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21
Structured Semidefinite Programs and Semialgebraic Geometry Methods in Robustness and Optimization
, 2000
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Calculating optimal system parameters to maximize the distance to saddle node bifurcations
 IEEETRANSACTIONS ON CIRCUITS AND SYSTEMSI: FUNDAMENTAL THEORY AND APPLICATIONS
, 1998
"... This paper presents a new methodology to calculate parameters of a nonlinear system, so that its distance to a saddlenode bifurcation is maximized with respect to the particular parameters that drive the system to bifurcation. The technique is thoroughly justified, specifying the conditions when it ..."
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Cited by 17 (6 self)
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This paper presents a new methodology to calculate parameters of a nonlinear system, so that its distance to a saddlenode bifurcation is maximized with respect to the particular parameters that drive the system to bifurcation. The technique is thoroughly justified, specifying the conditions when it can be applied and the numeric mechanisms to obtain the desired solutions. A comparison is also carried out between the proposed method and a known methodology to determine closest saddlenode bifurcations in a particular power system model, showing that the new technique is a generalization of the previous method. Finally, applications to power systems are discussed, particularly regarding the design of some FACTS devices, and a simple generatorlineload example is studied to illustrate the use of the proposed technique to determine the optimal shunt and/or series compensation to maximize distances to voltage collapse. The effect of the optimal compensation on the stability of the sample system is also analyzed.
Online RiskBased Security Assessment
 IEEE Transactions on Power Systems
, 2003
"... Abstract—The work described in this paper was motivated by a perceived increase in the frequency at which power system operators are encountering high stress in bulk transmission systems and the corresponding need to improve security monitoring of these networks. Online riskbased security assessmen ..."
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Cited by 13 (2 self)
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Abstract—The work described in this paper was motivated by a perceived increase in the frequency at which power system operators are encountering high stress in bulk transmission systems and the corresponding need to improve security monitoring of these networks. Online riskbased security assessment provides rapid online quantification of a security level associated with an existing or forecasted operating condition. One major advantage of this approach over deterministic online security assessment is that it condenses contingency likelihood and severity into indices that reflect probabilistic risk. Use of these indices in control room decision making leads to increased understanding of potential network problems, including overload, cascading overload, low voltages, and voltage instability, resulting in improved securityrelated decision making. Test results on largescale transmission models retrieved from the energymanagement system of a U.S. utility company are described. Index Terms—Cascading, control center, decision making, operations, overload, probabilistic risk, security assessment, uncertainty, voltage instability. I.
A Continuation Method Approach To Finding The Closest Saddle Node Bifurcation Point
 Proc. NSF/ECC Workshop on Bulk Power System Voltage Phenomena III
, 1994
"... The paper considers the problem of finding saddle node bifurcation points which are closest (in a local sense) to the power system operating point. This optimization problem leads to a set of equations which describe such critical points. Not all solutions of this set of equations are critical point ..."
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Cited by 12 (8 self)
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The paper considers the problem of finding saddle node bifurcation points which are closest (in a local sense) to the power system operating point. This optimization problem leads to a set of equations which describe such critical points. Not all solutions of this set of equations are critical points. The paper therefore explores the nature and characteristics of solutions. A two stage algorithm is proposed for solving the critical point problem. The first stage is simply to find a point on the singular surface, i.e., the surface of saddle node bifurcation points, which lies is a specified direction. The second stage uses a continuation method to move from that initial point to the desired critical point. Singularity of the critical point problem can have a significant influence on the robustness of the continuation method. The paper investigates singularity conditions. The proposed algorithm is tested on an eight bus power system example. Keywords: stability margin calculation, power...
Automatically generating visual syntaxdirected editors, Communications of the ACM
 Techniques, Proceedings of the IEEE Symposium on Visual Languages, 2027, IEEE Computer Society Press ZAPHIRIS P., SHNEIDERMAN
, 1997
"... AbstractThe paper presents applications of optimization techniques to voltage collapse studies. First a \Maximum Distance to Voltage Collapse " algorithm that incorporates constraints on the current operating conditions is presented. Second, an Optimal Power Flow formulation that incorporates volta ..."
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Cited by 9 (6 self)
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AbstractThe paper presents applications of optimization techniques to voltage collapse studies. First a \Maximum Distance to Voltage Collapse " algorithm that incorporates constraints on the current operating conditions is presented. Second, an Optimal Power Flow formulation that incorporates voltagestability criteria is proposed. The algorithms are tested on a 30bus system using a standard power ow model, where the e ect of limits on the maximum loading point is demonstrated.
Calculation of Oscillatory Stability Margins in the Space of Power System Controlled Parameters
 Proc. of the International Symposium on Electric Power Engineering Stockholm Power Tech: Power Systems
, 1995
"... The paper is devoted to finding the most dangerous (critical) changes of parameters which put the power system on either a saddle node or Hopf bifurcation boundary. The corresponding vectors in the space of system parameters provide information about stability margins, give a measure of and locally ..."
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Cited by 9 (4 self)
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The paper is devoted to finding the most dangerous (critical) changes of parameters which put the power system on either a saddle node or Hopf bifurcation boundary. The corresponding vectors in the space of system parameters provide information about stability margins, give a measure of and locally optimal ways to improve power system security, indicate parameters which badly affect stability. The paper contains a simplified form of the critical distance equations, analysis of their meanings, discussion of how to decrease dimension of the system, a robust numerical procedure for obtaining initial guesses and a solution of the system. The technique is tested on the New England Test System. I. Introduction Secure operation of a power system requires providing safe stability margins. It is convenient for practical purposes to define the stability margins in the controlled parameter space, because vectors in this space define control strategies. In particular, a vector connecting an oper...
OPTIMIZATION STRATEGIES FOR THE VULNERABILITY ANALYSIS OF THE ELECTRIC POWER GRID ∗
, 1786
"... Abstract. Identifying small groups of lines, whose removal would cause a severe blackout, is critical for the secure operation of the electric power grid. We show how power grid vulnerability analysis can be studied as a bilevel mixed integer nonlinear programming problem. Our analysis reveals a spe ..."
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Cited by 9 (2 self)
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Abstract. Identifying small groups of lines, whose removal would cause a severe blackout, is critical for the secure operation of the electric power grid. We show how power grid vulnerability analysis can be studied as a bilevel mixed integer nonlinear programming problem. Our analysis reveals a special structure in the formulation that can be exploited to avoid nonlinearity and approximate the original problem as a pure combinatorial problem. The key new observation behind our analysis is the correspondence between the Jacobian matrix (a representation of the feasibility boundary of the equations that describe the flow of power in the network) and the Laplacian matrix in spectral graph theory (a representation of the graph of the power grid). The reduced combinatorial problem is known as the network inhibition problem, for which we present a mixed integer linear programming formulation. Our experiments on benchmark power grids show that the reduced combinatorial model provides an accurate approximation, to enable vulnerability analyses of realsized problems with more than 16,520 power lines.
The Design Of Optimal Demand Management Programs
, 1998
"... Reliable operation in a deregulated environment and under conditions of uncertainty requires that loads be considered adjustable. This paper assumes that participation in demand management programs is entirely voluntary, and the compensation for participation is an integral part of any demand manage ..."
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Cited by 6 (3 self)
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Reliable operation in a deregulated environment and under conditions of uncertainty requires that loads be considered adjustable. This paper assumes that participation in demand management programs is entirely voluntary, and the compensation for participation is an integral part of any demand management program. Another consideration is simplicity: demand management programs must be simple to understand, simple to use and reliable in their response.
Costs of voltage security in electricity markets
 in Proc. 2000 IEEE Power Engineering Society Summer Meeting
, 2000
"... AbstractAs open access market principles are applied to power systems, an increased emphasis is being placed on determining ways to price different auxiliary services. The present paper studies the incorporation of voltage security into an optimal power ow formulation to analyze the aggregated cost ..."
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Cited by 6 (3 self)
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AbstractAs open access market principles are applied to power systems, an increased emphasis is being placed on determining ways to price different auxiliary services. The present paper studies the incorporation of voltage security into an optimal power ow formulation to analyze the aggregated costs associated with guaranteeing adequate voltage security levels in the system. Thus, several hybrid optimal power ow formulations that both minimizes generation costs and maximize distance to collapse are proposed and used to compare operational costs of power systems at di erent loading and voltage security levels. Basic principles of electricity markets are then used to propose a method to determine appropriate adjustments of control parameters accounting for the voltage stability ofapower network.
Applications of optimization to voltage collapse analysis
 Panel Session, Optimization Techniques in Voltage Collapse Analysis, IEEE/PES Summer Meeting
, 1998
"... AbstractThis paper describes several applications of optimization for voltage stability analysis (VSA) of power systems. Voltage stability problems, particularly those related to voltage collapse, are presented here as optimization problems, formally demonstrating, with the help of bifurcation theo ..."
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Cited by 4 (0 self)
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AbstractThis paper describes several applications of optimization for voltage stability analysis (VSA) of power systems. Voltage stability problems, particularly those related to voltage collapse, are presented here as optimization problems, formally demonstrating, with the help of bifurcation theory, that wellknown voltage collapse techniques are basically equivalent to some typical optimization methodologies. Recently developed analysis techniques and new research directions that have sprung up from bifurcation analysis of power systems and the application of optimization techniques to VSA are also presented in this paper. Throughout the paper, the advantages and disadvantages of using di erent optimization techniques for VSA in practical systems are discussed as well.