14 results found
Trask A, Wills K, Green T, et al., 2021, Impacts of COVID-19 on the Energy System, Impacts of COVID-19 on the Energy System
This Briefing Paper explores the impactthe COVID-19 pandemic had on the UK’senergy sector over the course of thefirst government-mandated nationallockdown that began on 23 March 2020.Research from several aspects of theIntegrated Development of Low-carbonEnergy Systems (IDLES) programme atImperial College London is presented inone overarching paper. The main aim isto determine what lessons can be learntfrom that lockdown period, given theunique set of challenges it presented inour daily lives and the changes it broughtabout in energy demand, supply, anduse. Valuable insights are gained intohow working-from-home policies,electric vehicles, and low-carbon gridscan be implemented, incentivised, andmanaged effectively.
Badesa L, Teng F, Strbac G, 2021, Conditions for regional frequency stability in power system scheduling—part I: theory, IEEE Transactions on Power Systems, Pages: 1-1, ISSN: 0885-8950
This paper considers the phenomenon of distinct regional frequencies recently observed in some power systems. First, a reduced-order mathematical model describing this behaviour is developed. Then, techniques to solve the model are discussed, demonstrating that the post-fault frequency evolution in any given region is equal to the frequency evolution of the Centre Of Inertia plus certain inter-area oscillations. This finding leads to the deduction of conditions for guaranteeing frequency stability in all regions of a power system, a deduction performed using a mixed analytical-numerical approach that combines mathematical analysis with regression methods on simulation samples. The proposed stability conditions are linear inequalities that can be implemented in any optimisation routine allowing the co-optimisation of all existing ancillary services for frequency support: inertia, multi-speed frequency response, load damping and an optimised largest power infeed. This is the first reported mathematical framework with explicit conditions to maintain frequency stability in a power system exhibiting inter-area oscillations in frequency.
Badesa L, Teng F, Strbac G, 2021, Conditions for regional frequency stability in power system scheduling—Part II: application to unit commitment, IEEE Transactions on Power Systems, ISSN: 0885-8950
In Part I of this paper we have introduced the closed-form conditions for guaranteeing regional frequency stability in a power system. Here we propose a methodology to represent these conditions in the form of linear constraints and demonstrate their applicability by implementing them in a generation-scheduling model. This model simultaneously optimises energy production and ancillary services for maintaining frequency stability in the event of a generation outage, by solving a frequency-secured Stochastic Unit Commitment (SUC). We consider the Great Britain system, characterised by two regions that create a non-uniform distribution of inertia: England in the South, where most of the load is located, and Scotland in the North, containing significant wind resources. Through several case studies, it is shown that inertia and frequency response cannot be considered as system-wide magnitudes in power systems that exhibit inter-area oscillations in frequency, as their location in a particular region is key to guarantee stability. In addition, securing against a medium-sized loss in the low-inertia region proves to cause significant wind curtailment, which could be alleviated through reinforced transmission corridors. In this context, the proposed constraints allow to find the optimal volume of ancillary services to be procured in each region.
Baig AM, Badesa L, Strbac G, 2021, Importance of linking inertia and frequency response procurement: the Great Britain case, Publisher: arXiv
In order to decarbonise the electricity sector, the future Great Britain (GB)power system will be largely dominated by non-synchronous renewables. This willcause low levels of inertia, a key parameter that could lead to frequencydeterioration. Therefore, the requirement for ancillary services that containfrequency deviations will increase significantly, particularly given theincrease in size of the largest possible loss with the commissioning of largenuclear plants in the near future. In this paper, an inertia-dependentStochastic Unit Commitment (SUC) model is used to illustrate the benefits oflinking inertia and frequency response provision in low-inertia systems. Wedemonstrate that the cost of procuring ancillary services in GB could increaseby 165% if the level of inertia is not explicitly considered when procuringfrequency response. These results highlight the need to re-think the structureof ancillary-services markets, which in GB are nowadays held one month ahead ofdelivery.
Badesa L, Strbac G, Magill M, et 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%.
Badesa L, Teng F, Strbac G, 2020, Optimal portfolio of distinct frequency response services in low-inertia systems, IEEE Transactions on Power Systems, Vol: 35, Pages: 4459-4469, ISSN: 0885-8950
A reduced level of system inertia due to renewable integration increases the need for cost-effective provision of ancillary services, such as Frequency Response (FR). In this paper a closed-form solution to the differential equation describing frequency dynamics is proposed, which allows to obtain frequency-security algebraic constraints to be implemented in optimization routines. This is done while considering any finite number of FR services with distinguished characteristics, such as different delivery times and activation delays. The problem defined by these frequency-security constraints can be formulated as a Mixed-Integer Second-Order Cone Program (MISOCP), which can be efficiently handled by off-the-shelf conic optimization solvers. This paper also takes into account the uncertainty in inertia contribution from the demand side by formulating the frequency-security conditions as chance constraints, for which an exact convex reformulation is provided. Finally, case studies highlighting the effectiveness of this frequency-secured formulation are presented.
Guo J, Badesa Bernardo L, Teng F, et 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.
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.
Badesa L, Teng F, Strbac G, 2019, Simultaneous scheduling of multiple frequency services in stochastic unit commitment, IEEE Transactions on Power Systems, Vol: 34, Pages: 3858-3868, ISSN: 0885-8950
The reduced level of system inertia in low-carbon power grids increases the need for alternative frequency services. However, simultaneously optimising the provision of these services in the scheduling process, subject to significant uncertainty, is a complex task given the challenge of linking the steady-state optimisation with frequency dynamics. This paper proposes a novel frequency-constrained Stochastic Unit Commitment (SUC) model which, for the first time, co-optimises energy production along with the provision of synchronised and synthetic inertia, Enhanced Frequency Response (EFR), Primary Frequency Response (PFR) and a dynamically-reduced largest power infeed. The contribution of load damping is modelled through a linear inner approximation. The effectiveness of the proposed model is demonstrated through several case studies for Great Britain’s 2030 power system, which highlight the synergies and conflicts among alternative frequency services, as well as the significant economic savings and carbon reduction achieved by simultaneously optimising all these services.
Camal S, Teng F, Michiorri A, et al., 2019, Scenario generation of aggregated wind, photovoltaics and small hydro production for power systems applications, Applied Energy, Vol: 242, Pages: 1396-1406, ISSN: 0306-2619
This paper proposes a methodology for an efficient generation of correlated scenarios of Wind, Photovoltaics (PV) and small Hydro production considering the power system application at hand. The merits of scenarios obtained from a direct probabilistic forecast of the aggregated production are compared with those of scenarios arising from separate production forecasts for each energy source, the correlations of which are modeled in a later stage with a multivariate copula. It is found that scenarios generated from separate forecasts reproduce globally better the variability of a multi-source aggregated production. Aggregating renewable power plants can potentially mitigate their uncertainty and improve their reliability when they offer regulation services. In this context, the first application of scenarios consists in devising an optimal day-ahead reserve bid made by a Wind-PV-Hydro Virtual Power Plant (VPP). Scenarios are fed into a two-stage stochastic optimization model, with chance-constraints to minimize the probability of failing to deploy reserve in real-time. Results of a case study show that scenarios generated by separately forecasting the production of each energy source leads to a higher Conditional Value at Risk than scenarios from direct aggregated forecasting. The alternative forecasting methods can also significantly affect the scheduling of future power systems with high penetration of weather-dependent renewable plants. The generated scenarios have a second application here as the inputs of a two-stage stochastic unit commitment model. The case study demonstrates that the direct forecast of aggregated production can effectively reduce the system operational cost, mainly through better covering the extreme cases. The comprehensive application-based assessment of scenario generation methodologies in this paper informs the decision-makers on the optimal way to generate short-term scenarios of aggregated RES production according to their risk aversion
Badesa L, Teng F, Strbac G, 2018, Optimal scheduling of frequency services considering a variable largest-power-infeed-loss, 2018 IEEE Power and Energy Society General Meeting, Publisher: IEEE, ISSN: 1944-9925
Low levels of inertia due to increasing renewable penetration bring several challenges, such as the higher need for Primary Frequency Response (PFR). A potential solution to mitigate this problem consists on reducing the largest possible power loss in the grid. This paper develops a novel modelling framework to analyse the benefits of such approach.A new frequency-constrained Stochastic Unit Commitment (SUC) is proposed here, which allows to dynamically reduce the largest possible loss in the optimisation problem. Furthermore, the effect of load damping is included by means of an approximation, while its effect is typically neglected in previous frequency-secured-UC studies. Through several case studies, we demonstrate that reducing the largest loss could significantly decrease operational cost and carbon emissions in the future Great Britain's grid.
Badesa L, Teng F, Strbac G, 2018, Economic value of inertia in low-carbon power systems, 2017 IEEE PES Innovative Smart Grid Technologies Conference Europe (ISGT-Europe), Publisher: IEEE
Most renewable energy sources (RES) do not provide any inertial response. Their integration in a power grid implies a highly reduced level of system inertia, which leads to a deteriorated frequency performance. Then, the requirement for frequency response is significantly increased in order to maintain frequency security. Alternatively, enhanced provision of inertia from auxiliary sources may alleviate this problem. However, the benefits of inertia provision are not yet fully understood. In this paper, an inertia-dependent Stochastic Unit Commitment (SUC) tool is applied to quantify the economic value of inertia. The results demonstrate that enhanced provision of inertia would lead to significant economic savings, although these savings vary under different system conditions. These results should be brought to the attention of both market operators and investors, in order to inform the design of an ancillary-services market for inertia and the investment in auxiliary provision of inertia.
Badesa L, Fathima S, Musavi MT, et al., 2016, Impact of Wind Generation on Dynamic Voltage Stability and Influence of the Point of Interconnection, 2016 IEEE Green Technologies Conference (GreenTech), ISSN: 2166-546X
Wu Y, Badesa L, Musavi MT, et al., 2015, Monitoring power system transient stability using synchrophasor data, 2015 IEEE Power and Energy Society General Meeting, ISSN: 1944-9925
Many interconnected power systems are constructed to meet the ever increasing electric power transfer demand. A disturbance anywhere in such an interconnected system will directly influence the power transfer capability of major transfer interfaces, as well as the transient stability of the system. Instead of monitoring the power transfer limit on a given interface, we propose a real-time synchrophasor measurement-based method to monitor the dynamic stability margin of the power system. This is accomplished by directly correlating the phase angle separation and voltage sag of critical buses to power transfer increase on the interface. The Eastern North American power system is used as a platform to illustrate the utility of the proposed method.
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