The volatility of the price of electricity in a Locational Marginal Price (LMP) market makes it necessary to introduce financial price risk hedging instruments. The congestion-related and marginal-loss-related revenue surpluses collected by the Regional Transmission Operator (RTO) are proposed to be redistributed to market players. It is important to be able to correctly decompose the LMP into its congestion and marginal-loss components, which are critical for the valuation and settlement of these financial instruments. A new energy reference bus independent LMP decomposition model using an AC Optimal Power Flow (OPF) model is presented to overcome the reference bus dependency disadvantage of the conventional approach. The marginal effect of the generators’ output variation with respect to load variation are used as the basis of this decomposition model. The theoretical derivation and a proof are given. The new model achieves a set of reference bus independent results. An example is presented comparing the new model with the conventional model.

Uploaded: March 9, 2006. IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 21, NO. 3, AUGUST 2006.

The traditional form of load control (shedding) tends to be quite disruptive to consumers, and so is often avoided. The paper suggests an alternative strategy that is based on controlling individual loads, such that interruptions effectively go unnoticed by consumers. An hierarchical control structure is required, with lower-level substation-based controllers consolidating information about available controllable load. The higher-level controller uses that information to formulate strategies to steer the system through events. Model predictive control is proposed for the higher-level control.

Uploaded: March 9, 2006. 2006 IEEE Power Engineering Society General Meeting. Montreal, Canada, June 2006.

Load modelling is a perennial source of consternation. Postmortem analyses of disturbances frequently conclude that load models must be adjusted to achieve an adequate match between measured and simulated behaviour. However the development of load models that are accurate over a wide range of system conditions requires,

1) testing that is undesirable for customers, and/or
2) measurement of behaviour during infrequent disturbances.

Furthermore, the stochastic nature of many loads implies load models that are accurate at one time may be inaccurate a short time later. In terms of quantitative analysis, for example matching simulations with measurements, it is absolutely clear that accurate load modelling is vitally important. But for qualitative investigations, where the aim is to assess the likelihood of a certain disturbance scenario remaining stable or causing instability, then the need for accurate load modelling is much reduced. The paper explores this conjecture through the use of trajectory sensitivity concepts. It is shown that for qualitative assessment, it is more important to know the sensitivity of behaviour to load parameters, than to precisely know the parameter values. However most power system failures are not initiated by instability, but rather by reactionary (unanticipated) protection operation. The ability to predict operation of protection devices, and hence potential protection-induced cascading failures, may be greatly affected by load model fidelity.

Uploaded: March 16, 2006. Presented at X_SEPOPE, Symposium of Specialists in Electric Operational and Expansion Planning, Florianopolis, Brazil, May 21-25, 2006.

Application of individual distributed generators can cause as many problems as it may solve. A better way to realize the emerging potential of distributed generation is to take a system approach which views generation and associated loads as a subsystem or a “ microgrid” . The sources can operate in parallel to the grid or can operate in island, providing UPS services. The system will disconnect from the utility during large events (i.e. faults, voltage collapses), but may also intentionally disconnect when the quality of power from the grid falls below certain standards. Utilization of waste heat from the sources will increase total efficiency, making the project more financially attractive. Laboratory verification of the Consortium for Electric Reliability Technology Solutions (CERTS) microgrid control concepts are included.

Uploaded: April 5, 2006. 2006 IEEE Power Engineering Society General Meeting, Montreal, Canada, June 2006.

Short-term resource adequacy, a key component of system reliability, is the ability of a system with a fixed resource mix to meet the load at all times. In the competitive environment, the interaction of markets and reliability has raised this issue to new prominence. Market design influences significantly the behavior of market players, which, in turn, impacts the capacity adequacy of the system. The extent of such impacts is well illustrated by the California market experience during the 2000– 2001 crisis. Current resource adequacy tools fail to explicitly consider the interactions between market design, the behavior of market players and system reliability. To overcome this deficiency, we construct an analytical framework for short-term resource adequacy that explicitly considers the interactions between markets and reliability. The framework models both the physical world by representing the contribution of the resources and the load demand to reliability, and the market world, by including the market design, the market players’ behavior and their interactions with the physical world. We use the framework to assess the impacts of market player behavior on various test systems. Representative results are provided.

Uploaded: April 25, 2006. 9th Proceedings of IEEE International Conference on Probabilistic Methods Applied to Power Systems (2006 PMAPS), Stockholm, Sweden, June 11-15, 2006.

This paper provides an overview of the scope and methodology for transient relay testing. The scope of transient relay testing is divided into: a) conformance test for examining the functionality and generic performance characteristics of relays, and b) application test for analyzing the specific performance issues and trouble-shooting relay misoperations. For conformance test, the methodology including system modeling, automated generation of test scenarios, relay modeling, and implementation of automated relay testing is discussed in detail. For application test, the key issue is the selection of typical scenarios for analyzing the relay behavior in vulnerable system conditions. A view about benefits and approaches of transient based relay testing is explained in this paper. A paper for PSerc T-30, "Transient Testing of Protective Relays: Study of Benefits and Methodology."

Uploaded: May 12, 2006. Paper is accepted by MELECON 2006. 2006 IEEE Mediterranean Electrotechnical Conference (2006 MELECON), Benalmá dena (Má laga), Spain, May 16-19, 2006.

This paper describes a simple yet effective method for identifying incorrect parameters associated with the power network model. The proposed method has the desired property of distinguishing between bad analog measurements and incorrect network parameters, even when they appear simultaneously. This is accomplished without expanding the state or the measurement vectors. There is also no need to specify a suspect parameter set. All these features are verified via simulations that are carried out using different size test systems for various possible cases. Implementation of the method involves minor changes in the weighted least squares state estimation code, hence it can be easily integrated into existing state estimators as an added feature.

Uploaded: May 12, 2006. IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 21, NO. 2, MAY 2006.

We present an empirical analysis of a supply function equilibrium model in the Texas spot electricity market. We derive conditions for optimal bidding behavior in a spot market with ex ante bilaterally contracted sales. By using generation cost information, we are able to derive a set of ex post- and ex ante-optimal supply functions and use a nonparametric model of firm behavior to compare our theoretically-optimal supply functions to actual offers made in years 2002 and 2003. Our results show that with the exception of the largest generators, firms make offers with markups and markdowns far in excess of what a model of profit-maximizing behavior suggests. For small generators, municipalities, and cogenerators we find evidence suggesting these firms may be acting to exclude themselves from the market by economically withholding their generation. By using a partial-linear behavior model we demonstrate some learning effects to have taken place during the first quarter of 2002.

Uploaded: May 17, 2006. Journal of Regulatory Economics, vol. 31, issue 1, pp. 1-35, February 2007.

This paper describes the development of a theoretical model to predict flashover voltage of nonceramic insulators. The model is based on reignition and arc constants that have been derived from electric field simulations and experimental data of flashover voltage and surface resistance measurements. New and field-aged silicone rubber and ethylene propylene diene monomer rubber samples were evaluated. A good correlation of the calculations from the model with experimental data has been demonstrated.

Uploaded: May 17, 2006. IEEE Transactions on Dielectrics and Electrical Insulation, vol. 13, issue 4, pp. 862-869, August 2006.

This paper proposes a methodology of compatibility and interoperability evaluation for all-digital protection system through automatic application testing. The paper starts with the introducing of compatibility and interoperability evaluation issues, explaining the importance of application tests. The paper then defines the performance indices and compatibility indices as well as the evaluation methodology. Making full use of the advantages of IEC 61850, a fully networked and automated application test solution for all-digital protection system is then proposed to calculate these indices. The related IEC 61850 information models and ACSI (Abstract Communication Service Interface) services which contribute to the automatic testing are described. Finally, the hardware architecture and software implementation are proposed in this paper. The framework technology is used to obtain an open software architecture, so that different power network models, transducer models as well as multiple performance evaluation criteria can be added to the system, without altering the overall software structure and control flow of the automatic testing system.

Uploaded: May 22, 2006. Accepted for 2006 IEEE Power Engineering Society General Meeting, Montreal, Canada, June 2006.

This paper presents experimental results associated with human factors aspects of using three-dimensional (3D) visualizations to display electric power system generation information on one-line diagrams. The paper’ s results are based on an experiment performed at the University of Illinois at Urbana-Champaign using electric power system students. The results indicate that compared to standard 2D one-line displays, 3D visualizations of generator output and reserves can be used successfully on one-line displays to improve both the speed and accuracy of certain tasks.

Uploaded: May 22, 2006. Accepted for presentation at 2006 IEEE Power Engineering Society General Meeting, Montreal, Canada, June 2006.

Load power is progressively shed as large, cascading blackouts of electric power transmission systems evolve. We propose a statistical estimator to measure the extent to which the load shedding is propagated. The estimator uses data from a series of simulated blackouts. The estimator is derived from a continuous state branching process that is a high level probabilistic model of the cascading process. The estimator is tested on failure data generated by a power system model of cascading line outages. The estimates for propagation of load shed are consistent with estimates for the propagation of line outages. Estimating the initial load shed and the propagation of load shed leads to estimates of the probability distribution of blackout size. This work opens up possibilities of monitoring infrastructure failures to quantify the vulnerability to cascading and the overall risk of large cascading failures.

Uploaded: May 23, 2006. (preprint) The Third International Conference on Critiical Infrastructures (2006 CRIS), Alexandria, Virginia, September 2006.

Cascading blackouts on a bulk power transmission system are potentially catastrophic events with a large impact on society characterized by a sequence of line trips and load shed. One spectacular example of a cascading blackout is the August 2003 blackout in North America that affected 50 million people. We propose using branching processes to model the line tripping and load shed behavior of cascading blackouts. We use an estimator of the offspring mean, lambda, to fit simulated blackout data to the branching process model. The parameter lambda is a measure of cascade propagation, and helps us to estimate how likely large blackouts are. We compute distributions of blackout size and total number of line failures from the model and match them against simulated data. The match with simulated data suggests that the branching process model captures important aspects of the cascade phenomenon. The line failures and load shed in cascades are seen to have similar lambda, meaning they propagate at the same rate. The branching process model is an efficient way to estimate line failure and load shed probability distributions.

Uploaded: May 23, 2006. This document is a Master of Science student thesis, Electrical and Computer Engineering, The University of Wisconsin at Madison, May 2006.

A model of two-settlement electricity markets is introduced, which accounts for flow congestion, demand uncertainty, system contingencies and market power. We formulate the subgame perfect Nash equilibrium for this model as an equilibrium problem with equilibrium constraints (EPEC), in which each firm solves a mathematical program with equilibrium constraints (MPEC). The model assumes linear demand functions, quadratic generation cost functions and a lossless DC network, resulting in equilibrium constraints as a parametric linear complementarity problem (LCP).We introduce an iterative procedure for solving this EPEC through repeated application of an MPEC algorithm. This MPEC algorithm is based on solving quadratic programming sub-problems and on parametric LCP pivoting. Numerical examples demonstrate the effectiveness of the MPEC and EPEC algorithms and the tractability of the model for realistic size power systems.

Uploaded: May 30, 2006. INFORMS - Pubs Online, Journal - Operations Research, vol. 56, issue 1, pp. 34-47, January-February 2008.

This research discuses several power system measurement pre-processing techniques, which may improve calculations like state estimation (SE). SE is a proven technology, but operates under assumptions which may be inappropriate. The concept of non-collocated power measurement error is introduced, where reactance between current and voltage instruments creates power calculation error. A calculation-based method for correcting these measurements is presented and shown to slightly improve state estimates. SE may assume balanced operation. However, unbalance is common in power systems. Under certain assumptions, single-phase power measurements and complex current unbalance factor (CCUF) can calculate three-phase power. This yields better measurements, but is shown to have little effect improving traditional SE. Methods for estimating or calculating CCUF are also presented. SE often assumes all measurements are simultaneous. A simple linear prediction method used to identify late measurements is studied and shown to work in systems with low measurement noise and low system dynamics.

Uploaded: June 5, 2006. This document is a Master's of Science student thesis, Electrical Engineering, Arizona State University, June 2006.

Voltage and current measurements are routinely used as inputs to transducers in order to obtain sensory information on active and reactive power. If the voltage and current measurements are not collocated, the power measurements will be incorrect. In this paper, a correction is calculated for non-collocated voltage and current measurements used to obtain power. The correction is obtained utilizing the non-collocated power and one voltage magnitude measurement. One application area is in state estimation sensory inputs.

Uploaded: June 5, 2006.Submitted for publication - proceedings of the 37th Annual North American Power Symposium (2005 NAPS), pp. 553-559, Ames, Iowa, October 23-25, 2005.

A complete fault analysis scheme for long transmission line represented with distributed parameters is proposed in this paper. The synchronized samples from both ends of the transmission line are the data sources for this scheme. The paper derives a specific feature which equals to zero for normal situation and external faults, and is close to fault current during the internal faults. This feature is used for fault detection and classification. Fault location is then implemented by selecting different methods according to the classified fault type. The results from a comprehensive evaluation study demonstrate an excellent performance of entire fault analysis.

Uploaded: July 19, 2006. 5th IFAC (International Federation of Automatic Control) Symposium on Power Plants and Power Systems Control, vol. 39, issue 7, pp. 137-142, Kananaskis, Alberta, Canada, June 25-28, 2006.

Parameters of power system models, in particular load models, are seldom known exactly. Yet dynamic security assessment relies upon simulation of those uncertain models. This paper proposes a computationally feasible approach to assessing the influence of uncertainty in simulations of power system dynamic behaviour. It is shown that trajectory sensitivities can be used to generate accurate first-order approximations of trajectories that arise from perturbed parameter sets. The computational cost of obtaining the sensitivities and perturbed trajectories is minimal. The mathematical structure of the trajectory approximations allows the effects of uncertainty to be quantified and visualized using worst-case analysis and probabilistic approaches.

Uploaded: July 25, 2006. Accepted for publication in the IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 21, NO. 4, NOVEMBER 2006.

Sufficient and efficient electricity supply is critical to the steady growth of economies. In the last two decades, many electricity sectors around the world have been undergoing a reform from a command-and-control industry to competitive markets. A major obstacle to a successful reform is locational market power. To address this issue, many markets have been following a multiple-settlement approach where forward transactions, day-ahead transactions, and real-time transactions are settled sequentially at different prices. In this thesis, we focus on centrally-dispatched markets, and explore the effect of forward contracting on energy prices and consumer benefits.

Uploaded: August 29, 2006. This document is a Doctor of Philosophy student dissertation, Industrial Engineering and Operations Research, University of California at Berkeley, August 2006.

Distributed MPC Strategies for Automatic Generation Control The paper considers distributed model predictive control (MPC) strategies that are appropriate for controlling large-scale systems such as power systems. The overall system is decomposed into subsystems, each with its own MPC controller. To achieve performance equivalent to centralized MPC, these distributed regulators must work iteratively and cooperatively towards satisfying a common, systemwide control objective. Automatic generator control (AGC) provides a practical example for contrasting the performance of centralized and decentralized controllers.

Uploaded: September 19, 2006. 5th IFAC (International Federation of Automatic Control) Symposium on Power Plants and Power Systems Control, vol. 39, issue 7, pp. 383-388, Kananaskis, Alberta, Canada, June 25-28, 2006

In this paper, a distributed output feedback model predictive control (MPC) framework with guaranteed nominal stability and performance properties is described. Distributed state estimation strategies are developed for supporting distributed output feedback MPC of large-scale systems, such as power systems. It is shown that under certain (easily verifiable) conditions, local measurements are sufficient for observer stability. More generally, stable observers can be designed by exchanging measurements between adjacent subsystems. Both estimation strategies are suboptimal, but the estimates generated converge exponentially to the optimal estimates. A disturbance modeling framework for achieving zero-offset control in the presence of nonzero mean disturbances and modeling errors is presented. Automatic generation control (AGC) provides a practical example for contrasting the performance of centralized and distributed controllers.

Uploaded: September 19, 2006. Proceedings of the 45th IEEE Conference on Decision & Control, San Diego, California, December 13-15, 2006.

Physical limits place bounds on the divergent behaviour of dynamical systems. The paper explores this situation, providing an example where generator field-voltage limits capture behaviour, giving rise to a stable, though non-smooth, limit cycle. It is shown that shooting methods can be adapted to solve for such non-smooth switching-induced limit cycles. By continuing branches of switching-induced and smooth limit cycles, the paper established the co-existence of equilibria, smooth and non-smooth limit cycles. Furthermore, it is shown that when branches of switching-induced and smooth limit cycles merge, the limit cycles are annihilated at a grazing bifurcation.

Uploaded: September 19, 2006. Nonlinear Dynamics (an International Journal of Nonlinear Dynamics and Chaos in Engineering Systems), vol. 50, issue 3, pp. 575-585, November 2007.

This paper proposes an optimization procedure for generation expansion and placement considering generation reliability in multi-area power systems. The objective is to obtain a suitable trade off between system reliability and cost. In this process, reliability evaluation is performed using the concept of global decomposition. The prospective generation locations are pre-selected but the magnitude of generation located in each area is determined by an optimization procedure. The structure of global decomposition is exploited to simplify the problem and solve it using dynamic programming. The method is illustrated by application to a 3-area power system and also implemented for an actual 12-area power system.

Uploaded: September 21, 2006. IEEE TRANSACTIONS ON POWER SYSTEMS, VOL 21, NO 3, AUGUST 2006.

This paper presents a method of deciding the best placement of additional generation for long term generation adequacy planning in multi-area power systems. The approach uses evaluation of the prospective scenarios of additional generation, and tie-lines. Maximum number of additional generators in each area will be determined from the cost with respect to overall budget constraint. The selection criterion is based on improvement in system reliability after unit additions. The reliability indices of different generation combinations will be evaluated utilizing global decomposition approach. Instead of making direct comparison after global decomposition is performed, this paper proposes an algorithm that combines comparison and decomposition phase for better computational efficiency. The best combination will yield maximum reliability with acceptable cost.

Uploaded: September 21, 2006.Proceedings of the 9th International Conference on Probablistic Methods Applied to Power Systems (2006 PMAPS), Stockholm, Sweden, June 2006.

This paper combines Tabu search with an optimization technique using dynamic programming for the solution of generation expansion and placement considering reliability in multi-area power systems. Instead of random selection, initial solution for Tabu search is obtained from optimizing a simplified problem utilizing dynamic programming and reliability assessment technique called global decomposition. The comparison between random initial solutions and the proposed method is made. The method is implemented for an actual 12-area power system.

Uploaded: September 21, 2006. 2006 International Conference on Power System Technology (2006 POWERCON), Chongqing, China, October 22-26, 2006.

This paper proposes a mixed-integer stochastic programming approach to the solution of generation expansion planning problem. Generation and Transmission line expansion planning including system reliability considerations is considered a challenging problem. The optimal solution is expected to yield a favorable trade off between system reliability and cost. This helps guide the development of additional generation capacity that is optimal with respect to cost and reliability. The problem is stochastic due to random uncertainties in area generation, transmission lines, and area loads. The problem is formulated as a two-stage recourse model. Reliability index used in this problem is expected cost of load loss. The objective is to minimize the expansion cost in the first stage and the expected loss of load cost in the second stage. The problem is then solved by L-shaped algorithm. The method is illustrated by application to a three-area power system.

Uploaded: September 21, 2006. 2006 IEEE PES POWER SYSTEMS CONFERENCE AND EXPOSITION, pp. 1327-1332, ATLANTA, GEORGIA, OCTOBER 29 - NOVEMBER 1, 2006.

From an economic perspective, the appropriate criterion for assessing the merits of a transmission investment is its impacts on social welfare. The underlying assumption in using this criterion is that side payments may be used to distribute the social gains among all market players. In reality, however, since the impacts of an electricity transmission project on different players may vary, such side payments are rather difficult to implement. Under these conditions, for an assessment methodology to be effective, it must be capable of evaluating the economic impacts on the various effected stakeholders and account for strategic responses that could enhance or impede the investment’ s objectives.

Uploaded: September 26, 2006. IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 22, NO. 4, PP. 1394-1405, NOVEMBER 2007.

Short-term resource adequacy is the ability of a system with a set of given resources to meet the load over the short term. In the aftermath of the 2000– 2001 California crisis, focus on resource adequacy has come to the forefront of market design issues. Various approaches, such as capacity requirements, capacity payments and financial options requirements, have been proposed to ensure resource adequacy in electricity markets. We propose a design of a short-term resource adequacy program based on capacity requirements expressed in terms of a price sensitive demand curve. The program is formulated so as to give incentives for providing capacity to markets and to mete out penalties for non-performance situations. The probabilistic modeling of the uncertainty in the availability of generating resources and in the load allows the evaluation of reliability in terms of widely-used metrics. Through the explicit representation of the strategic behavior of market players, capacity withholding impacts are directly measurable.
The analysis of the proposed design and the simulation of a simple implementation show that the program results in improved reliability. Reduction of the total system costs are obtained when key program parameters are appropriately chosen. The design has proven effective under an extensive range of different scenarios in the various systems tested. The improvements attainable with the implementation of the program design are illustrated with representative simulation results on different sized systems. The proposed design with the ability to evaluate the linkage between reliability and markets contributes to the electricity market design area.

Uploaded: October 17, 2006. Submitted to the IEEE Transactions on Power Systems. IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 23, NO. 3, PP. 916-926, AUGUST 2008.

The detection of island formation in power networks is prerequisite for the study of security analysis and control. We develop a combined graph-theoretic-algebraic approach to detect island formation in power system networks under multiple line outages. We construct the approach by gaining insights into the topological impacts of outaged lines on system connectivity from the use power transfer distribution factor information. We develop a one-to-one relationship between minimal cutsets and a matrix of the generalized line outage distribution factors for multiple line outages. This relationship requires computations on lower order matrices and so is able to provide rapidly essential information. The proposed approach detects the island formation and identifies the subset of outaged lines that is the causal factor. Furthermore, for cases in which the set of outaged lines does not result in system separation, the method has the ability to identify whether a set of candidate line outages separates the system. Consequently, the need for establishing nodal system connectivity is bypassed. We illustrate the capabilities of the proposed approach on two large-scale networks. The proposed approach provides an effective tool for both real-time and offline environments for security analysis and control.

Uploaded: October 17, 2006. To be published in IEEE Transactions on Power Systems. IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 22, NO. 2, PP. 505-513, MAY 2007.

Distribution factors play a key role in many system security analysis and market applications. The injection shift factors (ISFs) are the basic factors that serve as building blocks of the other distribution factors. The line outage distribution factors (LODFs) may be computed using the ISFs and, in fact, may be iteratively evaluated when more than one line outage is considered. The prominent role of cascading outages in recent black-outs has created a need in security applications for evaluating LODFs under multiple-line outages. In this letter, we present an analytic, closed-form expression for and the computationally efficient evaluation of LODFs under multiple-line outages.

Uploaded: October 17, 2006. To be published in IEEE Transactions on Power Systems. IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 22, NO. 2, PP. 879-881, MAY 2007.

Analytical investigations of real-world, hybrid dynamical systems are technically challenging. Consequently, simulation plays a vital role in their analysis. Simulation typically addresses forward problems though, offering limited insights into parametric influences. The paper addresses this issue, presenting computationally efficient algorithms that extend the capabilities of simulation. The starting point is a model that captures the intricacies of hybrid systems, yet is suited to numerical integration. It will be shown that trajectory sensitivities are well defined for hybrid systems, and can be computed efficiently. These sensitivities allow the mapping of parameter uncertainty into approximate error bounds on nominal (piecewise smooth) trajectories. Furthermore, they provide gradient information that facilitates the solution of inverse problems. A range of problems will be considered, including shooting methods for locating (possibly non-smooth) limit cycles and grazing phenomena, and optimization algorithms for parameter estimation and controller tuning.

Uploaded: October 23, 2006. Plenary presentation, 16th Bi-annual Congresso Brasilenro de Automatica (Brazilian Automation Conference [CBA 2006]), Salvador, Bahia, Brazil, October 3-6, 2006.

Power system operation is constantly facing contingencies such as from line faults and generator outages. For operational reliability, the system must be able to withstand all credible contingencies, either by itself (for N-1 contingency) or with the help of Special Protection Schemes (SPS) or Remedial Action Schemes (RAS) (for N-2 or worse contingencies). However, when the system is operating under unforeseen conditions or under unusually high stress, the system can experience the angle instability. In that case, the system breaks up into many islands, resulting in large loss of loads and generations and a potential blackout scenario.
In this paper, new algorithms are proposed for detecting the emergence of angle instability phenomenon while it is still evolving so that suitable countermeasures can be initiated to prevent the islanding. The proposed algorithms and the controller detect the fast separation of phase angles among the critical areas automatically by using the synchrophasors, and proceed to mitigate the instability by suitable switching action. Briefly, the algorithms initiate tripping of critical generators in the accelerating part of the system when necessary, and also initiate load shedding in the decelerating part of the system whenever necessary. The novelty of the algorithms is in the fact that all the decisions are made in real-time purely based on the wide-area synchrophasor measurements without any knowledge of the details of the relay actions that may have resulted in the angle stability phenomenon. The concept of a real-time transient energy function method for the large power system is also explored to solve the problem. The paper will discuss the new algorithms along with illustrative examples on standard IEEE test systems.

Uploaded: November 3, 2006. Proceedings of the 33rd Annual Western Protective Relay Conference, Spokane, Washington, October 17-19, 2006.

Two of the most expected objectives of transmission line protection are:

a) differentiating precisely the internal faults from external, and
b) indicating exactly the fault type using one end data only.

This paper proposes an improved solution based on wavelet transform and self-organized neural network. The measured voltage and current signals are preprocessed first and then decomposed using wavelet multi-resolution analysis to obtain the high frequency details and low frequency approximations. The patterns formed based on high frequency signal components are arranged as inputs of neural network #1, whose task is to indicate whether the fault is internal or external. The patterns formed using low frequency approximations are arranged as inputs of neural network #2, whose task is to indicate the exact fault type. The new method uses both low and high frequency information of the fault signal to achieve an advanced line protection scheme. The proposed approach is verified using frequency-dependent transmission line model and the test results prove its enhanced performance. A discussion of the application issues for the proposed approach is provided at the end where the generality of the proposed approach and guidance for future study are pointed out.

Uploaded: December 4, 2006. IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 22, NO. 2, PP. 859-869, APRIL 2007.

This dissertation studied new transmission line fault diagnosis approaches using new technologies and proposed a scheme to apply those techniques in preventing and mitigating cascading blackouts. The new fault diagnosis approaches are based on two time-domain techniques: neural network based, and synchronized sampling based. For a neural network based fault diagnosis approach, a specially designed fuzzy Adaptive Resonance Theory (ART) neural network algorithm was used. Several application issues were solved by coordinating multiple neural networks and improving the feature extraction method.
A new boundary protection scheme was designed by using a wavelet transform and fuzzy ART neural network. By extracting the fault generated high frequency signal, the new scheme can solve the difficulty of the traditional method to differentiate the internal faults from the external using one end transmission line data only. The fault diagnosis based on synchronized sampling utilizes the Global Positioning System of satellites to synchronize data samples from the two ends of the transmission line. The effort has been made to extend the fault location scheme to a complete fault detection, classification and location scheme. Without an extra data requirement, the new approach enhances the functions of fault diagnosis and improves the performance. Two fault diagnosis techniques using neural network and synchronized sampling are combined as an integrated real time fault analysis tool to be used as a reference of traditional protective relay. They work with an event analysis tool based on event tree analysis (ETA) in a proposed local relay monitoring tool. An interactive monitoring and control scheme for preventing and mitigating cascading blackouts is proposed. The local relay monitoring tool was coordinated with the system-wide monitoring and control tool to enable a better understanding of the system disturbances.
Case studies were presented to demonstrate the proposed scheme. An improved simulation software using MATLAB and EMTP/ATP was developed to study the proposed fault diagnosis techniques. Comprehensive performance studies were implemented and the test results validated the enhanced performance of the proposed approaches over the traditional fault diagnosis performed by the transmission line distance relay.

Uploaded: December 4, 2006. This document is a Ph.D. student dissertation, Graduate Studies, Texas A& M University, College Station, Texas, December 2006.

The FERC report on reactive power clearly and succinctly lays out the issues and raises important questions about market power, contingent-claim versus real-time markets, the need for an optimal power flow that incorporates reactive power, etc. Unfortunately, the economic/engineering models so far available in the literature fail to represent the true economic optimum. This optimum involves maximization of the expected net benefits of electricity production, transportation, and use under the constraint of a full alternating-current (AC) power flow where the expected net benefit is defined as the sum of the probability-weighted economic outcomes for all contingencies, including line and generator failures. This is the correct way, in terms of economics, to determine optimal reliability, levels of investment, and operation parameters under alternative contingencies, as well as efficient and optimal production and prices for real and reactive power. The purpose of this paper is to take a broad look at how markets should be organized, not only for reactive power but for real power and reliability, since these markets are fundamentally interdependent and essential for efficient and reliable delivery of electric power.

Uploaded December 5, 2006. CERTS (Consortium for Electric Reliability Technology Solutions): A White Paper, Report, Cornell University, 2006.

A framework of security-constrained adequacy evaluation (SCAE) based on analytical techniques is proposed to assess the ability of a bulk power system to supply electric load while satisfying security constraints. It encompasses three main steps: (a) critical contingency selection, (b) effects analysis, and (c) reliability index computation. Effects analysis is the most essential but computationally demanding procedure. It is important that effects analysis simulate contingencies in a realistic manner efficiently. However, effects analysis based on the traditional power flow technology often lacks the realistic system model and diverges when the system is severely stressed. In this paper, a non-divergent optimal quadratized power flow (NDOQPF) algorithm is proposed for effects analysis.
It is implemented based on a single phase quadratized power flow (SPQPF) model that can improve solution efficiency, and a constrained optimization problem, which incorporates operational practices, security constraints, and remedial actions, is formulated to simulate contingencies realistically. The non-divergence of power flow is achieved by introducing fictitious bus injections that are driven to zero as the solution progresses. It guarantees convergence if a solution exists; if a solution does not exist, it provides a suboptimal solution that may include load shedding. The NDOQPF algorithm is capable of efficiently solving the RTO/ISO operational model as well. Such operational procedure is formulated as an optimization problem with the objective function being the bid cost function and congestion constraints. The proposed SCAE framework also includes an improved contingency selection/enumeration scheme based on SPQPF and reliability index computations. The methodology is demonstrated with the IEEE reliability test system.

Uploaded: December 14, 2006. Proceedings of the 9th International Conference on Probablistic Methods Applied to Power Systems (2006 PMAPS), Stockholm, Sweden, June 2006.

Contingency simulation is an essential but computationally demanding procedure for power system security assessment, reliability evaluation, and real time operation. Simulation methods based on the traditional power flow (TPF) model usually suffer from lack of the realistic system model and slow convergence. To solve such problems, this paper proposes a contingency simulation methodology based on a single phase quadratized power flow (SPQPF) model that integrates the compensation method and sparsity techniques. Two major advantages of the SPQPF model exist in its ability to model realistic system component characteristics and its superior performance in achieving faster convergence, which are important to simulate contingencies realistically and efficiently. In the proposed framework, a hybrid contingency selection technique is applied first to categorize system contingencies into two classes:

(1) contingencies that cause system linear changes and
(2) contingencies that cause system nonlinear changes or discontinuities.

The first class constitutes the majority of contingencies while the second class includes only a small portion of contingencies. For contingencies in class 1, the very first iteration of SPQPF can provide satisfactory solutions due to its faster convergence feature, compared to the several iterations generally required by TPF. To further reduce the computational effort, a sparse oriented compensation method that performs the first iteration is developed based on the SPQPF model. For the second class of contingencies, a quasi compensation iterative method is developed to analyze contingencies with high efficiency and acceptable accuracy. The proposed methodology is able to simulate the post contingency situation efficiently in a realistic manner and provide a good balance between efficiency and accuracy in the procedure of contingency simulation. Its performance is demonstrated with IEEE reliability test systems.

Uploaded: December 14, 2006. Proceedings of the IX Probabilistic Methods Applied to Power Systems (PMAPS) Conference, Stockhom, Sweden, June 11-15, 2006. Uploaded: December 14, 2006.

Protection system hidden failures have been recognized as a contributing factor to power system cascading outages. However, in the current bulk power system reliability assessment practice, protection systems are generally assumed to be perfect, and the impact of protection system hidden failures are not taken into account. In this paper, a systematic methodology is proposed to evaluate the effects of protection system hidden failures on bulk power system reliability in the general bulk power system reliability assessment procedure.
In the proposed methodology, a breaker-oriented bulk power system network model is developed to include detailed system substation configurations and protection system schemes. Any protection system constituents, such as transducers, relays, and circuit breakers, may suffer from hidden failures. Although hidden failures existing in transducers and relays can be detected considerably by advanced system real-time monitoring and analysis technologies, such technologies do not detect the trip abilities of circuit breakers.
To conduct the analysis of hidden failures in circuit breaker trip mechanisms (CBTMs), the probabilistic model of the CBTM is built, based on which a hidden failure effects analysis method is developed to obtain contingences resulting from CBTM hidden failures. Such contingencies as well as other contingencies resulting from independent outages and common-mode outages are subjected to a security-constrained adequacy evaluation approach to evaluate their influence on system reliability. The proposed methodology is demonstrated with a breaker-oriented 24-substation reliability test system, which is derived from the IEEE 24-bus reliability test system by integrating explicit substation and protection system models in the network model. Evaluation results show that protection system hidden failures downgrade the system reliability level because they lead to the outages of undamaged equipment following initial system disturbances.

Uploaded: December 14, 2006. 38th North American Power Symposium (2006 NAPS), Carbondale, Illinois, September 17-19, 2006.

The increasing attention paid to reliability in regional transmission organizations provide the impetus for the investigation of stricter security criteria in the operation of the large-scale multi-area systems. However, as system and market operations strongly interact, any change in the system security impacts the economics and vice-versa. While the nature of the interactions between system and market operations is well understood qualitatively, the quantification of the system security impacts on the overall economics of electricity markets is, typically, not performed. In this paper, we develop a general approach to quantify the impacts of different security criteria on market performance using the day-ahead markets. The quantification provides meaningful measures of the financial and the resource dispatch impacts on both a system and an area basis. We illustrate the proposed approach on the ISO-NE system in the quantification of the comparative impacts of two different security criteria for the 2005 day-ahead markets. Through this study, we gain insights that the power systems may be operated under a stricter criterion without adversely impacting the economic efficiency of electricity markets.

Uploaded: December 14, 2006. In book "Innovations in Power Systems Reliability", pp. 221-257, Springer Series in Reliability Engineering, February 25, 2011.

This paper proposes three methods for choosing the transmission system expansion plan considering three reliability constraints, which are deterministic reliability criterion, probabilistic reliability criterion and security criterion based on N-a contingency in order to give more successful market operation. The proposed method minimizes total investment cost It models the transmission system expansion problem as an integer programming one. The method solves for the optimal strategy using a branch and bound method that utilizes a network flow approach and the maximum flow-minimum cut set theorem. The 21 bus system case study results demonstrate that the proposed method is practical for solving the power system expansion planning problem subject to practical future uncertainties.

Uploaded: February 9, 2007. Proceedings of the 39th Hawaii International Conference on System Sciences (2006 HICSS), January 4-7, 2006.

Identification of Market Power in Large-Scale Electric Energy Markets Market power potential is a serious concern for efficient and competitive operation of centrally dispatched electricity markets. Traditional measures for market power ignore underlying physical characteristics of the electric grid that may be exploited for local advantage. In our prior work we have proposed a revenue sensitivity-based approach for identifying market participants with market power potential, and we demonstrated detailed cases using a 30-bus system[1][2][3]. In this paper we address computational challenges for scaling our method to large systems, and we present practical extensions to a portion of our work that enables the evaluation of very large, RTO-scale electric power grids.

Uploaded: February 8, 2007. Proceedings of the 39th Hawaii International Conference on System Sciences (2006 HICSS), January 4-7, 2006.

A decoupled method is proposed to deal with time domain simulation for power system dynamic analysis. Traditionally,there are two main categories of numerical integration methods: explicit methods and implicit methods. The implicit methods are numerically stable but require more computational time to solve the nonlinear equations, while explicit methods are relatively efficient but may cause a numerical stability problem. This paper proposes a new hybrid method to take advantage of both explicit and implicit methods based on the invariant subspace partition. The original power system equations are decoupled into two parts that correspond to the stiff and nonstiff subspaces. For the stiff invariant subspace, the implicit method is applied to achieve numerical stability, and the explicit method is employed to handle nonstiff invariant subspace for the computational efficiency. As a result, the new hybrid method is both numerically stable and efficient. The approach is demonstrated through New England 39-bus and IEEE 118-bus systems.

Uploaded: February 9, 2007. IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 21, NO. 1, PP. 11-18, FEBRUARY 2006.

This paper presents continuation-based quasi-steadystate(CQSS) analysis to approximate the long-term evolution by tracing successive equilibrium points. Applying the parameterized continuation technique to QSS simulation can provide good convergence when the system approaches the bifurcation points. Parameterization of the load exponents through continuation method makes it possible to simulate dynamic load recovery models in the system without numerical integration. The tap dynamics are also included in the CQSS analysis. The simulation results with the modified WECC 179-bus system are described in order to demonstrate the overall methodology.

Uploaded: February 9, 2007. IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 21, NO. 1, PP. 171-179, FEBRUARY 2006.

We formulate a three-period model for studying how the exercise of local market power by generation firms affects the equilibrium investment between the generation and the transmission sectors. Using a 30-bus network example, we compare the transmission investment decisions made by a “ proactive” network planner (who proactively plans transmission investments to induce a more socially-efficient equilibrium of generation investments) with both those made by an integrated-resources planner (who jointly plans generation and transmission expansions) and those made by a “ reactive” network planner (who plans transmission investments only considering the currently installed generation capacities). We show that, although a proactive network planner cannot do better (in terms of social welfare) than an integrated-resources planner, it can recoup some of the lost welfare due to the separation of generation and transmission planning by proactively expanding transmission capacity. Conversely, a reactive network planner, who ignores the interrelationship between the transmission and the generation investments, foregoes this opportunity.

Uploaded: April 30, 2007. 2006 IEEE Power Engineering Society General Meeting, Montreal, Canada, June 2006.