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Reconstructing and Tracking Network State from a Limited Number of Synchrophasor Measurements ; Van Cutsem, Thierry in IEEE Transactions on Power Systems (2013), 28 A method is proposed to reconstruct and track network state from a limited number of Phasor Measurement Unit (PMU) data. To deal with the resulting unobservability, the state with bus powers and generator ... [more ▼] A method is proposed to reconstruct and track network state from a limited number of Phasor Measurement Unit (PMU) data. To deal with the resulting unobservability, the state with bus powers and generator voltages closest to previously estimated values is computed. Those values, treated as pseudomeasurements, are obtained from the last reconstructed state, in a recursive manner. The method involves solving an optimization problem with linear constraints. It is scalable insofar as it accommodates from a few PMUs up to configurations ensuring full network observability. Reconstruction of only a region is possible. These and other features are demonstrated on the Nordic32 test system, with synchronized phasors obtained from detailed time simulation of a situation evolving towards instability. Suitable choices of PMU location and pseudo-measurements are also discussed. [less ▲] Detailed reference viewed: 247 (32 ULg)Linearized Power Flow Equations Based Predictive Control of Transmission Voltages ; ; et al in Proceedings of the 46th Hawaii International Conference on System Sciences (HICSS-46) (2013, January) In this paper, an approach based on the concept of Model Predictive Control (MPC) is used to control transmission voltages and prevent long-term voltage instability. The MPC model is based on a linearized ... [more ▼] In this paper, an approach based on the concept of Model Predictive Control (MPC) is used to control transmission voltages and prevent long-term voltage instability. The MPC model is based on a linearized steady-state system model derived from power flow equations. Simulation results are presented for the case of Nordic32 test system. [less ▲] Detailed reference viewed: 199 (4 ULg)Wide-Area Adaptive Load Shedding Control to Counteract Voltage Instability ; ; Van Cutsem, Thierry in Proceedings of the Power Plant and Power System Control Conference (PPPSC 2012) (2012, September) A two-level adaptive load shedding scheme against voltage instability is proposed, adjusting its actions to the severity of the situation. The lower level includes a set of distributed controllers which ... [more ▼] A two-level adaptive load shedding scheme against voltage instability is proposed, adjusting its actions to the severity of the situation. The lower level includes a set of distributed controllers which curtail loads once the voltages at monitored transmission buses fall and stay for some time below threshold values. The adaptive nature of the proposed scheme comes from the upper level adjusting those thresholds in real-time. At the time instant the upper level detects that the system enters an emergency condition, it sends a signal to the lower-level controllers requesting them to take their currently measured voltages as threshold values. The upper-level emergency detection can be based on various criteria, the key-point being that it takes advantage of a wide-area monitoring of the system. In particular, the paper illustrates the use of a voltage instability detection scheme based on sensitivity computation. In case the upper level fails sending its signal, the lower-level controllers act in purely distributed mode, each using its preset threshold voltage. The capabilities of the proposed scheme are illustrated on a small but realistic test system. [less ▲] Detailed reference viewed: 128 (7 ULg)State Reconstruction from a Limited Number of Synchronized Phasor Measurements: Application to Voltage Instability Detection ; Van Cutsem, Thierry in Proceedings of the IEEE PES General Meeting (2012, July) This paper deals with the performance of the wide-area monitoring previously proposed by the authors in [1], [2] for early detection of voltage instability, when a limited number of synchronized phasor ... [more ▼] This paper deals with the performance of the wide-area monitoring previously proposed by the authors in [1], [2] for early detection of voltage instability, when a limited number of synchronized phasor measurements is available. This sensitivity-based scheme assumed that phasor measurements are sufficient in number and location for a state estimator to determine the voltages at all buses of the region prone to voltage instability. This paper demonstrates that the method still performs well when relying on bus voltages obtained from a state reconstruction procedure exploiting a limited number of synchronized phasor measurements which do not make the region of concern observable. The state reconstruction is formulated as the minimization, under constraints, of a weighted least square objective involving the available phasor measurements together with bus power pseudo-measurements relative to a reference state. The presented results relate to a 52-bus system with phasor measurements obtained from detailed time simulation of a long-term voltage unstable evolution triggered by a large disturbance. [1] M. Glavic, T. Van Cutsem, “Wide-Area Detection of Voltage Instability From Synchronized Phasor Measurements. Part I: Principle,” IEEE Trans. Power Syst., Vol. 24, No. 3, pp. 1408-1416, Aug. 2009 [2] M. Glavic, T. Van Cutsem, “Wide-Area Detection of Voltage Instability From Synchronized Phasor Measurements. Part II: Simulation Results,” IEEE Trans. Power Syst., Vol. 24, No. 3, pp. 1417-1425, Aug. 2009 [less ▲] Detailed reference viewed: 67 (7 ULg)State Reconstruction from Synchronized Phasor Measurements ; Van Cutsem, Thierry in Proceedings of the IEEE PES Innovative Smart Grid Technologies Europe 2011 (2011, December) The traditional state estimator relies on measurements affected by time skew and, while the whole system can be made observable, it cannot track the post-disturbance dynamics. Synchronized phasor ... [more ▼] The traditional state estimator relies on measurements affected by time skew and, while the whole system can be made observable, it cannot track the post-disturbance dynamics. Synchronized phasor measurements, on the other hand, can track those dynamics but, in a foreseeable future, they will be available in scarce configurations that do not allow estimating the whole system state. State reconstruction precisely aims at using the available phasor measurements to track the evolution of the power system - at least in a region of interest - in between two runs of a traditional state estimator. It minimizes under constraints a weighted least square objective involving both the phasor measurements and bus power pseudo-measurements relative to a reference state. The placement of phasor measurement units at the generator buses is recommended for accuracy. Tests are reported with phasor measurements obtained from time simulation of post-disturbance system evolution. The results deal with the effect on accuracy of the relative weights assigned to phasor and pseudo-measurements, the benefit of taking the reference bus powers from the last reconstructed instead of the pre-disturbance state, and the rate of the state reconstructions. [less ▲] Detailed reference viewed: 61 (5 ULg)Distributed MPC of wide-area electromechanical oscillations of large-scale power systems Wang, Da ; ; Wehenkel, Louis in Proceedings of ISAP 2011 (2011, September) We investigate distributed Model Predictive Control (MPC) to damp wide-area electromechanical oscillations. Our distributed MPC schemes are derived from and compared with a fully centralized MPC scheme ... [more ▼] We investigate distributed Model Predictive Control (MPC) to damp wide-area electromechanical oscillations. Our distributed MPC schemes are derived from and compared with a fully centralized MPC scheme proposed in a previous publication. Based on simulations carried out using a 16-generator, 70-bus, two-area test power system, we show that simple coordination schemes based on additional local measurements’ feedback yield already a significant improvement with respect to a scheme with only implicit coordination, improve significantly with respect to purely local controls, and in this respect reach about 75% of the improvements obtained by an ideal centralized MPC scheme. [less ▲] Detailed reference viewed: 33 (7 ULg)Receding-horizon multi-step optimization to correct nonviable or unstable transmission voltages ; ; et al in IEEE Transactions on Power Systems (2011), 26(3), 1641-1650 In this paper, a receding-horizon multi-step optimization is proposed to correct non viable transmission voltages and prevent long-term voltage instability. The proposed control scheme is based on real ... [more ▼] In this paper, a receding-horizon multi-step optimization is proposed to correct non viable transmission voltages and prevent long-term voltage instability. The proposed control scheme is based on real-time control, inspired by model predictive control, and steady state power-flow-based equations. In order to anticipate load behavior and avoid using dynamic equations in the control scheme, explicit formulations are used to model evolution of load with time. The simulation results of the proposed technique are presented on the Nordic32 test system. [less ▲] Detailed reference viewed: 131 (25 ULg)A short Survey of Methods for Voltage Instability Detection ; Van Cutsem, Thierry in Proceedings of the IEEE PES General Meeting (2011, July) This paper shortly surveys existing and proposed methods for voltage instability detection. The emphasis is on methods relying on real-time measurements as well as on long-term voltage instability ... [more ▼] This paper shortly surveys existing and proposed methods for voltage instability detection. The emphasis is on methods relying on real-time measurements as well as on long-term voltage instability. Methods are classified according to the required measurement configuration: local vs. wide-area, standard SCADA-type vs. synchronized phasor measurements, etc. In the various categories, some of the features are summarized, and what appears to the authors as advantages or limitations is shortly discussed. An important feature is the ability to anticipate instability. Some tracks for further work on the subject are also outlined. [less ▲] Detailed reference viewed: 188 (7 ULg)A new MPC scheme for damping wide-area electromechanical oscillations in power systems Wang, Da ; ; Wehenkel, Louis in the 2011 IEEE PES PowerTech (2011, June) This paper introduces a new Model Predictive Control (MPC) scheme to damp wide-area electromechanical oscillations. The proposed MPC controller, based on a linearized discrete-time state space model ... [more ▼] This paper introduces a new Model Predictive Control (MPC) scheme to damp wide-area electromechanical oscillations. The proposed MPC controller, based on a linearized discrete-time state space model, calculates the optimal input sequence for local damping controllers over a chosen time horizon by solving a quadratic programming problem. Local controllers considered include: Power Systems Stabilizers (PSSs), Thyristor Controlled Series Compensators (TCSCs) and Static Var Compensators (SVCs). The MPC scheme is realized and tested first in ideal conditions (complete state observability and controllability, neglecting communication and computing delays). Next, the effects of state-estimation errors, computation and communication delays, and of the number and type of available local damping controllers are studied in order to assess the versatility of this scheme. Realistic simulations are carried out using a 16 generators, 70 bus test system. [less ▲] Detailed reference viewed: 26 (3 ULg)Investigating State Reconstruction from Scarce Synchronized Phasor Measurements ; Van Cutsem, Thierry in Proceedings of the IEEE Trondheim Power Tech 2011 conference (2011, June) Synchronized phasor measurements can potentially track the system dynamics between two classical state estimations. However, in the PMU configurations available nowadays and in the near future, those ... [more ▼] Synchronized phasor measurements can potentially track the system dynamics between two classical state estimations. However, in the PMU configurations available nowadays and in the near future, those measurements are too scarce for the whole system state to be estimated. Therefore, we investigate the possibility to reconstruct coherent, time-synchronized system states from the available PMU data. State reconstruction is formulated as an optimization problem. The objective is to minimize, in the space of bus powers, the distance between the reconstructed state and the last state estimate provided by a standard state estimator. PMU data are imposed as equality constraints. Furthermore, the placement of PMUs near generators is advocated for higher accuracy of state reconstruction. The performance and potential benefits of the approach are illustrated by processing snapshots obtained from detailed time simulation of a test system subject to a disturbance and corrective actions. [less ▲] Detailed reference viewed: 57 (5 ULg)Adaptive Wide-Area Closed-Loop Undervoltage Load Shedding Using Synchronized Measurements ; Van Cutsem, Thierry in Proceedings of IEEE PES 2010 General Meeting (2010, July) This paper proposes an emergency load shedding scheme aimed at stopping a developing voltage instability before system disruption. The proposed scheme has a wide-area view of the system, adapts itself to ... [more ▼] This paper proposes an emergency load shedding scheme aimed at stopping a developing voltage instability before system disruption. The proposed scheme has a wide-area view of the system, adapts itself to the emergency situation to be handled, and works in closed-loop. It relies on the detection of voltage instability from synchronized measurements recently proposed by the authors. It inherits the assumptions of this detection method (availability of a rich phasor measurement set and communication infrastructure). The method is adaptive in so far as the voltage thresholds used by this undervoltage load shedding scheme are determined from the measurements of the system evolution itself, and the curtailed power is adjusted to the severity of the situation. The features of the proposed scheme are illustrated on a small but realistic system. [less ▲] Detailed reference viewed: 99 (9 ULg)Minimal Reduction of Unscheduled Flows for Security Restoration: Application to Phase Shifter Control Marinakis, Adamantios ; ; Van Cutsem, Thierry in IEEE Transactions on Power Systems (2010), 25(1), 506-515 More and more transmission system operators, noticeably in Europe, equip their systems with phase shifting transformers to counteract transit flows that take place in a large meshed interconnection. This ... [more ▼] More and more transmission system operators, noticeably in Europe, equip their systems with phase shifting transformers to counteract transit flows that take place in a large meshed interconnection. This paper proposes algorithms for the coordinated control of several phase shifters by one operator with the objective of reducing the unscheduled flow through its system. Minimum reduction of unscheduled flow and minimum deviation with respect to present operating point are sought in order to minimize the trouble caused, while ensuring secure operation. Attention is paid to combining pre and post-contingency controls. The resulting algorithms, simple and compatible with real-time applications, are illustrated on a realistic test system. [less ▲] Detailed reference viewed: 120 (24 ULg)Wide-area Detection of Voltage Instability from Synchronized Phasor Measurements. Part I: Principle ; Van Cutsem, Thierry in IEEE Transactions on Power Systems (2009), 24(3), 1408-1416 This two-part paper deals with the early detection of an impending voltage instability from the system states provided by synchronized phasor measurements. Recognizing that voltage instability detection ... [more ▼] This two-part paper deals with the early detection of an impending voltage instability from the system states provided by synchronized phasor measurements. Recognizing that voltage instability detection requires assessing a multi-dimensional system, the method fits a set of algebraic equations to the sampled states, and performs an efficient sensitivity computation in order to identify when a combination of load powers has passed through a maximum. The important effects of overexcitation limiters are accounted for. The approach does not require any load model. This first part of the paper is devoted to theoretical foundations of sensitivity calculation along the system trajectory, derivation of the algebraic model, and illustration on a simple 5-bus system involving the long-term dynamics of a load tap changer and a field current limiter. [less ▲] Detailed reference viewed: 246 (26 ULg)Wide-area Detection of Voltage Instability from Synchronized Phasor Measurements. Part II: Simulation results ; Van Cutsem, Thierry in IEEE Transactions on Power Systems (2009), 24(3), 1417-1425 This two-part paper deals with the early detection of an impending voltage instability from the system states provided by synchronized phasor measurements. Recognizing that voltage instability detection ... [more ▼] This two-part paper deals with the early detection of an impending voltage instability from the system states provided by synchronized phasor measurements. Recognizing that voltage instability detection requires assessing a multidimensional system, the method fits a set of algebraic equations to the sampled states, and performs an efficient sensitivity in order to identify when a combination of load powers has passed through a maximum. This second part of the paper presents simulation results obtained from detailed time-domain simulation of the Nordic32 test system, without and with measurement noise, respectively. Several practical improvements are described such as anticipation of overexcitation limiter activation, and use of a moving average filter. Robustness to load behaviour, non updated topology and unobservability is also shown. Finally a comparison with Thevenin impedance matching criterion is provided. [less ▲] Detailed reference viewed: 229 (31 ULg)Security Assessment by Multiple Transmission System Operators Exchanging Sensitivity and Tie-Line Power Flow Information Fabozzi, Davide ; ; Wehenkel, Louis et al in Proceedings of the 2009 IEEE PES Power Tech conference (2009, July) This paper considers a procedure for multi-area static security assessment of large interconnected power systems operated by a team of Transmission System Operators (TSOs). In this procedure, each TSO ... [more ▼] This paper considers a procedure for multi-area static security assessment of large interconnected power systems operated by a team of Transmission System Operators (TSOs). In this procedure, each TSO provides the other TSOs with his own equivalent model as well as the detailed effects of contingencies in his control area on all tie-line flows. The paper deals with the implementation of sensitivity-based equivalents suitable for static security assessment. Accuracy with respect to the unreduced model and computational efficiency are considered in evaluating the proposed approach. The relevance of the procedure in the context of recent UCTE operational security policy recommendations is also stressed. The procedure has been implemented in an AC power flow program and tested on a three-area variant of the IEEE 118-bus test system. [less ▲] Detailed reference viewed: 108 (23 ULg)Reinforcement learning versus model predictive control: a comparison on a power system problem Ernst, Damien ; ; Capitanescu, Florin et al in IEEE Transactions on Systems, Man & Cybernetics : Part B (2009), 33(2), 517-519 This paper compares reinforcement learning (RL) with model predictive control (MPC) in a unified framework and reports experimental results of their application to the synthesis of a controller for a ... [more ▼] This paper compares reinforcement learning (RL) with model predictive control (MPC) in a unified framework and reports experimental results of their application to the synthesis of a controller for a nonlinear and deterministic electrical power oscillations damping problem. Both families of methods are based on the formulation of the control problem as a discrete-time optimal control problem. The considered MPC approach exploits an analytical model of the system dynamics and cost function and computes open-loop policies by applying an interior-point solver to a minimization problem in which the system dynamics are represented by equality constraints. The considered RL approach infers in a model-free way closed-loop policies from a set of system trajectories and instantaneous cost values by solving a sequence of batch-mode supervised learning problems. The results obtained provide insight into the pros and cons of the two approaches and show that RL may certainly be competitive with MPC even in contexts where a good deterministic system model is available. [less ▲] Detailed reference viewed: 127 (14 ULg)Detecting with PMUs the onset of voltage instability caused by a large disturbance ; Van Cutsem, Thierry (2008, July) This paper deals with long-term voltage instability triggered by the outage of transmission or generation equipments. It is shown how the onset of voltage instability could be detected in real-time from ... [more ▼] This paper deals with long-term voltage instability triggered by the outage of transmission or generation equipments. It is shown how the onset of voltage instability could be detected in real-time from post-disturbance bus voltages provided by Phasor Measurement Units (PMUs), assuming observability of the whole region prone to voltage instability. An extended set of equilibrium equations is fitted to the measurements and the change in sign of sensitivities is onitored. The latter are easily computed even for a large system. The important effects of overexcitation limiters and load tap changers are taken into account. The approach is illustrated on a 52-bus 20-machine system, where PMU outputs are simulated from detailed time simulation. [less ▲] Detailed reference viewed: 107 (5 ULg)Analyzing transient instability phenomena beyond the classical stability boundary ; ; et al in Proceedings of the 40th North American Power Symposium (NAPS 2008) (2008) We consider power systems for which the amount of power produced by their individual power plants is small with respect to the total generation of the system, and analyze how the transient instability ... [more ▼] We consider power systems for which the amount of power produced by their individual power plants is small with respect to the total generation of the system, and analyze how the transient instability mechanisms of these systems change qualitatively when their size or the dispersion of their generators increases. Simulation results show that loss of synchronism will propagate more slowly and even stop propagating. Given the evolution of power systems towards more dispersed generation and geographically larger interconnections, we conclude that research in transient stability should focus more on the propagation of the loss of synchronism over longer time periods, so as to assess what happens to the overall system subsequently to the loss of synchronism of the first generators. We also argue that such studies might be very useful in order to provide guidelines for setting up power system control schemes to contain the propagation of instabilities, and we discuss some ideas for designing islanding based emergency control schemes for this. [less ▲] Detailed reference viewed: 224 (2 ULg)Distributed undervoltage load shedding ; ; Van Cutsem, Thierry in IEEE Transactions on Power Systems (2007), 22(4), 2283-2284 A new design of load shedding against long-term voltage instability is proposed. It uses a set of distributed controllers, each monitoring a transmission voltage, controlling a group of loads, acting in ... [more ▼] A new design of load shedding against long-term voltage instability is proposed. It uses a set of distributed controllers, each monitoring a transmission voltage, controlling a group of loads, acting in closed-loop, and adjusting its action to the voltage evolution. The whole system operates without information exchange between controllers. [less ▲] Detailed reference viewed: 103 (3 ULg)Model predictive control to alleviate thermal overloads ; Marinakis, Adamantios ; et al in IEEE Transactions on Power Systems (2007), 22(3), 1384-1385 An approach inspired by model predictive control is proposed to determine a sequence of control actions aimed at alleviating thermal overloads. The algorithm brings the line currents below their limits in ... [more ▼] An approach inspired by model predictive control is proposed to determine a sequence of control actions aimed at alleviating thermal overloads. The algorithm brings the line currents below their limits in the time interval left by protections while accounting for constraints on control changes at each step. Its closed-loop nature allows to compensate for model inaccuracies. [less ▲] Detailed reference viewed: 139 (14 ULg) |
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