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  • 1.
    Abrahamson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Fast calculation of the dimensioning factors of the railway power supply system2007In: Computational Methods and Experimental Measurements XIII, WIT Press, 2007, Vol. 46, p. 85-95Conference paper (Refereed)
    Abstract [en]

    Because of environmental and economical reasons, in Sweden and the rest of Europe, both personal and goods transports on railway are increasing. Therefore great railway infrastructure investments are expected to come. An important part of this infrastructure is the railway power supply system. Exactly how much, when and where the traffic will increase is not known for sure. This means investment planning for an uncertain future. The more uncertain parameters, such as traffic density and weight of trains, and the further future considered, the greater the inevitable amount of cases that have to be considered. When doing simulations concerning a tremendous amount of cases, each part of the simulation model has to be computationally fast - in real life this means approximations. The two most important issues to estimate given a certain power system configuration, when planning for an electric traction system, are the energy consumption of the and and the train delays that a too weak system would cause. In this paper, some modeling suggestions of the energy consumption and the maximal train velocities are presented. Two linear, and one nonlinear model are presented and compared. The comparisons regard both computer speed and representability. The independent variables of these models are a selection of parameters describing the power system, i.e.: power system technology used on each section, and traffic intensity.

  • 2.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Skogberg, Ronny
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Lagos, Mario
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Identifying electrically infeasible traffic scenarios on the iron ore line: Applied on the present-day system, converter station outages, and optimal locomotive reactive power strategies2015In: PROCEEDINGS OF THE ASME JOINT RAIL CONFERENCE, 2015, AMER SOC MECHANICAL ENGINEERS , 2015Conference paper (Refereed)
    Abstract [en]

    This paper presents the main findings of a Master's Thesis project carried out in cooperation between Transrail and Royal Institute of Technology (KTH). The main objective was to create a plugin for checking the electric power system feasibility of a train traffic plan with an associated driving strategy created by TRAINS a Transrail software product. Secondary aims with the project was to study power system feasibilities during converter station outages, and to which extent optimal operation of the locomotive converters' reactive power assure power system feasibilities. In the developed optimal reactive power strategies, the main priority was to fulfill the desired traffic plans, whereas the secondary priority was to minimize railway power system power consumption. The case studies are applied on representative traffic scenarios and power system models representing the northern part of the Iron Ore line in Northern Sweden. The focus of the study is set on the IORE locomotives and the iron ore trains they haul. The optimized locomotive reactive power regards IORE, so also the investigated power system feasibilities of the traffic plans.

  • 3.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    An SOS2-based moving trains,fixed nodes, railway power system simulator2012In: WIT Transactions on the Built Environment, WIT Press, 2012, p. 813-823Conference paper (Refereed)
    Abstract [en]

    This paper presents and proposes an optimization model for railway power supply system simulations. It includes detailed power systems modeling train movements in discretized time considering running resistance and other mechanical constraints, and the voltage-drop-induced reduction of possible train tractive forces. The model has a xed number of stationary power system nodes. The proposed model uses SOS2 (special ordered sets of type 2) variables to distribute the train loads to the two most adjacent power system nodes available. The impact of the number of power system nodes along the contact line and the discretized time step length impacts on model accuracy and computation times are investigated. The program is implemented in GAMS (General Algebraic Modeling System). Experiences from various solver choices are also presented. The train traveling times are minimized in the example. Other studies could, e.g. consider energy consumption minimization. The numerical example is representative for a Swedish non-centralized, rotary-converter fed railway power supply system. The proposed concept is however generalizable and could be applied for all kinds of moving load power system studies.

  • 4.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Basic modeling for electric traction systems under uncertainty2006In: PROCEEDINGS OF THE 41ST INTERNATIONAL UNIVERSITIES POWER ENGINEERING CONFERENCE, VOLS 1 AND 2, NEW YORK: IEEE , 2006, p. 252-256Conference paper (Refereed)
    Abstract [en]

    The objective of this paper is initially to present a basic modeling of the railway traction system. This model includes the basic technologies used today. The voltage dependencies of the maximal possible power consumption as well as the maximal velocity of the common Re-locomotives are included. The latter is very crucial for the studies of time table sensitivity, which is of our immediate interest. Moreover, a method is presented, that estimates the expected train delay time for a given feeding technology. The reference timetable assumes the same train and surrounding conditions, but no voltage drops. In the numerical example where the developed model is applied to a realistic test system, a set of possible amounts of railway traffic are treated as uncertainties. Mainly, the contributions of this paper are three: compiling and connecting already accepted models, the development of a method for numerical calculations using this model compilation, and an example to apply this model on.

  • 5.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Fast calculation of some important dimensioning factors of the railway power supply system2007Conference paper (Refereed)
    Abstract [en]

    Because of environmental and economical reasons, in Sweden and the rest of Europe, both personal and goods transports on railway are increasing. Therefore great railway infrastructure investments are expected to come. An important part of this infrastructure is the railway power supply system. Exactly how much, when and where the traffic will increase is not known for sure. This means investment planning for an uncertain future. The more uncertain parameters, such as traffic density and weight of trains, and the further future considered, the greater the inevitable amount of cases that have to be considered. When doing simulations concerning a tremendous amount of cases, each part of the simulation model has to be computationally fast – in real life this means approximations. The two most important issues to estimate given a certain power system configuration, when planning for an electric traction system, are the energy consumption of the grid and the train delays that a too weak system would cause. In this paper, some modeling suggestions of the energy consumption and the maximal train velocities are presented. Two linear models, and one nonlinear model are presented and compared. The comparisons regard both computer speed and representability. The independent variables of these models are a selection of parameters describing the power system, i.e.: power system technology used on each section, and traffic intensity.

  • 6.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    Fast estimation of aggregated results of many load flow solutions in electric traction systems2008In: COMPUTERS IN RAILWAYS XI, WIT Press, 2008, Vol. 103, p. 411-423Conference paper (Other academic)
    Abstract [en]

    Transports on rail are increasing and major railway infrastructure investments are expected. An important part of this infrastructure is the railway power supply system. The future railway power demands are naturally not known for certain. This means investment planning for an uncertain future. The more remote the uncertain future, the greater the amount of scenarios that have to be considered. Large numbers of scenarios make time demanding (some tens of minutes, each) simulations less attractive and simplifications more so. The aim of this paper is to present a fast approximator that uses aggregated traction system information as inputs and outputs. This facilitates studies of many future railway power system loading scenarios, combined with different power system configurations, for investment planning analysis. Since the electrical and mechanical relations governing an electric traction system are quite intricate, an approximator based on neural networks (NN), is applied. This paper presents a design suggestion for a NN estimating power system caused limits on active and reactive power load, i.e., limits on the levels of train traffic.

  • 7.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Fast Estimation of Relations Between Aggregated Train Power System Data and Traffic Performance2011In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 60, no 1, p. 16-29Article in journal (Refereed)
    Abstract [en]

    Transports via rail are increasing, and major railway infrastructure investments are expected. An important part of this infrastructure is the railway power supply system (RPSS). Future railway power demands are not known. The more distant the uncertain future, the greater the number of scenarios that have to be considered. Large numbers of scenarios make time-demanding (some minutes, each) full simulations of electric railway power systems less attractive and simplifications more so. The aim, and main contribution, of this paper is to propose a fast approximator that uses aggregated traction system information as inputs and outputs. This approximator can be used as an investment planning constraint in the optimization. It considers that there is a limit on the intensity of the train traffic, depending on the strength of the power system. This approximator approach has not previously been encountered in the literature. In the numerical example of this paper, the approximator inputs are the power system configuration; the distance between a connection from contact line to the public grid, to another connection, or to the end of the contact line; the average values and the standard deviations of the inclinations of the railway; the average number of trains; and their average velocity for that distance. The output is the maximal attainable average velocity of an added train for the described railway power system section. The approximator facilitates studies of many future railway power system loading scenarios, combined with different power system configurations, for investment planning analysis. The approximator is based on neural networks. An additional value of the approximator is that it provides an understanding of the relations between power system configuration and train traffic performance.

  • 8.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Fast estimation of the relation between aggregated train power system information and the power and energy converted2009In: Australian Journal of Electrical and Electronic Engineering, ISSN 1448-837X, Vol. 6, no 3, p. 311-318Article in journal (Refereed)
    Abstract [en]

    Transports on rail are increasing and major investments in the railway infrastructure, including the railway power supply system (RPSS), are expected. The future railway power demands are naturally not known for certain. The more remote the uncertain future, the greater the number of scenarios that have to be considered. Large numbers of scenarios make time-demanding simulations unattractive. The aim of this paper is to present a fast approximator that uses aggregated RPSS information. Since the electrical and mechanical relations governing an RPSS are quite intricate, an approximator based on neural networks (NN) is applied. This paper presents a design suggestion for an NN estimating the power and energy flows through each converter station, given RPSS data and levels of train traffic. Even if the future usage of the NN is investment planning, the modelling of such an approximator has a value in itself concerning the understanding of the relations between RPSS and train traffic.

  • 9.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Fast estimation of the relation between aggregated train power system information and the power and energy converted2008In: 2008 Australasian Universities Power Engineering Conference, AUPEC 2008, IEEE conference proceedings, 2008, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Transports on rail are increasing and major investments in the railway infrastructure, including the Railway Power Supply System (RPSS), are expected. The future railway power demands are naturally not known for certain. The more remote the uncertain future, the greater the number of scenarios that have to be considered. Large numbers of scenarios make time demanding simulations unattractive. The aim of this paper is to present a fast approximator that uses aggregated RPSS information. Since the electrical and mechanical relations governing an RPSS are quite intricate, an approximator based on Neural Networks (NN), is applied. This paper presents a design suggestion for an NN estimating the power and energy flows through each converter station, given RPSS data and levels of train traffic. Even if the future usage of the NN is investment planning, the modeling of such an approximator has a value in itself concerning the understanding of the relations between RPSS and train traffic.

  • 10.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Operation simulation of traction systems2008In: COMPUTERS IN RAILWAYS XI, 2008, Vol. 103, p. 283-292Conference paper (Refereed)
    Abstract [en]

    The objective of this paper is initially to present a basic modeling of the railway traction system. This model includes the basic technologies used today. The voltage dependencies of the maximal possible power consumption as well as the maximal velocity of the common Rc-locomotives are included. The latter is very crucial for the studies of time table sensitivity, which is of our immediate interest. Moreover, a method is presented that estimates the expected train delay time for a given feeding technology. The reference timetable assumes the same train and surrounding conditions, but no voltage drops. In the numerical example where the developed model is applied to a realistic test system, a set of possible amounts of railway traffic are treated as uncertainties. Mainly, the contributions of this paper are three: compiling and connecting already accepted models, the development of a method for numerical calculations using this model compilation, and an example to apply this model on.

  • 11.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Railway power supply investment decisions considering the voltage drops: Assuming the future traffic to be known2009In: 2009 15th International Conference on Intelligent System Applications to Power Systems, ISAP '09, 2009Conference paper (Other academic)
    Abstract [en]

    Transports on rail are increasing and major railway infrastructure investments are expected. An important part of this infrastructure is the railway power supply system. The future railway power demands are naturally not known for certain. The more distant the uncertain future is, the greater the number of scenarios that have to be considered. Large numbers of scenarios make time demanding simulations unattractive. Therefore a fast approximator that uses aggregated railway power supply system information has been developed. In particular the approximator studies the impacts of voltage drops on the traffic flow. The weaker the power system and the heavier the traffic, the greater the voltage drops. And the greater the voltage drops, the more limited the maximal attainable tractive force on the locomotives. That approximator is in this paper used as a constraint in the embryo of a railway power supply system investment planning program, where investment decisions are assumed to be realized immediately, and there is no preexisting power supply system to consider. The traffic forecasts are in this first approach assumed to be perfect. This stepwise creation of the planning program makes evaluating it easier. The basic investment planning model presented here constitutes the foundation for further improvements.

  • 12.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Traction Power System Capacity Limitations at Various Traffic Levels2011In: WCRR, World Congress on Railway Research, 2011Conference paper (Refereed)
    Abstract [en]

    The aim, and main contribution, of this paper is to propose a fine-tuned fast approximator, based on neural networks, that uses aggregated traction system information as inputs and outputs. This approximator can be used as an investment planning constraint in the optimization. It considers that there is a limit on the intensity of the train traffic, depending on the strength of the power system. In the numerical examples of this paper, the approximator inputs are the power system configuration, the distance between a connection from contact line to the public grid to another connection, and the average number of trains for that distance. The output is the maximal attainable average velocity of trains of a specific kind for the by the inputs described railway power system section. An alternative output – the traveling time is also presented. The main emphasis of this paper is on the example section, since the contribution of this paper is mainly to show on the improved simplicity and reality compliance. The applicative contribution is twofold, an improved TPSA as a planning/decision making program constraint, whereas it also can be used as a scientifically developed rule of thumb for a planner active in the field. The aim is not primarily to show that the idea works, or to motivate the principal idea, since that is done earlier. The approximator facilitates studies of many railway power system loading scenarios, combined with different power system configurations, for investment planning analysis. The approximator is based on neural networks. An additional value of the approximator is that it provides an understanding of the relations between power system configuration and train traffic performance.

  • 13.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Schütte, Thorsten
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    An electromechanical moving load fixed node position and fixed node number railway power supply systems optimization model2013In: Transportation Research Part C: Emerging Technologies, ISSN 0968-090X, E-ISSN 1879-2359, Vol. 30, p. 23-40Article in journal (Refereed)
    Abstract [en]

    This paper presents an optimization model for simulations of railway power supply systems. It includes detailed power systems modeling, train movements in discretized time considering running resistance and other mechanical constraints, and the voltage-drop-induced reduction of possible train tractive forces. The model has a fixed number of stationary power system nodes, which alleviates optimized operation overtime. The proposed model uses SOS2 (Special Ordered Sets of type 2) variables to distribute the train loads to the two most adjacent power system nodes available. The impacts of the number of power system nodes along the contact line and the discretized time step length on model accuracy and computation times are investigated. The program is implemented in GAMS. Experiences from various solver choices are also discussed. The train traveling times are minimized in the example. Other studies could e.g. consider energy consumption minimization. The numerical example is representative for a Swedish decentralized, rotary-converter fed railway power supply system. The proposed concept is however generalizable and could be applied for all kinds of moving load power system studies.

  • 14.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    HVDC feeding with OPF and unit commitment for electric railways2012In: Electrical Systems for Aircraft, Railway and Ship Propulsion (ESARS), 2012, IEEE , 2012, p. 6387481-Conference paper (Refereed)
    Abstract [en]

    In this paper a railway power system design based on an HVDC feeder is suggested. The converter stations between the public grid and the HVDC feeder can be sparsely distributed, in the range of 100 km or more, whereas the converters connecting the HVDC feeder to the catenary are distributed with a much closer spacing. The ratings of the catenary-connected ones can be lower than substation transformers or rotary converters, since the power conversion can be fully controlled. Simulations of the proposed solution show clear advantages regarding transmission losses and voltages compared to conventional systems, especially for cases with long catenary sections, and when there are substantial shares of regeneration from the trains.

  • 15.
    Abrahamsson, Lars
    et al.
    KTH, Superseded Departments, Electric Power Systems.
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Optimal PowerFlow (OPF) Model with Unified AC-DC Load Flow and Optimal Commitmentfor an AC-catenary Railway Power Supply System (RPSS) fed by aHigh Voltage DC (HVDC) transmission lineManuscript (preprint) (Other academic)
    Abstract [en]

    In this paper an alternative railway power systems design based on an HVDC feeder is studied. The HVDC feeder is connected to the catenary by converters. Such an HVDC line is also appropriate for DC-fed railways and AC-fed railways working at public frequency.

    A unit commitment optimal power flow model has been developed and is applied on a test system. In this paper, the model is presented in detail. The model, in the form of an MINLP program, uses unified AC-DC power flow to minimize the entire railway power system losses.

    Simulations of the proposed solution show clear advantages regarding transmission losses and voltages compared to conventional systems, especially for cases with long distances between feeding points to the catenary, and when there are substantial amounts of regeneration from the trains.

  • 16.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Optimal PowerFlow (OPF) Model with Unified AC-DC Load Flow and Optimal Commitmentfor an AC-catenary Railway Power Supply System (RPSS) fed by aHigh Voltage DC (HVDC) transmission line2012Article in journal (Refereed)
    Abstract [en]

    In this paper an alternative railway power systems design based on an HVDC feeder is studied. The HVDC feeder is connected to the catenary by converters. Such an HVDC line is also appropriate for DC-fed railways and AC-fed railways working at public frequency. A unit commitment optimal power flow model has been developed and is applied on a test system. In this paper, the model is presented in detail. The model, in the form of an MINLP program, uses unified AC-DC power flow to minimize the entire railway power system losses. Simulations of the proposed solution show clear advantages regarding transmission losses and voltages compared to conventional systems, especially for cases with long distances between feeding points to the catenary, and when there are substantial amounts of regeneration from the trains.

  • 17.
    Ackermann, Thomas
    et al.
    KTH, Superseded Departments.
    Andersson, G.
    Söder, Lennart
    KTH, Superseded Departments.
    Distributed generation: a definition2001In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 57, no 3, p. 195-204Article in journal (Refereed)
  • 18.
    Ackermann, Thomas
    et al.
    KTH, Superseded Departments.
    Andersson, G.
    Söder, Lennart
    KTH, Superseded Departments.
    Overview of government and market driven programs for the promotion of renewable power generation2001In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 22, no 1-3, p. 197-204Article in journal (Refereed)
  • 19.
    Ackermann, Thomas
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Andersson, Göran
    Söder, Lennart
    KTH, Superseded Departments.
    Electricity market regulations and their impact on distributed generation2000In: Electric Utility Deregulation and Restructuring and Power Technologies, 2000. Proceedings. DRPT 2000. International Conference on, 2000, p. 608-613Conference paper (Refereed)
    Abstract [en]

    Distributed generation (DG) has attracted a lot of attention recently and might become more important in future power generation systems. As different definitions are used worldwide, the paper briefly discusses the definition of DG. The future development of DG, however, will, to a not insignificant part, depend on the legal framework. As the legal framework can vary significantly for different competitive electricity markets, this paper briefly identifies and analyses some variations in the regulatory approaches, e.g. for power exchanges, balance services and ancillary services, in different countries. It also illustrates the influence of market regulations on the development of distributed power generation. Based on this analysis, it can be concluded that regulatory aspects might decisively influence the development of distributed power generation

  • 20.
    Ackermann, Thomas
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Centeno-Lopez, Eva
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Grid Issues for Electricity Production Based on Renewable Energy Sources in Spain, Portugal, Germany, and United Kingdom2008Book (Other academic)
  • 21.
    Ackermann, Thomas
    et al.
    KTH, Superseded Departments.
    Söder, Lennart
    KTH, Superseded Departments.
    An overview of wind energy-status 20022002In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 6, no 1-2, p. 67-128Article, review/survey (Refereed)
  • 22.
    Ackermann, Thomas
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    The Value of Wind Power2012In: Wind Power in Power Systems, John Wiley & Sons, 2012, 2, p. 131-155Chapter in book (Refereed)
    Abstract [en]

    The aim of the power plants in a power system is to supply the load in an economical, reliable and environmentally acceptable way. Different power plants can fulfil these requirements in different ways. In order to select the right sources it is important to compare the value of the different sources using an objective approach. The aim of this chapter is describe the different needs of a power system and how these needs can be met with wind power, that is, the value of wind power in a certain system. The values are operating cost value, capacity value, control value, grid loss reduction value and grid investment value. The values can be calculated for different types of power plants, they can be both positive and negative, and they can be calculated both as a physical cost value and a market value.

  • 23.
    Ackermann, Thomas
    et al.
    KTH, Superseded Departments.
    Söder, Lennart
    KTH, Superseded Departments.
    Wind energy technology and current status: a review2000In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 4, no 4, p. 315-374Article, review/survey (Refereed)
  • 24. Ali, Muhammad
    et al.
    Matevosyan, Julija
    Milanovic, J. V.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Effect of wake consideration on estimated costs of wind energy curtailments2009In: 8th International Workshop on Large Scale Integration of Wind Power into Power Systems as well as on Transmission Networks of Offshore Wind Farms, 14-15 Oct. 2009 Bremen, 2009Conference paper (Refereed)
    Abstract [en]

    Measures such as energy curtailment or gridreinforcement are required to integrate the upcoming windgeneration in parts of the power system with existing transmissionbottlenecks. In order to choose between these two measurespotential wind energy curtailments and its costs need to becarefully evaluated. The paper analyzes the effect of wakeconsideration on the overall energy curtailment cost. For thispurpose detailed wake model was used taking into account partialand multiple shading of wind turbines. It is shown that not onlywind speed but also wind direction of the incoming wind affects theamount of energy produced by a wind farm. A comparison ofcurtailment cost with cost for grid reinforcement in areas withlimited transmission capacity was carried out with and withoutconsideration of wake effect. The effect on curtailment cost due toavailability of wind turbines is also investigated both with andwithout wake effect consideration. The results have proven thatwith consideration of wake effect and availability potential windenergy curtailments are reduced and hence curtailment costs arelowered, making curtailment a cheaper option than gridreinforcement. The method illustrated in the paper can be used inpre-feasibility study to compare the costs of wind curtailment withthe costs of grid reinforcement in order to make sound economicdecision. The method can also be applied in wind farm energy yield estimation.

  • 25.
    Alvehag, Karin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    A Reliability Model for Distribution Systems Incorporating Seasonal Variations in Severe Weather2011In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 26, no 2, p. 910-919Article in journal (Refereed)
    Abstract [en]

    In distribution system planning and operation, accurate assessment of reliability performance is essential for making informed decisions. Also, performance-based regulation, accompanied by quality regulation, increases the need to understand and quantify differences in reliability performance between networks. Distribution system reliability performance indices exhibit stochastic behavior due to the impact of severe weather. In this paper, a new reliability model is presented which incorporates the stochastic nature of the severe weather intensity and duration to model variations in failure rate and restoration time. The model considers the impact of high winds and lightning and can be expanded to account for more types of severe weather. Furthermore, the modeling approach considers when severe weather is likely to occur during the year by using a nonhomogeneous Poisson process (NHPP). The proposed model is validated and applied to a test system to estimate reliability indices. Results show that the stochasticity in weather has a great impact on the variance in the reliability indices.

  • 26.
    Alvehag, Karin
    et al.
    KTH, School of Electrical Engineering (EES).
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    A stochastic approach for modeling residential interruption costs2008In: 16th Power Systems Computation Conference, PSCC 2008, Power Systems Computation Conference (PSCC) , 2008Conference paper (Refereed)
    Abstract [en]

    In power system planning and operation, accurate assessment of reliability worth is essential for making informed decisions. The accuracy of the reliability worth estimation is directly affected by the interruption cost model used in the analysis. Residential interruption costs vary with season, day of week and time of day, and can be difficult to handle because of their intangible characteristics. This paper develops a cost model for residential customers that includes the timing of the outage by modeling the underlying factors that give rise to the temporal variations in residential interruption costs. By considering the stochastic nature of the underlying factors, as for example outdoor temperature, the proposed model makes it possible to estimate the costs for an event that is extreme in other senses than having a long duration. Time sequential Monte Carlo simulations were applied to a test system in order to assess reliability worth. The results show that the commonly used customer damage function overestimates the reliability worth. By accounting for the timing of the outages a more realistic estimation of the interruption costs can be obtained.

  • 27.
    Alvehag, Karin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    A Stochastic Weather Dependent Reliability Model for Distribution Systems2008In: 2008 10TH INTERNATIONAL CONFERENCE ON PROBABILISTIC METHODS APPLIED TO POWER SYSTEMS, New York, USA: IEEE , 2008, p. 243-250Conference paper (Refereed)
    Abstract [en]

    In power system planning and operation, accurate assessment of reliability worth is essential for making informed decisions. One common simplification when modeling power system reliability is assuming constant failure rates and non time-varying restoration times. However, historical outages show differently; failure rates and restoration times for especially overhead lines are dependent upon time-varying factors as, for instance, weather conditions. When modeling this time dependence a two or three-state weather model is often used. The reliability model proposed in this paper does in contrast use the stochastic nature of the severe weather intensity and duration to model variations in failure rate and restoration time. Further, the model also considers when severe weather is likely to occur during the year by using a non-homogeneous Poisson process (NHPP). A time-sequential Monte Carlo technique is applied to a radial distribution system. By combining the proposed reliability model with a time-dependent interruption cost model, the effect of the inclusion of time-varying failure rates and restoration times is investigated and found to be of importance when assessing reliability worth.

  • 28.
    Alvehag, Karin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    An activity-based interruption cost model for households to be used in cost-benefit analysis2007In: Proceedings of Power Tech 2007, 2007, p. 1611-1616Conference paper (Refereed)
    Abstract [en]

    This paper develops an interruption cost model for households that, as well as outage duration uses activity patterns, outdoor temperature and daylight to describe the impact of different electrical power outages. For households the interruption costs usually measure the inconvenience associated with interrupted activities and uncomfortable indoor temperature due to the outage. Further, the model also captures the large variations in interruption costs for identical outages among households. The model is applied to a test system, and using a Monte Carlo technique the total interruption cost is studied. The results imply that both the time of occurrence and the distributed nature of residential interruption costs have a significant impact on ECOST.

  • 29.
    Alvehag, Karin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Comparison of cost models for estimating customer interruption costs2012In: Proceedings in Probabilistic Methods Applied to Power Systems (PMAPS), 2012Conference paper (Refereed)
    Abstract [en]

    Customer interruption costs are functions of many different factors such as interruption duration, timing and customer sector. Various cost models with different number of outage and customer characteristics included have been proposed during the years. This paper compares the customer interruption cost assessments of seven different cost models in a case study.Time sequential Monte Carlo simulations are used to simulate the customers’ benefits of increased reliability in a test system. The investigated cost models’ estimations of the Expected Customer Interruption Cost (ECOST) are compared and used in a costbenefitanalysis. Results show that the ECOST results are so different that the cost model choice affects the outcome of the cost-benefit analysis. Only when using some of the cost models the investigated reinvestments are estimated to be socioeconomically beneficial.

  • 30.
    Alvehag, Karin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Considering extreme outage events in cost-benefit analysis of distribution systems2008In: Proceedings of Australasian Universities Power Engineering Conference (AUPEC), 2008Conference paper (Refereed)
    Abstract [en]

    To find an acceptable level of reliability in distribution systems, cost-benefit analysis using customer interruption costs can be applied. In a case study of a test distribution system, investment in cables instead of overhead lines, aimed to increase reliability, is investigated. In addition to considering average values of reliability indices, tools for risk analysis in the financial industry, value-at-risk (VaR) and conditional value-at-risk (CVaR), are also used for the evaluation. Applying these tools allows for extreme events to be given more weight in the investment decision-making process. Even though these kind of events are very infrequent, the consequences are devastating and extreme cases should be included in cost-benefit analysis. By the help of VaR and CVaR the case study shows that cables can cause higher customer interruption costs for some load points in the system during extreme years.

  • 31.
    Alvehag, Karin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Evaluation of quality regulation incentives for distribution system reliability investments2011In: Utilities Policy, ISSN 0957-1787, E-ISSN 1878-4356Article in journal (Other academic)
    Abstract [en]

    Designing a quality regulation that results in an adequate level of reliability in a distribution system is indeed a challenging task for the regulator. If the regulation is not well designed a socioeconomically beneficial reinvestment project is not beneficial for the DSO, and hence is not selected. This paper proposes an evaluation method for quality regulation designs. The proposed method is applied in a case study to evaluate what incentives for investments in distribution system reliability two different quality regulation designs give. One design is similar to the Swedish quality regulation that will apply from 2012 and the other design is similar to the current Norwegian quality regulation. The effect on network investment decisions when the two designs are modified to give optimal incentives for reliability on system level is also investigated. The case study result shows that even though the quality regulation on system level is designed to give incentives for socioeconomically beneficial investments, these investments may not be beneficial for the regulated DSO if the reward/penalty on the system level is capped too low.

  • 32.
    Alvehag, Karin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Financial risk assessment for distribution system operators regulated by quality regulation2010In: Proceedings of Probabilistic Methods Applied to Power Systems (PMAPS), 2010Conference paper (Refereed)
    Abstract [en]

    In the reregulated electricity market, performance-based regulations accompanied by quality regulations are gaining ground. The quality regulation results in new financial risks for the distribution system operators (DSOs) which calls for risk assessment methods that can simulate what costs a certain regulation implies for the DSO. When, for example, guaranteed standards for worst-served customers is combined with a reward and penalty scheme the methods must be able to predict both customer and system reliability. This paper presents a new risk assessment methodology based on time sequential Monte Carlo simulations that can handle both of these levels of reliability to simulate the total regulation cost due to an arbitrary quality regulation. Since most quality regulations are corrected ex-post for each year, variations in yearly reliability can cause large variations in the total regulation cost. Instead of only considering the average total regulation cost the developed methodology uses risk tools from the financial industry to also measure the costs of more extreme years. Doing so gives the DSOs a better understanding of the financial risks they are exposed to. The developed risk assessment methodology is used to evaluate different investment alternatives in a case study.

  • 33.
    Alvehag, Karin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Quality regulation impact on investment decisions in distribution system reliability2012In: 9th International Conference on the European Energy Market, EEM 12, IEEE , 2012, p. 6254646-Conference paper (Refereed)
    Abstract [en]

    Performance-based regulations accompanied by quality regulations are gaining ground. Quality regulations imply new financial risks for the distribution system operator (DSO). In fact, the development of the regulatory model has been identified as a key factor in operations planning for a DSO. Lifetimes of distribution system components are very long and how the quality regulation might develop in the future is unknown. This paper develops a method - the regulation impact method - that can be used to investigate how changes in the quality regulation parameters affect the economic performance of an investment strategy. The proposed regulation impact method is based on net present value calculations of the total reliability cost. The new method is applied to the current Swedish quality regulation in a case study. In the case study, possible future parameter changes and their effect on the DSO's financial risk when adopting different investment strategies are investigated. With the new method it is possible to analyze how robust an investment strategy is to changes in quality regulation design.

  • 34.
    Alvehag, Karin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Risk-based method for distribution system reliability investment decisions under performance-based regulation2011In: IET Generation, Transmission & Distribution, ISSN 1751-8687, Vol. 5, no 10, p. 1062-1072Article in journal (Refereed)
    Abstract [en]

    In the reregulated electricity market there is a growing interest in performance-based regulation accompanied by quality regulation for electric distribution networks. This paper develops a new risk-based method for reliability investment decisions when the distribution system operator (DSO) is exposed to financial risks defined by a quality regulation. As quality regulation design becomes more complex, more detailed risk management methods are needed in order to adequately capture the financial risk the DSO is exposed to. The proposed method applies a Monte Carlo simulation technique in order to assess the risks of the considered reinvestment projects. By using the proposed method the impacts that different risk strategies (risk-neutral/risk-averse) and risk models (non-time-varying/time-varying) have on which reinvestment project is selected is investigated in a case study. This is investigated for two different quality regulation designs. The result show that primarily the quality regulation design but also the risk model formulation and risk strategy have a major impact on which reinvestment project is selected.

  • 35.
    Alvehag, Karin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    The impact of risk modeling accuracy on cost-benefit analysis of distribution system reliability2011In: Proceedings of the 17th Power System Computational Conference (PSCC), Power Systems Computation Conference ( PSCC ) , 2011Conference paper (Refereed)
    Abstract [en]

    This paper develops a new risk-based cost-benefit analysis method for distribution system reliability applications. In the conventional cost-benefit analysis, decisions are based on expected values which correspond to assuming that society is risk-neutral. Furthermore, input variables are assumed to be uncorrelated. In contrast to previous work this paper incorporates risk into the analysis by using time-sequential Monte Carlo simulations. By using the proposed method the impact that different risk strategies (risk-neutral/risk-averse) and risk models (non-time-varying/time-varying) have on the result of a cost-benefit analysis is investigated in a case study. Results show that when incorporating time-dependent failure rates, restoration times, customer interruption costs, and loads (correlated input data) a different reinvestment project is selected compared to when these time dependencies are ignored. This result holds regardless if decisions are made based on a risk-averse or a risk-neutral strategy.

  • 36.
    Amelin, M.
    et al.
    KTH, Superseded Departments.
    Söder, L.
    KTH, Superseded Departments.
    On Monte Carlo simulation of electricity markets with uncertainties in precipitation and load forecasts2001In: Power Tech Proceedings, 2001 IEEE Porto, 2001, Vol. 1, p. 6-1Conference paper (Refereed)
    Abstract [en]

    Long-term planning of a power system requires that the electricity market can be simulated. One important aspect that should be simulated is that the owners of hydro power plants with reservoirs (generally referred to as dispatchable hydro power) are forced to base their scheduling on uncertain forecasts on precipitation and load. It is inevitable that this lack of perfect information has an impact on the operation costs and reliability of the system. Hence, a simulation of an electricity market should include this property of dispatchable hydro, power. This paper shows how the consequences of hydro power planning based on uncertain forecasts can be incorporated in a Monte Carlo model by using random water value errors

  • 37.
    Amelin, Mikael
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Knazkins, Valerijs
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Estimation of maximum power consumption in the grid area of Fortum, Stockholm2005Conference paper (Refereed)
  • 38.
    Amelin, Mikael
    et al.
    KTH, Superseded Departments.
    Söder, Lennart
    KTH, Superseded Departments.
    A fast multi-area economic hydro-thermal power system model1999In: NAPS, 1999Conference paper (Refereed)
  • 39.
    Amelin, Mikael
    et al.
    KTH, Superseded Departments.
    Söder, Lennart
    KTH, Superseded Departments.
    Cost estimations for power sources in rural electrification schemes1999In: ICEET, 1999, p. 98-105Conference paper (Refereed)
  • 40.
    Amelin, Mikael
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Taking Credit: The Impact of Wind Power on Supply Adequacy-Experience from the Swedish Market2010In: IEEE POWER ENERGY MAG, ISSN 1540-7977, Vol. 8, no 5, p. 47-52Article in journal (Refereed)
    Abstract [en]

    This article presents some general concepts about capacity credit values, which are illustrated by theoretical examples as well as practical experience from the Swedish electricity market. The capacity credit of a wind generating unit (or a block of generating units) represents the contribution of the unit to the supply adequacy of the system. The capacity credit of a power plant is an abstract quantity based on probability calculations and requires knowledge of the probability distributions for available generation capacity and load. To secure the reliability of supply, the Swedish system operator was given the responsibility to purchase annual contracts for a "power reserve".

  • 41.
    Amelin, Mikael
    et al.
    KTH, Superseded Departments.
    Söder, Lennart
    KTH, Superseded Departments.
    The Strata Tree: A Useful Tool for Simulation of Electricity Markets2002In: PMAPS 2002, Naples, Italy, 2002Conference paper (Refereed)
  • 42. Bird, Lori
    et al.
    Lew, Debra
    Milligan, Michael
    Carlini, E. Maria
    Estanqueiro, Ana
    Flynn, Damian
    Gomez-Lazaro, Emilio
    Holttinen, Hannele
    Menemenlis, Nickie
    Orths, Antje
    Eriksen, Peter Borre
    Smith, J. Charles
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric power and energy systems.
    Sorensen, Poul
    Altiparmakis, Argyrios
    Yasuda, Yoh
    Miller, John
    Wind and solar energy curtailment: A review of international experience2016In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 65, p. 577-586Article, review/survey (Refereed)
    Abstract [en]

    Greater penetrations of variable renewable generation on some electric grids have resulted in increased levels of curtailment in recent years. Studies of renewable energy grid integration have found that curtailment levels may grow as the penetration of wind and solar energy generation increases. This paper reviews international experience with curtailment of wind and solar energy on bulk power systems in recent years, with a focus on eleven countries in Europe, North America, and Asia. It examines levels of curtailment, the causes of curtailment, curtailment methods and use of market based dispatch, as well as operational, institutional, and other changes that are being made to reduce renewable energy curtailment.

  • 43.
    Brolin, Magnus
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Estimation of hydropower system equivalentsIn: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679Article in journal (Refereed)
  • 44. Brostrom, Elin
    et al.
    Alvehag, Karin
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Calculation of Residential Interruption Costs caused by Adverse Weather using Monte Carlo Methods2008Conference paper (Refereed)
    Abstract [en]

    The main contribution of this paper is a residential interruption cost model that aims to capture households? inconvenience due to power outages caused by adverse weather. Commonly, the customer interruption cost is modelled to be a function of the outage duration. However, other factors also affect the interruption cost. For example, the cost for a household increases if public services also are affected by the outage. The number of public services that a household cannot use is often correlated to the total number of customers affected by the outage. This relationship is explored in the proposed cost model in order to consider the impact of widespread and long-lasting outages caused by, for example, adverse weather. An adverse weather model gives wind and ice loads. These loads in combination with a vulnerability model for components in a transmission system and a restoration time model give the outage duration. In a case study, the impact of adverse weather on a meshed test system with residential customers is studied using Monte Carlo simulations. It is concluded that more surveys investigating the increased costs for households due to long-lasting and widespread outages are needed.

  • 45. Brostrom, Elin
    et al.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    ON TRANSMISSION RESTORATION EVALUATION AFTER ICE STORMS USING MONTE CARLO TECHNIQUES2006In: CRIS 2006 in Alexandria, USA, 2006Conference paper (Refereed)
  • 46.
    Broström, Elin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ahlberg, Jesper
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Modelling of ice storms and their impact applied to a part of the Swedish Transmission network2007In: 2007 IEEE LAUSANNE POWERTECH, VOLS 1-5, NEW YORK: IEEE , 2007, p. 1593-1598Conference paper (Refereed)
    Abstract [en]

    In this paper a technique of modelling severe weather for power system reliability calculations is developed. The model is based on geographically moving winds and precipitation and is suitable for transmission network. A scenario represents a weather situation with given parameters. Besides the weather model a stochastic vulnerability model for the components is required for each scenario that connects the risk of failure to the weather situation. In order to mitigate severe consequences of future ice storms in an efficient way it is essential to be able to estimate the consequences based on assumptions of the technical system and the severity of possible storms. It is assumed that the probability of a failure due to a given weather depends on load functions for wind and ice together with the component vulnerability model which is based on the design of the components. The wind load is direct and the ice load is given by a known ice accretion model. Conclusions about the reliability of the studied lines under ice storms are presented as well as a graph of the critical conditions for the studied lines with ice thickness on the x-axis and gust wind on the y-axis. The numerical examples show the impact of different weather situations on a part of the Swedish Transmission network using data both from real weather situations in Sweden and the weather model.

  • 47.
    Broström, Elin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ice Storm Impact on Power System Reliability2007In: 12 th International Workshop on Atmospheric Icing on Structures (IWAIS 2007), Yokohama, Japan, 2007Conference paper (Refereed)
    Abstract [en]

    Ice storms are freezing rain that coats everything in ice, often in combination with heavy wind. The aim of the methods developed in this paper is to estimate the risk of failure due to ice storms. This includes a severe weather model, a new method for choosing weather parameters and a component vulnerability model. The weather model is based on how a low pressure behaves and consists of functions that describe the wind and precipitation parts of the weather. An ice accretion model is used to estimate the ice loads. The method for choosing weather parameters is useful for Monte Carlo simulations where the effects of many different weather situations are studied. In the stochastic component vulnerability model the failure rates are based on how an increased ice load influences the critical wind. Swedish weather conditions and transmission components are used in the case study and the loads and their impact are estimated for many different weather situations.

  • 48.
    Broström, Elin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Modelling of Ice Storms for Power Transmission Reliability Calculations2005In: Proceedings 15th Power Systems Computation Conference PSCC2005, Liège, Belgium: PSCC , 2005Conference paper (Refereed)
    Abstract [en]

    This paper describes a new technique of modelling adverse weather for power system reliability calculations. The reliability calculation is based on a Monte-Carlo technique where each scenario represents a certain weather situation with certain parameters. For each scenario a model of the adverse weather is needed and in this paper a model based on geographically moving winds and ice storms is developed. The benefit of this is that it is possible to estimatethe time difference between mean times to failure indifferent lines, not only the outage risk. For each scenario a weather impact model is also required, where the risk of transmission outage is connected to the weather situation.The here-developed model connects the direct wind impact with the integrating impact from the ice storm. The developed method is applied to a numerical example.

  • 49.
    Calvillo, Christian F.
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Czechowski, Karolina
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Sanchez-Miralles, Alvaro
    Villar, Jose
    Vehicle-to-Grid Profitability Considering EV Battery Degradation2016In: 2016 IEEE PES ASIA-PACIFIC POWER AND ENERGY ENGINEERING CONFERENCE (APPEEC), IEEE conference proceedings, 2016, p. 310-314Conference paper (Refereed)
    Abstract [en]

    The electrification of the transportation sector is likely to contribute reducing the global dependency on oil and is expected to drive investments to renewable and intermittent energy sources, by taking advantage of it energy storage capacity. In order to facilitate the EV integration to the grid, and to take advantage of the battery storage and the Vehicle-to-Grid (V2G) scheme, smart charging strategies will be required. However, these strategies rarely consider all relevant costs, such as battery degradation. This work analyses the profitability of bidirectional energy transfer, i.e. the possibility of using aggregated EV batteries as storage for energy which can be injected back to the grid, by considering battery degradation as a cost included in the proposed strategy. A mixed integer linear problem (MILP) for minimizing energy costs and battery ageing costs for EV owners is formulated. The battery degradation due to charging and discharging in the V2G scheme is accounted for in the model used. Two case studies of overnight charging of EVs in Sweden and in Spain are proposed. Results show that given current energy prices and battery costs, V2G is not profitable for EV owners, but if battery prices decrease as expected, the V2G will be present in the medium term.

  • 50. Carvajal-Carreño, W.
    et al.
    García, A. P. C.
    Fernández-Cardador, A.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Efficient driving algorithms for non-disturbed and disturbed trains with the CBTC signalling system2015In: 2015 International Conference on Models and Technologies for Intelligent Transportation Systems, MT-ITS 2015, IEEE conference proceedings, 2015, p. 418-425Conference paper (Refereed)
    Abstract [en]

    Trains with automatic train operation (ATO)-communication-based train control (CBTC) have the capability to follow a predesigned or calculated speed profile and also can change the control command at any point of the route. This paper presents the advances in the research about designing driving profiles for ATO trains under the CBTC signalling system. Two algorithms based on simulation are proposed, one for the offline design of single undisturbed train trajectories and the other is a real-time algorithm to save energy when there is interaction between two consecutive trains. These algorithms were tested using a simulation-based metaheuristic optimization for the first case and a two-train tracking simulator for the second. The results showed that energy savings could be attained using the proposed algorithms maintaining the required safety and passenger comfort levels in the railway operation.

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