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Coupling optimization and dynamic simulation for preventive-corrective control of voltage instability Capitanescu, Florin ; Van Cutsem, Thierry ; Wehenkel, Louis in IEEE Transactions on Power Systems (2009), 24(2), 796-805 This paper proposes an approach coupling security constrained optimal power flow with time-domain simulation to determine an optimal combination of preventive and corrective controls ensuring a voltage ... [more ▼] This paper proposes an approach coupling security constrained optimal power flow with time-domain simulation to determine an optimal combination of preventive and corrective controls ensuring a voltage stable transition of the system towards a feasible long-term equilibrium, if any of a set of postulated contingencies occurs. A security-constrained optimal power flow is used to adjust the respective contribution of preventive and corrective actions. Furthermore, information is extracted from (quasi steady-state) time-domain simulations to iteratively adjust the set of coupling constraints used by a corrective security constrained optimal power flow until its solution is found dynamically secure and viable. Numerical results are provided on a realistic 55-bus test system. [less ▲] Detailed reference viewed: 118 (19 ULg)Evaluation of network equivalents for voltage optimization in multi-area power systems ; ; et al in IEEE Transactions on Power Systems (2009), 24(2), 729-743 The paper addresses the problem of decentralized optimization for a power system partitioned into several areas controlled by different transmission system operators (TSOs). The optimization variables are ... [more ▼] The paper addresses the problem of decentralized optimization for a power system partitioned into several areas controlled by different transmission system operators (TSOs). The optimization variables are the settings for taps, generators’ voltages and compensators’, and the objective function is either based on the minimization of reactive power support, the minimization of active power losses, or a combination of both criteria. We suppose that each TSO assumes an external network equivalent for its neighboring areas and optimizes without concern for the neighboring systems’ objectives its own optimization function. We study, in the context where every TSO adopts the same type of objective function, the performance of an iterative scheme, where every TSO refreshes at each iteration the parameters of its external network equivalents depending on its past internal observations, solves its local optimization problem, and then, applies its “optimal actions” to the power system. In the context of voltage optimization, we find out that this decentralized control scheme can converge to nearly optimal global performance for relatively simple equivalents and simple procedures for fitting their parameters. [less ▲] Detailed reference viewed: 70 (16 ULg)A new iterative approach to the corrective security-constrained optimal power flow problem Capitanescu, Florin ; Wehenkel, Louis in IEEE Transactions on Power Systems (2008), 23(4), 1342-1351 This paper deals with techniques to solve the corrective security-constrained optimal power flow (CSCOPF) problem. To this end, we propose a new iterative approach that comprises four modules: a CSCOPF ... [more ▼] This paper deals with techniques to solve the corrective security-constrained optimal power flow (CSCOPF) problem. To this end, we propose a new iterative approach that comprises four modules: a CSCOPF which considers only a subset of potentially binding contingencies among the postulated ones, a (steady-state) security analysis (SSSA), a contingency filtering (CF) technique, and an OPF variant to check post-contingency state feasibility when taking into account post-contingency corrective actions. We compare performances of our approach and its possible variants with classical CSCOPF approaches such as the direct approach and Benders decomposition (BD), on three systems of 60, 118, and 1203 buses. [less ▲] Detailed reference viewed: 48 (2 ULg)Local Identification of Voltage Emergency Situations ; Van Cutsem, Thierry in IEEE Transactions on Power Systems (2008), 23(3), 1239-1248 This paper proposes a simple procedure to identify the onset of long-term voltage instability from the time evolution of the distribution voltages controlled by load tap changers. The moving average of ... [more ▼] This paper proposes a simple procedure to identify the onset of long-term voltage instability from the time evolution of the distribution voltages controlled by load tap changers. The moving average of sampled measurements is computed and used to trigger local emergency signals. The method is validated on voltage signals obtained from time simulation of a realistic test system. The ability to identify instability in the critical area is demonstrated in three test cases. [less ▲] Detailed reference viewed: 89 (11 ULg)Undervoltage load shedding using distributed controllers ; Van Cutsem, Thierry in IEEE Transactions on Power Systems (2007), 22(4), 1898-1907 A new load shedding scheme against long-term voltage instability is proposed. It uses a set of distributed controllers, each monitoring transmission voltages in a zone and controlling a group of related ... [more ▼] A new load shedding scheme against long-term voltage instability is proposed. It uses a set of distributed controllers, each monitoring transmission voltages in a zone and controlling a group of related loads. Each controller acts in closed-loop, shedding amounts that vary in magnitude and time according to the evolution of its monitored voltage. The whole system can operate without information exchange between controllers, the latter being implicitly coordinated through network voltages. The operation, design and robustness features are illustrated through simulations of a real system. [less ▲] Detailed reference viewed: 90 (10 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)Contingency filtering techniques for preventive security-constrained optimal power flow Capitanescu, Florin ; ; Ernst, Damien et al in IEEE Transactions on Power Systems (2007), 22(4), 1690-1697 This paper focuses on contingency filtering to accelerate the iterative solution of preventive security-constrained optimal power flow (PSCOPF) problems. To this end, we propose two novel filtering ... [more ▼] This paper focuses on contingency filtering to accelerate the iterative solution of preventive security-constrained optimal power flow (PSCOPF) problems. To this end, we propose two novel filtering techniques relying on the comparison at an intermediate PSCOPF solution of post-contingency constraint violations among postulated contingencies. We assess these techniques by comparing them with severity index-based filtering schemes, on a 60- and a 118-bus system. Our results show that the proposed contingency filtering techniques lead to faster solution of the PSCOPF, while being more robust and meaningful, than severity-index based ones. [less ▲] Detailed reference viewed: 73 (12 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)Improving the statement of the corrective security-constrained optimal power flow problem Capitanescu, Florin ; Wehenkel, Louis in IEEE Transactions on Power Systems (2007), 22(2), 887-889 This letter proposes a formulation of the corrective security-constrained optimal power-flow problem imposing, in addition to the classical post-contingency constraints, existence and viability ... [more ▼] This letter proposes a formulation of the corrective security-constrained optimal power-flow problem imposing, in addition to the classical post-contingency constraints, existence and viability constraints on the short-term equilibrium reached just after contingency. The rationale for doing so is discussed and supported by two examples. [less ▲] Detailed reference viewed: 52 (2 ULg)Reference transmission network: A game theory approach ; Ernst, Damien ; et al in IEEE Transactions on Power Systems (2006), 21(1), 249-259 The transmission network plays a key role in an oligopolistic electricity market. In fact, the capacity of a transmission network determines the degree to which the generators in different locations ... [more ▼] The transmission network plays a key role in an oligopolistic electricity market. In fact, the capacity of a transmission network determines the degree to which the generators in different locations compete with others and could also greatly influence the strategic behaviors of market participants. In such an oligopolistic framework, different agents may have distinct and sometimes opposite interests in urging or hindering certain transmission expansions. Therefore, the regulatory authority, starting from the existing grid, faces the challenge of defining an optimal network upgrade to be used as benchmark for approval or rejection of a given transmission expansion. The aim of this paper is to define the concept of reference transmission network (RTN) from an economic point of view and to provide a tool for the RTN assessment in a deregulated framework where strategic behaviors are likely to appear. A general game-theoretic model for the RTN evaluation is presented, and the solution procedure is discussed. The strategic behavior of market agents in the spot market is modeled according to a Supply Function Equilibrium approach. The impact of transmission capacity expansion on market participants' strategic behavior is studied on a three-bus test network. The RTN is computed and compared with the optimal expansion found when perfect competition among power producers is assumed. [less ▲] Detailed reference viewed: 66 (3 ULg)Unified sensitivity analysis of unstable or low voltages caused by load increases or contingencies Capitanescu, Florin ; Van Cutsem, Thierry in IEEE Transactions on Power Systems (2005), 20(1), 321-329 This paper deals with the analysis of situations where load increases and/or contingencies cause transmission voltages to become unstable or unacceptably low. Simple sensitivities are proposed to ... [more ▼] This paper deals with the analysis of situations where load increases and/or contingencies cause transmission voltages to become unstable or unacceptably low. Simple sensitivities are proposed to determine the relative efficiency of candidate remedial actions, which are parameter changes likely to strengthen the system. To this purpose, the sensitivities of the bus voltage magnitude experiencing the largest drop are considered. In the neighborhood of a loadability limit or a critical point, it is shown that these sensitivities and those based on eigenvalue and eigenvector computation are essentially the same. However, the proposed analysis can also deal with low but stable situations. The accuracy of the proposed sensitivities is demonstrated on the models of two real systems, in which the parameters of concern are bus power injections. [less ▲] Detailed reference viewed: 62 (6 ULg)Combining a stability and a performance-oriented control in power systems ; Ernst, Damien ; Wehenkel, Louis in IEEE Transactions on Power Systems (2005), 20(1), 525-526 This paper suggests that the appropriate combination of a stability-oriented and a performance-oriented control technique is a promising way to implement advanced control schemes in power systems. The ... [more ▼] This paper suggests that the appropriate combination of a stability-oriented and a performance-oriented control technique is a promising way to implement advanced control schemes in power systems. The particular approach considered combines control Lyapunov functions (CLF) and reinforcement learning. The capabilities of the resulting controller are illustrated on a control problem involving a thyristor-controlled series capacitor (TCSC) device for damping oscillations in a four-machine power system. [less ▲] Detailed reference viewed: 26 (1 ULg)Definition and Classification of Power System Stability ; ; et al in IEEE Transactions on Power Systems (2004), 19(2), 1387-1401 The problem of defining and classifying power system stability has been addressed by several previous CIGRE and IEEE Task Force reports. These earlier efforts, however, do not completely reflect current ... [more ▼] The problem of defining and classifying power system stability has been addressed by several previous CIGRE and IEEE Task Force reports. These earlier efforts, however, do not completely reflect current industry needs, experiences and understanding. In particular, the definitions are not precise and the classifications do not encompass all practical instability scenarios. This report developed by a Task Force, set up jointly by the CIGRE Study Committee 38 and the IEEE Power System Dynamic Performance Committee, addresses the issue of stability definition and classification in power systems from a fundamental viewpoint and closely examines the practical ramifications. The report aims to define power system stability more precisely, provide a systematic basis for its classification, and discuss linkages to related issues such as power system reliability and security. [less ▲] Detailed reference viewed: 620 (10 ULg)An educational simulation tool for power system control and stability ; ; et al in IEEE Transactions on Power Systems (2004), 19(1), 48-55 This paper presents a Simulink-based educational tool developed for the purpose of illustrating power system control and stability notions as well as introducing students to realistic, though tractable in ... [more ▼] This paper presents a Simulink-based educational tool developed for the purpose of illustrating power system control and stability notions as well as introducing students to realistic, though tractable in size, design problems. Relevant courses are taught to last-year undergraduate as well as graduate students at the University of, Liege, Belgium, and the National Technical University of Athens, Greece.. After a brief description of the corresponding curricula, the paper describes the simulation tool and gives examples of problems and assignments given to the students. [less ▲] Detailed reference viewed: 195 (14 ULg)Power systems stability control: Reinforcement learning framework Ernst, Damien ; ; Wehenkel, Louis in IEEE Transactions on Power Systems (2004), 19(1), 427-435 In this paper, we explore how a computational approach to learning from interactions, called reinforcement learning (RL), can be applied to control power systems. We describe some challenges in power ... [more ▼] In this paper, we explore how a computational approach to learning from interactions, called reinforcement learning (RL), can be applied to control power systems. We describe some challenges in power system control and discuss how some of those challenges could be met by using these RL methods. The difficulties associated with their application to control power systems are described and discussed as well as strategies that can be adopted to overcome them. Two reinforcement learning modes are considered: the online mode in which the interaction occurs with the real power system and the offline mode in which the interaction occurs with a simulation model of the real power system. We present two case studies made on a four-machine power system model. The first one concerns the design by means of RL algorithms used in offline mode of a dynamic brake controller. The second concerns RL methods used in online mode when applied to control a thyristor controlled series capacitor (TCSC) aimed to damp power system oscillations. [less ▲] Detailed reference viewed: 65 (8 ULg)Preventive control of voltage security margins: A multicontingency sensitivity-based approach Capitanescu, Florin ; Van Cutsem, Thierry in IEEE Transactions on Power Systems (2002), 17(2), 358-364 This paper addresses the problem of changing the operating point of a power system in order to keep voltage security margins with respect to contingencies above some minimal value. Margins take on the ... [more ▼] This paper addresses the problem of changing the operating point of a power system in order to keep voltage security margins with respect to contingencies above some minimal value. Margins take on the form of maximum pre-contingency power transfers either between a generation and a load area or between two generation areas. They are determined by means of a fast time-domain method. We will first discuss the use of a general optimal power flow, in which linear voltage security constraints are added. The simultaneous control of several (possibly conflicting) contingencies is considered. Then, we will focus on the minimal control change objective. Among the possible controls, emphasis is put on generation rescheduling and load curtailment. Examples are presented on an 80-bus test system as well as on a real system. [less ▲] Detailed reference viewed: 87 (13 ULg)Closure of "a unified approach to transient stability contingency filtering, ranking, and assessment" Ernst, Damien ; ; Pavella, Mania et al in IEEE Transactions on Power Systems (2002), 17(2), 528-529 Detailed reference viewed: 35 (2 ULg)A unified approach to transient stability contingency filtering, ranking and assessment Ernst, Damien ; ; Pavella, Mania et al in IEEE Transactions on Power Systems (2001), 16(3), 435-443 This paper proposes a unified approach to contingency filtering, ranking and assessment in power system transient stability studies. The approach consists of two-block techniques in which the first block ... [more ▼] This paper proposes a unified approach to contingency filtering, ranking and assessment in power system transient stability studies. The approach consists of two-block techniques in which the first block selects from a list of contingencies the a priori “interesting” ones, that the second block ranks and assesses. This Filtering, Ranking and Assessment (FILTRA) approach relies on SIME (for SIngle Machine Equivalent). SIME is a hybrid direct-time-domain stability method which combines accuracy and flexibility skills of time-domain methods with sound additional possibilities of direct methods. The FILTRA approach is fully general: it may adapt itself to the specifics of any power system (modeling, protection characteristics, etc.), any contingency scenario and mode of (in)stability (first- or multi-swing, local or inter-area mode) and any application context (planning, operation planning and real-time operation). The approach is illustrated on two EHV power systems, having different structures, control and protective devices. The adequacy of its filtering and ranking capabilities is illustrated in terms of performance criteria such as reliability (ability to consistently capture all dangerous contingencies), effectiveness (ability to avoid false alarms) and computational efficiency (ability to comply with real-time requirements). Further, the assessment task is shown to provide the operator with sound information and effective means of control. [less ▲] Detailed reference viewed: 66 (3 ULg)Determination of secure operating limits with respect to voltage collapse Van Cutsem, Thierry ; ; in IEEE Transactions on Power Systems (1999), 14(1), 327-335 A secure operating limit is the most stressed among a given set of operating points, such that the system can withstand specified contingencies. It is a general measure of security with respect to ... [more ▼] A secure operating limit is the most stressed among a given set of operating points, such that the system can withstand specified contingencies. It is a general measure of security with respect to incidents, incorporating pre-contingency operator or controller actions and post-contingency corrective controls. The proposed approach deals with long-term voltage stability limits. It combines a dichotomic search with quasi steady-state simulation to compute these limits with the efficiency required by real-time applications. The limit search acceleration and contingency filtering issues are also discussed. Illustrative examples are given on the Hydro-Quebec power system [less ▲] Detailed reference viewed: 42 (2 ULg)Validation of a fast voltage stability analysis method on the Hydro-Québec system Van Cutsem, Thierry ; in IEEE Transactions on Power Systems (1997), 12 Detailed reference viewed: 31 (0 ULg) |
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