Power pooling among electric utility companies aims at effectively harnessing operating economics and reliability benefits through coordinated interchange of power, energy, and related services. In the existing utility industry structure, the operation of power pools brings about the necessary level of coordination to maintain the integrity of large interconnections. In light of growing competition, the continuation of such pools is difficult. This project examines the structures of existing and proposed power pools. It aims to construct analytical frameworks for such coordinated operations. The work will explore the minimal requirements for coordination to maintain system reliability and security. The frameworks will also be used to assess the economic efficiency of pooling.

The most challenging aspects of multiarea studies is to model realistically the loads and resources in each area and to construct computationally efficient schemes for their simulation. Typical applications are to interchange contract evaluation, geographically differentiated marginal costing studies, transmission services pricing, and strategic and resource planning. The multiarea production cost simulation model must correctly take into account the impacts of transmission constraints as well as interconnection operational policies. Our objective is to build a general model to simulate the operation of multiarea power systems under various operational policies, ranging from totally centralized dispatch to decentralized bidding dispatch.

We have developed a general framework for the analysis of competitive electricity markets modeled after the so-called Poolco concept. Under the assumption of perfect competition, we formulated optimal bidding strategies for supply-side bidders. We are extending this framework to include the consideration of demand-side bidding in electricity markets. Strategies for maximizing profits of demand-side bidders are studied. Additional areas of investigation are the relaxation of the perfect competition assumption, the study of market power, the impacts of transmission, and the incorporation of financial contracts into the strategies of bidders.

AIMS is a computerized hourly interchange matching system whose goal is to promote the maximum economic savings among all the participating players. This is accomplished by matching of bids to sell and offers to buy so that the sum of the savings for all the participants is maximized. We are evaluating the matching scheme from the point of view of the system, a buyer, and a seller.

Our interest is to study the strategic behavior of players in formulating their bids to sell and offers to buy. We are investigating the truth revelation characteristics of the bids/offers, the role of transmission availability and the overall impact on system operations.

In a restructured environment, electric utility consumers will eventually choose providers of electrical energy. Hence, there will be greater use of the system for transmission between various players and a much higher level of power flowing through the power grid. This, in turn, will bring about the need to quantify the amount of transmission service that a network can provide. Our research aims to develop a consistent definition of transmission transfer capability and a general set of procedures for its evaluation. We will investigate the information requirements and the computational aspects and will study the use of a real-time information network as a medium for sharing the necessary information among various parties involved in the transmission of electricity.

A Web-based simulator of the Federal Energy Regulatory Commission mandated Open Access Same-Time Information System (OASIS) network is being implemented. The purpose of the simulator is to provide a tool to study the various aspects of an OASIS network, to gain a strong intuitive feel for its operations, and to train users. For a specified time period, the OASIS NET simulator reproduces an OASIS network of multiple nodes using the same communications medium as the actual system, the Internet, and with multiple players using the simulator simultaneously. Salient features of the simulator are its modular architecture, the ability to simulate multinode OASIS network operations, and to accept simultaneous access from remote users through use of client/server technology. The simulation focuses on the dissemination and use of the available transmission capability information. Sample applications of the new simulator are investigated.

The entrenchment of competition, the drive for unbundling of services and products, and the new regulatory decisions are resulting in the development of new structures for power systems. A key consideration in the formulation of new structures is the need to have minimum requirements for coordination to ensure the integrity, reliability, and security of the system. This investigation is focusing on the economic efficiency, engineering/technical considerations/constraints, and critical informational aspects of various structural paradigms.

Modern microprocessors and both analog and digital circuits are being designed for lower voltages to support high densities and fast operation. This project considers solutions for power supplies operating in the range of 1 V to 3 V. Synchronous rectifiers and related techniques are being developed for this operating range. Control methods to minimize power loss and provide robust operation have been identified. A complete integrated circuit power converter for this range has been designed and fabricated in the MOSIS process. This converter will help support extensive experimental work.

Power conversion circuits are large-signal nonlinear networks controlled exclusively through the action of switches. Several new approaches are being developed for power converter control. One approach explands on geometric methods, such as sliding mode control, used successfully in other nonlinear applications. In this boundary control approach, geometric structures in state space are used to control the evolution of converter voltages and currents. Methods such as boundary control offer precise, reliable converter operation with minimum influence by unknown parameters and external noise.

A complete hybrid electric car, combining an electric traction system with an engine-generator set, has been built and is now under study in the laboratory and on the highway. The car is designed to meet all performance, safety, and convenience characteristics of standard automobiles, while reducing exhaust emissions by as much as 90%. Objectives are to characterize major subsystems of a practical hybrid car in depth. Tests of efficiency, fuel economy, and emissions are being conducted. Parametric studies of subsystems are in progress. The data and information will assist industrial firms in the evaluation, design, and development of hybrid vehicle technology.

Field orientation is a widely used control method for ac induction motors. Recent results in nonlinear control theory, including feedback linearization and integrator backstepping, offer possible alternatives for ac servo systems. Observer techniques allow high performance without expensive sensors. This project examines the operating performance of new motor control alternatives. Methods are studied analytically, through detailed simulation, and experimentally. A digital signal processing motor drive system has been designed and built for tests.

Comparisons are being made among various simulation approaches for switching power conversion systems. The switching nonlinearities of these systems are well suited to piecewise simulation approaches, but less well suited to conventional methods. The project compares SPICE-based circuit simulators and mathematical simulation methods such as MATLAB. The objective is to learn the considerations needed when preparing a simulation tool suitable for power electronics modeling and analysis.

Pulse-width-modulated inverters are experiencing growing application for control of ac motors. Modern systems support motors at power levels up to about 100 kW, although cost increases rapidly above 20 kW or so. An alternative at high power levels is to use several inverters in parallel. To make such an arrangement reliable, tight coordination of individual inverters is necessary. The project is studying coordination techniques. Both device-level and system-level approaches are being examined through analysis, simulation, and experimental tests.

Power supplies and other electronic circuits for energy processing are usually designed on a case-by-case basis. In this project, a general framework leading to a step-by-step design process, suitable for automation, is being developed. A user would provide specifications, then select from alternatives presented by this CAD system. The system would establish a baseline design, then perform an optimization procedure to refine it and meet the user's specifications. The heart of this CAD system is a component selection algorithm that takes an alternative circuit and establishes component values needed to establish the baseline design.

Rechargeable batteries are used in long series strings for many industrial applications. The recharge process is not uniform, and the weakest battery in the string limits the performance of the set. An equalization process is required to restore battery balance. In this project, a clocked switched-capacitor circuit has been developed to exchange charge between adjacent batteries in a series string. This exchange drives all batteries to identical voltages, without regard to component values, battery technology, or state of charge. This equalization process can proceed while the batteries are in use or under charge, or separately.

As power systems become more heavily loaded, system operation will be increasingly constrained by contingent cases for which the power flow equations have no real solution. The goal of this project is to develop a measure to quantify the unsolvability of such cases and to determine the optimal controls to restore the case to solvability. A Euclidean norm is used in parameter space to measure the degree of unsolvability. The sensitivity of this measure to different system controls is then used to determine the best controls to restore the case to solvability. Both the static and dynamics aspects of the problem are considered.

In the restructuring of the electric power industry, a number of alternative paradigms for the future industry structure are under consideration. We are developing a modular simulation/visualization tool to effectively analyze and evaluate the effects these proposed paradigms will have on power system operations. Key research goals in- clude methods to assess transmission system capacity, pric- ing of transmission capacity, and development of criteria for an equitable and consistent comparison of alternative paradigms.

Parallel processing algorithms for dynamic response calculations of large power systems have been developed. The differential-algebraic system of equations of the power system are algebraized using the simultaneous-implicit method. The resulting system of linear equations at each time step are solved using the conjugate gradient method which belongs to the family of iterative solver techniques. Use of preconditioners such as the ILU(s) speeds up the convergence. Further enhancement in speed-up is obtained by using the preconditioner only when the number of iterations increase. The general minimal residual (GMRES) method suitable for matrices that are unsymmetric and not positive definite was found to be more robust than other iterative solver algorithms.

In this research, we compute trajectory sensitivities of the post-fault system with respect to prefault loading conditions and for a given set of contingencies. From this we compute whether the system is stressed and, if so, identify the critical machines. Thus we develop an alternative to the transient energy function (TEF) method. Results on a 17-machine IEEE test system as well as systems described by differential-algebraic equations have been obtained. In view of the fast computing power available these days, sensitivity theory offers an alternative to existing techniques for security assessment and preventive control.

In this research, we expand upon the MATLAB-based small-signal analysis formulation developed at the University of Illinois to include FACTS devices such as the static var compensator (SVC) and Thyristor Controlled Series Capacitor (TCSC). In particular, we focus on controlling Hopf bifurcation through proper placement of these devices. Auxiliary controllers are used when necessary to improve system damping.

We used the asymptotic expansion theory for the ``inner'' and ``outer'' solutions of a singularly perturbed two time- scale system to systematically integrate the fast and slow subsystems in their respective time scales thus removing the ``stiffness'' of the original system. This is an alternative to using the integral manifold theory. The two approaches are compared in terms of their computational speed and convenience for simulation using the example of a synchronous machine subjected to a disturbance.

We used interval matrix theory to see if the linearized model of a power system is Hurwitz stable with respect to variations of the elements of the matrix in a given interval. The initial application has been with respect to power system stabilizer (PSS) parameter variation, which can be expressed in a matrix polytope form. Using interval matrix theory, we can plot the stability region in the parameter space with respect to uncertainties in the parameters. Multimachine application is now being done with loads being taken as perturbations.

Physically based preconditioners will be developed for fast nonlinear simulation of power systems using the general minimal residual (GMRES) iterative solver technique. It will be compared with the LU factorization method. Both will be developed on the MATLAB platform and integrated with the existing small-signal stability program and the transient energy function program. Ultimately, the idea is to develop a power system dynamics toolbox useful for R&D of small to medium sized systems.

The purpose of this project under the Indo-U.S. Science Cooperative Program is to collaborate in the area of small-signal analysis of large-scale power systems. Specifically, the topics to be addressed are the design of power system stabilizers, investigation of torsional oscillations, and computation of selected eigenvalues of the system. The goal of the project is to produce a research monograph in this area useful to the power engineering community. A preliminary set of lecture notes has been developed. Also, some collaborative research work in the area of Flexible AC Transmission System (FACTS) controllers for system damping is being pursued.

There is rich literature in control theory regarding Kharitonov's theorem and its extensions for robust stability. We plan to use it for power systems where load variations are considered as uncertainties. In particular we will focus on matrix equivalents of Kharitonov's theorem where parameters appear explicitly.

This project examines new approaches to the rapid computation of available transfer capability in electric power systems. It focuses on efficient techniques to simultaneously include thermal, voltage, voltage collapse, and transient stability margin constraints. New approaches to quantify the transmission reliability margin and capacity benefit margin are investigated.

This project examines methods to eliminate sustained oscillations when they appear in power systems. An eigenvalue sensitivity approach is being tested to determine the effectiveness of operator controls that may eliminate oscillations. Effectiveness of discrete control actions, such as disabling a voltage regulator, is also being investigated.

This project is investigating the importance of data accuracy in the real-time control of power systems. Sensitivities of static and dynamic response calculations to input data are being examined and related to results such as security margins, transfer capability, stability limits, and economic dispatch.

A solar electrical car is being designed and constructed by students to compete in a cross-country solar car race (SunRayce 1997) to be held in June 1997. Mechanical engineering considerations include the minimization of drag coefficient, rolling resistance, and weight. Electrical engineering considerations include optimizing the amount of power transferred from a solar array to storage batteries and maximizing the efficiency of the drive motor and the inverter that supplies its energy. All this must be done while producing an operating vehicle that conforms to the rules of the competition. This project involves approximately 100 students.

For improved braking and to detect problems, it is desirable that each car in a freight train have available a source of electrical energy. The goal of this project is to determine all the possible ways this energy can be supplied and to evaluate them. More detailed studies of the most promising schemes will be conducted.