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  • 1.
    Abolpour, Roozbeh
    et al.
    Shiraz Univ, Sch Elect & Comp Engn, Shiraz 7134851154, Iran..
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Dehghani, Maryam
    Shiraz Univ, Sch Elect & Comp Engn, Shiraz 7134851154, Iran..
    A New Power Flow Model With a Single Nonconvex Quadratic Constraint: The LMI Approach2022In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 37, no 2, p. 1218-1229Article in journal (Refereed)
    Abstract [en]

    In this paper, we propose a new mathematical model for power flow problem based on the linear and nonlinear matrix inequality theory. We start with rectangular model of power flow (PF) problem and then reformulate it as a Bilinear Matrix Inequality (BMI) model. A Theorem is proved which is able to convert this BMI model to a Linear Matrix Inequality (LMI) model along with One Nonconvex Quadratic Constraint (ONQC). Our proposed LMI-ONQC model for PF problem has only one single nonconvex quadratic constraint irrespective of the network size, while in the rectangular and BMI models the number of nonconvex constraints grows as the network size grows. This interesting property leads to reduced complexity level in our LMI-ONQC model which in turn makes it easier to solve for finding a PF solution. The non-conservativeness, iterative LMI solvability, well-defined and easy-to-understand geometry and pathwise connectivity of feasibility region are other important properties of proposed LMI-ONQC model which are discussed in this paper. An illustrative two-bus example is carefully studied to show different properties of our LMI-ONQC model. We have also tested our LMI-ONQC model on 30 different power-system cases including four ill-conditioned systems and compared it with a group of existing approaches. The numerical results show the promising performance of our LMI-ONQC model and its solution algorithm to find a PF solution.

  • 2.
    Alvehag, Karin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Awodele, Kehinde
    Impact of Reward and Penalty Scheme on the Incentives for Distribution System Reliability2014In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 29, no 1, p. 386-394Article in journal (Refereed)
    Abstract [en]

    Performance-based regulations accompanied by quality regulations are gaining ground in the electricity distribution business. Several European countries apply quality regulations with reward and penalty schemes (RPSs), where the distribution system operator (DSO) is rewarded (or penalized) when fulfilling (or not fulfilling) an adequate level of reliability to its customers. This paper develops a method that the regulator can use before enforcing a regulation to get an understanding of the impact different RPS design solutions have on the DSO's financial risk and incentives to invest in reliability. The proposed method also includes a sensitivity analysis to identify which are the most important parameters in an RPS. The new method is applied to three regulatory challenges to evaluate their RPS design solutions. Results show that the choice of scheme design and cost model used to decide the incentive rate have a large impact on the DSO's financial risk and incentive to invest.

  • 3.
    Amelin, Mikael
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    An Evaluation of Intraday Trading and Demand Response for a Predominantly Hydro-Wind System Under Nordic Market Rules2015In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 30, no 1, p. 3-12Article in journal (Refereed)
    Abstract [en]

    Many countries are planning for a large-scale expansion of wind power. This development will have a significant impact on power system operation and economics. One of the challenges is that the difficulty to forecast wind power generation will increase the need for real-time balancing. This paper presents a study of how the impact of wind power forecast errors can be reduced by changes in the market design. The study is based on the conditions in the Nordic electricity market. A characteristic of this market is that there is a large share of flexible hydro generation; hence, ramp and unit commitment constraints rarely constrain dispatch. The need for regulation during real-time is provided in a voluntary real-time balancing market, where players can be compensated for their redispatch costs. Case studies are presented which show that a shift from day-ahead to intraday trading and increased demand response can improve the performance when the share of wind power is increasing.

  • 4.
    Amelin, Mikael
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Comparison of Capacity Credit Calculation Methods for Conventional Power Plants and Wind Power2009In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 24, no 2, p. 685-691Article in journal (Refereed)
    Abstract [en]

    Several methods for computing capacity credit values of power plants have been presented over the years. This paper uses an empirical approach to investigate and compare different properties of four typical capacity credit definitions. It is shown that the choice of definition indeed can have a significant impact on the results. Concerning three of the analyzed methods, it is found that important factors that influence the capacity credit are the overall generation adequacy and the penetration factor of the power plant; this means that the same generating unit will generally have a higher capacity credit if added to a system with high loss of load probability, and the unit will have a higher capacity credit if its installed capacity is small compared to the total installed capacity of the system. The results of the fourth method only depend on the size and availability of the generating units.

  • 5.
    Andreasson, Martin
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Wiget, R.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Andersson, G.
    Distributed Frequency Control Through MTDC Transmission Systems2017In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 32, no 1, p. 250-260, article id 7456314Article in journal (Refereed)
    Abstract [en]

    In this paper, we propose distributed dynamic controllers for sharing both frequency containment and restoration reserves of asynchronous ac systems connected through a multi-terminal HVDC (MTDC) grid. The communication structure of the controller is distributed in the sense that only local and neighboring state information is needed, rather than the complete state. We derive sufficient stability conditions, which guarantee that the ac frequencies converge to the nominal frequency. Simultaneously, a global quadratic power generation cost function is minimized. The proposed controller also regulates the voltages of the MTDC grid, asymptotically minimizing a quadratic cost function of the deviations from the nominal dc voltages. The results are valid for distributed cable models of the HVDC grid (e.g., $\pi$-links), as well as ac systems of arbitrary number of synchronous machines, each modeled by the swing equation. We also propose a decentralized communication-free version of the controller. The proposed controllers are tested on a high-order dynamic model of a power system consisting of asynchronous ac grids, modeled as IEEE 14 bus networks, connected through a six-terminal HVDC grid. The performance of the controller is successfully evaluated through simulation.

  • 6.
    Anh, Nguyen Tua
    et al.
    KU Leuven.
    Vanfretti, Luigi
    KTH, School of Electrical Engineering (EES), Electric Power Systems. Statnett SF.
    Van Hertem, Dirk
    KU Leuven.
    A Quantitative Method to Determine ICT Delay Requirements for Wide-Area Power System Damping Controllers2015In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, ISSN 0885-8950, Vol. 30, no 4, p. 2023-2030Article in journal (Refereed)
    Abstract [en]

    This paper presents a quantitative method to determine delay requirements of the information and communication technology (ICT) system supporting wide-area power oscillation damping (WAPOD) controllers. An allowable time delay for the ICT infrastructure named “equivalent time delay (ETD)” is defined. The ETD is calculated by numerically comparing the damping behavior of the system when local input signals (LI) and remote input signals (RI) are used in the damping controller. The use of a WAPOD is only justified when its response outperforms that of a controller using local inputs. Therefore, the total time delay in the control loop must be below the calculated ETD. As such, the ETD serves as a design criteria to determine ICT latency requirements. The selection of an effective RI signal can be carried out by considering the maximum delays (ETDs) of different wide-area measurements. A damping improvement ETDx% has been proposed using the same methodology indicating a minimum outperformance of the remote signals. The proposed method is demonstrated using the well-known Klein-Rogers-Kundur multi-machine power system and the Vietnamese power system model.

  • 7. Bakhtiari, H.
    et al.
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Bunn, D.
    TSO-DSO Operational Coordination Using a Look-Ahead Multi-Interval Framework2022In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, p. 1-18Article in journal (Refereed)
    Abstract [en]

    With the rise of distributed energy resources and the increasing activation of flexibility resources by Distribution Systems Operators (DSOs), the Transmission System Operators (TSOs) need to co-ordinate their actions with those of the DSOs. This research uses a look-ahead multi-interval (LA-MI) framework for analyzing this coordination and explores two formulations. Firstly in the exogenous DSO model, a mixed-integer linear program is developed to reflect the pragmatic approach in many real situations whereby the TSO can only anticipate statistically the actions of the DSO. In the embedded DSO model, as a comparator, we propose a new organizational setup for the TSO-DSO operational coordination mechanism. In the resulting bilevel decomposition, a new method to calculate Benders cuts is developed and tested on a modified IEEE 118-bus test system as a transmission network and two modified IEEE 33-bus test systems as distribution networks. The benefits of the LA-MI coordination framework are substantial in comparison with the current Look-Ahead Single-Interval (LA-SI) coordination framework widely used in Europe. 

  • 8.
    Baradar, Mohamadreza
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    A Multi-Option Unified Power Flow Approach for Hybrid AC/DC Grids Incorporating Multi-Terminal VSC-HVDC2013In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 28, no 3, p. 2376-2383Article in journal (Refereed)
    Abstract [en]

    This paper proposes a multi-option power flow approach for hybrid AC/DC grids. A unified AC-DC unit is introduced which can be used in two different cases: case a) AC grids with embedded VSC-based MTDC grids, and case b) asynchronous AC grids connected via a common VSC-based MTDC grid. In the proposed method for each MTDC grid (regardless of the number of converters), a new state variable is introduced to handle any kind of converter loss models. For the case (b), the AC-DC unit can be used in two different analyses, namely, a1) the separated analysis and a2) the integrated analysis. Both a1) and a2) can be used in the practical analysis of the real-size power systems. However, it is shown that the separated analysis not only offers a shorter computational time but it is also very suitable for the future connection between large existing AC systems and other AC systems or remote renewable energy sources through the DC grids. The proposed methodology is implemented in MATLAB software and verified using commercial software SIMPOW.

  • 9.
    Baradar, Mohamadreza
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Hesamzadeh, Mohammad R.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Transmission Loss Minimisation in Power Systems with Embedded Smart-Grid Technologies2013In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679Article in journal (Other academic)
  • 10.
    Baradar, Mohamadreza
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Hesamzadeh, Mohammad R.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Second-order cone programming for optimal power flow in VSC-type AC-DC grids2013In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 28, no 4, p. 4282-4291Article in journal (Refereed)
    Abstract [en]

    This paper presents a second order cone programming (SOCP) formulation of the optimal power flow problem for AC-DC systems with voltage source converter (VSC) technology. Approximation techniques have been used to derive the SOCP formulation of the AC-DC OPF problem. Later, the SOCP formulation can be solved using the interior point method (IPM) by considering the limits on AC-DC grid. The accuracy of SOCP formulation of AC OPF has been proven with numerical examples using IEEE 14-bus, IEEE 30-bus, and IEEE 57-bus example systems. The results of the SOCP formulation are compared with available commercial software. Then a DC system with VSC technology is modeled in the IEEE 30-bus example system. The SOCP formulation of AC-DC OPF is applied to the modified IEEE 30-bus example system and the results are discussed. The limitations of derived SOCP formulation are also discussed.

  • 11.
    Baradar, Mohamadreza
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    AC Power Flow Representation in Conic Format2015In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 30, no 1, p. 546-547Article in journal (Refereed)
    Abstract [en]

    This letter presents a second-order cone formulation for AC power flow problem. The power flow equations are first derived as functions of more practical variables of power systems and then placed in a second-order cone programming (SOCP) problem. The proposed conic power flow (CPF) model can be solved efficiently through IPMs, and at the same time, it has a very good accuracy as compared to the full AC power flow model. Also, the proposed CPF can efficiently handle the ill-conditioned networks. The numerical efficiency and good accuracy of the model are shown by simulating various case studies.

  • 12.
    Bertling, Lina M.
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Allan, R.
    Eriksson, Roland
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A reliability-centered asset maintenance method for assessing the impact of maintenance in power distribution systems2005In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 20, no 1, p. 75-82Article in journal (Refereed)
    Abstract [en]

    This paper proposes a method for comparing the effect of different maintenance strategies on system reliability and cost. This method relates reliability theory with the experience gained from statistics and practical knowledge of component failures and maintenance measures. The approach has been applied to rural and urban distribution systems. In particular, a functional relationship between failure rate and maintenance measures has been developed for a cable component. The results show the value of using a systematic quantitative approach for investigating the effect of different maintenance strategies.

  • 13.
    Bidadfar, Ali
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Zhang, Lidong
    Harnefors, Lennart
    Namayantavana, Sanaz
    KTH.
    Abedi, Mehrdad
    Karrari, Mehdi
    Gharehpetian, Gevork B.
    Power System Stability Analysis Using Feedback Control System Modeling Including HVDC Transmission Links2016In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 31, no 1, p. 116-124Article in journal (Refereed)
    Abstract [en]

    A general platform is introduced to study the dynamics of power systems with high voltage dc (HVDC) transmission links. Small-signal stability, voltage stability, and interaction phenomena of power systems with both line-commutated-converter HVDC (LCC-HVDC) and voltage-source-converter HVDC (VSC-HVDC) are addressed using the proposed platform. In this platform, the entire power system is modeled as a multivariable feedback control system (FCS) which consists of three interconnected blocks. The contents as well as the inputs and outputs of the blocks are selected such that the conventional analysis tools for power system stability are applicable, both in the time and frequency domains. In the FCS model, the relationships between different instabilities are clear, and participant agents of each instability can be determined. The model is developed in a modular and hybrid style, to make it feasible for a large power system. The proposed model is validated against an electromagnetic transient simulation program (PSCAD) using time responses.

  • 14. Billinton, R.
    et al.
    Fotuhi-Firuzabad, M.
    Bertling, Lina M.
    KTH, Superseded Departments (pre-2005), Electric Power Systems.
    Bibliography on the application of probability methods in power system reliability evaluation 1996-19992001In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 16, no 4, p. 595-602Article in journal (Refereed)
    Abstract [en]

    This paper presents a bibliography of papers on the subject of power system reliability evaluation. Papers in such areas as: probabilistic load flow, probabilistic production costing, probabilistic transient stability evaluation etc. have not been included except where they specifically address power system reliability evaluation. It includes material which has been made available since the publication of six previous papers Bibliography on the Application of Probability Methods in Power System Reliability Evaluation, IEEE Transactions on Power Apparatus and Systems PAS-91, 1972, pp. 649-660, Pas-97, 1978, pp. 2235-2242, PAS-103, 1984, pp. 275-282, IEEE Transactions on Power Systems, Vol. 3, no. 4, Nov. 1988, pp. 1555-1564, Vol. 9, No. 1, Feb. 1994, pp. 41-49, and Vol. 14, no. 1, Feb. 1999, pp. 51-57.

  • 15.
    Björk, Joakim
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control).
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control).
    Harnefors, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Fundamental Performance Limitations in Utilizing HVDC to Damp Interarea Modes2019In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 34, no 2, p. 1095-1104Article in journal (Refereed)
    Abstract [en]

    This paper considers power oscillation damping (POD) using active power modulation of high-voltage dc transmissions. An analytical study of how the proximity between interarea modal frequencies in two interconnected asynchronous grids puts a fundamental limit to the achievable performance is presented. It is shown that the ratio between the modal frequencies is the sole factor determining the achievable nominal performance. To illustrate the inherent limitations, simulations using a proportional controller tuned to optimize performance in terms of POD are done on a simplified two-machine model. The influence of limited system information and unmodeled dynamics is shown. The analytical result is then further validated on a realistic model with two interconnected 32-bus networks.

  • 16.
    Björk, Joakim
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control).
    Obradovic, Danilo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Harnefors, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems. ABB, Corp Res, S-72178 Västerås, Sweden..
    Johansson, Karl H.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control).
    Influence of Sensor Feedback Limitations on Power Oscillation Damping and Transient Stability2022In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 37, no 2, p. 901-912Article in journal (Refereed)
    Abstract [en]

    Fundamental sensor feedback limitations for improving rotor angle stability using local frequency or phase angle measurement are derived. Using a two-machine power system model, it is shown that improved damping of inter-area oscillations must come at the cost of reduced transient stability margins, regardless of the control design method. The control limitations stem from that the excitation of an inter-area mode by external disturbances cannot be estimated with certainty using local frequency information. The results are validated on a modified Kundur four-machine two-area test system where the active power is modulated on an embedded high-voltage dc link. Damping control using local phase angle measurements, unavoidably leads to an increased rotor angle deviation following certain load disturbances. For a highly stressed system, it is shown that this may lead to transient instability. The limitations derived in the paper may motivate the need for wide-area measurements in power oscillation damping control.

  • 17.
    Björk, Joakim
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control).
    Pombo, Daniel
    Tech Univ Denmark DTU, Dept Elect Engn, DK-4000 Roskilde, Denmark.;Denmark Res & Dev Vattenfall AB, S-16956 Solna Stockholm, Sweden..
    Johansson, Karl H.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control).
    Variable-Speed Wind Turbine Control Designed for Coordinated Fast Frequency Reserves2022In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 37, no 2, p. 1471-1481Article in journal (Refereed)
    Abstract [en]

    Modern power systems present low levels of inertia due to the growing shares of converter-interfaced generation. Consequently, renewable energy sources are increasingly requested to provide frequency support. In addition, due to the inertia loss, the requirements regarding frequency containment reserves (FCR) are becoming tough to meet with traditional units such as hydro, whose non-minimum phase (NMP) characteristic reduces the closed-loop stability margins. The shortcomings of traditional synchronous generation motivates new protocols for fast frequency reserves (FFR). In this work, we design a wind turbine (WT) model useful for FFR. It is shown that the dynamical shortcomings of the WT, in providing steady-power or slow FCR support, are suitably described by a first-order transfer function with a slow NMP zero. The WT model is tested in a 5-machine representation of the Nordic synchronous grid. It is shown that the NMP model is useful for designing a controller that coordinates FFR from wind with slow FCR from hydro turbines. By simulating the disconnection of a 1400 MW importing dc link in a detailed nonlinear model, it is shown that the wind-hydro combination not only satisfies the latest regulations, but also presents a smooth response avoiding overshoot and secondary frequency dips during frequency recovery.

  • 18. Bompard, E.
    et al.
    Correia, P.
    Gross, G.
    Amelin, Mikael
    KTH, Superseded Departments (pre-2005).
    Congestion-management schemes: A comparative analysis under a unified framework2003In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 18, no 1, p. 346-352Article in journal (Refereed)
    Abstract [en]

    The restructuring of the electricity industry has spawned the introduction of new independent grid operators (IGOs), typically called transmission system operators (TSOs); independent system operator (ISOs); or regional transmission organizations (RTOs), in various parts of the world. An important task of an IGO is congestion management (CM) and pricing. This activity has significant economic implications on every. market participant in the IGO's region. The paper briefly reviews the CM schemes and the associated pricing mechanism used by the IGOs in five representative schemes. These were selected to illustrate the various CM approaches in use: England and Wales, Norway, Sweden, PJM, and California. We develop a unified framework for the mathematical representation of the market dispatch and redispatch problems that the IGO must solve in CM in these various jurisdictions. We use this unified framework to develop meaningful metrics to compare the various CM approaches so as to assess their efficiency and the effectiveness of the market signals provided to the market participants. We compare, using a small test system, side by side, the performance of these schemes.

  • 19.
    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)
  • 20.
    Cao, Xin
    et al.
    North China Elect Power Univ, Sch Elect & Elect Engn, Beijing 102206, Peoples R China.;State Grid Beijing Elect Power Res Inst, Beijing 100071, Peoples R China..
    Han, Minxiao
    North China Elect Power Univ, Sch Elect & Elect Engn, Beijing 102206, Peoples R China..
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Yan, Wenli
    Power Univ, Mathe & Phys Sch North China Elect, Beijing 102206, Peoples R China..
    A New Method for Simplifying Complex DC Systems and Obtaining the Controller Droop Coefficients2022In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 37, no 2, p. 996-1006Article in journal (Refereed)
    Abstract [en]

    DC grid has become an important application in power transmission. However, the exist works only have the method to obtain the droop coefficient in a radial topology. Also, this droop coefficient is for V-I droop control. There is no such like method to obtain the droop coefficient for the P-V droop control. This paper proposed a new method for a complex dc grid to obtain the droop coefficients. Firstly, based on the converter control strategies, the types of converter were classified. It will help to find out which kinds of converter can be participated into the dc-side voltage control. Secondly, a virtual node was defined, and the matrix of the dc grid was reshaped to fit the new added virtual node by using the proposed simplification method. An example was shown how this method worked. After that a new method of calculating the P-V droop coefficient was proposed. Finally, a simulation model was investigated to verify if the proposed method can operate in a real system. The results showed that the simplification method can ensure the mathematical relationships of the dc system. And simulations show good performances of the droop coefficient calculation method.

  • 21. Chamorro Vera, Harold Rene
    et al.
    Guel-Cortez, A.
    Kim, E.
    Gonzalez-Longat, F.
    Ortega, A.
    Martinez, W.
    Information Length Quantification and Forecasting of Power Systems Kinetic Energy2022In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 37, no 6, p. 4473-4484Article in journal (Refereed)
    Abstract [en]

    Power systems operation and planning are facing several short-coming challenges due to the large inclusion of non-synchronous generation and the constant expansion of the electrical network. One of these challenges corresponds to the monitoring and forecasting of power systems Kinetic Energy (KE) to show on-line additional information for the Transmission System Operators (TSOs). In view of this challenge, KE monitoring requires innovative methods to analyse the continuous fluctuations in the system. Moreover, KE forecasting can foresee the status of the strength to overcome further events. In this work, we propose the use of information theory (specifically the concept of information length) as a way to provide useful insight in the power system KE variability and to demonstrate its usage as a starting point in decision making for power systems management. Additionally, a short-period forecasting using a Long Short Term Memory (LSTM) neural network model is proposed to estimate the value of information length in real time. The methodology is applied to a monthly collected data from the Nordic Power System. Results show that our method provides an effective description of the seasonal statistical variability. 

  • 22.
    Chompoobutrgool, Yuwa
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Vanfretti, Luigi
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Identification of power system dominant inter-area oscillation paths2013In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 28, no 3, p. 2798-2807Article in journal (Refereed)
    Abstract [en]

    This paper presents three algorithms for identification of dominant inter-area oscillation paths: a series of interconnected corridors in which the highest content of the inter-area modes propagates through. The algorithms are developed to treat different sets of data: 1) known system model; 2) transient; and 3) ambient measurements from phasor measurement units (PMUs). These algorithms take feasibility into consideration by associating the network variables made available by PMUs, i.e., voltage and current phasors. All algorithms are demonstrated and implemented on a conceptualized Nordic Grid model. The results and comparison among three algorithms are provided. The applications of the algorithms not only facilitate in revealing critical corridors which are mostly stressed but also help in indicating relevant feedback input signals and inputs to mode meters which can be determined from the properties of dominant paths.

  • 23. Chow, J. H.
    et al.
    Chakrabortty, A.
    Vanfretti, L.
    Arcak, M.
    Estimation of Radial Power System Transfer Path Dynamic Parameters Using Synchronized Phasor Data2008In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 23, no 2, p. 564-571Article in journal (Refereed)
    Abstract [en]

    This paper develops a measurement-based method for estimating a two-machine reduced model to represent the interarea dynamics of a radial, multimachine power system. The method uses synchronized bus voltage phasor measurements at two buses and the line current on the power transfer path. The innovation is the application of the interarea oscillation components in the voltage variables resulting from disturbances for extrapolating system impedances and inertias beyond the measured buses. Expressions for the amplitudes of the bus voltage and bus frequency oscillations as functions of the location on the transmission path are derived from a small-signal perturbation approach. The reduced model provides approximate response to disturbances on the transfer path and offers an alternative to model reduction techniques based on detailed system models and data.

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  • 24.
    Cucuzzella, M.
    et al.
    University of Groningen, Groningen.
    Bouman, T.
    University of Groningen, Groningen.
    Kosaraju, K. C.
    Department of Electrical Engineering, University of Notre Dame, Notre Dame, IN, USA.
    Schuitema, G.
    College of Business, University College Dublin, Dublin, Ireland.
    Lemmen, N. H.
    University of Groningen, Groningen.
    Johnson-Zawadzki, S.
    University of Groningen, Groningen.
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Steg, L.
    University of Groningen, Groningen.
    Scherpen, J. M. A.
    University of Groningen, Groningen.
    Distributed Control of DC Grids: Integrating Prosumers' Motives2022In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 37, no 4, p. 3299-3310Article in journal (Refereed)
    Abstract [en]

    In this paper, a novel distributed control strategy addressing a (feasible) psycho-social-physical welfare problem in islanded Direct Current (DC) smart grids is proposed. Firstly, we formulate a (convex) optimization problem that allows prosumers to share current with each other, taking into account the technical and physical aspects and constraints of the grid (e.g., stability, safety), as well as psycho-social factors (i.e., prosumers' personal values). Secondly, we design a controller whose (unforced) dynamics represent the continuous time primal-dual dynamics of the considered optimization problem. Thirdly, a passive interconnection between the physical grid and the controller is presented. Global asymptotic convergence of the closed-loop system to the desired steady-state is proved and simulations based on collected data on psycho-social aspects illustrate and confirm the theoretical results.

  • 25. Enyioha, Chinwendu
    et al.
    Magnusson, Sindri
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering. KTH - Royal Institute of Technology.
    Heal, Kathryn
    Na, Li
    Carlo, Fischione
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering.
    Tarokh, Vahid
    On Variability of Renewable Energy and Online Power Allocation2018In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 33, no 1, p. 451-462Article in journal (Refereed)
    Abstract [en]

    As electric power system operators shift from conventional energy to renewable energy sources, power distribution systems will experience increasing fluctuations in supply. These fluctuations present the need to not only design online decentralized power allocation algorithms, but also characterize how effective they are given fast-changing consumer demand and generation. In this paper, we present an online decentralized dual descent (OD3) power allocation algorithm and determine (in the worst case) how much of observed social welfare can be explained by fluctuations in generation capacity and consumer demand. Convergence properties and performance guarantees of the OD3 algorithm are analyzed by characterizing the difference between the online decision and the optimal decision. We demonstrate validity and accuracy of the theoretical results in the paper through numerical experiments using real power generation data.

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    fulltext
  • 26.
    Eriksson, Robert
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Current Sharing in Multiterminal DC Grids-The Analytical Approach2018In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 33, no 6, p. 6278-6288Article in journal (Refereed)
    Abstract [en]

    This paper presents a new analytical approach for dc voltage control in dc grids. The control approach aims at improving the de voltage droop control by generalized feedback which combines the local voltage signal available at the converter terminals with remote voltage signals at different locations in the dc system by means of communication. The main contribution is an analytical approach to derive the generalized feedback gain allowing to differentiating the system response for different converter outages. The goal of the system response is to share the power, in the event of disconnection of a converter, between the remaining converters according to a predetermined scheme. The local voltage feedback control is used for fast and reliable system response, and remote signals to achieve the goal. The analysis of the feasibility space the power shares is also presented, which is a direct function of the grid layout. Simulation results show the validity of the proposed control scheme.

  • 27.
    Fan, Bo
    et al.
    Aalborg Univ, Dept Energy AAU Energy, DK-9220 Aalborg, Denmark..
    Wang, Xiongfei
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems. Aalborg Univ, Dept Energy AAU Energy, DK-9220 Aalborg, Denmark.
    Fault Recovery Analysis of Grid-Forming Inverters With Priority-Based Current Limiters2023In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 38, no 6, p. 5102-5112Article in journal (Refereed)
    Abstract [en]

    Grid-forming (GFM) inverters are required to operate robustly against grid faults. However, due to the limited over-current capability of inverters, current-limiting controls are usually applied to protect these semiconductor devices, which may prevent GFM inverters from a successful fault recovery. To understand this phenomenon, this study analyzes the fault recovery process of a GFM inverter with a priority-based current limiter. According to whether the GFM inverter can ensure transient stability and exit the current-limiting mode after fault clearance, three post-fault scenarios are identified, including normal operation, current limitation, and oscillations. Further, the impacts of the short-circuit ratio and control parameters on the post-fault behavior of GFM inverters are demonstrated. To illustrate the implications of these theoretical results, typical numerical examples are presented. Finally, the theoretical findings are validated through experimental tests.

  • 28.
    Ghandhari, Mehrdad
    et al.
    KTH, Superseded Departments (pre-2005), Electrical Systems.
    Andersson, G.
    Hiskens, I. A.
    Control Lyapunov functions for Controllable Series Devices2001In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 16, no 4, p. 689-694Article in journal (Refereed)
    Abstract [en]

    Controllable Series Devices (CSD), i.e., series-connected Flexible AC Transmission Systems (FACTS) devices, such as Unified Power Controller (UPFC), Controllable Series Capacitor (CSC) and Quadrature Boosting Transformer (QBT) with a suitable control scheme can improve transient stability and help to damp electromechanical oscillations. For these devices, a general model, which is referred to as injection model, is used. This model is valid for load flow and angle stability analysis and is helpful for understanding the impact of the CSD on power system stability. Also, based on Lyapunov theory a control strategy for damping of electromechanical power oscillations in a multi-machine power system Is derived. Lyapunov theory deals with dynamical systems without inputs. For this reason, it has traditionally been applied only to closed-loop control systems, that is, systems for which the input has been eliminated through the substitution of a predetermined feedback control. However, in this paper, we use Lyapunov function candidates in feedback design itself by making the l.yapunov derivative negative when choosing the control. This control strategy is called Control Lyapunov Function (CLF) for systems with control inputs.

  • 29.
    Grahn, Pia
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Munkhammar, Joakim
    Widén, Joakim
    Alvehag, Karin
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    PHEV Home-Charging Model Based on Residential Activity Patterns2013In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 28, no 3, p. 2507-2515Article in journal (Refereed)
    Abstract [en]

    Plug-in hybrid electric vehicles (PHEVs) have received an increased interest lately since they provide an opportunity to reduce greenhouse gas emissions. Based on the PHEV introduction level in the car park, the charging behaviors in an area will induce changes in the load profiles of the power system. Hence, it becomes important to investigate what impact a given PHEV introduction level has on load profiles due to expected charging behavior of residents.

  • 30.
    Hamon, Camille
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Perninge, Magnus
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    A Stochastic Optimal Power Flow Problem With Stability Constraints-Part I: Approximating the Stability Boundary2013In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 28, no 2, p. 1839-1848Article in journal (Refereed)
    Abstract [en]

    Stochastic optimal power flow can provide the system operator with adequate strategies for controlling the power flow to maintain secure operation under stochastic parameter variations. One limitation of stochastic optimal power flow has been that only line flows have been used as security constraints. In many systems voltage stability and small-signal stability also play an important role in constraining the operation. In this paper we aim to extend the stochastic optimal power flow problem to include constraints for voltage stability as well as small-signal stability. This is done by approximating the voltage stability and small-signal stability constraint boundaries with second-order approximations in parameter space. Then we refine methods from mathematical finance to be able to estimate the probability of violating the constraints. In this first part of the paper, we derive second-order approximations of stability boundaries in parameter space. In the second part, the approximations will be used to solve a stochastic optimal power flow problem.

  • 31.
    Herre, Lars
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Mathieu, Johanna L.
    University of Michigan, Ann Arbor, Michigan United States .
    Söder, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Impact of Market Timing on the Profit of a Risk-Averse Load Aggregator2020In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 35, no 5, p. 3970-3980Article in journal (Refereed)
    Abstract [en]

    Non-generating resources such as thermostatically controlled loads (TCLs) can arbitrage energy prices and provide balancing reserves when aggregated due to their thermal energy storage capacity. An aggregator that wants to quantify this flexibility in order to place optimal bids before gate closure, would be affected by market timing. The market timing can be quantified by parameters such as lead time and contract period. This paper explores the impact of market timing on TCL aggregate power consumption and reserve capacity bids and quantifies trade-offs between market timing and flexibility. We first optimize the power consumption and reserve capacity offers at given lead times and contract periods, varying from 24 hours ahead to real-time. We then introduce uncertainty in prices and TCL availability, formulate a two-stage chance-constrained optimization problem of a risk-averse aggregator, implement it on a rolling horizon basis, and evaluate how the trade-offs change. The results show that shorter lead times and contract periods positively impact TCL profit as well as flexibility if the prediction horizon is sufficiently long. The proposed method can be used by aggregators to decide on optimal bids and incentive payments to consumers to reward flexibility.

  • 32.
    Hesamzadeh, Mohammad
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Biggar, D. R.
    Hosseinzadeh, N.
    Wolfs, P. J.
    Transmission augmentation with mathematical modeling of market power and strategic generation expansion - Part I2011In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, ISSN 0885-8950, Vol. 26, no 4, p. 2040-2048Article in journal (Refereed)
    Abstract [en]

    This paper proposes a new mathematical structure for evaluating the economic efficiency of transmission investment in a liberalized electricity market. The problem faced by a transmission planner is modeled using the concept of social welfare from economics. The behavior of generators is modeled as the Nash equilibrium of a strategic game. The Nash solution concept is reformulated as an optimization problem and a new concept - the Stackelberg-Worst Nash equilibrium - is introduced to resolve the problem of multiple equilibria. The proposed structure can take into account the effects of a transmission augmentation on both market power and strategic generation investment. Accordingly, the optimal solution to the transmission planner's problem may allow additional transmission capacity both to reduce market power and to defer investment in the generation sector. A methodology is proposed to decompose the benefits of a transmission augmentation policy into the efficiency benefit, competition benefit, and the deferral benefit. The outcomes of the proposed approach to transmission augmentation are compared with the outcomes of two other approaches to transmission augmentation using a simple three-bus network example.

  • 33.
    Hesamzadeh, Mohammad
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Biggar, D. R.
    Hosseinzadeh, N.
    Wolfs, P. J.
    Transmission augmentation with mathematical modeling of market power and strategic generation expansion - Part II2011In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, ISSN 0885-8950, Vol. 26, no 4, p. 2049-2057Article in journal (Refereed)
    Abstract [en]

    This paper describes a numerical approach to solving the mathematical structure proposed in the first part of this paper. The numerical approach employs a standard genetic algorithm (GA) embedded with an island parallel genetic algorithm (IPGA). The GA handles the decision variables of the transmission network service provider, (TNSP) while the IPGA module finds the equilibrium of the electricity market. The IPGA module uses the concept of parallel islands with limited communication. The islands evolve in parallel and communicate with each other at a specific rate and frequency. The communication pattern helps the IPGA module to spread the best-found genes across all isolated islands. The isolated evolution removes the fitness pressure of the already-found optima from the chromosomes in other islands. A stability operator has been developed which detects stabilized islands and through a strong mutation process re-employs them in exploring the search space. To improve the efficiency of the proposed numerical solution, two high performance computing (HPC) techniques are used - shared-memory architecture and distributed-memory architecture. The application of the proposed approach to the assessment of transmission augmentation is illustrated using an IEEE 14-bus example system.

  • 34.
    Hesamzadeh, Mohammad
    et al.
    Swinburne University of Technology, Australia.
    Hosseinzadeh, N.
    Wolfs, P. J.
    Transmission System Augmentation Based on the Concepts of Quantity Withheld and Monopoly Rent for Reducing Market Power2010In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, ISSN 0885-8950, Vol. 25, no 1, p. 167-180Article in journal (Refereed)
    Abstract [en]

    This paper proposes two mathematical structures for considering the market power effect of transmission capacity in transmission augmentation assessment. These mathematical structures use the concepts of monopoly rent and quantity withheld in economics for market power modeling in the assessment process of transmission augmentation. The simultaneous-move and sequential-move games in applied mathematics are used to model the interactions of the transmission network service provider, generating companies, and the market management company in the proposed mathematical structures. The solution concept of Nash equilibria is reformulated as an optimization problem, and the multiple Nash equilibria is tackled through an introduced concept termed worst Nash equilibrium. A numerical solution is developed to solve the proposed mathematical structures. The numerical solution is an island parallel genetic algorithm nested in a standard genetic algorithm. The six-bus Garver's example system and the IEEE 14-bus test system are modified and studied. The results prove the strong mechanism of the developed structures for modeling the market power effect of transmission capacity in the assessment of transmission augmentation.

  • 35.
    Hesamzadeh, Mohammad R.
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Biggar, D. R.
    Computation of extremal-nash equilibria in a wholesale power market using a single-stage MILP2012In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 27, no 3, p. 1706-1707Article in journal (Refereed)
    Abstract [en]

    This letter proposes a new approach to the computation of extremal-Nash equilibria in a wholesale power market with transmission constraints. The approach uses linearization techniques to formulate the extremal-Nash equilibrium problem as a single-stage mixed-integer linear programming problem which can be solved with standard software. Through the introduced concept of extremal-Nash equilibria, the derived structure can efficiently locate all Nash equilibria of the game. We show that this approach offers significant performance improvements over existing approaches to computing Nash equilibria.

  • 36.
    Hesamzadeh, Mohammad Reza
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Biggar, Darryl Ross
    Merger Analysis in Wholesale Power Markets Using the Equilibria-Band Methodology2013In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 28, no 2, p. 819-827Article in journal (Refereed)
    Abstract [en]

    Around the world, electricity market regulators and competition authorities are struggling to find ways to reliably assess the likely market impact of mergers of generators. Conventional indicators of market power fail to capture key aspects of the exercise of market power in wholesale electricity markets. On the other hand, full-scale computation of Nash equilibria has historically been time consuming, non-transparent, and typically results in multiple Nash equilibria. In this paper we propose two methodological advances: an efficient approach to computing extremal-Nash equilibria in a wholesale power market with market power and the application of this approach in the assessment of wholesale market mergers. The extremal-Nash equilibria are those equilibria which have the highest or the lowest social cost to the society. The resulting formulation is a Mixed Integer Linear Program which efficiently finds the full set of extremal-Nash equilibria. The continuum of these extremal-Nash equilibria over a range of demand conditions describes the upper and lower envelopes of the Equilibria Band. To illustrate the advantages of the proposed approach, two case studies are explored, involving the New South Wales region of the Australian National Electricity Market, on the one hand, and the IEEE 14-Bus Test System, on the other.

  • 37.
    Hesamzadeh, Mohammad Reza
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Yazdani, Mohammad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Transmission Capacity Expansion in Imperfectly Competitive Power Markets2014In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 29, no 1, p. 62-71Article in journal (Refereed)
    Abstract [en]

    This paper proposes a mathematical model for transmission planning in an environment where there is imperfect competition in electricity supply industry. The model is developed based on the concept of the leader-followers game in applied mathematics. The leader of the game is the transmission planner and the followers are the strategic electricity producing firms. The reaction of the strategic electricity producing firms to the transmission planning decision is modeled using the introduced concept of the worst-Cournot-Nash equilibrium. The worst-Cournot-Nash equilibrium can handle the multiple Nash equilibria problem. The whole mathematical formulation is a bilevel mixed-integer linear programming problem. This formulation is achieved using the Karush-Kuhn-Tucker optimality conditions and a binary mapping approach. The application of the proposed approach to the three-node example system and the modified six-node Garver's example system are studied. The transmission planning with perfect competition is formulated and used as the benchmark. The numerical results show that the proposed approach in this paper can efficiently allocate the additional transmission capacity to the transmission grid such that it reduces the market power cost in the electricity supply industry. However, further studies should be carried out to scale up the proposed approach to the larger case studies.

  • 38.
    Hilber, Patrik
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Miranda, Vladimiro
    Faculty of Engineering, University of Porto.
    Matos, Manuel A.
    Faculty of Engineering, University of Porto.
    Bertling, Lina
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Multiobjective Optimization Applied to Maintenance Policy for Electrical Networks2007In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 22, no 4, p. 1675-1682Article in journal (Refereed)
    Abstract [en]

    A major goal for managers of electric power networks is maximum asset performance. Minimal life cycle cost and maintenance optimization becomes crucial in reaching this goal, while meeting demands from customers and regulators. This necessitates the determination of the optimal balance between preventive and corrective maintenance in order to obtain the lowest total cost.

    The approach of this paper is to study the problem of balance between preventive and corrective maintenance as a multiobjective optimization problem, with customer interruptions on one hand and the maintenance budget of the network operator on the other. The problem is solved with meta-heuristics developed for the specific problem, in conjunction with an evolutionary particle swarm optimization algorithm.

    The maintenance optimization is applied in a case study to an urban distribution system in Stockholm, Sweden. Despite a general decreased level of maintenance (lower total maintenance cost), better network performance can be offered to the customers. This is achieved by focusing the preventive maintenance on components with a high potential for improvements. Besides this, this paper displays the value of introducing more maintenance alternatives for every component and choosing the right level of maintenance for the components with respect to network performance.

  • 39.
    Holmgren, Åke J.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
    Westin, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
    Evaluating Strategies for Defending Electric Power Networks against Antagonistic Attacks2007In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 22, no 1, p. 76-84Article in journal (Refereed)
    Abstract [en]

    We show how concepts from game theory can be used to find and evaluate strategies for defending an electric power system against antagonistic attacks. Consequently, the interaction between the antagonist and the defender of the system is envisaged as a game. In a numerical example, we study the performance of different defense strategies against a number of attack scenarios. Particularly, we study whether there is a dominant defense strategy and an optimal allocation of resources between protection of components and recovery.

  • 40. Holttinen, H.
    et al.
    Kiviluoma, J.
    Flynn, D.
    Smith, J. C.
    Orths, A.
    Eriksen, P. B.
    Cutululis, N.
    Söder, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Korpas, M.
    Estanqueiro, A.
    Macdowell, J.
    Tuohy, A.
    Vrana, T. K.
    Oamalley, M.
    System Impact Studies for Near 100% Renewable Energy Systems Dominated by Inverter Based Variable Generation2022In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 37, no 4, p. 3249-3258Article in journal (Refereed)
    Abstract [en]

    The demand for low carbon energy calls for close to 100% renewable power systems, with decarbonization of other energy sectors adding to the anticipated paradigm shift. Rising levels of variable inverter-based renewable energy sources (VIBRES) are prompting questions about how such systems will be planned and operated when variable renewable generation becomes the dominant technology. Here, we examine the implications of this paradigm shift with respect to planning, operation and system stability, also addressing the need for integration with other energy vectors, including heat, transport and Power-to-X. We highlight the knowledge gaps and provide recommendations for improved methods and models needed as power systems transform towards 100% VIBRES.

  • 41.
    Jahn, Ilka
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Hohn, Fabian
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Chaffey, Geraint
    Katholieke Universiteit Leuven Departement Elektrotechniek, 82302 Leuven Belgium 3100.
    Norrga, Staffan
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    An Open-Source Protection IED for Research and Education in Multiterminal HVDC Grids2020In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 35, no 4, p. 2949-2958Article in journal (Refereed)
    Abstract [en]

    The integration of large amounts of renewable energy will require multiterminal high-voltage direct-current (MTDC) grids to reliably transport the energy over long distances. However, before building an MTDC grid, a functional protection system design is needed. Realistic and industrial studies are required to validate the functionality of such a system. In addition, further academic research as well as education in the field are needed. This paper presents an open-source, low-cost protection intelligent electronic device (IED) prototype for use in a laboratory environment. In particular, the IED design, its fastest measured performance, example results for different fault scenarios, and an assessment of its use in education are shown. The open-source IED is useful to accelerate industrial and academic research, as well as to enable education in protection for MTDC grids.

  • 42.
    Johansson, Nicklas
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Ängquist, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    A Comparison of Different Frequency Scanning Methods for Study of Subsynchronous Resonance2011In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 26, no 1, p. 356-363Article in journal (Refereed)
    Abstract [en]

    This paper compares four different methods for determining the electrical damping of a power system seen from one generator as a function of frequency. This information is useful when the risk for subsynchronous resonance (SSR) in the system is evaluated. The study compares one frequency scanning method which is implemented in a time-domain digital simulation program with three methods of different complexity based on analytical calculations. The time-domain simulation method is easily implemented with a detailed model of the power system including complex load and generator models, whereas the analytical methods are based on simpler models of the power system. The computational effort is much larger for the time-domain method than for the analytical methods. In the study, all methods were used to determine the damping characteristics of a four-machine power system in different configurations. The study shows that fast analytical methods may provide results which closely agree with the detailed method of time-domain simulation. However, the study also shows that the level of accuracy in the analytical model is very important.

  • 43.
    Johansson, Nicklas
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Ängquist, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    An Adaptive Controller for Power System Stability Improvement and Power Flow Control by Means of a Thyristor Switched Series Capacitor (TSSC)2010In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 25, no 1, p. 381-391Article in journal (Refereed)
    Abstract [en]

    In this paper, a controller for a thyristor switched series capacitor (TSSC) is presented. The controller aims to stabilize the power system by damping interarea power oscillations and by improving the transient stability of the system. In addition to this, a power flow control feature is included in the controller. The power oscillation damping controller is designed based on a nonlinear control law, while the transient stability improvement feature works in open loop. The damping controller is adaptive and estimates the power system parameters according to a simplified generic model of a two-area power system. It is designed for systems where one poorly damped dominant mode of power oscillation exists. In the paper, a verification of the controller by means of digital simulations of one two-area, four-machine power system, and one 23-machine power system is presented. The results show that the controller improves the stability of both test systems significantly in a number of fault cases at different levels of interarea power flow.

  • 44.
    Johansson, Nicklas
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Ängquist, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    An Adaptive Controller for Power System Stability Improvement and Power Flow Control by Means of a Thyristor Switched Series Capacitor (TSSC) (vol 25, pg 381, 2010)2010In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 25, no 2, p. 1200-1200Article in journal (Refereed)
  • 45. Keane, A.
    et al.
    Milligan, M.
    Dent, C. J.
    Hasche, B.
    D'Annunzio, C.
    Dragoon, K.
    Holttinen, H.
    Samaan, N.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    O'Malley, M.
    Capacity value of wind power2011In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 26, no 2, p. 564-572Article in journal (Refereed)
    Abstract [en]

    Power systems are planned such that they have adequate generation capacity to meet the load, according to a defined reliability target. The increase in the penetration of wind generation in recent years has led to a number of challenges for the planning and operation of power systems. A key metric for generation system adequacy is the capacity value of generation. The capacity value of a generator is the contribution that a given generator makes to generation system adequacy. The variable and stochastic nature of wind sets it apart from conventional energy sources. As a result, the modeling of wind generation in the same manner as conventional generation for capacity value calculations is inappropriate. In this paper a preferred method for calculation of the capacity value of wind is described and a discussion of the pertinent issues surrounding it is given. Approximate methods for the calculation are also described with their limitations highlighted. The outcome of recent wind capacity value analyses in Europe and North America, along with some new analysis, are highlighted with a discussion of relevant issues also given.

  • 46.
    Khastieva, Dina
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Mohammadi, Saeed
    Hesamzadeh, Mohammad Reza
    Bunn, Derek
    Optimal Transmission Investment with Regulated Incentives based upon Forward Considerations of Firm and Intermittent Resources with BatteriesIn: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679Article in journal (Refereed)
  • 47.
    Khastieva, Dina
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Mohammadi, Saeed
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Bunn, Derek W
    Optimal Transmission Investment with Regulated Incentives based upon Forward Considerations of Firm and Intermittent Resources with Batteries2021In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, IEEE Transactions on Power Systems, ISSN 0885-8950, Vol. 36, no 5, p. 4420-4434Article in journal (Refereed)
    Abstract [en]

    Regulatory support for transmission investment by private investors follows a complex process of dialogue, information sharing, commitments, and incentives. Whilst this process has attracted substantial research, the formulation of efficient solutions still remains an open question and this has become more complex with the emergence of new intermittent and battery-storage resources. We propose an optimal incentive solution in which the private transmission company earns congestion rents and an incentive fee, set by agreement with the regulator. This fee is set in the context of assessing the impact of current and future generation resources (conventional, intermittent, and batteries) on the congestion rents. The welfare-optimizing solution follows from a mixed integer, nonlinear, bilevel optimization problem, which is computationally challenging. We re-cast the problem for tractability and devise a disjunctive-based decomposition algorithm. Its performance has been successfully demonstrated on two standard IEEE case studies.

  • 48.
    Knazkins, Valerijs
    et al.
    KTH, Superseded Departments (pre-2005), Electrical Systems.
    Canizares, C. A.
    Söder, Lennart
    KTH, Superseded Departments (pre-2005), Electrical Systems.
    On the parameter estimation and modeling of aggregate power system loads2004In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 19, no 2, p. 1023-1031Article in journal (Refereed)
    Abstract [en]

    This paper addressed some theoretical and practical issues relevant to the problem of Power system load modeling and identification. Two identification techniques are developed in the theoretical framework of stochastic system identification. The identification techniques presented in this paper belong to the family of output error models; both techniques are based on well-established equations describing load recovery mechanisms having a commonly recognized physical appeal. Numerical experiments with artificially created data were first performed on the proposed techniques and the estimates obtained proved to be asymptotically unbiased and achieved the corresponding Cramer-Rao lower bound. The proposed techniques were then tested using actual field measurements taken at a paper mill, and the corresponding results were used to validate a commonly used aggregate load model. The results reported in this paper indicate that the existing load models satisfactorily describe the actual behavior of the physical load and can be reliably estimated using the identification techniques presented herein.

  • 49. Masoumzadeh, Amin
    et al.
    Nekouei, Ehsan
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control).
    Alpcan, Tansu
    Chattopadhyay, Deb
    Impact of Optimal Storage Allocation on Price Volatility in Energy-Only Electricity Markets2018In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 33, no 2, p. 1903-1914Article in journal (Refereed)
    Abstract [en]

    Recent studies show that the fast growing expansion of wind power generation may lead to extremely high levels of price volatility in wholesale electricity markets. Storage technologies, regardless of their specific forms, e.g., pump-storage hydro, large-scale, or distributed batteries, are capable of alleviating the extreme price volatility levels due to their energy usage time shifting, fast-ramping, and price arbitrage capabilities. In this paper, we propose a stochastic bilevel optimization model to find the optimal nodal storage capacities required to achieve a certain price volatility level in a highly volatile energy-only electricity market. The decision on storage capacities is made in the upper level problem and the operation of strategic/regulated generation, storage, and transmission players is modeled in the lower level problem using an extended stochastic (Bayesian) Cournot-based game. The South Australia (SA) electricity market, which has recently experienced high levels of price volatility, and a 30-bus IEEE system are considered as the case studies. Our numerical results indicate that 50% price volatility reduction in the SA electricity market can be achieved by installing either 430-MWh regulated storage or 530-MWh strategic storage. In other words, regulated storage firms are more efficient in reducing the price volatility than strategic storage firms.

  • 50.
    Matevosyan, Julija
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Minimization of Imbalance Cost Trading Wind Power on the Short-Term Power Market2006In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 21, no 3, p. 1396-1404Article in journal (Refereed)
    Abstract [en]

    Present power markets are designed for trading conventional generation. For wind generation to participate in a short-term energy market, lengthy wind power production forecasts are required. Although wind speed forecasting techniques are constantly improving, wind speed forecasts are never perfect, and resulting wind power forecast errors imply imbalance costs for wind farm owners. In this paper, a new method for minimization of imbalance costs is. developed. Stochastic programming is used to generate optimal wind power production bids for a short-term power market. A Wind power forecast error is represented as a stochastic process. The imbalance costs resulting from this strategy are then compared to the case when wind power production bids on a short-term power market are based directly on a wind speed forecast.

123 1 - 50 of 107
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