Showing papers by "Thomas J. Overbye published in 2011"
TL;DR: A reactive load control optimization algorithm to improve the voltage profile in distribution grid is presented and integrates agent-based technologies to manage the data and control actions required to operate this type of architecture.
Abstract: The introduction of remotely controlled network devices is transforming the way the power system is operated and studied. The ability to provide real and reactive power support can be achieved at the end-user level. In this paper, a framework and algorithm to coordinate this type of end-user control is presented. The algorithm is based on a layered architecture that would follow a chain of command from the top layer (transmission grid) to the bottom layer (distribution grid). At the distribution grid layer, certain local problems can be solved without the intervention of the top layers. A reactive load control optimization algorithm to improve the voltage profile in distribution grid is presented. The framework presented in this paper integrates agent-based technologies to manage the data and control actions required to operate this type of architecture.
137 citations
TL;DR: Two methods for contingency screening with complementary properties are presented and the results show that the screening algorithms are able to detect nearly all of the contingencies that will result in violations, while requiring only a small fraction of the contingency set to be solved.
Abstract: This paper presents a method for determining the double outage contingencies that threaten the system without solving the full contingency set. Two methods for contingency screening with complementary properties are presented. The results of the algorithms are compared to the full double outage contingency analysis results for a large North American case. The results show that the screening algorithms are able to detect nearly all of the contingencies that will result in violations, while requiring only a small fraction of the contingencies to be solved.
122 citations
28 Mar 2011
TL;DR: In this article, a clustering based algorithm for cable layout of a large scale wind power plant is proposed, which shows that real power losses in collector system are lowered and greater reliability is achieved with the proposed design.
Abstract: The goal of achieving 20% wind power penetration by 2030 in the US has stimulated the installation of large scale wind farms in recent years, both on-shore and off-shore. Collector systems consolidate the power generated by turbine units distributed over the geographical area of the wind farm to a substation from where the generated power is transmitted to the electric grid. Design of a wind farm collector system must take into consideration the economics and reliability of operation. Most modern day large scale wind farms consist of hundreds of wind turbines and are generally electrically connected in a radial feeder cable configuration or daisy chains. While these configurations are generally accepted as convention, not much research has been done to analyze other cable layout configurations. This paper proposes a clustering based algorithm for cable layout of a large scale wind power plant. Comparison of the proposed method with the radial feeder cable configuration shows that real power losses in collector system are lowered and greater reliability is achieved with the proposed design. An economic analysis has also been done to compare the cost of generated energy associated with the proposed design and the conventional configuration.
68 citations
20 Mar 2011
TL;DR: In this paper, the authors presented a method for computing an optimal storage dispatch for a storage unit coupled with a wind farm over the period of one hour with the objective of minimizing generation schedule deviations and taking into consideration the uncertainties involved in wind power predictions.
Abstract: Incorporation of energy storage units with wind farms is being considered critical for wind farms to address variability in wind power generation and meeting committed generation schedules. However, operational constraints such as limited energy of storage units, in addition to the inherent variability of wind power, limit the maximum generation commitment that can be met reliably by a wind farm operating in combination with a storage plant. This paper presents a method for computing an optimal storage dispatch for a storage unit coupled with a wind farm over the period of one hour with the objective of minimizing generation schedule deviations and taking into consideration the uncertainties involved in wind power predictions. The optimization uses a stochastic dynamic programming framework in discrete time. The algorithm minimizes the total expected deviations from a steady power delivery schedule of the combined wind farm-energy storage plant. Tests on a simplified model of a wind-storage plant connected to a load verify the desired objectives. The deviations when generated wind power is known accurately are also presented as a special case. Results provide insights about the maximum generation commitment the combined wind-storage unit can meet without deviations over the scheduling horizon given the probabilities of power generation from wind.
19 citations
TL;DR: In this article, the impact of network constraints on admissible price perturbations are used to group generators that have the potential to exhibit local market power, which is most commonly observed in load pockets, where ISO policies mitigate market power.
Abstract: Market power gives certain market participants the ability to manipulate the market to their advantage when their product is not substitutable by competitors. Identification of generators which have the potential for market power either individually or within a small group is performed using sensitivity information from the linear programming optimal power flow (LP OPF). The impact of network constraints on admissible price perturbations are used to group generators that have the potential to exhibit local market power. Specific price perturbation vectors are found that highlight a constraint-induced locational advantage for these suppliers. In practice, this is most commonly observed in “load pockets,” for which ISO policies mitigate market power.
19 citations
23 Sep 2011
TL;DR: In this paper, the effects of geomagnetic induced currents (GICs) on high voltage power transformers were explored and a 37-bus critical infrastructure case was presented, where it is not plausible to protect all the high voltage transformers in the power grid, but by protecting critical transformers, and bypassing others, the grid's integrity can be maintained.
Abstract: Geomagnetic induced currents (GICs) generated by space weather, such as solar storms, currently pose a threat to North American electric grids. GICs enter the power grid through the neutral connection of high voltage transformers causing unusual megawatt and megavar flows, voltage fluctuation, frequency shifts, undesired relay operations, high third harmonic currents, and telemetry and supervisory alarm failures in the power grid. A storm on the order of 5000 nT/min is believed to occur in the not too distant future. Once this storm occurs, widespread damage to the power grid of unprecedented proportions will take place. Mitigation strategies must be considered. Systems involved in restoration and reinstitution of the power grid need to be prioritized, and the effectiveness of existing black-start procedures need to be evaluated. This paper explores the effects of GICs on high voltage power transformers and presents a 37-bus critical infrastructure case. In the event of a geomagnetic disturbance, it is not plausible to protect all the high voltage transformers in the power grid, but by protecting critical transformers, and bypassing others, the grid's integrity can be maintained.
17 citations
20 Mar 2011
TL;DR: In this article, the use of data from phasor measurement units (PMUs) to expose information about the underlying system topology is examined and an equivalent network at the PMU buses is obtained.
Abstract: With the growing prevalence of phasor measurement units (PMUs), an abundance of high-resolution data is becoming available for analysis. The problem arises of how to use the data to obtain information about the operating conditions of the system. We examine the use of data from PMUs to expose information about the underlying system topology. An equivalent network at the PMU buses is obtained. Changes in the equivalent line flows can also be mapped back to events in the full system if the normal system structure is known.
17 citations
04 Jan 2011
TL;DR: This paper discusses the implementation of several different clustering methods for identifying load pockets with potential market advantage in a power system.
Abstract: When lines in a power system are constrained, the sensitivity of the power flows on these lines to generator output provides information about how the constraints divide the system and about the ability of sets of generators to increase revenue without increasing dispatch. Clustering is used to identify generators into groups with the potential for market advantage. In this paper, we discuss the implementation of several different clustering methods for identifying load pockets with potential market advantage.
12 citations
28 Mar 2011
TL;DR: A hybrid approach with AC and DC power flow models for power flow analysis is presented and it is shown that the hybrid approach can be used for applications requiring more accuracy than DC model allows.
Abstract: This paper presents a hybrid approach with AC and DC power flow models for power flow analysis. Power flow problems are solved with the AC model in a part of system, whereas with the DC model in other parts. The proposed methodology can obtain benefits from both AC (non-linear) and DC (linear) models. In other words, this approach formulates both nonlinear and linear algebraic equations, and deals with tradeoff issues between accuracy of the AC model and faster solution of the DC model. A case study with an IEEE 14-bus system is provided to compare accuracy between the proposed and the DC model. It is shown that the hybrid approach can be used for applications requiring more accuracy than DC model allows.
11 citations
23 Sep 2011
TL;DR: Network-level benefits of reactive power injection control using a PowerWorld simulation are presented and a proposed control framework is simulated in Simulink for a single smart device and future work is outlined.
Abstract: Smart devices are becoming more common. Many of them already possess the hardware and software capabilities to implement the reactive power injection control as discussed in this paper. In the near future, such devices would be dispersed over a large portion of the electric distribution network, thus making distributed reactive voltage support feasible. This paper presents network-level benefits of such a scheme using a PowerWorld simulation. Applications are discussed, a proposed control framework is simulated in Simulink for a single smart device and future work is outlined.
1 citations
19 Jun 2011
TL;DR: In this paper, the relationship between events in the system and the measured modal content of the oscillations is examined in the context of linear system theory and control theory, and it is shown that with knowledge of the nominal modes of certain generators, it is often possible to distinguish an event at one of these generators.
Abstract: Disturbances in power systems cause oscillations which can be observed in measured signals throughout the network. This paper examines the relationship between events in the system and the measured modal content of the oscillations. Identifying patterns or distinguishing characteristics from oscillation monitoring data is examined in the context of linear system theory and control theory. Our results show that with knowledge of the nominal modes of certain generators, it is often possible to distinguish an event at one of these generators.