Showing papers by "Thomas J. Overbye published in 2005"

PTDF-based power system equivalents

Abstract: The large size of power systems makes behavioral analysis of electricity markets computationally taxing. Reducing the system into a smaller equivalent, based on congestion zones, can substantially reduce the computational requirements. In this paper, we propose a scheme to determine the equivalent reactance of interfaces of a reduced system based upon the zonal power transfer distribution factors of the original system. The dc power flow model is used to formulate the problem. Test examples are provided using both an illustrative six-bus system and a more realistically sized 12 925-bus system.

A comparison of the optimal multiplier in polar and rectangular coordinates

Abstract: Studies of the optimal multiplier (or optimal step size) modification to the standard Newton-Raphson (NR) load flow have mainly focused on highly stressed and unsolvable systems. This paper extends these previous studies by comparing performance of the NR load flow with and without optimal multipliers for a variety of unstressed, stressed, and unsolvable systems. Also, the impact of coordinate system choice in representing the voltage phasor at each bus is considered. In total, four solution methods are compared: the NR algorithm with and without optimal multipliers using polar and rectangular coordinates. This comparison is carried out by combining analysis of the optimal multiplier technique with empirical results for two-bus, 118-bus, and 10 274-bus test cases. These results indicate that the polar NR load flow with optimal multipliers is the best method of solution for both solvable and unsolvable cases.

Reducing the risk of major blackouts through improved power system visualization

Abstract: Many blackouts occur with time scales that would permit emergency control by the operators. However, in order to perform this control the operators need to quickly know the state of system and implement timely, corrective control actions. This paper describes several visualization techniques that can be used to provide this information. Techniques discussed include the use of dynamically sized pie charts on transmission lines, the use of transmission line flow animation, and the use of contouring.

Human factor aspects of power system flow animation

Abstract: This paper presents experimental results associated with human factor aspects of using animation to display electric power system flow information, including transmission line megawatt flow and power transfer distribution factor (PTDF) values. The paper's results are based on two experiments performed at the University of Illinois at Urbana-Champaign using electric power system students. The results indicate that animated motion of power system flows can be used successfully in displays to improve both the speed and accuracy of certain tasks. This effect was most apparent on displays showing PTDFs. However, the results also show that motion may not provide a clear advantage in the visualization of transmission line flows for uncomplicated analysis tasks.

Market Power Potential Examination for Electricity Markets Using Perturbation Analysis in Linear Programming OPF Context

Abstract: Market power potential is a major concern in design, planning, operations and control of electricity markets. This paper uses a perturbation analysis in the linear programming (LP) OPF context to examine market power potentials of generation companies (GenCos) gained by small-scale output withholdings. Based on the definition for market power, we use a two-step scheme. With small-scale withholdings simulated by bid perturbations, the GenCos' profitability from bid perturbations is first examined, and then the effects on locational marginal prices (LMPs) of the identified profitable bid perturbations are investigated. With the LP OPF, LMPs and generators' dispatched output might be differentiable or discontinuous as bidding parameters perturb. For the differentiable case, profit and LMP sensitivities are calculated to analyze profitability and market power potentials. For the discontinuous cases, we explicitly calculate the jumps in LMPs or dispatches, and examine the incentive of GenCos to cause these jumps as well as the effects of these jumps on market outcomes. The proposed perturbation analysis provides valuable insights for both the GenCos and the independent system operator (ISO). For the GenCos, the profitability analysis provides guidance in how to perturb their bids and with which other GenCos they should merge or collude to reap more profit. For the ISO, the market power potential results are insightful in examining the vulnerability of the market in face of generation bidding manipulations and predicting GenCos' bidding behaviors.