is promising to predict DSA as their predictionsare immediately available. Classifiers are offline trained on operatingconditions and then used in real-time to identify operating conditions that areinsecure. However, the predictions of classifiers can be sometimes wrong andhazardous if an alarm is missed for instance. A probabilistic output of the classifier is explored in more detail andproposed for probabilistic security assessment. An ensemble classifier istrained and calibrated offline by using Platt scaling to provide accurateprobability estimates of the output. Imbalances in the training database and acost-skewness addressing strategy are proposed for considering that missedalarms are significantly worse than false alarms. Subsequently, risk-minimisedpredictions can be made in real-time operation by applying cost-sensitivelearning. Through case studies on a real data-set of the French transmissiongrid and on the IEEE 6 bus system using static security metrics, it isshowcased how the proposed approach reduces inaccurate predictions and risks.The sensitivity on the likelihood of contingency is studied as well as onexpected outage costs. Finally, the scalability to several contingencies andoperating conditions are showcased.

Journal article

Badesa L, Strbac G, Magill M, Stojkovska Bet al., 2021, Ancillary services in Great Britain during the COVID-19 lockdown: A glimpse of the carbon-free future, Applied Energy, Vol: 285, Pages: 1-10, ISSN: 0306-2619

The COVID-19 pandemic led to partial or total lockdowns in several countries during the first half of 2020, which in turn caused a depressed electricity demand. In Great Britain (GB), this low demand combined with large renewable output at times, created conditions that were not expected until renewable capacity increases to meet emissions targets in coming years. The GB system experienced periods of very high instantaneous penetration of non-synchronous renewables, compromising system stability due to the lack of inertia in the grid. In this paper, a detailed analysis of the consequences of the lockdown on the GB electricity system is provided, focusing on the ancillary services procured to guarantee stability. Ancillary-services costs increased by £200m in the months of May to July 2020 compared to the same period in 2019 (a threefold increase), highlighting the importance of ancillary services in low-carbon systems. Furthermore, a frequency-secured scheduling model is used in the present paper to showcase the future trends that GB is expected to experience, as penetration of renewables increases on the road to net-zero emissions by 2050. Several sensitivities are considered, demonstrating that the share of total operating costs represented by ancillary services could reach 35%.

Journal article

Shabazbegian V, Ameli H, Ameli MT, Strbac G, Qadrdan Met al., 2021, Co-optimization of resilient gas and electricity networks; a novel possibilistic chance-constrained programming approach, Applied Energy, Vol: 284, ISSN: 0306-2619

Gas-fired power plants are commonly employed to deal with the intermittency of renewable energy resources due to their flexible characteristics. Therefore, the intermittency in the power system transmits to the gas system through the gas-fired power plants, which makes the operation of these systems even more interdependent. This study proposes a novel possibilistic model for the integrated operation of gas and power systems in the presence of electric vehicles and demand response. The model takes into account uncertainty in demand prediction and output power of wind farms, which is based on possibility and necessity theories in fuzzy logic through modeling uncertain parameters by Gaussian membership function. Moreover, a contingency analysis algorithm based on maximin optimization is developed to enhance the resiliency in the integrated operation of these systems by finding the worst-case scenario for the outage of components. The proposed model is implemented on a Belgium gas network and IEEE 24-bus electricity network. It is demonstrated that the possibilistic model allows the gas network to respond to the demand variations by providing a sufficient level of linepack within the pipelines. As a result, gas-fired power plants are supposed to commit more efficiently to cope with the intermittency of wind farms, which reduce the wind curtailment by 26%. Furthermore, it is quantified that through applying the contingency analysis algorithm in presence of demand response and electrical vehicles, the costs of operation and load shedding is reduced up to 17% and 83%, respectively.

Journal article

Tindemans SH, Strbac G, 2021, Low-Complexity Decentralized Algorithm for Aggregate Load Control of Thermostatic Loads, IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, Vol: 57, Pages: 987-998, ISSN: 0093-9994

Journal article

Badesa L, Teng F, Strbac G, 2020, Optimal Portfolio of Distinct Frequency Response Services in Low-Inertia Systems, Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

Working paper

Aunedi M, Pantaleo AM, Kuriyan K, Strbac G, Shah Net al., 2020, Modelling of national and local interactions between heat and electricity networks in low-carbon energy systems, Applied Energy, Vol: 276, Pages: 1-18, ISSN: 0306-2619

Decarbonisation of the heating and cooling sector is critical for achieving long-term energy and climate change objectives. Closer integration between heating/cooling and electricity systems can provide additional flexibility required to support the integration of variable renewables and other low-carbon energy sources. This paper proposes a framework for identifying cost-efficient solutions for supplying district heating systems within both operation and investment timescales, while considering local and national-level interactions between heat and electricity infrastructures. The proposed optimisation model minimises the levelised cost of a portfolio of heating technologies, and in particular Combined Heat and Power (CHP) and polygeneration systems, centralised heat pumps (HPs), centralised boilers and thermal energy storage (TES). A number of illustrative case studies are presented, quantifying the impact of renewable penetration, electricity price volatility, local grid constraints and local emission targets on optimal planning and operation of heat production assets. The sensitivity analysis demonstrates that the cost-optimal TES capacity could increase by 41–134% in order to manage a constraint in the local electricity grid, while in systems with higher RES penetration reflected in higher electricity price volatility it may be optimal to increase the TES capacity by 50–66% compared to constant prices, allowing centralised electric HP technologies to divert excess electricity produced by intermittent renewable generators to the heating sector. This confirms the importance of reflecting the whole-system value of heating technologies in the underlying cost-benefit analysis of heat networks.

Journal article

Li J, Ye Y, Strbac G, 2020, Stabilizing peer-to-peer energy trading in prosumer coalition through computational efficient pricing, Electric Power Systems Research, Vol: 189

Load balancing issues in distribution networks have emerged alongside the large-scale deployment of distributed renewable generation sources. In light of this challenge, peer-to-peer (P2P) energy trading constitutes a promising approach for delivering secure and economic supply-demand balance when faced with variable load and intermittent renewable generation through matching energy demand and supply locally. However, state-of-the-art mechanisms for governing P2P energy trading either fail to suitably incentivize prosumers to participate in P2P trading or suffer severely from the curse of dimensionality with their computational complexity increase exponentially with the number of prosumers. In this paper, a P2P energy trading mechanism based on cooperative game theory is proposed to establish a grand energy coalition of prosumers and a computationally efficient pricing algorithm is developed to suitably incentivize prosumers for their sustainable participation in the grand coalition. The performance of the proposed algorithm is demonstrated by comparing it to state-of-the-art mechanisms through numerous case studies in a real-world scenario. The superior computational performance of the proposed algorithm is also validated.

Journal article

Ameli H, qadrdan M, Strbac G, 2020, Coordinated operation of gas and electricity systems for flexibility study, Frontiers in Energy Research, Vol: 8, ISSN: 2296-598X

The increase interdependencies between electricity and gas systems, driven by gas-fired power plants and gas electricity-driven compressors, necessitates detailed investigation of such interdependencies, especially in the context of increased share of renewable energy sources.6 In this paper, the value of an integrated approach for operating gas and electricity systems is assessed. An outer approximation with equality relaxation (OA/ER) method is used to deal with the optimization class of mixed integer non-linear problem of integrated operation of gas and electricity systems. This method significantly improved the efficiency of the solution algorithm and achieved nearly 40% reduction in computation time compared to successive linear programming. The value of flexibility technologies including flexible gas compressors, demand side response, battery storage, and power-to-gas is quantified in the operation of integrated gas and electricity systems in GB 2030 energy scenarios for different renewable generation penetration levels. The modeling demonstrates that the flexibility options will enable significant cost savings in the annual operational costs of gas and electricity systems (up to 21%). On the other hand, the analysis carried out indicates that deployment of flexibility technologies support appropriately the interaction between gas and electricity systems.

Journal article

Oderinwale T, Papadaskalopoulos D, Ye Y, Strbac Get al., 2020, Investigating the impact of flexible demand on market-based generation investment planning, International Journal of Electrical Power & Energy Systems, Vol: 119, Pages: 105881-105881, ISSN: 0142-0615

Demand flexibility has attracted significant interest given its potential to address techno-economic challenges associated with the decarbonisation of electricity systems. However, previous work has investigated its long-term impacts through centralized generation planning models which do not reflect the current deregulated environment. At the same time, existing market-based generation planning models are inherently unable to capture the demand flexibility potential since they neglect time-coupling effects and system reserve requirements in their representation of the electricity market. This paper investigates the long-term impacts of demand flexibility in the deregulated environment, by proposing a time-coupling, bi-level optimization model of a self-interested generation company’s investment planning problem, which captures for the first time the energy shifting flexibility of the demand side and the operation of reserve markets with demand side participation. Case studies investigate different cases regarding the flexibility of the demand side and different market design options regarding the allocation of reserve payments. The obtained results demonstrate that, in contrast with previous centralised planning models, the proposed model can capture the dependency of generation investment decisions and the related impacts of demand flexibility on the electricity market design and the subsequent strategic response of the self-interested generation company.

Journal article

Guo J, Badesa Bernardo L, Teng F, Chaudhuri B, Hui S, Strbac Get al., 2020, Value of point-of-load voltage control for enhanced frequency response in future GB power system, IEEE Transactions on Smart Grid, Vol: 11, Pages: 4938-4948, ISSN: 1949-3053

The need for Enhanced Frequency Response (EFR)is expected to increase significantly in future low-carbon GreatBritain (GB) power system. One way to provide EFR is touse power electronic compensators (PECs) for point-of-loadvoltage control (PVC) to exploit the voltage dependence of loads.This paper investigates the techno-economic feasibility of suchtechnology in future GB power system by quantifying the totalEFR obtainable through deploying PVC in the urban domesticsector, the investment cost of the installment and the economicand environmental benefits of using PVC. The quantificationis based on a stochastic domestic demand model and genericmedium and low-voltage distribution networks for the urbanareas of GB and a stochastic unit commitment (SUC) modelwith constraints for secure post-fault frequency evolution is usedfor the value assessment. Two future energy scenarios in thebackdrop of 2030 with ‘smart’ and ‘non-smart’ control of electricvehicles and heat pumps, under different levels of penetration ofbattery energy storage system (BESS) are considered to assessthe value of PEC, as well as the associated payback period. Itis demonstrated that PVC could effectively complement BESStowards EFR provision in future GB power system.

Journal article

Ameli H, Qadrdan M, Strbac G, Ameli MTet al., 2020, Investing in flexibility in an integrated planning of natural gas and power systems, IET Energy Systems Integration, Vol: 2, Pages: 101-111, ISSN: 2516-8401

The growing interdependencies between natural gas and power systems, driven by gas-fired generators and gas compressors supplied by electricity, necessitates detailed investigation of the interactions between these vectors, particularly in the context of growing penetration of renewable energy sources. In this research, an expansion planning model for integrated natural gas and power systems is proposed. The model investigates optimal investment in flexibility options such as battery storage, demand side response, and gas-fired generators. The value of these flexibility options is quantified for gas and electricity systems in GB in 2030. The results indicate that the flexibility options could play an important role in meeting the emission targets in the future. However, the investment costs of these options highly impact the future generation mix as well as the type of reinforcements in the natural gas system infrastructure. Through deployment of the flexibility options up to £24.2b annual cost savings in planning and operation of natural gas and power systems could be achieved, compared to the case that no flexibility option is considered.

Journal article

Shen F, Wu Q, Xu Y, Li F, Teng F, Strbac Get al., 2020, Hierarchical service restoration scheme for active distribution networks based on ADMM, International Journal of Electrical Power & Energy Systems, Vol: 118, Pages: 1-10, ISSN: 0142-0615

Effective self-healing schemes enhance the resilience of active distribution networks (ADNs). As a critical part of self-healing, service restoration aims to restore outage areas with minimal un-supplied demands. With the increasing complexity and size of ADNs, distribution system operators (DSOs) face a more complicated service restoration problem. Thus, it is important to obtain optimal service restoration plans and reduce computational complexity. To achieve this goal, a hierarchical service restoration scheme is proposed to obtain service restoration plans based on the alternating direction method of multipliers (ADMM). The optimal service restoration problem is formulated as a mixed-integer linear programming (MILP) model considering the switching sequence, distributed generation (DG) units and controllable loads, and is solved using the ADMM-based algorithm in a hierarchical manner. In the proposed scheme, each zone of the ADN has a local service restoration controller solving its sub-problem with information from a central service restoration controller. The central controller solves a global coordination problem with information from all the zones. Three case studies were conducted with the 44-node test system, modified IEEE 123-node system and Brazil 948-node system. The results show that the proposed hierarchical service restoration can obtain optimal service restoration plans and reduce computational complexity. Moreover, computation time can be reduced substantially by using the proposed hierarchical scheme for large-scale ADNs.

Journal article

Li J, Ye Y, Strbac G, 2020, Stabilizing Peer-to-Peer Energy Trading in Prosumer Coalition Through Computational Efficient Pricing, 21st Power Systems Computation Conference

Load balancing issues in distribution networks have emerged alongside the large-scale deployment of distributed renewable generation sources. In light of this challenge, peer-to-peer (P2P) energy trading constitutes a promising approach for delivering secure and economic supply-demand balance when faced with variable load and intermittent renewable generation through matching energy demand and supply locally. However, state-of-the-art mechanisms for governing P2P energy trading either fail to suitably incentivize prosumers to participate in P2P trading or suffer severely from the curse of dimensionality with their computational complexity increase exponentially with the number of prosumers. In this paper, a P2P energy trading mechanism based on cooperative game theory is proposed to establish a grand energy coalition of prosumers and a computationally efficient pricing algorithm is developed to suitably incentivize prosumers for their sustainable participation in the grand coalition. The performance of the proposed algorithm is demonstrated by comparing it to state-of-the-art mechanisms through numerous case studies in a real-world scenario. The superior computational performance of the proposed algorithm is also validated.

Conference paper

Fu P, Pudjianto D, Zhang X, Strbac Get al., 2020, Integration of hydrogen into multi-energy systems optimisation, Energies, Vol: 13, Pages: 1606-1606, ISSN: 1996-1073

Hydrogen presents an attractive option to decarbonise the present energy system. Hydrogen can extend the usage of the existing gas infrastructure with low-cost energy storability and flexibility. Excess electricity generated by renewables can be converted into hydrogen. In this paper, a novel multi-energy systems optimisation model was proposed to maximise investment and operating synergy in the electricity, heating, and transport sectors, considering the integration of a hydrogen system to minimise the overall costs. The model considers two hydrogen production processes: (i) gas-to-gas (G2G) with carbon capture and storage (CCS), and (ii) power-to-gas (P2G). The proposed model was applied in a future Great Britain (GB) system. Through a comparison with the system without hydrogen, the results showed that the G2G process could reduce £3.9 bn/year, and that the P2G process could bring £2.1 bn/year in cost-savings under a 30 Mt carbon target. The results also demonstrate the system implications of the two hydrogen production processes on the investment and operation of other energy sectors. The G2G process can reduce the total power generation capacity from 71 GW to 53 GW, and the P2G process can promote the integration of wind power from 83 GW to 130 GW under a 30 Mt carbon target. The results also demonstrate the changes in the heating strategies driven by the different hydrogen production processes.

Journal article

Qiu D, Ye Y, Papadaskalopoulos D, Strbac Get al., 2020, A Deep Reinforcement Learning Method for Pricing Electric Vehicles with Discrete Charging Levels, IEEE Transactions on Industry Applications, ISSN: 0093-9994

The effective pricing of electric vehicles (EV) charging by aggregators constitutes a key problem towards the realization of the significant EV flexibility potential in deregulated electricity systems, and has been addressed by previous work through bi-level optimization formulations. However, the solution approach adopted in previous work cannot capture the discrete nature of the EV charging / discharging levels. Although reinforcement learning (RL) can tackle this challenge, state-of-the-art RL methods require discretization of state and / or action spaces and thus exhibit limitations in terms of solution optimality and computational requirements. This paper proposes a novel deep reinforcement learning (DRL) method to solve the examined EV pricing problem, combining deep deterministic policy gradient (DDPG) principles with a prioritized experience replay (PER) strategy, and setting up the problem in multi-dimensional continuous state and action spaces. Case studies demonstrate that the proposed method outperforms state-of-the-art RL methods in terms of both solution optimality and computational requirements, and comprehensively analyze the economic impacts of smart-charging and vehicle-to-grid (V2G) flexibility on both aggregators and EV owners.

Journal article

Huyghues-Beaufond N, Tindemans S, Falugi P, Sun M, Strbac Get al., 2020, Robust and automatic data cleansing method for short-term load forecasting of distribution feeders, Applied Energy, Vol: 261, Pages: 1-17, ISSN: 0306-2619

Distribution networks are undergoing fundamental changes at medium voltage level. To support growing planning and control decision-making, the need for large numbers of short-term load forecasts has emerged. Data-driven modelling of medium voltage feeders can be affected by (1) data quality issues, namely, large gross errors and missing observations (2) the presence of structural breaks in the data due to occasional network reconfiguration and load transfers. The present work investigates and reports on the effects of advanced data cleansing techniques on forecast accuracy. A hybrid framework to detect and remove outliers in large datasets is proposed; this automatic procedure combines the Tukey labelling rule and the binary segmentation algorithm to cleanse data more efficiently, it is fast and easy to implement. Various approaches for missing value imputation are investigated, including unconditional mean, Hot Deck via k-nearest neighbour and Kalman smoothing. A combination of the automatic detection/removal of outliers and the imputation methods mentioned above are implemented to cleanse time series of 342 medium-voltage feeders. A nested rolling-origin-validation technique is used to evaluate the feed-forward deep neural network models. The proposed data cleansing framework efficiently removes outliers from the data, and the accuracy of forecasts is improved. It is found that Hot Deck (k-NN) imputation performs best in balancing the bias-variance trade-off for short-term forecasting.

Journal article

Ye Y, Qiu D, Sun M, Papadaskalopoulos D, Strbac Get al., 2020, Deep reinforcement learning for strategic bidding in electricity markets, IEEE Transactions on Smart Grid, Vol: 11, Pages: 1343-1355, ISSN: 1949-3053

Bi-level optimization and reinforcement learning (RL) constitute the state-of-the-art frameworks for modeling strategic bidding decisions in deregulated electricity markets. However, the former neglects the market participants' physical non-convex operating characteristics, while conventional RL methods require discretization of state and / or action spaces and thus suffer from the curse of dimensionality. This paper proposes a novel deep reinforcement learning (DRL) based methodology, combining a deep deterministic policy gradient (DDPG) method with a prioritized experience replay (PER) strategy. This approach sets up the problem in multi-dimensional continuous state and action spaces, enabling market participants to receive accurate feedback regarding the impact of their bidding decisions on the market clearing outcome, and devise more profitable bidding decisions by exploiting the entire action domain, also accounting for the effect of non-convex operating characteristics. Case studies demonstrate that the proposed methodology achieves a significantly higher profit than the alternative state-of-the-art methods, and exhibits a more favourable computational performance than benchmark RL methods due to the employment of the PER strategy.

Journal article

Malekpour M, Azizipanah-Abarghooee R, Teng F, Strbac G, Terzija Vet al., 2020, Fast Frequency Response From Smart Induction Motor Variable Speed Drives, IEEE TRANSACTIONS ON POWER SYSTEMS, Vol: 35, Pages: 997-1008, ISSN: 0885-8950

Journal article

Soder L, Tomasson E, Estanqueiro A, Flynn D, Hodge B-M, Kiviluoma J, Korpas M, Neau E, Couto A, Pudjianto D, Strbac G, Burke D, Gomez T, Das K, Cutululis NA, Van Hertem D, Hoschle H, Matevosyan J, von Roon S, Carlini EM, Caprabianca M, de Vries Let al., 2020, Review of wind generation within adequacy calculations and capacity markets for different power systems, RENEWABLE & SUSTAINABLE ENERGY REVIEWS, Vol: 119, ISSN: 1364-0321

Journal article

Heylen E, Papadaskalopoulos D, Konstantelos I, Strbac Get al., 2020, Dynamic modelling of consumers’ inconvenience associated with demand flexibility potentials, Sustainable Energy, Grids and Networks, Vol: 21, Pages: 1-13, ISSN: 2352-4677

Demand flexibility, involving the potential to reduce or temporally defer electricity demand, is regarded as a key enabler for transitioning to a secure, cost-efficient and low-carbon energy future. However, previous work has not comprehensively modelled the inconvenience experienced by end-consumers due to demand modifications, since it has focused on static modelling approaches. This paper presents a novel model of inconvenience cost that simultaneously accounts for differentiated preferences of consumer groups, time and duration of interruptions, differentiated valuation of different units of power and temporal redistribution of shiftable loads. This model is dynamic and future-agnostic, implying that it captures the time-coupling characteristics of consumers’ flexibility and the temporal evolution of interruptions, without resorting to the unrealistic assumption that time and duration of interruptions are foreknown. The model is quantitatively informed by publicly available surveys combined with realistic assumptions and suitable sensitivity analyses regarding aspects excluded from existing surveys. In the examined case studies, the developed model is applied to manage an aggregator’s portfolio in a scenario involving emergence of an adequacy issue in the Belgian system. The results illustrate how considering each of the above factors affects demand management decisions and the inconvenience cost, revealing the value of the developed model.

Journal article

Ye Y, Qiu D, Wu X, Strbac G, Ward Jet al., 2020, Model-Free Real-Time Autonomous Control for A Residential Multi-Energy System Using Deep Reinforcement Learning, IEEE Transactions on Smart Grid, Vol: 11, Pages: 3068-3068, ISSN: 1949-3053

Multi-energy systems (MES) are attracting increasing attention driven by its potential to offer significant flexibility in future smart grids. At the residential level, the roll-out of smart meters and rapid deployment of smart energy devices call for autonomous multi-energy management systems which can exploit real-time information to optimally schedule the usage of different devices with the aim of minimizing end-users’ energy costs. This paper proposes a novel real-time autonomous energy management strategy for a residential MES using a model-free deep reinforcement learning (DRL) based approach, combining state-of-the-art deep deterministic policy gradient (DDPG) method with an innovative prioritized experience replay strategy. This approach is tailored to align with the nature of the problem by posing it in multi-dimensional continuous state and action spaces, facilitating more cost-effective control strategies to be devised. The superior performance of the proposed approach in reducing end-user’s energy cost while coping with the MES uncertainties is demonstrated by comparing it against state-of-the-art DRL methods as well as conventional stochastic programming and robust optimization methods in numerous case studies in a real-world scenario.

Journal article

Ye Y, Qiu D, Wu X, Strbac G, Ward Jet al., 2020, Model-Free Real-Time Autonomous Control for A Residential Multi-Energy System Using Deep Reinforcement Learning, IEEE Transactions on Smart Grid, Pages: 1-1, ISSN: 1949-3053

Multi-energy systems (MES) are attracting increasing attention driven by its potential to offer significant flexibility in future smart grids. At the residential level, the roll-out of smart meters and rapid deployment of smart energy devices call for autonomous multi-energy management systems which can exploit real-time information to optimally schedule the usage of different devices with the aim of minimizing end-users’ energy costs. This paper proposes a novel real-time autonomous energy management strategy for a residential MES using a model-free deep reinforcement learning (DRL) based approach, combining state-of-the-art deep deterministic policy gradient (DDPG) method with an innovative prioritized experience replay strategy. This approach is tailored to align with the nature of the problem by posing it in multi-dimensional continuous state and action spaces, facilitating more cost-effective control strategies to be devised. The superior performance of the proposed approach in reducing end-user’s energy cost while coping with the MES uncertainties is demonstrated by comparing it against state-of-the-art DRL methods as well as conventional stochastic programming and robust optimization methods in numerous case studies in a real-world scenario.

Journal article

Li J, Ye Y, Strbac G, 2020, Incentivizing Peer-to-Peer Energy Sharing Using a Core Tâtonnement Algorithm, 2020 IEEE IEEE Power & Energy Society General Meeting

Conference paper

Badesa L, Teng F, Strbac G, 2020, Pricing inertia and Frequency Response with diverse dynamics in a Mixed-Integer Second-Order Cone Programming formulation, Applied Energy, Vol: 260, Pages: 1-11, ISSN: 0306-2619

Low levels of system inertia in power grids with significant penetration of non-synchronous Renewable Energy Sources (RES) have increased the risk of frequency instability. The provision of a certain type of ancillary services such as inertia and Frequency Response (FR) is needed at all times, to maintain system frequency within secure limits if the loss of a large power infeed were to occur. In this paper we propose a frequency-secured optimisation framework for the procurement of inertia and FR with diverse dynamics, which enables to apply a marginal-pricing scheme for these services. This pricing scheme, deduced from a Mixed-Integer Second-Order Cone Program (MISOCP) formulation that represents frequency-security constraints, allows for the first time to appropriately value multi-speed FR.

Journal article

Georgiou S, Aunedi M, Strbac G, Markides CNet al., 2020, On the value of liquid-air and Pumped-Thermal Electricity Storage systems in low-carbon electricity systems, Energy, Vol: 193, ISSN: 0360-5442

We consider two medium-to-large scale thermomechanical electricity storage technologies currently under development, namely ‘Liquid-Air Energy Storage’ (LAES) and ‘Pumped-Thermal Electricity Storage’ (PTES). Consistent thermodynamic models and costing methods based on a unified methodology for the two systems from previous work are presented and used with the objective of integrating the characteristics of the technologies into a whole-electricity system assessment model and assessing their system-level value in various scenarios for system decarbonization. It is found that the value of storage depends on the cumulative installed capacity of storage in the system, with storage technologies providing greater marginal benefits at low penetrations. The system value of PTES was found to be slightly higher than that of LAES, driven by a higher storage duration and efficiency, although these results must be seen in light of the uncertainty in the (as yet, not demonstrated) performance of key PTES components, namely the reciprocating-piston compressors and expanders. At the same time, PTES was also found to have a higher power capital cost. The results indicate that the complexity of the decarbonization challenge makes it difficult to identify clearly a ‘best’ technology and suggest that the uptake of either technology can provide significant system-level benefits.

Journal article

Giannelos S, Djapic P, Pudjianto D, Strbac Get al., 2020, Quantification of the energy storage contribution to security of supply through the F-factor methodology, Energies, Vol: 13, Pages: 826-826, ISSN: 1996-1073

The ongoing electrification of the heat and transport sectors is expected to lead to a substantial increase in peak electricity demand over the coming decades, which may drive significant investment in network reinforcement in order to maintain a secure supply of electricity to consumers. The traditional way of security provision has been based on conventional investments such as the upgrade of the capacity of electricity transmission or distribution lines. However, energy storage can also provide security of supply. In this context, the current paper presents a methodology for the quantification of the security contribution of energy storage, based on the use of mathematical optimization for the calculation of the F-factor metric, which reflects the optimal amount of peak demand reduction that can be achieved as compared to the power capability of the corresponding energy storage asset. In this context, case studies underline that the F-factors decrease with greater storage power capability and increase with greater storage efficiency and energy capacity as well as peakiness of the load profile. Furthermore, it is shown that increased investment in energy storage per system bus does not increase the overall contribution to security of supply.

Journal article

Song Y, Ding Y, Siano P, Meinrenken C, Zheng M, Strbac Get al., 2020, Optimization methods and advanced applications for smart energy systems considering grid-interactive demand response, APPLIED ENERGY, Vol: 259, ISSN: 0306-2619

Journal article

Qiu D, Papadaskalopoulos D, Ye Y, Strbac Get al., 2020, Investigating the Effects of Demand Flexibility on Electricity Retailers’ Business through a Tri-Level Optimization Model, IET Generation, Transmission & Distribution, Vol: 14, Pages: 1739-1750, ISSN: 1751-8687

The investigation of the effects of demand flexibility on the pricing strategies and the profits of electricity retailers has recently emerged as a highly interesting research area. However, the state-of-the-art, bi-level optimization modelling approach makes the unrealistic assumption that retailers treat wholesale market prices as exogenous, fixed parameters. This paper proposes a tri-level optimization model which drops this assumption and represents endogenously the wholesale market clearing process, thus capturing the realistic implications of a retailer’s pricing strategies and the resulting demand response on the wholesale market prices. The scope of the examined case studies is threefold. First of all, they demonstrate the interactions between the retailer, the flexible consumers and the wholesale market and analyse the fundamental effects of the consumers’ time-shifting flexibility on the retailer’s revenue from the consumers, its cost in the wholesale market, and its overall profit. Furthermore, they analyse how these effects of demand flexibility depend on the retailer’s relative size in the market and the strictness of the regulatory framework. Finally, they highlight the added value of the proposed tri-level model by comparing its outcomes against the state-of-the-art bi-level modelling approach.

Journal article

Ye Y, Papadaskalopoulos D, Kazempour J, Strbac Get al., 2020, Incorporating non-convex operating characteristics into bi-level optimization electricity market models, IEEE Transactions on Power Systems, Vol: 35, Pages: 163-176, ISSN: 0885-8950

Bi-level optimization constitutes the most popular mathematical methodology for modeling the deregulated electricity market. However, state-of-the-art models neglect the physical non-convex operating characteristics of market participants, due to their inherent inability to capture binary decision variables in their representation of the market clearing process, rendering them problematic in modeling markets with complex bidding and unit commitment (UC) clearing mechanisms. This paper addresses this fundamental limitation by proposing a novel modeling approach enabling incorporation of these non-convexities into bi-level optimization market models, which is based on the relaxation and primal-dual reformulation of the original, non-convex lower level problem and the penalization of the associated duality gap. Case studies demonstrate the ability of the proposed approach to closely approximate the market clearing solution of the actual UC clearing algorithm and devise more profitable bidding decisions for strategic producers than the state-of-the-art bi-level optimization approach, and reveal the potential of strategic behavior in terms of misreporting non-convex operating characteristics.

Journal article

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