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  • 1.
    Hamon, Camille
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Shayesteh, Ebrahim
    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.
    Two partitioning methods for multi-area studies in large power systems2015In: International Transactions on Electrical Energy Systems, E-ISSN 2050-7038, Vol. 25, no 4, p. 648-660Article in journal (Refereed)
    Abstract [en]

    Multi-area studies are an important tool for today's and future power systems. In this paper, a two-step algorithm for creating multi-area models is presented that, first, identifies areas, and, second, computes reduced models of these areas. For the first step, two new methods to identify areas in power systems have been developed. The first method is based upon spectral partitioning, whereas the second one is formulated as a linear optimization problem. The methods are compared in terms of computation time on the IEEE 118 bus system, and the first method clearly stands out in this comparison. The first method is then applied to the IEEE 300 bus system and to a model of the Polish power system with 2746 buses to study how it scales in large power systems. Even in the latter case, it runs in less than 30s. For the second step, existing equivalencing methods can be used. As an example, radial, equivalent, and independent equivalents are used to model the areas identified by the partitioning methods. The partitioning and equivalencing methods have been tested on the IEEE 118 bus system by running 1000 regular and optimal power flows. Comparisons with the original IEEE 118 bus system in terms of flows, costs and losses are carried out.

  • 2.
    Leelaruji, Rujiroj
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Vanfretti, Luigi
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Uhlen, Kjetil
    Gjerde, Jan Ove
    Computing Sensitivities from Synchrophasor Data for Voltage Stability Monitoring and Visualization2015In: International Transactions on Electrical Energy Systems, E-ISSN 2050-7038, Vol. 6, p. 933-947Article in journal (Refereed)
    Abstract [en]

    Wide-area early warning systems are dependent on synchrophasor data-based applications for providing timely information to operators so that preventive actions can be taken. This article proposes the use of voltage sensitivities computed from synchrophasor data for voltage stability monitoring, and a visualization approach that can be implemented in widearea early warning systems. In order to provide reliable information, this article addresses the issue of data filtering and correction, and proposes a filtering methodology for robust voltage sensitivity computation. The methodology is developed considering both positive-sequence simulations for methodology development purposes, and real phasor measurement data from a real-time (RT) hardware-in-the-loop (HIL) laboratory for testing the robustness of the developed approach under more realistic conditions. The limitations of the positive-sequence simulation approach for developing PMU-data applications are highlighted, and the challenges of working with the RT HIL lab are recognized. The proposed sensitivity computation approach have also been applied to a real PMU-data obtained from the Nordic transmission system where results are sustained.

  • 3. 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. 

  • 4.
    Vanfretti, Luigi
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems. Statnett SF, Sweden.
    Bengtsson, Sebastian
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Gjerde, Jan O.
    Preprocessing synchronized phasor measurement data for spectral analysis of electromechanical oscillations in the Nordic Grid2015In: International Transactions on Electrical Energy Systems, E-ISSN 2050-7038, Vol. 25, no 2, p. 348-358Article in journal (Refereed)
    Abstract [en]

    Spectral analysis techniques have successfully been applied for near real-time monitoring of power system small-signal electromechanical oscillations using synchronized phasor data from PMUs. The methods used for this purpose commonly assume that random load variations adopt the distribution function of Gaussian noise. Hence, careful attention has to be paid so that the preprocessing of synchronized phasor measurements is capable of providing data with the characteristics expected for these methods to work properly. This can be viewed as a conditioning step in the data handling process that has an impact on the results from spectral analysis which consume this data. This article aims to revisit the crucial step of preprocessing of PMU data in a tutorial fashion. The goal is to share the authors' experience when dealing with real PMU data originating from the Nordic Grid. This article offers a systematic and detailed methodology developed by the authors which has been successfully used in studies on estimation of electromechanical modes in the Nordic Grid.

  • 5.
    Vardanyan, Yelena
    et al.
    KTH, School of Electrical Engineering (EES), Electric power and energy systems.
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering (EES), Electric power and energy systems.
    Coordinated production planning of risk-averse hydropower producer in sequential markets2016In: International Transactions on Electrical Energy Systems, E-ISSN 2050-7038, Vol. 26, no 6, p. 1226-1243Article in journal (Refereed)
    Abstract [en]

    This paper proposes a quadratic programming (QP) model for optimal coordinated production of a risk-averse hydropower producer. The day-ahead, intra-day and real-time markets are considered. A rolling planning approach is used to take advantage of sequential clearing of mentioned markets. The multi-period risk of trading in different markets is modelled as quadratic terms in the objective function. To cope with uncertain prices, three price forecasting techniques are used. The best forecasting technique is selected based on a designed Markov switch. The discrete behaviour of intra-day and real-time market prices are modelled as different Markov states. The proposed QP model is coded in gams (GAMS Development Corporation, Washington, DC, USA) platform and solved using the mosek (Mosek ApS, Copenhagen, Denmark) solver. An example of a three-reservoir system from a Swedish hydropower producer is used to examine the proposed QP model. The results show the economic gains from coordinated production planning in sequential markets.

  • 6.
    Wallnerström, Carl Johan
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Stenberg, Sabina
    Svenska Kraftnät.
    Asset management framework applied to power distribution for cost-effective resource allocation2014In: International Transactions on Electrical Energy Systems, E-ISSN 2050-7038, Vol. 24, no 12, p. 1791-1804Article in journal (Refereed)
    Abstract [en]

    There is an international tendency toward increased demand for both cost-efficiency and high reliability of power distribution systems. To meet these demands, asset management methods, including reliability analyses, have been developed. These reliability analyses often utilize only mean values and hence do not take into consideration the consequences of severe events. This paper proposes a framework for more detailed quantitative risk analysis methods. The aim is to allocate resources more cost-effectively. The suggested framework is exemplified and evaluated by implementing it within the analyses of a real power distribution system. The main concept is to divide comprehensive projects into minor analyses and then in a final step compile the results. The proposed analysis framework can be used independently or combined with earlier proposed vulnerability methods. The latter provides a two-dimensional analysis framework. It is shown that totally different investment alternatives could be preferred depending on whether a traditional analysis method using average values is employed compared with the proposed analysis framework, which also considers severe system states. This demonstrates the risks involved in using average values and the strength of the proposed method. Furthermore, it is shown that already available information can be used for improved asset management decision support. In addition, the performed case study gives combined reliability and weather statistics useful as reference material.

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