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In this paper we investigate the multiplexing of heterogeneous applications and the pricing of transmission services on an ATM network. Pricing is of interest for network management to promote efficient utilization of resources. A... more
In this paper we investigate the multiplexing of heterogeneous applications and the pricing of transmission services on an ATM network. Pricing is of interest for network management to promote efficient utilization of resources. A framework is presented in which users select from a menu of services, are peak-rate policed, and are charged according to their usage and connection time. We illustrate the considerable improvement in network utilization possible compared to a traditional
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Meter measurements in the power grid are susceptible to manipulation by adversaries, that can lead to errors in state estimation. This paper presents a general framework to study attacks on state estimation by adversaries capable of... more
Meter measurements in the power grid are susceptible to manipulation by adversaries, that can lead to errors in state estimation. This paper presents a general framework to study attacks on state estimation by adversaries capable of injecting bad-data into measurements and further, of jamming their reception. Through these two techniques, a novel `detectable jamming' attack is designed that changes the state estimation despite failing bad-data detection checks. Compared to commonly studied `hidden' data attacks, these attacks have lower costs and a wider feasible operating region. It is shown that the entire domain of jamming costs can be divided into two regions, with distinct graph-cut based formulations for the design of the optimal attack. The most significant insight arising from this result is that the adversarial capability to jam measurements changes the optimal 'detectable jamming' attack design only if the jamming cost is less than half the cost of bad-data...
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This paper introduces a two-stage stochastic program for transmission planning. The model has two dependent random variables, namely, total electric load and available wind power. Given univariate marginal distributions for these two... more
This paper introduces a two-stage stochastic program for transmission planning. The model has two dependent random variables, namely, total electric load and available wind power. Given univariate marginal distributions for these two random variables and their correlation coefficient, the joint distribution is modeled using a Gaussian copula. The optimal power flow (OPF) problem is solved based on the linearized direct current (DC) power flow. The Electric Reliability Council of Texas (ERCOT) network model and its load and wind data are used for a test case. A 95% confidence interval is formed on the optimality gap of candidate solutions obtained using a sample average approximation with 200 and 300 samples from the joint distribution of load and wind.
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In recent years, high penetration of variable generating sources, such as wind power, has challenged independent system operators (ISO) in keeping a cheap and reliable power system operation. Any deviation between expected and real wind... more
In recent years, high penetration of variable generating sources, such as wind power, has challenged independent system operators (ISO) in keeping a cheap and reliable power system operation. Any deviation between expected and real wind production must be absorbed by the power system resources (reserves), which must be available and ready to be deployed in real time. To guarantee this resource availability, the system resources must be committed in advance, usually the day-ahead, by solving the so-called unit commitment (UC) problem. If the quantity of committed resources is extremely low, there will be devastating and costly consequences in the system, such as significant load shedding. On the other hand, if this quantity is extremely high, the system operation will be excessively expensive, mainly because facilities will not be fully exploited.This thesis proposes computationally efficient models for optimal day-ahead planning in (thermal) power systems to adequately face the stochastic nature of wind production in the real-time system operation. The models can support ISOs to face the new challenges in short-term planning as uncertainty increases dramatically due to the integration of variable generating resources. This thesis then tackles the UC problem in the following aspects: Power system representation: This thesis identifies drawbacks of the traditional energy-block scheduling approach, which make it unable to adequately prepare the power system to face deterministic and perfectly known events. To overcome those drawbacks, we propose the ramp-based scheduling approach that more accurately describes the system operation, thus better exploiting the system flexibility.UC computational performance: Developing more accurate models would be pointless if these models considerably increase the computational burden of the UC problem, which is already a complex integer and non-convex problem. We then devise simultaneously tight and compact formulations under the mixed-integer programming (MIP) approach. This simultaneous characteristic reinforces the convergence speed by reducing the search space (tightness) and simultaneously increasing the searching speed (compactness) with which solvers explore that reduced space.Uncertainty management in UC: By putting together the improvements in the previous two aspects, this thesis contributes to a better management of wind uncertainty in UC, even though these two aspects are in conflict and improving one often means harming the other. If compared with a traditional energy-block UC model under the stochastic (deterministic) paradigm, a stochastic (deterministic) ramp-based UC model: 1) leads to more economic operation, due to a better and more detailed system representation, while 2) being solved significantly faster, because the core of the model is built upon simultaneously tight and compact MIP formulations.To further improve the uncertainty management in the proposed ramp-based UC, we extend the formulation to a network-constrained UC with robust reserve modelling. Based on robust optimization insights, the UC solution guarantees feasibility for any realization of the uncertain wind production, within the considered uncertainty ranges. This final model remains as a pure linear MIP problem whose size does not depend on the uncertainty representation, thus avoiding the inherent computational complications of the stochastic and robust UCs commonly found in the literature.
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J. Aguado and V. Quintana comment on the paper by R. Ebrahimian and R. Baldick (see ibid., vol.15, no.4, p.1240-6, 2000), and ask for comments on five points relating to their own work in this area of power network state estimation. The... more
J. Aguado and V. Quintana comment on the paper by R. Ebrahimian and R. Baldick (see ibid., vol.15, no.4, p.1240-6, 2000), and ask for comments on five points relating to their own work in this area of power network state estimation. The original authors reply to the comments
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Research Interests: Computer Science, Optimal Control, Power System, Parallel Processing, Power Generation, and 10 moreReactive Power, Optimal Power Flow, Load Flow, Distributed Optimization, Coarse Grained Soil, Power flow, Electrical And Electronic Engineering, Power System Simulation, Distributed Algorithm, and System testing
We consider transmission owners that bid capacity, under appropriate Regional Transmission Organization (RTO) market rules, at a positive price into forward and spot (dispatch) auctions to derive congestion revenues. This can encompass... more
We consider transmission owners that bid capacity, under appropriate Regional Transmission Organization (RTO) market rules, at a positive price into forward and spot (dispatch) auctions to derive congestion revenues. This can encompass daily, monthly, or multimonthly auctions, allowing for commitment of transmission to reflect market needs in different time periods, e.g., seasons. We provide two and three node examples and
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Reactive Power is a Cheap Constraint. ... Author Info. Edward Kahn Ross Baldick Abstract. Hogan (1993) has proposed a version of marginal cost pricing for electricity transmission transactions that include a component for reactive power... more
Reactive Power is a Cheap Constraint. ... Author Info. Edward Kahn Ross Baldick Abstract. Hogan (1993) has proposed a version of marginal cost pricing for electricity transmission transactions that include a component for reactive power to support voltage at demand nodes. ...
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We study a non-convex Transmission-Constrained Economic Dispatch (TCED) problem that uses the traditional linear DC model of the transmission system together with a non-linear representation of losses. This problem is typically... more
We study a non-convex Transmission-Constrained Economic Dispatch (TCED) problem that uses the traditional linear DC model of the transmission system together with a non-linear representation of losses. This problem is typically approximated by the convex problem obtained by linearizing the constraints around some base-case state. Electricity prices and dispatch decisions are then chosen based on the resulting linearly-constrained economic dispatch (LCED) problem. Different LCED problems have been suggested in the literature and they are all derived using one of two linearization techniques, which we call direct and indirect linearization, respectively. An LCED problem often used in practice that uses Loss Distribution Factors (LDFs) is derived using indirect linearization and is termed the common LCED problem. This paper studies the assumptions required to recover the optimal dispatch of the non-convex TCED problem from the solution of the common LCED problem. We show that the common LCED problem may have multiple minimizers, in which case small perturbations of the base-case state may result in large dispatch approximation error. Furthermore, even if the base-case state matches a minimizer of the non-convex TCED problem, it is proven that there does not always exist a choice of LDFs such that the optimal dispatch of the TCED problem is also optimal for the common LCED problem. On the other hand, such LDFs do exist and are identified for the special case where no line limits are binding.
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Data attacks on meter measurements in the power grid can lead to errors in state estimation. This paper presents a new data attack model where an adversary produces changes in state estimation despite failing bad-data detection checks.... more
Data attacks on meter measurements in the power grid can lead to errors in state estimation. This paper presents a new data attack model where an adversary produces changes in state estimation despite failing bad-data detection checks. The adversary achieves its objective by making the estimator incorrectly identify correct measurements as bad data. The proposed attack regime's significance lies in reducing the minimum sizes of successful attacks to more than half of that of undetectable data attacks. Additionally, the attack model is able to construct attacks on systems that are resilient to undetectable attacks. The conditions governing a successful data attack of the proposed model are presented along with guarantees on its performance. The complexity of constructing an optimal attack is discussed and two polynomial time approximate algorithms for attack vector construction are developed. The performance of the proposed algorithms and efficacy of the hidden attack model are d...
Power transfer distribution factors depend on the operating point and topology of an electric power system. However, in a recent paper, the power transfer distribution factors were shown theoretically to be relatively insensitive to the... more
Power transfer distribution factors depend on the operating point and topology of an electric power system. However, in a recent paper, the power transfer distribution factors were shown theoretically to be relatively insensitive to the operating point. In this paper, we provide empirical corroboration of this theoretical result. The observations are consistent with those made in several recent papers; however, the systems considered in this paper are considerably larger than have been reported in other studies.
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ABSTRACT The supply function equilibrium model has been used widely to study strategic behavior and market power in electricity markets. However, theoretically there exists a continuum of supply function equilibria, which limits the... more
ABSTRACT The supply function equilibrium model has been used widely to study strategic behavior and market power in electricity markets. However, theoretically there exists a continuum of supply function equilibria, which limits the predictive value of this model. We refine the supply function equilibria by a stability analysis. The local behavior of supply function equilibrium under small perturbations in the form of piecewise linear functions is analyzed. We demonstrate the effectiveness of this method through a symmetric example, and find out that the stable supply function equilibria set that survive piecewise linear function perturbations is significantly smaller than the set of all theoretical SFEs. On the other hand, since practically any form of perturbation function can be reasonably approximated by some piecewise linear perturbation function, if some of the supply functions do not behave chaotically under piecewise linear function perturbations, it suggests that they are likely to be sustainable in reality. This stability analysis method is not limited to symmetric models, and is applicable to asymmetric supply function equilibrium models as well.
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ABSTRACT Transportation is one of the major consumer of energy in US and around the world. According to the latest Department of Energy (DOE) Transportation Data Book [1], 27.8% of total US energy consumption is attributed to... more
ABSTRACT Transportation is one of the major consumer of energy in US and around the world. According to the latest Department of Energy (DOE) Transportation Data Book [1], 27.8% of total US energy consumption is attributed to transportation. Of this amount, 58.9% is consumed by cars and light duty trucks to make up 16.4% of total energy consumed by Americans. To put this in perspective, according to DOE energy usage estimates [2] 39.2% of energy consumed in US is spent for electricity generation.
Abstract In this paper, a single comprehensive algorithm for distribution system switch reconfiguration and capacitor control is proposed. Simulated annealing is employed to optimize the switch configuration of the distribution system,... more
Abstract In this paper, a single comprehensive algorithm for distribution system switch reconfiguration and capacitor control is proposed. Simulated annealing is employed to optimize the switch configuration of the distribution system, while a discrete optimization ...
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We present approximations to non-smooth continuous functions by differentiable functions which are parameterized by a scalar β> 0 and have convenient limit behavior as β→ 0. For standard numerical methods, this translates into a... more
We present approximations to non-smooth continuous functions by differentiable functions which are parameterized by a scalar β> 0 and have convenient limit behavior as β→ 0. For standard numerical methods, this translates into a tradeoff between solution quality and speed. We show the utility of our approximations for wirelength and delay estimations used by analytical placers for VLSI layout. Our approximations lead to more “solvable” problems
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ABSTRACT This paper generalizes previous work on automatic generation control (AGC) gain in a single balancing authority system. In previous work, a control performance standard 1 (CPS1)-compliant AGC gain for a single balancing authority... more
ABSTRACT This paper generalizes previous work on automatic generation control (AGC) gain in a single balancing authority system. In previous work, a control performance standard 1 (CPS1)-compliant AGC gain for a single balancing authority interconnection was proposed, assuming that frequency response can be decoupled from AGC dynamics by widening governor dead bands. However, current practices suggest that widening dead bands may not be a wise course to take as it may deteriorate primary frequency response. This paper formulates sufficient conditions for the adequacy of the joint operation of AGC control and primary frequency response to be consistent with frequency response adequacy. Historical data and a simulation of ERCOT are presented to show numerical results.
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Summary form only as given. In both the United States and Europe, large electric utilities are interconnected with each other. In the past, ad hoc methods have been used to coordinate operations on wide scales. However, with increasing... more
Summary form only as given. In both the United States and Europe, large electric utilities are interconnected with each other. In the past, ad hoc methods have been used to coordinate operations on wide scales. However, with increasing trades, there is a pressing need for paradigms that allow commercial activity to be roughly consistent with Kirchhoff's laws and to rationally
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ABSTRACT The integration of wind power has imposed new requirements for regulation reserves. For ensuring adequate regulation reserves, wind power variability and uncertainty must be estimated, and system frequency must comply with... more
ABSTRACT The integration of wind power has imposed new requirements for regulation reserves. For ensuring adequate regulation reserves, wind power variability and uncertainty must be estimated, and system frequency must comply with frequency performance standards. This work determines regulation capacity and ramping capability requirements as a function of wind-installed capacity to comply with CPS1, the North American Electric Reliability Corporation (NERC) Control Performance Standard 1 for the case of a single balancing authority. A simulation of the Electric Reliability Council of Texas (ERCOT) will be presented to examine the performance of the formulation.
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ABSTRACT Recent results in the literature have demonstrated the value of energy storage assets in increasing the efficiency of power grid. As operation of most assets in the grid is governed by their generated economic value to their... more
ABSTRACT Recent results in the literature have demonstrated the value of energy storage assets in increasing the efficiency of power grid. As operation of most assets in the grid is governed by their generated economic value to their owner, it is imperative to study the optimal operation of storage assets in response to pricing signals from the market. In this work we consider the problem of optimal operation of a generic energy storage device under stochastic energy prices. We show that under certain conditions, the optimal policy for operating the storage asset follows an extended threshold form and can be obtained in a computationally efficient manner.