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  • 51.
    Latorre, Hector F.
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Use of Local and Remote Information in POD Control of a VSC-HVdc2009In: 2009 IEEE BUCHAREST POWERTECH / [ed] Toma L; Otomega B, NEW YORK: IEEE , 2009, p. 793-798Conference paper (Refereed)
    Abstract [en]

    VSC-HVdcs have shown to be effective means to increase margins of stability in transmission systems. An appropriate control strategy and a correct selection of input signals allow VSC-HVdcs to enhance transient stability, damp power oscillations and provide voltage support in a significant way. In this paper the use of local and remote information in control strategies for POD in the control of a VSC-HVdc are studied. Two main control strategies are considered one of them based on linear control and the other one based on nonlinear control. As local signals current through transmission lines and frequency at connecting nodes of the VSC-HVdc are used. Rotor angles and speed of the generators are used as remote signals.

  • 52.
    Latorre, Hector Fabio
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Application of Control Lyapunov Functions to voltage source converters-based high voltage direct current for improving transient stability2007In: 2007 IEEE LAUSANNE POWERTECH, VOLS 1-5, NEW YORK: IEEE , 2007, p. 244-249Conference paper (Refereed)
    Abstract [en]

    VSC-HVdc has become an important member in the field of power electronics with application in transmission systems thanks to its capability of fast response operation and independent control of active and reactive power. An appropriate control strategy and a correct selection of input signals allow the VSC-HVdc to enhance transient stability, damp power oscillations and provide voltage support in power systems in a significant way. This paper presents, as part of a development of a Multichoice Control for a VSC-HVdc, the derivation of a control strategy for transient stability, based on Control Lyapunov Function. The VSC-HVdc is represented by a general model, referred to as Injection Model which represents the VSC-HVdc as an element in the power system that provides adequate interaction with other system elements.

  • 53.
    Latorre, Hector Fabio
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Multichoice control strategy for VSC-HVdc2007In: 2007 IREP SYMPOSIUM- BULK POWER SYSTEM DYNAMICS AND CONTROL: VII REVITALIZING OPERATIONAL RELIABLITY, NEW YORK: IEEE , 2007, p. 38-44Conference paper (Refereed)
    Abstract [en]

    Multichoice Control Strategy -MCS- consists in the selection of the correct input signals that will allow the VSC-HVdc to enhance the transient stability of the system, increase the level of damping, provide voltage support at specific nodes or change the power flow in the system, as it is required by the system when disturbances occur or ordered by the operator. This paper gives a description of the MCS and presents the procedure followed in the calculation of POD signals and a comparison of those signals with the signal derived from Lyapunov theory (Control Lyapunov Function -CLF-). All the signals were used in both small and large disturbances. The formulation of the MCS is based on a synchronous connection of the VSC-HVdc.

  • 54.
    Latorre, Hector
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Improvement of Power System Stability by Using a VSC-HVdc2011In: International Journal of Electrical Power & Energy Systems, ISSN 0142-0615, E-ISSN 1879-3517, Vol. 33, no 2, p. 332-339Article in journal (Refereed)
    Abstract [en]

    The capabilities of a VSC-HVdc to improve the stability in power systems are analyzed in this paper. The analysis considers a power system which has the need for increasing the transmission capacity. Two options are analyzed: connection of a new ac transmission line or connection of a VSC-HVdc link. Different disturbances are applied in the system in order to analyze the dynamic response of the system. Supplementary control is included in the control of the VSC-HVdc. The control strategies in the supplementary control are based on nonlinear and linear theory. Furthermore, remote and local information are used as input signals in the control strategies. Simulation results clearly showed the benefits of VSC-HVdc in the improvement of power system stability.

  • 55.
    Latorre, Hector
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Active and reactive power control of a VSC-HVdc2008In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 78, no 10, p. 1756-1763Article in journal (Refereed)
    Abstract [en]

    Voltage source converter-based HVdc(VSC-HVdc) systems have the ability to rapidly control the transmitted active power, and also to independently exchange reactive power with transmissions systems. Due to these characteristics, VSC-HVdcs with a suitable control scheme can offer an alternative means to enhance transient stability, to improve power oscillations damping, and to provide voltage support. In this paper, a VSC-HVdc is represented by a simple model, referred to as the injection model. Based on this model, an energy function is developed for a multi-machine power system including VSC-HVdcs. Furthermore, based on Lyapunov theory (control Lyapunov function) and small signal analysis (modal analysis), various control strategies for transient stability and damping of low-frequency power oscillations are derived.

  • 56.
    Latorre, Hector
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Control of a VSC-HVDC operating in Parallel with AC Transmission Lines2006In: 2006 IEEE/PES TRANSMISSION & DISTRIBUTION CONFERENCE & EXPOSITION, 2006, p. 917-921Conference paper (Refereed)
    Abstract [en]

    As part of an analysis of a VSC-HVDC operating in parallel with AC transmission lines, this paper presents an adaptive control of VSC-HVDC that allows the device: to provide voltage support by means of reactive control at both ends; to damp power oscillations and improve transient stability by controlling either active or reactive power; and to control the power flow through the HVDC link. Simulations showed that the control operated correctly and that the VSC-HVDC significantly contributed to voltage stability, damping of power oscillations and improving of transient stability.

  • 57.
    Leelaruji, Rujiroj
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Vanfretti, Luigi
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Coordination of protection and VSC-HVDC systems for mitigating cascading failures2010In: 2010 International Conference on Power System Technology: Technological Innovations Making Power Grid Smarter, POWERCON2010, VDE Verlag GmbH, 2010, p. 5666604-Conference paper (Refereed)
    Abstract [en]

    This paper proposes a methodology to coordinate protection relays with a VSC-HVDC link for mitigating the occurrence of cascading failures in stressed power systems. The methodology uses a signal created from an evaluation of the relay's status and simplifications of certain system parameters. This signal is sent to a Central Control Unit (CCU) which determines corrective action in order to reduce the risk of cascading failures.

  • 58.
    Nasri, Amin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Chamorro Vera, Harold Rene
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Multi-parameter trajectory sensitivity approach to analyze the impacts of wind powerpenetration on power system transient stability2014In: CIGRE, AORC Technical meeting 2014, 2014, p. 7-Conference paper (Refereed)
    Abstract [en]

    In the most real-world power systems, the share of wind power penetration in total installed generationcapacity is rapidly increasing. This large-scale integration of wind power into an electric power systemposes challenges to the power system operators and planners. One of the main challenges is tomaintain sufficient margins for transient stability. High penetration of wind power causes reduction ofthe total kinetic energy stored in through rotating masses since wind generators are decoupled from thegrid by power electronic converters, and therefore, cannot contribute to the inertia of the grid. Theresulting reduction of grid inertia may cause higher risk of transient instability. In this paper, trajectorysensitivity analysis (TSA) technique is used to determine the impacts of decreasing inertia of differentgenerating units on the transient stability of power system. Numerical results from IEEE 10-machine39-bus test system demonstrate the usefulness of the proposed approach.

  • 59.
    Nasri, Amin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Conejo, Antonio J.
    University of Castilla-la Mancha.
    Kazempour, Seyed Jalal
    University of Castilla-la Mancha.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Minimizing Wind Power Spillage Using an OPF With FACTS Devices2014In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 29, no 5, p. 2150-2159Article in journal (Refereed)
    Abstract [en]

    This paper proposes an optimal power flow (OPF) model with flexible AC transmission system (FACTS) devices to minimize wind power spillage. The uncertain wind power production is modeled through a set of scenarios. Once the balancing market is cleared, and the final values of active power productions and consumptions are assigned, the proposed model is used by the system operator to determine optimal reactive power outputs of generating units, voltage magnitude and angles of buses, deployed reserves, and optimal setting of FACTS devices. This system operator tool is formulated as a two-stage stochastic programming model, whose first-stage describes decisions prior to uncertainty realization, and whose second-stage represents the operating conditions involving wind scenarios. Numerical results from a case study based on the IEEE RTS demonstrate the usefulness of the proposed tool.

  • 60.
    Nasri, Amin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Eriksson, Robert
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Suitable placements of multiple FACTS devices to improve the transient stability using trajectory sensitivity analysis2013In: North American Power Symposium (NAPS), 2013, IEEE conference proceedings, 2013, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Trajectory sensitivity analysis (TSA) is used as a tool for suitable placement of multiple series compensators in the power system. The goal is to maximize the benefit of these devices in order to enhance the transient stability of the system. For this purpose, the trajectory sensitivities of the rotor angles of the most critical generators with respect to the reactances of transmission lines are calculated in the presence of the most severe faults. Based on the obtained trajectory sensitivities, a method is proposed to determine how effective the series compensation of each transmission line is for improving the transient stability. This method is applied to the Nordic-32 test system to find the priorities of the transmission lines for installation of several series compensators. Simulation with industrial software shows the validity and efficiency of the proposed method.

  • 61.
    Nasri, Amin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Eriksson, Robert
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Using trajectory sensitivity analysis to find suitable locations of series compensators for improving rotor angle stability2014In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 111, p. 1-8Article in journal (Refereed)
    Abstract [en]

    This paper proposes an approach based on trajectory sensitivity analysis (TSA) to find most suitable placement of series compensators in the power system. The main objective is to maximize the benefit of these devices in order to enhance the rotor angle stability. This approach is formulated as a two-stage problem, whose first-stage describes prior to fault occurrence and whose second-stage represents the power system behavior involving a set of severe faults. The first-stage focuses on small signal stability, while the second-stage deals with transient stability of power system. In this vein, the trajectory sensitivities of the rotor angles of generators with respect to the reactances of transmission lines are calculated. Two equivalent rotor angles are introduced to find stability indices corresponding to the first- and the second-stage of the proposed approach. Numerical results from IEEE 10-machine 39-bus test system demonstrate the usefulness of the proposed method.

  • 62.
    Nasri, Amin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Eriksson, Robert
    Appropriate placement of series compensators to improve transient stability of power system2012In: Innovative Smart Grid Technologies-Asia (ISGT Asia), 2012 IEEE, IEEE conference proceedings, 2012, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Trajectory sensitivity analysis is used to find the best places for installation of thyristor controlled series capacitors (TCSC) to improve transient stability of the power system. Based on the rotor angles of generators, an equivalent angle (δeq) is defined by determining accelerating and decelerating machines, and then using trajectory sensitivities of this angle with respect to the impedances of the transmission lines in the post-fault system, appropriate locations for placing TCSC will be found. Severity of the faults is also considered in this calculation. This method is applied to the IEEE 3-machine 9-bus test system to find the priorities of the transmission lines for installation of TCSC. Simulation with industrial software verifies the obtained results.

  • 63.
    Nasri, Amin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Eriksson, Robert
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Transient stability assessment of power systems in the presence of shunt compensators using trajectory sensitivity analysis2013In: 2013 IEEE Power and Energy Society General Meeting (PES), IEEE , 2013, p. 6672163-Conference paper (Refereed)
    Abstract [en]

    Trajectory sensitivity analysis (TSA) is used as analysis tool for suitable placement of shunt compensators in the power system. The goal is to maximize the benefit of these devices in order to enhance the transient stability of the system. For this purpose, the trajectory sensitivities of the rotor angles of generators with respect to the reactive power injected into different nodes of the system are calculated in the presence of most probable severe faults. Based on the obtained trajectory sensitivities, a method is proposed to determine how effective the shunt compensation in each node is for improving the transient stability. This method is applied to the IEEE 3-machine 9-bus to find the priorities of system's nodes for installation of shunt compensators. Simulation with industrial software shows the validity and efficiency of the proposed method.

  • 64.
    Nasri, Amin
    et al.
    KTH, School of Electrical Engineering (EES).
    Kazempour, S. Jalal
    Conejo, Antonio J.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES).
    Network-Constrained AC Unit Commitment Under Uncertainty: A Benders' Decomposition Approach2016In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 31, no 1, p. 412-422Article in journal (Refereed)
    Abstract [en]

    This paper proposes an efficient solution approach based on Benders' decomposition to solve a network-constrained ac unit commitment problem under uncertainty. The wind power production is the only source of uncertainty considered in this paper, which is modeled through a suitable set of scenarios. The proposed model is formulated as a two-stage stochastic programming problem, whose first-stage refers to the day-ahead market, and whose second-stage represents real-time operation. The proposed Benders' approach allows decomposing the original problem, which is mixed-integer nonlinear and generally intractable, into a mixed-integer linear master problem and a set of nonlinear, but continuous subproblems, one per scenario. In addition, to temporally decompose the proposed ac unit commitment problem, a heuristic technique is used to relax the inter-temporal ramping constraints of the generating units. Numerical results from a case study based on the IEEE one-area reliability test system (RTS) demonstrate the usefulness of the proposed approach.

  • 65.
    Nasri, Amin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Seyed Jalal, Kazempour
    Mechanical Engineering, Johns Hopkins University.
    Conejo, Antonio J.
    The Ohio State University.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Network-constrained AC Unit Commitment under Uncertainty: A Benders’ Decomposition ApproachManuscript (preprint) (Other academic)
    Abstract [en]

    This paper proposes an efficient solution approachbased on Benders’ decomposition to solve a network-constrainedac unit commitment problem under uncertainty. The wind powerproduction is the only source of uncertainty considered in thispaper, which is modeled through a suitable set of scenarios.The proposed model is formulated as a two-stage stochasticprogramming problem, whose first-stage refers to the day-aheadmarket, and whose second-stage represents real-time operation.The proposed Benders’ approach allows decomposing the originalproblem, which is mixed-integer non-linear and generallyintractable, into a mixed-integer linear master problem and aset of non-linear, but continuous subproblems, one per scenario.In addition, to temporally decompose the proposed ac unitcommitment problem, a heuristic technique is used to relaxthe inter-temporal ramping constraints of the generating units.Numerical results from a case study based on the IEEE one-areareliability test system (RTS) demonstrate the usefulness of theproposed approach.

  • 66.
    Nazari, Mohammad
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Baradar, Mohamadreza
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    On-line control of multi-terminal HVDC systems connected to offshore wind farms using the POF-based multi-agent approarch2015Conference paper (Other academic)
    Abstract [en]

    Multi-terminal HVDC systems are an attractive option to connect offshore wind farms to onshore grids. Although scheduling the multi-terminal HVDC system is based on forecasted wind power, the forecasted values may differ from their real time ones. This paper presents a new controller based on multi-agent system which optimally tries to follow the variations of real time wind power outputs. Since a fast optimal power flow algorithm is needed, a convexified AC-OPF model which can be efficiently solved through interior point methods (IPMs) is embedded into the proposed online controller. Simulations are carried out and validated using GAMS platform and MATLAB/Simulink.

  • 67.
    Nazari, Mohammad
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Application of Multi-Agent Control to Multi-Terminal HVDC Systems2013In: 2013 IEEE Electrical Power & Energy Conference (EPEC), IEEE Computer Society, 2013, p. 6802960-Conference paper (Refereed)
    Abstract [en]

     This paper addresses control of DC voltage in a multi-terminal HVDC system. The proposed control strategy in this paper utilizes multi-agent control methodology to control the set values of the DC voltages of converters. The input data used for the proposed control is based on either local or a combination of local and remote information. For the remote data, a time delay for received information is considered. Some case studies are presented using MATLAB / Simulink to show the performance of the proposed control method.

  • 68.
    Nilsson, Martin
    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.
    Eriksson, Robert
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Ghandari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Ericsson, Göran
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Designing new proactive control-room strategies to decrease the need for automatic reserves2017In: 2017 IEEE PES Innovative Smart Grid Technologies Conference Europe, ISGT-Europe 2017 - Proceedings, 2017Conference paper (Refereed)
    Abstract [en]

    Maintaining automatic reserve capacities is essential for a sustainable and reliable power system. Today, many power systems experience more frequent frequency deviations coming from increased power variations. This implies an increased utilization of automatic reserves. To decrease frequency deviations, one can increase the automatic reserve capacities. However, the solution tends to be costly and ineffective. Therefore, it is urgent to develop better solutions to cease this trend. Here we have designed new proactive control-room strategies to decrease the need for automatic reserves. We design strategies for a process called Re-Scheduling of Generation and for the Tertiary Frequency Control process. The new control-room strategies are tested using an intra-hour model comparing already used strategies against new ones. It is shown that the historical used strategies are well executed. Nevertheless, results show that the proactive TFC-strategy using a forecasted frequency as control parameter would improve system security significantly.

  • 69. Noroozian, M.
    et al.
    Ghandhari, Mehrdad
    KTH, Superseded Departments, Electric Power Systems.
    Andersson, Göran
    KTH, Superseded Departments, Electric Power Systems.
    Grönquist, J.
    Hiskens, I.
    A robust control strategy for shunt and series reactive compensators to damp electromechanical oscillations2001In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 16, no 4, p. 812-817Article in journal (Refereed)
    Abstract [en]

    This paper examines the enhancement of power system stability properties by use of thyristor controlled series capacitors (TCSCs) and static var systems (SVCs). Models suitable for incorporation in dynamic simulation programs used to study angle stability are analyzed. A control strategy for damping of electromechanical power oscillations using an energy function method is derived. Using this control strategy each device (TCSC and SVC) will contribute to the damping of power swings without deteriorating the effect of the other power oscillation damping (POD) devices. The damping effect is robust with respect to loading condition, fault location and network structure. Furthermore, the control inputs are based on local signals. The effectiveness of the controls are demonstrated for model power systems.

  • 70. Noroozian, M.
    et al.
    Ängquist, L.
    Ghandhari, Mehrdad
    KTH, Superseded Departments, Electrical Systems.
    Andersson, Göran
    KTH, Superseded Departments, Electrical Systems.
    Improving power system dynamics by series-connected facts devices1997In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 12, no 4, p. 1635-1640Article in journal (Refereed)
    Abstract [en]

    This paper examines improvement of power system dynamics by use of unified power flow controller (UPFC), thyristor controlled phase shifting transformer (TCPST) and thyristor controlled series capacitor (TCSC). Models suitable for incorporation in dynamic simulation programs for studying angle stability are analysed. A control strategy for damping of electromechanical power oscillations using an energy function method is derived. The achieved control laws are shown to be effective both for damping of large signal and small signal disturbances and are robust with respect to loading condition, fault location and network structure. Furthermore, the control inputs are easily attainable from the locally measurable variables. The effectiveness of the controls are demonstrated for model power systems.

  • 71. Noroozian, M.
    et al.
    Ängquist, L.
    Ghandhari, Mehrdad
    KTH, Superseded Departments, Electric Power Systems.
    Andersson, Göran
    KTH, Superseded Departments, Electric Power Systems.
    Use of UPFC for optimal power flow control1997In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 12, no 4, p. 1629-1634Article in journal (Refereed)
    Abstract [en]

    This paper deals with optimal power flow control in electric power systems by use of unified power flow controller (UPFC). Models suitable for incorporation in power flow programs are developed and analysed. The application of UPFC for optimal power flow control is demonstrated through numerical examples. It is shown that a UPFC has the capability of regulating the power flow and minimising the power losses simultaneously. An algorithm is proposed for determining the optimum size of UPFC for power flow applications. The performance of UPFC is compared with that of a phase shifting transformer (PST).

  • 72.
    Obradovic, Danilo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Eriksson, Robert
    Swedish Natl Grid, Market & Syst Dev, Sundbyberg, Sweden..
    Assessment and Design of Frequency Containment Reserves with HVDC Interconnections2018In: 2018 2018 North American Power Symposium (NAPS), Institute of Electrical and Electronics Engineers (IEEE), 2018, article id 8600593Conference paper (Refereed)
    Abstract [en]

    Frequency control is one of the main actions in power system operation, since large frequency deviation from the nominal value can lead to automatic frequency protection triggering to avoid equipment damaging. The three main factors which affect the dynamical response of the frequency include the amount of power imbalance due to a disturbance, available reserves and total inertia of the system. Due to increased integration of renewable energy sources, the total inertia of the system decreases and makes the speed of the response more sensitive to power balance disturbances. This paper assesses the dynamical performance of generators involved in the Frequency Containment Reserves and correlates them with additional Emergency Power Control from High Voltage Direct Current (HVDC) interconnections. The currently used constant power ramp control and a new proposed frequency droop control of HVDC interconnections are investigated for different amounts of inertia in a test system representing the Nordic Power System. The performance of each HVDC control is evaluated with respect to the maximum Instantaneous Frequency Deviation and the amount of power required for provided frequency control actions.

  • 73.
    Oluic, Marina
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Berggren, Bertil
    ABB Corp Res, S-72178 Vasteras, Sweden..
    Echavarren, Francisco M.
    Comillas Pontificia Univ, Inst Res Technol, ICAI Sch Engn, Madrid 28015, Spain..
    Ghandari, Mehrdad
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Rouco, Luis
    Univ Pontificia Comillas, Inst Invest Tecnol, Madrid 28015, Spain..
    On the Nature of Voltage Impasse Regions in Power System Dynamics Studies2018In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 33, no 3, p. 2660-2670Article in journal (Refereed)
    Abstract [en]

    This paper presents a fundamental study of voltage collapses that occur on a post-fault trajectory of a stressed power system in seconds after large disturbances. The focus of the study are voltage collapses that are induced by certain load models. Using an n-machine-N-bus power system model, the paper explicitly shows that the voltage collapse is caused by the non-existence of a real, positive solution for a load voltage magnitude in different areas of a relative rotor angle space when the load is of non-linear type. These "areas without voltage solution" are denoted as Voltage Impasse Regions (VIR) and are mathematically characterized as trigonometric functions of (n-1) relative rotor angles. Once the post-fault trajectory enters a VIR, voltage magnitude solutions become complex or negative, the algebraic Jacobian becomes singular, and the behaviour of a system becomes undefined. The case study has been carried out using a simple 3-machine-1-load system with static load models. In the study, VIR appeared and enlarged as the non-linear (constant power and constant current) load increased. Furthermore, the non-convergence of time-domain solution occurred exactly at VIR, thereby confirming that the problem is of structural nature.

  • 74.
    Oluic, Marina
    et al.
    KTH, School of Electrical Engineering (EES).
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric power and energy systems.
    Berggren, B.
    ABB Corporate Research.
    On the parametrization of Rotor Angle transient Stability region2015In: 2015 North American Power Symposium, NAPS 2015, 2015Conference paper (Refereed)
    Abstract [en]

    In this paper, we introduce a wider perspective in Rotor Angle Stability (RAS) analysis, by mapping parts of state-space boundary of interest to parameter space boundary points. These points are obtained using the Time Domain Simulation (TDS), the Closest Unstable Equilibrium Point (UEP) approximation, and the Potential Energy Boundary Surface (PEBS) concepts. Then analytical parameter-space boundaries are constructed using polynomial regression model with optimal fit coefficients in least squares terms. Security boundaries constructed in this manner directly give information about critical clearing times for different faults and operating states, and are suitable as an on-line tool for transient stability assessment.

  • 75.
    Oluic, Marina
    et al.
    KTH, School of Electrical Engineering (EES), Electric power and energy systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric power and energy systems.
    Berggren, Bertil
    ABB.
    Methodology for Rotor Angle Transient Stability Assessment in Parameter Space2016In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, no 99Article in journal (Refereed)
    Abstract [en]

    In this paper, an efficient methodology to assess Rotor Angle Stability (RAS) in parameter-space has been proposed. This methodology maps deformations of the power system RAS region under operational changes to a security region in parameter-space that can be assessed on-line. In order to choose the proper parametrization, security boundaries have been constructed using polynomial regression models with coefficients obtained from Ordinary Least Squares (OLS). The identification of suitable parametrization has been carried out, and the newly introduced sensitivity of a SIngle Machine Equivalent (SIME) has been employed to describe the behaviour of a power system along different parameter-space directions. For the chosen parametrization, Constrained Least Squares (CLS) optimization set up as a Quadratic Programming (QP) problem has been used in order to keep the estimates inside the security region. The case study has been carried out using small test systems in two and three-dimensional parameter-spaces.

  • 76.
    Raak, Fredrik
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems. Kyoto University, Japan.
    Susuki, Yoshihiko
    Hikihara, Takashi
    Chamorro, Harold
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Partitioning Power Grids via Nonlinear Koopman Mode Analysis2014In: 2014 IEEE PES Innovative Smart Grid Technologies Conference, ISGT 2014, IEEE conference proceedings, 2014, p. 6816374-Conference paper (Refereed)
    Abstract [en]

    This paper proposes a new method for partitioning power grids based on the nonlinear Koopman Mode Analysis (KMA). Grid partitioning is the fundamental problem in the controlled islanding strategy. The KMA is a new technique of nonlinear modal decomposition based on properties of the point spectrum of the so-called Koopman operator. The key idea in the proposed method is to determine a set of islanded sub-grids using KMA of data on voltage angle dynamics of every bus. The method is numerically investigated with the IEEE 118-bus test system. It is shown that the proposed method provides partitions on a multiple frequency scale as well as captures the intrinsic structural properties of a grid characterized by spectral graph theory.

  • 77. Sahlin, Jakob
    et al.
    Eriksson, Robert
    Ali, Muhammad Taha
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Ghandari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Transmission Line Loss Prediction Based on Linear Regression and Exchange Flow Modelling2017In: 2017 IEEE Manchester PowerTech, Powertech 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7980810Conference paper (Refereed)
    Abstract [en]

    Inaccurate line loss predictions leads to additional regulation costs for Transmission System Operators (TSOs) that place energy bids at the day-ahead market to account for these losses. This paper presents a line loss prediction model design, applicable with the TSOs forecast conditions, that can reduce additional expenditure due to inaccurate predictions. The model predicts line losses for the next day per bidding area in relation to prognosis data on electrical demand, supply, renewable energy generation and regional exchange flows. Linear regression analysis can extract these relation factors, known as line loss rates, and derive a line loss prediction with increased accuracy and precision. Required input data is available at the power exchange markets apart from future exchange flows, which instead have been modelled as an optimisation problem and predicted by linear programming. Simulations performed on the Swedish National Grid for 2015 demonstrate the models performance and adequacy for TSO application.

  • 78.
    Samadi, Afshin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Eriksson, Robert
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Jose, Della
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Mahmood, Farhan
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Comparison of a Three-Phase Single-Stage PV System in PSCAD and PowerFactory2012In: Proceedings of the 2nd International Workshop on Integration of Solar Power into Power Systems, Energynautics GmbH , 2012, p. 237-244Conference paper (Refereed)
  • 79.
    Samadi, Afshin
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Reactive Power Dynamic Assessment of a PV System in a Distribution Grid2012In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 20, p. 98-107Article in journal (Refereed)
    Abstract [en]

    Accommodating more and more PV systems in grids has raised new challenges that formerly had not been considered and addressed in standards. According to recently under-discussed standards, each PV unit is allowed to participate in reactive power contributions to the grid to assist voltage control. There are some PV models in the literature however those models mostly assumed unity power factor operation for PV systems owing to the contemporary standards. Therefore, there is a need to develop a PV model considering the reactive power contribution and its dynamic influence on power system. This paper describes non-proprietary modeling of a three-phase, single stage PV system consisting of controller scheme design procedure and coping with the important aspects of three different reactive power regulation strategies and their impact assessment studies. The model is implemented in PSCAD to examine the behavior of the proposed model for recently codified reactive power strategies. Furthermore, this model is integrated in a distribution grid with two PV systems in order to effectively investigate consequences of the different reactive power control strategies on the distribution network.

  • 80. Shi, Z. P.
    et al.
    Wang, J. P.
    Gajic, Z.
    Sao, C.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    The comparison and analysis for loss of excitation protection schemes in generator protection2012In: Developments in Power Systems Protection, 2012. DPSP 2012. 11th International Conference on, 2012, no 593 CP, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Loss-Of-Excitation (LOE) condition of a generator may cause severe damages on both generator and the interconnected systems. This paper analyses the behaviours of different LOE protection schemes, such as R-X, G-B, P-Q and U-I schemes, for a hydro generator, which is connected to an infinite bus. Based on the simulation results, the reliability and stability of existing LOE protection schemes are compared and a preferred scheme is selected. An improvement to the scheme is also proposed to prevent the LOE relay incorrect operation during external faults, such as short-circuit faults on busbar or transmission lines.

  • 81. Singh, J. G.
    et al.
    Qazi, H. W.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric power and energy systems.
    Load curtailment minimization by optimal placement of Unified Power Flow Controller2016In: International Transactions on Electrical Energy Systems, ISSN 2050-7038, Vol. 26, no 10, p. 2272-2284Article in journal (Refereed)
    Abstract [en]

    In this paper, a new sensitivity-based approach is proposed to minimize the load curtailment by optimal placement of series controller of the Unified Power Flow Controller (UPFC) in the power system. The proposed sensitivity factors are derived in terms of change in load curtailment with respect to change in UPFC series control parameters. The effectiveness of the proposed method has been investigated by formulating an optimal power flow problem with an objective to minimize the load curtailment. Results have been obtained on IEEE 14-bus and IEEE 30-bus systems. It has been shown that required load curtailment drastically reduced with placement of UPFC and could be effective in various operating conditions of power system. With this technique, a large amount of power curtailment could be avoided, hence, saved from revenue loss, social disobedience, and customer service interruption.

  • 82.
    Van Hertem, Dirk
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Eriksson, Robert
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Coordination of multiple power flow controlling devices in transmission systems2010In: ACDC 2010: 9th International Conference on AC and DC Power Transmission, 2010Conference paper (Refereed)
  • 83.
    van Hertem, Dirk
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Eriksson, Robert
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Coordination of multiple power flow controlling devices in transmission titles2010In: Proceedings of 9th international conference on AC and DC transmission, 2010, Vol. 9Conference paper (Refereed)
    Abstract [en]

    Power flow controlling devices are increasingly present in meshed systems. These devices have strong influence on the power flows throughout the power system. As such, they influence each others operation. In order to make a more optimal and efficient use of their controllability, coordination is needed. This coordination can increase transmission capacity and security, both in steady-state and dynamically. The effect of coordination is shown using two simple examples.

  • 84.
    Van Hertem, Dirk
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Multi-terminal VSC HVDC for the European supergrid: Obstacles2010In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 14, no 9, p. 3156-3163Article, review/survey (Refereed)
    Abstract [en]

    For many, the supergrid is seen as the solution that allows the massive integration of renewable energy sources in the European power system. It connects different remote energy sources to the existing grid while offering additional control. It offers balancing through geographic spread and allows a more diversified energy portfolio. In the meanwhile it increases the security of supply. However, technical limitations exist, and it is not yet possible to construct such a supergrid. Several outstanding issues need to be solved. This paper first describes the potential and need for a supergrid. The paper focuses on a meshed, multi-terminal VSC HVDC, and it is explained why this relatively new technology is believed to be the best suitable one for such a grid. The different difficulties or challenges that still exist are addressed. Not only the remaining technical limitations are addressed, but also the techno-economic, control and operational issues are discussed, as well as some regulatory obstacles.

  • 85.
    Van Hertem, Dirk
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems. Department of Electrical Engineering, Belgium .
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Curis, J. B.
    Despouys, O.
    Marzin, A.
    Protection requirements for a multi-terminal meshed DC grid2011In: Cigrè International Symposium THE ELECTRIC POWER SYSTEM OF THE FUTURE Integrating supergrids and microgrids location, 2011Conference paper (Refereed)
    Abstract [en]

    Multi-terminal high voltage direct current (HVDC) or meshed DC grid is considered to be the preferable option for the much anticipated future supergrid for Europe. This supergrid should connect distant generators to increase the introduction of renewable energy sources and to provide an increased security to the pan- European power system. Although many technical limitations remain, the protection system is often regarded as the most critical one. The protection system for a meshed DC system has particular difficulties compared to the traditional AC system because of the DC current that has no zero crossings and the line impedance that does not limit the fault current. As a consequence, the DC currents will rise much faster and interrupting the fault current is significantly more difficult in the meshed DC than it is in an AC meshed system. Furthermore, traditional protection devices such as impedance relays cannot be used. New alternatives must be found, such as considering a joint strategy between the protection devices and the VSC converter controls. In order to provide a reliable supply of electric energy, the protection system of a meshed DC system should have a number of minimum requirements: fast fault detection, selectivity in opening the correct breakers, and redundancy.

    This paper discusses the different requirements for the protection of a multi-terminal meshed HVDC system. It will provide a list of boundary conditions for such a protection system, as well as an overview of the current state of the technology and the remaining gaps. Some pointers to potential technologies that may be used in the future grid protection are given. The paper will not focus on hardware developments, but will rather indicate the requirements that these devices (or joint set of devices) must fulfill.

  • 86.
    Van Hertem, Dirk
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Delimar, Marko
    Technical limitations towards a SuperGrid - A European prospective2010In: Energy Conference and Exhibition (EnergyCon), 2010 IEEE International, 2010, p. 302-309Conference paper (Refereed)
    Abstract [en]

    In the search for a more sustainable energy supply, renewable energy sources are increasingly introduced into the power system. However, most of these sources are located far from the load centers, and the existing power system is getting overloaded. A supergrid is by many seen as a viable solution that allows a massive integration of these renewable energy sources into the European power system. By connecting energy sources that are located far from each other and by offering enhanced control, balancing services can be delivered. The geographic spread in its turn allows a more diversified energy portfolio. In the meanwhile it increases the security of supply. Although the supergrid has gotten much attention, it cannot be built yet. While the basic technology might seem available, several technical limitations still exist. This paper first describes the potential and need for a supergrid. The paper focuses on a meshed, multi-terminal VSC HVDC, and it is explained why this relatively new technology is believed to be the best suitable one for such a grid. Next the different difficulties or challenges that still exist are addressed.

  • 87.
    Xi, Jiangnan
    et al.
    KTH.
    Chamorro, Harold R.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Persson, Jonas
    Westberg, Andreas
    Wall, Daniel
    Ghandari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    On the Influence of the Backlash Governor Settings on the Frequency Response in Power Systems2016In: 2016 IEEE PES ASIA-PACIFIC POWER AND ENERGY ENGINEERING CONFERENCE (APPEEC), IEEE conference proceedings, 2016, p. 732-737Conference paper (Refereed)
    Abstract [en]

    The automatic frequency containment reserve (FCR-N) is in place to keep the electric frequency within the interval 50.0 +/-0.1 Hz during normal operation. This function is mainly provided by a number of hydropower plants where the turbine governor is set to control the discharge in proportion to the measured frequency deviation. In later years it has been shown that the disturbance damping is very low in an interval around 1160 Hz and it is believed that proper tuning of the turbine governors that provide FCR-N can help mitigating this problem. New regulator settings have been suggested to improve the performance of the FCR-N, yet keeping the system robust and the wear on participating units at a minimum. It is now desired to investigate the possible effects of new governor settings on the overall power system frequency response. In a word, the overall performance for new governor settings are tested in a large scale power system model in this thesis paper. The frequency response with the newly suggested governor settings have been investigated when introducing a disturbance into the system. Secondly, the effects of the new governor settings on electro-mechanical oscillations are also investigated.

  • 88. Zhou, Ye
    et al.
    Tian, Yuan
    Wang, Keyou
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    ROBUST OPTIMIZATION FOR AC-DC POWER FLOW BASED ON SECOND-ORDER CONE PROGRAMMING2017In: The Journal of Engineering, ISSN 1872-3284, E-ISSN 2051-3305Article in journal (Refereed)
    Abstract [en]

    This paper presents an adjustable robust optimization method for AC-DC optimal power flow (OPF) considering the uncertainty of renewable energy source (RESs). The optimal power flow of AC-DC system is modeled as a second-order cone (SOC) problem, and the affinely adjustable robust OPF (AAROPF) formulation is proposed. To apply AAROPF, the base-point generation is calculated and determined to match the power with forecasted RES output before the realization of the uncertainty. And once the uncertainty is revealed, generators reschedule its output through participation factors responding to the uncertain fluctuation of RES output to ensure a feasible solution for all realizations of RES output within a prescribed uncertainty set. Numerical results are obtained on a modified AC-DC IEEE 30-bus to minimize the expected operational cost. Results reveal a higher cost using AAROPF than the deterministic case, but it obtains a more robust solution with higher successful rates.

  • 89.
    Zografos, Dimitrios
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Estimation of Power System Inertia2016In: Power and Energy Society General Meeting (PESGM), 2016 17-21 July 2016, 2016Conference paper (Refereed)
    Abstract [en]

    Information about power system inertia is of utmost importance for the Transmission System Operators (TSOs), so that it can be guaranteed that the stability of the system is not under risk. A new offline inertia estimation method is proposed in this paper. The method includes the calculation of the total power change after a disturbance in the system, based on selection of appropriate time ranges of the Rate Of Change Of Frequency(ROCOF) curve. Nordic32 test system is used for the simulations, where different disturbances, load dynamics and data processing tools are considered. Finally, a comparison of the proposed method to two methods proposed in the past takes place.

  • 90.
    Zografos, Dimitrios
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Power system inertia estimation by approaching load power change after a disturbance2017In: Power & Energy Society General Meeting, 2017 IEEE, Chicago, IL, USA: Institute of Electrical and Electronics Engineers (IEEE), 2017Conference paper (Refereed)
    Abstract [en]

    The substitution of conventional synchronous power plants by intermittent generation leads to reduced power system inertia. This transition deteriorates system's frequency response and necessitates the estimation of power system inertia, so that adequate power resources are preserved. An offline estimation method is proposed in this paper, which aims to estimate the power change of the loads due to voltage dependency after a disturbance. To do that, data available at the generator buses are employed. The proposed method is applied on a modified version of Nordic32 test system under twenty different scenarios, which include generator and load disconnections. Finally, a comparison with two offline methods presented in the past literature takes place and demonstrates the advantages and disadvantages of the proposed method.

  • 91.
    Zografos, Dimitrios
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Eriksson, R.
    Power system inertia estimation: Utilization of frequency and voltage response after a disturbance2018In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 161, p. 52-60Article in journal (Refereed)
    Abstract [en]

    Power system inertia is gradually being reduced due to the ongoing replacement of conventional synchronous power plants by intermittent generation. This affects the frequency response of the system and necessitates the estimation of power system inertia, so that sufficient power reserves are retained. This paper contributes with a novel disturbance-based inertia estimation method, that simultaneously estimates the power change after a disturbance. The proposed method accommodates the frequency and voltage dynamics, which significantly affect the system's power change, and hence the inertia estimation. Two separate approaches – that are also capable of standing alone – are combined, in order to accommodate the dynamics. An extended version of the Nordic32 test system is used for the application of the method, where several case studies and a comparison are investigated, so as to examine the method's accuracy and robustness.

  • 92.
    Zografos, Dimitrios
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Paridari, Kaveh
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Estimation of power system inertia using particle swarm optimization2017In: 2017 19th International Conference on Intelligent System Application to Power Systems, ISAP 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 8071383Conference paper (Refereed)
    Abstract [en]

    Power system inertia is being globally reduced, due to the substitution of conventional synchronous power plants by intermittent generation. This threatens the frequency stability of the system and makes the estimation of power system inertia necessary, so that proactive measures can be imposed. A disturbance-based method is proposed in this paper, which estimates the total inertia constant of the power system. The method applies particle swarm optimization (PSO) to minimize a cost function, which is defined based on the swing equation. To do that, data available at the generator buses are employed. The proposed method is applied on the Nordic57 test system under twenty different scenarios, which include generator and load disconnections. Furthermore, a comparison with two methods presented in the literature is performed and demonstrates the higher performance of the proposed method, in the sense of the mean and the variance of the errors.

  • 93.
    Zografos, Dimitrios
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Rabuzin, Tin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Eriksson, Robert
    Prediction of Frequency Nadir by Employing a Neural Network Approach2018In: 2018 IEEE PES Innovative Smart Grid Technologies Conference Europe (ISGT-Europe), Institute of Electrical and Electronics Engineers (IEEE), 2018Conference paper (Refereed)
    Abstract [en]

    The increased integration rate of inverter-interfaced devices is affecting the frequency response of the modern power systems. This leads to an increase of the variability of the power generation and to a reduction of the total system's inertia. This evolution of the system necessitates the prediction of frequency metrics, so that the frequency stability of the system can be guaranteed and that necessary mitigation measures can be taken. This paper proposes a method to predict the frequency nadir by using a Neural Network (NN) approach. As the approach uses measurements during a first short time period after the event, it more accurately predicts the frequency nadir compared to using static values. Several inputs for the NN are examined and when the appropriate ones are selected, a highly accurate prediction is accomplished.

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