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  • 251.
    Samadi, Afshin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Shayesteh, Ebrahim
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Optimal Coordination of Q(P) Characteristics for PV Systems in Distribution Grids for Minimizing Reactive Power Consumption2014In: AORC Technical Meeting 2014, 2014Conference paper (Refereed)
  • 252.
    Samadi, Afshin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Shayesteh, Ebrahim
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Eriksson, Robert
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Static Equivalent of Distribution Grids with High Penetration of PV SystemsManuscript (preprint) (Other academic)
  • 253.
    Samadi, Afshin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Shayesteh, Ebrahim
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Eriksson, Robert
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Static Equivalent of Distribution Grids With High Penetration of PV Systems2015In: IEEE Transactions on Smart Grid, ISSN 1949-3053, E-ISSN 1949-3061, Vol. 6, no 4, p. 1763-1774Article in journal (Refereed)
    Abstract [en]

    High penetrations of photovoltaic (PV) systems within load pockets in distribution grids have changed pure consumers to prosumers. This can cause technical challenges in distribution and transmission grids, such as overvoltage and reverse power flow. Embedding voltage support schemes into PVs, such as standard cos phi(P) characteristic proposed by the German grid codes, may cause more changes in the steady-state behavior of distribution grids and, in turn, the transmission side. Accordingly, it is important to properly model active distribution grids to analyze the system impacts of these changes to plan and operate future smart power grids. However, due to the high dimension of distribution grids, considering a detailed distribution grid to study the transmission side or a fraction of the distribution grid is either cumbersome or impractical. Therefore, it is required to develop a reasonable equivalent that can fairly capture the dominant behavior of the distribution grids. The aim of this paper is to use gray-box modeling concepts to develop a static equivalent of distribution grids comprising a large number of PV systems embedded with voltage support schemes. In the proposed model, the PV systems are aggregated as a separate entity, and not as a negative load, which is traditionally done. The results demonstrate the superior quality of the proposed model compared with the model with PV systems as the negative load.

  • 254.
    Scharff, Richard
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Egerer, Jonas
    Workgroup for Infrastructure Policy, Berlin University of Technology, Berlin, Germany; Department of Energy, Transportation, Environment, German Institute for Economic Research (DIW Berlin), Berlin, Germany.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    A description of the operative decision-making process of a power generating company on the Nordic electricity market2014In: Energy Systems, Springer Verlag, ISSN 1868-3967, E-ISSN 1868-3975, Vol. 5, no 2, p. 349-369Article in journal (Refereed)
    Abstract [en]

    In a liberalised electricity market, power generating companies face various trading possibilities. In addition, they have to take scheduling decisions. Both kinds of decisions are affected by uncertainties, e.g. power plant outages, uncertain market prices for electricity or imperfect wind power forecasts. This paper presents an overview of the decision-making process of a power generating company on the Nordic electricity market and illustrates how uncertainties affect this process. As a power generating company’s return on investment arises - at least partly - from its trading and scheduling decisions, it is important to optimise those decisions. Therefore, selected optimisation models are listed in a condensed manner. The paper also includes a both detailed and comprehensive description of the market design in the Nordic countries.

  • 255. Sendegeya, A.
    et al.
    Lugujjo, E.
    Da Silva, I. P.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Amelin, Mikael
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Application of Price Sensitivity Measurement Method to Assess the Acceptance of Electricity Tariffs2009In: 2009 AFRICON, VOLS 1 AND 2, NEW YORK: IEEE , 2009, p. 158-162Conference paper (Refereed)
    Abstract [en]

    Understanding the way customers respond to price changes is vital for any business. The price sensitivity measurement (PSM) analysis is widely used by marketers and researchers to assess customers' price sensitivity. This paper applies the concept of PSM analysis to assess electricity consumers' tariff perceptions, attitude to tariff changes and generally acceptance of tariffs. The method is tested using field survey data obtained from low demand consumers (households and small businesses) in urban and rural areas of Uganda after tariff increase. The results indicate that the new tariff approved by the regulator is within the range of tariffs possibly expected and likely to be accepted by consumers, but higher than the tariffs which consumers consider to be worthy. Also it is realized from the results that in Uganda, tariff expectations of rural consumers are different from the urban counterparts, the former expect lower tariffs with high degree of price sensitivity. Households show a higher degree of price sensitivity than commercial consumers. Conclusively, the information obtained from PSM can be used by utilities to make a preliminary assessment of consumers' expectations and/or acceptance levels of a certain range of tariffs during tariff review.

  • 256. Sendegeya, Al-Mas
    et al.
    Amelin, Mikael
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Lugujjo, E.
    Da Silva, I. P.
    Altruistic versus profit maximising system operators of rural power systems2007In: 2007 IEEE POWER ENGINEERING SOCIETY CONFERENCE AND EXPOSITION IN AFRICA, VOLS 1 AND 2, NEW YORK: IEEE , 2007, p. 157-163Conference paper (Refereed)
    Abstract [en]

    This paper presents a methodology using Monte Carlo Simulation for analysing and compare the impact of two types of monopolistic rural power system operators (altruistic and profit maximising operators) on the probability distribution of tariff levels and reliability of the system. The market has price sensitive consumers. The developed model has been demonstrated on two power systems: only diesel genset and a wind-diesel hybrid system showing the impact of the generation costs and capacity of generation from wind on the tariff levels, expected profit and reliability.

  • 257. Sendegeya, Al-Mas
    et al.
    Amelin, Mikael
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Lugujjo, E.
    Da Silva, I. P.
    Consumer price sensitivity impact on tariff level in isolated rural power systems2006In: PROCEEDINGS OF THE 41ST INTERNATIONAL UNIVERSITIES POWER ENGINEERING CONFERENCE, VOLS 1 AND 2, NEW YORK: IEEE , 2006, p. 1-5Conference paper (Refereed)
    Abstract [en]

    Uncertainties in demand and supply are among the challenging aspects when planning isolated power systems as well as one of the reasons why plans are not as optimal as expected. Most consumers in these areas are price sensitive and their sensitivity may change over time. To be able to estimate the outcome of certain investments in such markets with uncertainties, it is important to have a realistic modelling of the market. The modelling of markets can be performed using probability methods. This paper presents a methodology using Monte Carlo simulation to analyse the impact of price sensitivity of consumers on the probability distribution of tariff as a basis for making decision during planning. The stochastic nature of the market due to uncertainties in sensitivity, demand and supply has been modelled explicitly by random variables of given distributions. The developed model has been demonstrated on a small test system. The results include probability distributions showing the impact on the tariff levels for various system configurations.

  • 258.
    Shayesteh, Ebrahim
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Amelin, Mikael
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Area equivalents for spinning reserve determination in interconnected power systems2015In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 88, p. 907-916Article in journal (Refereed)
    Abstract [en]

    The current study applies the cost-benefit analysis method to determine the optimal amount of spinning reserve. However, it is difficult for the method to handle large size problem, like large interconnected power systems with several control areas, directly. Therefore, this paper proposes a power system equivalent for the original system to reduce the complexity of the original problem. According to the proposed algorithm, each area of the system is first modeled by an equivalent system, obtained by the RE! (radial - equivalent - independent) method, and an interconnected REI equivalent is obtained for the original interconnected system. A cost-benefit analysis is then performed to determine the spinning reserve requirements of both the original and equivalent systems. The cost-benefit algorithm considers either the SCUC (security constrained unit commitment) or the SCED (security constrained economic dispatch). Finally, the proposed interconnected REI equivalent is evaluated by comparing the spinning reserve of each control area in the original system with that in the equivalent system. Numerical studies are performed on two IEEE test systems. (C) 2015 Elsevier Ltd. All rights reserved.

  • 259.
    Shayesteh, Ebrahim
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Amelin, Mikael
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Multi-Station Equivalents for Short-Term Hydropower Scheduling2016In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 31, no 6, p. 4616-4625Article in journal (Refereed)
    Abstract [en]

    Hydropower scheduling in day-ahead electricity markets is complex due to uncertainty in the electricity price. Internal cascade dependency of hydro power plants can also increase this complexity. One way to overcome this complexity is to replace the original hydropower system by an equivalent system, which provides simulation results sufficiently close to the ones of the original system. This paper presents a method to obtain multi-station equivalent models using a bilevel optimization problem, where the objective is to minimize the difference in outcomes between the original and the equivalent models. This bilevel problem is then transformed into a single-level optimization problem that can be solved using standard optimization techniques. Finally, the errors between the simulation results of the original and equivalent hydropower models are computed and analyzed for a Swedish system to show the accuracy of different multi-station equivalents.

  • 260.
    Shayesteh, Ebrahim
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Amelin, Mikael
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Power system equivalents for spinning reserve determination in multi-area power systemsManuscript (preprint) (Other academic)
  • 261.
    Shayesteh, Ebrahim
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Hamon, Camille
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Amelin, Mikael
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    REI method for multi-area modeling of power systems2014In: International Journal of Electrical Power & Energy Systems, ISSN 0142-0615, E-ISSN 1879-3517, Vol. 60, p. 283-292Article in journal (Refereed)
    Abstract [en]

    Interconnections between different electricity markets and high penetration levels of wind power have resulted in an increase in the size of power systems with higher levels of uncertainties. This paper presents an algorithm for bulk power system simulations with large wind power penetrations, based on multi-area modeling with transmission constraints. The present study differs from previous multi-area studies by taking into account the capacity of intra-area lines during the simulations, which leads to more accurate results. The method that we introduce consists of three steps. First, a power system with high wind power penetration is divided into several areas using a practical measure, admittance matrix. Second, the internal system of each area is replaced with a smaller system, to which an improved version of the REI (Radial, Equivalent, and Independent) method is developed and applied. Finally, the technical properties of the reduced power system (such as voltage limits and transmission capacities) are tuned by adjusting optimization, in a way that the simulation results of the reduced power system are comparable with those of the original system. The IEEE 30-bus and IEEE 118-bus test systems are used to show the efficiency of the proposed algorithm.

  • 262.
    Shayesteh, Ebrahim
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Hobbs, B. F.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Amelin, Mikael
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    ATC-Based System Reduction for Planning Power Systems With Correlated Wind and Loads2015In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 30, no 1, p. 429-438Article in journal (Refereed)
    Abstract [en]

    Simulations of production costs, flows, and prices are crucial inputs to generation and transmission planning studies. To calculate average system performance for many alternatives over long time periods, it is necessary to simulate large numbers of hourly combinations of renewable production and loads across large regions. As this is usually impractical for full network representations of such systems, aggregation of buses and lines is desirable. We propose an improved aggregation method for creating multi-area representations of power systems that yields more accurate estimates of the quantities required by planners. The method is based on partitioning the original large system into smaller areas and making a reduced equivalent for each area. The partitioning is based on available transfer capability (ATC) between each pair of network buses. Because ATC depends on net load conditions, separate partitions are defined for subsets of similar load and wind conditions, significantly enhancing the accuracy of optimal power flow solutions. We test the method on the IEEE 118-bus test system and the Polish 3120-bus system considering 150 load/wind scenarios, comparing the results to those of admittance-based partitioning methods. Accuracy is improved with only a negligible increase in simulation time.

  • 263.
    Simab, Mohsen
    et al.
    Tarbiat Modares University, Tehran.
    Alvehag, Karin
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Haghifam, Mahmoud-Reza
    Tarbiat Modares University, Tehran.
    Designing reward and penalty scheme in performance-based regulation for electric distribution companies2012In: IET Generation, Transmission & Distribution, ISSN 1751-8687, E-ISSN 1751-8695, Vol. 6, no 9, p. 893-901Article in journal (Refereed)
    Abstract [en]

    A reward and penalty scheme (RPS) in performance-based regulation (PBR) penalises companies for providing poor reliability and rewards them for providing good reliability. In this study, an algorithm is presented to obtain the parameters of RPS for each electric company by using data envelopment analysis (DEA) and fuzzy c-means clustering (FCM). This algorithm is based on system average interruption duration index (SAIDI) and customers' value of interruptions. FCM algorithm is applied to find similar distribution companies and cluster companies into different clusters. The best performer in each cluster is utilised as a benchmark for other companies and DEA is used to set a quality target for each electric distribution company. The performance of the proposed algorithm is demonstrated in a case study to design RPS for Iranian electricity distribution companies. The results of the algorithm include DEA efficiency score, parameters of RPS and financial risk assessment.

  • 264. Singh, J. G.
    et al.
    Singh, S. N.
    Srivastava, S. C.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Power system security enhancement by optimal placement of UPFC2010In: Proceedings of the 4th IASTED Asian Conference on Power and Energy Systems, AsiaPES 2010, 2010, p. 228-235Conference paper (Refereed)
    Abstract [en]

    In this paper, a new approach to enhance power system security has been suggested by optimal placement of UPFC based on sensitivity indices. The sensitivity indices have been obtained, using ac power flow method, in terms of change in line real power flow Performance Index (PI) with respect to the change in the UPFC parameters viz., injected voltage magnitude and phase angle. In order to validate the accuracy of the proposed method, an Optimal Power Flow (OPF) formulation has been used to measure the security in terms of minimum PI values, with placement of UPFC based on the proposed sensitivity factors. The results have also been compared with existing dc power flow based method on IEEE 30-bus and practical NREB 246-bus Indian systems. Test results obtained on the two systems show that the new sensitivity factors could be effectively used for the optimal placement of UPFC in order to enhance the static security of the power system.

  • 265. Singh, Jai Govind
    et al.
    Thakurta, Priyanko Guha
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric power and energy systems.
    Load curtailment minimization by optimal placements of SVC/STATCOM2015In: International Transactions on Electrical Energy Systems, E-ISSN 2050-7038, Vol. 25, no 11, p. 2769-2780Article in journal (Refereed)
    Abstract [en]

    In this paper, a new sensitivity-based methodology has been proposed for optimal placement of a static VAr compensator (SVC)/static synchronous compensator (STATCOM) to minimize load curtailment that is required to ensure system security, integrity and reliability after undesirable changes occur in the system. SVC/STATCOM has a significant impact on control of reactive power and thereby system bus voltages. This motivated to develop an appropriate approach to find their optimal location in order to accomplish the above said objective. The suggested sensitivity factors have been defined as the rate of change in load curtailment with respect to the change in SVC/STATCOM control settings. To investigate the effectiveness of the proposed methodology an optimal power flow problem has been formulated with an objective to minimize the load curtailment and is tested on IEEE 14-bus and practical 75-bus Indian systems. It is observed from the obtained results that the required load curtailment drastically reduced with the placement of SVC/STATCOM, along with improvement in system voltage profile at various operating conditions. This methodology can be used to limit the amount of load curtailment, thereby reducing lost revenue, outage cost, customer's service interruption and possibly civil unrest in some areas. 

  • 266.
    Soder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Statisk Analys av Elsystem2005Report (Other academic)
    Abstract [sv]

    I detta kompendium behandlas modeller och beräkningsmetoder för statiska förhållanden i elsystem. I kapitel 2 beskrivs hur elkraftsystemet är uppbyggt och kapitel 3 behandlar den grund-läggande växelströmsteorin. Modeller för kraftledningar och transformatorer utvecklas i kapitel 4 och i kapitel 5 beskrivs några viktiga teorem som används vid analys av trefaskretsar. I kapitel 6 och 7 används bl a dessa till att utföra beräkningar i elsystem under symmetriska förhållanden. Kapitel 5-7 bygger på att man kan beskriva laster i elsystemet såsom impedanser. Detta leder till linjära förhållanden vilket ger relativt enkla lösningsmetoder. I vissa situationer är det mer relevant att beskriva elsystemets laster med effekter. Hur elsystemet analyseras under dessa förhållanden beskrivs närmare i kapitel 8. I kapitel 9 ges en översyn till möjligheterna att utnyttja linjära transformationer för att förenkla beräkningar i elsystem. I kapitel 10-13 beskrivs grunderna för analys under osym-metriska förhållanden. Vid osymmetrisk analys utnyttjas normalt symmetriska komponenter vilka beskrivs utförligt i kapitel 10. Vid osymmetriska förhållanden måste ledningar, kablaroch transformatorer få en noggrannare beskrivning vilket behandlas i kapitel 11-12. I kapitel 13 beskrivs hur ett osymmetriskt trefasnät med impedanslaster kan analyseras. Kapitel 3-13 förutsätter att man i elsystemet har en konstant frekvens och linjära komponenter dvs sinusformade spänningar ger upphov till sinusformade strömmar. Med olinjärakomponenter, såsom t ex kraftelektronik, i systemet uppstår icke rent sinusformade strömmar och spänningar. Vilka effekter det kan få på ett elsystem beskrivs översiktligt i kapitel 14.

  • 267.
    Solver, Torbjörn
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Lydén, Per
    Svensson, Stefan
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Impact of System Related Factors on the Distribution Reliability, a Statistical analysis of two Swedish Distribution Grids2006In: CIDEL Argentina 2006: International Congress of Electrical Distribution, 2006Conference paper (Refereed)
    Abstract [en]

    Regulatory regimes that put focus on performance rather than looking at the actual costs of the distribution system operators (DSOs) create strong cost-cutting incentives, and to avoid system reliability deterioration the quality of supply is most often a feature in the performance yardstick. This has raised the stakes due to quality and consequently increased the interest that the DSOs have regarding their quality of supply. As in many European countries, this is the scenario in Sweden. As a tool to value the DSOs? performance the Swedish regulator uses the Network Performance Assessment Model (NPAM), which is a reference network model. Since the direct link between the DSOs? costs and income is weak, the costcutting incentives are rather strong, thus the quality of supply features within the regulation makes a significant contribution in the performance yardstick. This have resulted in that now the distribution system operators can be penalized due to poor quality of supply, which means that greater effort is now put into analysing and evaluation their quality performance. The underlying project is result of this evelopment. This paper presents some of the main conclusions of a project conducted during 2005, where comprehensive outage statistics, covering tree years from two separate distribution grids, have been gathered, organized and analyzed. The purpose has been to analyse the connection certain system related factors and the interruptions that occur in the distribution systems. The analyses are categorized according to customer related and interruption related factors.

  • 268.
    Solver, Torbjörn
    et al.
    KTH, Superseded Departments, Electrical Systems.
    Söder, Lennart
    KTH, Superseded Departments, Electrical Systems.
    Analysis of distribution reliability in performance-based regulation2004In: 2004 International Conference On Probabilistic Methods Applied To Power Systems, 2004, p. 82-87Conference paper (Refereed)
    Abstract [en]

    As a consequence of the liberalization of the electricity sector where electricity markets are deregulated and grid ownership are privatized, the need for regulation of Distribution Grid Owners (DGOs) due to the monopoly nature of electric distribution has increased. The regulation of DGOs is in many countries conducted based on the DGOs' performance, Le. Performance-Based Regulation (PBR). PBR is meant as a substitute for a competitive market by rewarding efficient DGOs and/or penalizing inefficient DGOs. A risk however is that distribution quality suffers due to lack of maintenance and postponed investments as the DGOs become more financially challenged. In order to prevent this the efficiency regulation can be combined with quality regulation in which poor quality either means decreased revenue or increased expenses. Quality regulation usually is conducted on one-year basis, this means that the yearly variation of system reliability brings financial uncertainty to DGOs. In order to make more accurate financial risk assessments the yearly variation of system reliability must be considered. In this paper a sequential Monte Carlo Simulations (MCS) method is described and applied on a reliability test system in order to conduct comparative analyzes of quality regulation model within PBR.

  • 269.
    Solver, Torbjörn
    et al.
    KTH, Superseded Departments, Electrical Systems.
    Söder, Lennart
    KTH, Superseded Departments, Electrical Systems.
    Comparison of incentives for distribution system reliability in performance-based regulation2004In: PROCEEDINGS OF THE 2004 IEEE INTERNATIONAL CONFERENCE ON ELECTRIC UTILITY DEREGULATION, RESTRUCTURING AND POWER TECHNOLOGIES, VOLS 1 AND 2, NEW YORK: IEEE , 2004, p. 485-490Conference paper (Refereed)
    Abstract [en]

    In recent years as many European electricity markets are deregulated, Network Utilities are liberalized and privatized. Consequently, the economic regulations of Distribution Utilities, which is applied due to the monopoly nature of network activities, have switched from cost-based regulation to Performance Based Regulation (PBR). PBR gives Distribution Utilities incentives to reduce costs. However, increased cost efficiency may lead to decrements in distribution quality, therefore is quality regulation necessary. In this paper the basic outlines of Distribution Utility regulation in Sweden, Norway, Spain and the Netherlands are compared. Focus in the comparison lie on the quality regulation framework and the incentives brought upon the Distribution Utilities based on the PBR-models' framework.

  • 270.
    Solver, Torbjörn
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    On risk mitigation strategies with focus on distribution system reliability in performance-based regulation2005In: Eighteenth International Conference and Exhibition on Electricity Distribution, CIRED 2005, Technical Reports - Session 1: Network Components, 2005, p. 119-123Conference paper (Refereed)
    Abstract [en]

    Financial risks are not usually associated with grid operation but regulatory regimes with focus on performance that applies quality dependent revenue or price caps are used to greater extend than before to regulate Distribution System Operators. Due to the uncertainty in annual system reliability, the financial risks within grid operation are therefore tangible. This paper is an introduction to the complex area of risk management in Performance-Based Regulation (PBR). A general strategy framework for risk management is described and then put into a PBR environment. The basic idea is to manage the risk of performance-based revenues by mitigating the uncertainty in regulatory outcome. The main focus lies on markets in which the grid ownership is totally separated from generation and retail such as the Swedish and Norwegian markets.

  • 271.
    Solver, Torbjörn
    et al.
    KTH, Superseded Departments, Electrical Systems.
    Söder, Lennart
    KTH, Superseded Departments.
    Optimal distribution tariffs in presence of flexible customers in deregulated markets2003In: 2003 IEEE Bologna Power Tech Conference Proceedings, 2003, Vol. 4, p. 8-Conference paper (Refereed)
    Abstract [en]

    The issue of variation of distribution tariffs in order for distribution grid companies to maximize their profits in presence of flexible customers is presented. First, present and future regulation of distribution grid companies and the main issues of transmission and distribution tariffs are described. Second, the fundamental theory on consumers’ surplus, grid companies’ profit maximisation are described as well as assumptions and simplifications made in the paper. Third, a numerical example is presented in order to highlight the main issues of the paper. Finally, conclusions based upon the numerical example and the fundamental theory can be found.

  • 272.
    Stankovic, Stefan
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Analytical Estimation of Reactive Power Capability of a Radial Distribution System2018In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679Article in journal (Refereed)
    Abstract [en]

    The control of reactive power exchange between grids of different voltage levels has always been a concern for system operators. With production moving from the transmission to the distribution level, its importance increases. This paper proposes a novel approach to estimate reactive power capability of the grid as a whole. A linearized analytical model for an estimation of available reactive power exchange at the interface between two grids has been developed. The maximum estimation error for the scenarios we tested was only 2%. The model gives the relation between important grid parameters and the supported reactive power. The conclusions drawn from the model are confirmed on typical Swedish distribution network with scattered wind power and small industry consumers. Common scenarios in development of distribution grids are applied to show relevant parameters influence. One studied scenario is replacement of overhead lines with cables. It is shown that this particular change enhances the reactive power capability of the grid which is directly seen from the analytical analysis without running any optimal power flow. The analytical model proposed in this paper gives fundamental understanding of the reactive power capability of radial distribution grids.

  • 273.
    Stankovic, Stefan
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Cable Impact on Integration of Wind and Solar Power2017Conference paper (Refereed)
  • 274.
    Stankovic, Stefan
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Identification of Reactive Power Provision Boundaries of a Distribution Grid with DFIGs to a Transmission Grid2017In: 2017 IEEE PES Innovative Smart Grid Technologies Conference Europe, ISGT-Europe 2017 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2017Conference paper (Refereed)
    Abstract [en]

    Development of the distribution grids brings alsonew challenges. With efficient exploitation of all the availableresources in the grid, many related problems can be solved. Theproblem addressed in this paper is becoming more and morecommon in the practice. There is a need to control reactivepower exchange between the grids of different voltage levels. Thisneed becomes more pronounced with increasing penetration ofdistributed generation and cables in the system. But, the causeof the problem can be also a part of its solution. This papershows that it is possible to control the reactive power exchangeto a noticeable extent using the distributed generation locatedin the grid and the on-load tap changers. The results have beenobtained from the analysis of a representative model of Swedishdistribution network with installed DFIG wind turbines. Whilenot going deeper into the control strategies, the reactive powerboundaries of the system are identified. Critical elements arefound for different case scenarios. Solutions on adjustment ofreactive power capabilities of the grid are proposed.

  • 275.
    Stankovic, Stefan
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Optimal Power Flow Based on Genetic Algorithms and Clustering Techniques2018In: 2018 POWER SYSTEMS COMPUTATION CONFERENCE (PSCC), IEEE , 2018Conference paper (Refereed)
    Abstract [en]

    Optimal power flow problems have been studied extensively for the past decades. Two approaches for solving the problem have been distinguished: mathematical programming and evolutionary algorithms. The first is fast but is not converging to a global optimum for every case. The second ones are robust but time-consuming. This paper proposes a method that combines both approaches to eliminate their flaws and take advantage of their benefits. The method uses properties of genetic algorithms to group their chromosomes around optima in the search space. The centers of these groups are identified by clustering techniques and furthermore used as initial points for gradient based search methods. At the end, the proposed method finds global optimum and its closest local optima. Continuous Newton-Raphson method is used to overcome ill-conditioned points in search space when calculating power flows. The proposed method is compared against similar methods showing considerable improvement.

  • 276. Sveca, Julija
    et al.
    Söder, Lennart
    KTH, Superseded Departments, Electric Power Systems.
    Wind Power Integration in Areas with Congestion Problems and Storage Capabilities2003In: European Wind Energy Conference, Madrid, Spain, 2003Conference paper (Refereed)
  • 277.
    Sveca, Julija
    et al.
    KTH, Superseded Departments, Electrical Systems.
    Söder, Lennart
    KTH, Superseded Departments.
    Wind power integration in power systems with bottleneck problems2003In: 2003 IEEE Bologna Power Tech Conference Proceedings, 2003, Vol. 2Conference paper (Refereed)
    Abstract [en]

    The number of installed wind power plants continues to increase, but the existing transmission system is usually not dimensioned for large new generation plants. Some measures are necessary to make installation of large-scale wind power possible: grid reinforcement, optimal planning and control of wind power plants and existing conventional power sources. Methods presented in this paper allow us to estimate the amounts of wind power that can be installed in areas with bottleneck problems without grid reinforcement. The first method gives a simplified estimation based on several assumptions; the second is similar to probabilistic production cost simulation. The estimation methods are applicable to discrete variables (measurements) and also generalised for continuous variables with known distribution. The developed methods are applied to the Swedish transmission system.

  • 278.
    Sveca, Julija
    et al.
    KTH, Superseded Departments, Electric Power Systems.
    Söder, Lennart
    KTH, Superseded Departments, Electric Power Systems.
    Wind Power Integrations in Power Systems with Bottleneck Problems2002In: Vind2002 Conference, Malmö, Sweden, 2002Conference paper (Refereed)
  • 279.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Analysis of Electricity Markets2011Report (Other academic)
    Abstract [en]

    This report is a compendium used for education concerning analysis of electricty markets. It includes basic market modelling, interaction between different markets, market power, environmental restrictions, planning and operation for an e±cient production-load balance and some issues concerning investment analysis

  • 280.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Analysis of Electricity Markets,: New 98 page compendium in the course 2C1119 - Electricity Market Analysis2007Other (Other academic)
  • 281.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Analysis of Pricing and Volumes in Selective Capacity Markets2010In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 25, no 3, p. 1415-1422Article in journal (Refereed)
    Abstract [en]

    The requirements concerning reliability in power supply are high. This paper treats the issue of system adequacy, i.e., there should be enough installed capacity to meet the load with an acceptable reliability. The challenge in a liberalized market is that the utilization time of rarely used peak units is so low that they require extremely high prices in order to be profitable. This has led to different methods, including the creation of capacity markets. The aim of this paper is to analyze the connection between peak prices, system reliability, required amount of subsidized capacity, i.e., the volume of the capacity market. In the studied market setup, only some selected units, so-called "reserve plants", receive a capacity payment. The paper also provides an example concerning change of capacity market volume in presence of wind power.

  • 282.
    Söder, Lennart
    KTH, Superseded Departments, Electric Power Systems.
    Benefit assessment of wind power in hydro-thermal power systems1988Other (Other academic)
  • 283.
    Söder, Lennart
    KTH, Superseded Departments, Electrical Systems.
    Effektiv drift och planering av kraftsystem1999Report (Other academic)
    Abstract [sv]

    Detta kompendium behandlar modeller och metoder som kan användas för beräkningar avseende effektiv balanshållning mellan produktion och konsumtion i ett kraftsystem.

  • 284.
    Söder, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    EG2220 Power Generation, Environment and Markets: Compendium for future system design2017Report (Other academic)
    Abstract [en]

    Design of future power systems includes several tasks including power plant type, power plant location,transmission design, market design etc. In this compendium we will study only the design of the amountsand types of power plants and some issues which are of high relevance and importance. This means,e.g., that we will not discuss transmission expansion planning here. There are then many dierentalternatives both concerning the dierent types of units with dierent costs etc, but also many dierentways of dening what a "good" future power system is. Here we will analyze the impact from dierenttypes of assumptions on the resulting future power system.

  • 285.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Estimation of reduced electrical distribution losses depending on dispersed small scale energy production1996In: Proceedings of12th Power Systems Computation Conference, August 19-23, 1996, Dresden, Germany, 1996Conference paper (Refereed)
  • 286.
    Söder, Lennart
    KTH, Superseded Departments.
    Explaining power system operation to nonengineers2002In: IEEE Power Engineering Review, ISSN 0272-1724, E-ISSN 1558-1705, Vol. 22, no 4, p. 25-27Article in journal (Refereed)
  • 287.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    IEA Task 25 - Design and Operation of Power Systems with large amounts of Wind Power: Elforsk rapport 09:072009Report (Other academic)
  • 288.
    Söder, Lennart
    KTH, Superseded Departments.
    If you sell electricity you should have electricity to sell2001In: Sveriges Energiting 2001, Eskilstuna, 2001Conference paper (Refereed)
  • 289.
    Söder, Lennart
    KTH, Superseded Departments.
    Imbalance management and reserve requirements2002Conference paper (Refereed)
    Abstract [en]

    The amount of wind power in Sweden increases continously. At the end of April 2002 the installed capacity in Sweden was 306 MW which is 12 % more than one year earlier. There is though a continous discussion about how to balance the continous variations caused by wind power as well as the required amounts of reserves. In this paper first the general value of a power plant will be described and the imbalance management is here included as the so called “control value”. This value is negative if the power source, such as wind power, causes an increased amount of control in the system. The “true” values as well as the market values will be analyzed.

  • 290.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric power and energy systems.
    Kommentarer till rapporten ”100 procent förnybar elenergi år 2020 – 2025 – 2030?” samt till repliker på denna.2016Report (Other (popular science, discussion, etc.))
    Abstract [sv]

    På DN debatt publicerades en artikel med titeln ”Satsning på solceller kan göra Sverige helt förnybart 2020” 2016-07-11 [1]. Den bygger is sin tur på en rapport kallad ”100 procent förnybar elenergi år 2020 – 2025 – 2030” [2]. DN-artikeln har sedan fått 3 kommentarer. Då jag själv har författat en del rapporter på samma tema, t ex ” På väg mot en elförsörjning baserad på enbart förnybar el i Sverige: En studie om kraftsystemets balansering: Version 4.0”, så har jag därmed en del kommentarer till dessa rapporter/inlägg vilka summeras i denna rapport.

  • 291.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    KVA sprider missuppfattningar om vindkraft2010In: Ny teknik, ISSN 0550-8754, no 23Article in journal (Other (popular science, discussion, etc.))
  • 292.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Modelling Approach impact on estimation of integration cost of wind power2005In: Proceedings of 7th IAEE European Energy Conference European Energy Markets in Transition, 2005Conference paper (Refereed)
  • 293.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Möjligheterna att balansera vindkraftens variationer2010Report (Other academic)
    Abstract [sv]

    Syftet med detta dokument är att ge en översikt över de utmaningar som kan uppkomma då en större mängd vindkraft ska integreras i ett kraftsystem. Syftet har varit att inte gå in för mycket på alla detaljer eftersom texten i så fall skulle bli alldeles för lång. Problematiken är till viss del generell, men många av beskrivningarna är mest relevanta för det svenska elsystemet. Detta dokument är baserat på hittillsvarande kunskap och studier som är kända av författaren vid publiceringsdatumet. De värderingar som görs och de slutsatser som dras är författarens egna.

  • 294.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Nuclear Energy and Renewables: System Effects in Low-carbon Electricity Systems: Method comments to a NEA report2012Report (Other (popular science, discussion, etc.))
    Abstract [en]

    OECD Nuclear Energy Agency (NEA) released a new report on 29 November 2012. The study recommends that decision-makers should take full electricity system costs into account in energy choices and that such costs should be internalised according to a “generator pays” principle.

    The study, entitled Nuclear Energy and Renewables: System Effects in Low-carbon Electricity Systems, addresses the increasingly important interactions of variable renewables and dispatchable energy technologies, such as nuclear power, in terms of their effects on electricity systems.

    System effects refer to the costs above plant-level costs to supply electricity at a given load and level of security of supply. The NEA report focuses on “grid-level system costs”, the subset of system costs mediated by the electricity grid, which include a) the costs of extending and reinforcing transport and distribution grids as well as connecting new capacity, and b) the costs of increased short-term balancing and maintaining the long-term adequacy of electricity supply.

    In this document we will describe in more details the NEA report concerning System Effects in Low-carbon Electricity Systems. We will also comment on the results.

    The final conclusion is that there are several question marks concerning the calculation methods used to calculate the “grid-level systems costs” in the (OECD-NEA, 2012) report.

  • 295.
    Söder, Lennart
    KTH, Superseded Departments, Electrical Systems.
    On limits for wind power generation2004In: International Journal of Global Energy Issues, ISSN 0954-7118, E-ISSN 1741-5128, Vol. 21, no 3, p. 243-254Article in journal (Refereed)
    Abstract [en]

    The amount of wind power in the world increases fast. The background for this development is improved technology, decreased costs for the units and an increased concern of the environmental problems of competing technologies such as fossil fuels. For the future it is now interesting to evaluate where the limits are for wind power generation, and which points are crucial. Since there is no power from the wind when there is no breeze, the customers have to get power from other sources during these situations. The question then is whether it is the power system that sets the limits or it is the environmental consequences or the economy? In this paper these questions will be discussed with focus on power system integration. The results from several case studies are also presented.

  • 296.
    Söder, Lennart
    KTH, Superseded Departments, Electrical Systems.
    Operation and planning of power systems1999Report (Other academic)
    Abstract [en]

    This compendia treats models and methods that can be used to keep an efficient balance between production and consumption in a power system.

  • 297.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Possibilities for Balancing Wind Power Variations2010Report (Other academic)
    Abstract [en]

    This paper has the goal to provide an overview about the challenges that we may face with the integration of large-scale wind power into the power system. We do not intend to give a comprehensive description of all details because the resulting text would be much too long.

    The issue is partially of general interest, but many of the descriptions are mainly relevant for the Swedish power system. This document is based on current know-how and studies that have been available to the author by the publishing date. The evaluations and conclusions drawn in this paper are the author’s. This document will be updated when new information becomes available. Anybody who wishes to comment on this article can send his comments tolennart.soder@ee.kth.se.

  • 298.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric power and energy systems.
    På väg mot en elförsörjning baserad på enbart förnybar el i Sverige: En analys av lämplig marknadshantering Version 1.02016Report (Other (popular science, discussion, etc.))
    Abstract [sv]

    Under de senaste åren har skett en stor förändring av såväl förutsättningar som prognoser för hur vi i Sverige ska kunna få ett väl fungerande och hållbart kraftsystem jämfört med vad som diskuterades bara för ett par år sedan. Förändringar är bland annat:

    • Kärnkraften sågs tidigare, i många framtidsscenarier som fullt fungerande och ett konkurrenskraftigt kraftslag länge till. I Energimyndighetens prognos som publicerades i januari 2013 skriver man: ”I beräkningarna antas att kärnkraftverken har en teknisk livslängd på 60 år”. Nu, 3 år senare, är läget ett helt annat. R1-R2 stängs nu istället efter ca 45 år, dvs på 2 år har den faktiska livslängden minskat med 15 år jämfört med vad Energimyndigheten antog. O2 stängs efter 41 år och O1 efter ca 46 år.
    • Elpriserna på marknadsplatserna är betydligt lägre än tidigare. Bland annat detta har medfört att ägarna till de svenska kärnkraftverken, med olika motivering, ifrågasätter om man kan fortsätta driva kärnkraftverk pga ekonomin. Denna typ av fråga har aldrig diskuterats öppet förrän under senaste året.

    En fråga som nu ställs är bland annat: Måste vi göra en förändring av elmarknadens regler för att få en stabil elmarknad i Sverige. Många förslag finns rörande detta inkluderande såväl ett förstatligande av kärnkraften som en ren energy-only-marknad, med borttagande av såväl effektreserv som certifikat-system. Analysen här leder snarare till att ungefär samma marknad som idag kan fungera med nödvändiga justeringar vilka kommenteras och motiveras. Med ”dagens elmarknad” avses det generella upplägget med en energy-only-marknad som är kompletterad med ett certifikat-system samt en effektreserv.

  • 299.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    På väg mot en elförsörjning baserad på enbart förnybar el i Sverige: En studie om behovet av reglerkraft. Version 1.02012Report (Other (popular science, discussion, etc.))
    Abstract [sv]

    Syftet med denna rapport är att ge en kvalitativ förståelse om det förändrade behovet av reglerkraft vid en mycket större andel variabel förnybar elproduktion än idag.  Detta är en första upplaga där möjligheterna att integrera 45 TWh vindkraft och 10 TWh solkraft studeras. I rapporten visas att trots en mycket större andel variabel förnybar kraft så sker inga dramatiska förändringar av behovet av reglerkraft jämfört med idag, dvs kraftsystemets förmåga att följa med nettoförbrukningen  från timme till timme. Nettoförbrukningen avser [förbrukning]-[vindkraft+solkraft] dvs den förbrukning som övriga kraftverk, inom eller utom landet, ska klara av. Anledningen är att vindkraftens variation från timme till timme är relativt liten, under ca 10% av installerad effekt, medan elförbruknings variation är betydligt större. En mer detaljerad studie, där upp till 30 TWh vindkraft har studerats och vattenkraften studerats på älv- och aggregat-nivå, ger liknande resultat, dvs inga dramatiska förändringar av behovet av reglerkraft. En annan aspekt av reglerkraft är förmågan att klara den högsta elförbrukningen i ett system med mycket variabel elproduktion, ofta benämnd högeffektreserver. I rapporten visas att den generella slutsatsen är att storleksordningen i kostnad för att klara denna utmaning är på nivån noll eller enstaka ören per kWh.

  • 300.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    På väg mot en elförsörjning baserad på enbart förnybar el i Sverige: En studie om behovet av reglerkraft. Version 2.02013Report (Other (popular science, discussion, etc.))
    Abstract [sv]

    Syftet med denna rapport är att ge en kvalitativ förståelse om det förändrade behovet av reglerkraft vid en mycket större andel variabel förnybar elproduktion än idag. Detta är en andra upplaga där möjligheterna att integrera 55 TWh vind‐ och solkraft studeras. I rapporten visas att trots en mycket större andel variabel förnybar kraft så sker inga dramatiska förändringar av behovet av reglerkraft jämfört med idag, dvs kraftsystemets förmåga att följa med nettoförbrukningen från timme till timme. Nettoförbrukningen avser [förbrukning]‐[vindkraft+solkraft] dvs den förbrukning som övriga kraftverk, inom eller utom landet, ska klara av. Anledningen är att vindkraftens variation från timme till timme är relativt liten, under ca 10% av installerad effekt, medan elförbruknings variation är betydligt större. En mer detaljerad studie, där upp till 30 TWh vindkraft har studerats och vattenkraften studerats på älv‐ och aggregat‐nivå, ger liknande resultat, dvs inga dramatiska förändringar av behovet av reglerkraft. En annan aspekt av reglerkraft är förmågan att klara den högsta elförbrukningen i ett system med mycket variabel elproduktion, ofta benämnd högeffektreserver. I rapporten visas att den generella slutsatsen är att storleksordningen i kostnad för att klara denna utmaning är på nivån noll eller enstaka ören per kWh.

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