No description available.

No description available.

No description available.

This dissertation presents a new, highly robust algorithm for electric power system state estimation. A graph theory-based system decomposition scheme is coupled with a high breakdown point estimator to allow reliable identification of multiple interacting bad data even in cases of conforming errors. The algorithm is inherently resistant to bad measurements in positions of leverage, makes no a priori measurement error probability distribution assumptions, and is applicable in a real-time environment. In addition to presenting a new state estimation algorithm, the weaknesses of two prominent state determination methods are explored. The comparative advantages of high breakdown point estimators are then summarized. New theorems quantifying the previously unexamined effect system sparsity has on the exact fit point of some members of this estimator family are presented. These results serve as the catalyst for the overall state estimation algorithm presented. Numerous practical implementation issues are addressed with efficient implementation techniques described at each step. / Ph. D.

A new network model has been developed which allows the calculation of state estimates for unbalanced electric power systems. This model incorporates the effects of mutually coupled conductors, earth return paths, unbalanced device configurations, and multiple voltage references. Development of the new model appeals to multiport network theory and graph theoretic principles. Model equations are employed directly to obtain least squares estimators in the phase-voltage reference frame. The concept of power system segments is introduced and segment multiport equations are developed. The concept of power system modified primitive networks is introduced and system multiport equations are developed. Segment and system multiport equations are used to obtain a state estimator formulation in variables suitable for practical systems analysis. / Ph. D.

No description available.

Electric vehicles present an opportunity to reduce the substantial global footprint of road transportation. Cost and range anxiety issues, however, remain major roadblocks to their widespread adoption. One of the simplest ways to reduce cost is to remove components from the vehicle via novel topologies, estimation and control; to reduce range anxiety, charging infrastructure needs to be simplified and the power electronics in the vehicle made more efficient. This thesis proposes a bidirectional non-isolated fast charger integrated in the traction drivetrain of an electric vehicle that is enabled by a modular power electronic converter topology called the autoconverter module. The autoconverter module is an evolution of previous modular power electronic concepts with the goal of a highly integrated, high performance converter capable of being used in a number of applications through simple parallelization. By simplifying system design through the use of one base power conversion block, overall system cost can be reduced. Key to the realization of the power module is state estimation. To enable high performance operation of the system, low noise state information must be provided to the controller. State estimation is capable of filtering measurement noise to achieve this goal. However, conventional estimation techniques typically have low bandwidth and a convergence time associated with them, limiting the overall control system's performance. Higher performance techniques, such as receding horizon estimation, offer near-instantaneous estimation with noise rejection capabilities, which makes it an attractive solution. State estimators can also realize a cost reduction through the removal of sensors with little to no performance degradation. Using high performance state estimation and three autoconverter modules in parallel, a novel three-phase inverter/rectifier topology is conceived. Using this topology, a bidirectional non-isolated integrated fast charger capable of universal, i.e. single- and three-phase AC and DC, electric vehicle charging is realized. To interface with the AC power grid and AC traction motor, a novel three-phase common mode voltage controller is developed. By controlling the common mode voltage, leakage currents, which are generated by the fluctuation of the common mode voltage across a parasitic capacitance, can be attenuated and the transformer safely removed from the system. The removal of the transformer presents a significant cost and efficiency gain for both on-board chargers and dedicated charging units. With no transformer, the need for a dedicated on-board charger is obviated; instead, the existing high power traction inverter can be used as the primary charging interface, significantly reducing the cost, size and weight of on-board charging. High efficiency in charging mode is demonstrated, with a peak efficiency of 99.4% and an efficiency at rated power of 11kW of 98.4% shown. Traction mode efficiency with the proposed integrated charger is increased by 0.6% relative to a standard drive at the motor's rated power of 5kW. Damaging leakage currents and shaft voltages are reduced by over 90% because of the common mode voltage control, which will increase drive reliability and lifetime. The topology can be applied to motor drive applications outside automotive to increase efficiency and reliability. State estimation theory for permanent magnet synchronous machine drives is expanded upon and guarantees for estimatability and stability of the estimators are provided. Two estimation schemes, a Luenberger observer and a receding horizon estimator, are studied for sensor removal and the development of a failsafe operating mode involving one phase current sensor. Both estimators function equivalently in the steady state with the receding horizon estimator having slightly better transient performance. The Luenberger observer has conditions on estimatability, whereas the receding horizon estimator has none. Both estimators permit the removal of one current sensor for cost reduction. In regular operation, there is no performance degradation.

M.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Includes bibliographical references. / by Pierre Dersin. / Ph.D.

The ability to implement Wide Area Monitoring and Control in power systems is developing into a need in order to prevent wide scale cascading outages. Monitoring of events in the power system provides a great deal of insight into the behaviour of the system. The research work presented in this thesis focussed on two tools that aid in monitoring: State Estimation and Synchronised Phasors provided by Phasor Measurement Units (PMU). State Estimation is essentially an on-line data processing scheme used to estimate the best possible state (i.e. voltage phasors) from a monitored set of measurements (active and reactive powers/voltage phasor measurements). The ever growing complexity and developments in the state of art calls for robust state estimators that converge accurately and rapidly. Newton’s method forms the basis for most of the solution approaches. For real-time application in modern power systems, the existing Newton-based state estimation algorithms are too fragile numerically. It is known that Newton’s algorithm may fail to converge if the initial nominal point is far from the optimal point. Sometimes Newton’s algorithm can converge to a local minima. Also Newton’s step can fail to be a descent direction if the gain matrix is nearly singular or ill-conditioned. This thesis proposes a new and more robust method that is based on linear programming and trust region techniques. The proposed formulation is suitable for Upper Bound Linear Programming. The formulation is first introduced and its convergence characteristics with the use of Upper Bound Linear Programming is studied. In the subsequent part, the solution to the same formulation is obtained using trust region algorithms. Proposed algorithms have been tested and compared with well known methods. The trust region method-based state estimator is found to be more reliable. This enhanced reliability justifies the additional time and computational effort required for its execution. One of the key elements in the synchrophasor based wide area monitoring is the Phasor Measurement Unit. Synchronized, real time, voltage phasor angle, phasor measurements over a distributed power network presents an excellent opportunity for major improvements in power system control and protection. Two of the most significant applications include state estimation and instability prediction. In recent years, there has been a significant research activity on the problem of finding the suitable number of PMUs and their optimal locations. For State Estimation, such procedures, which basically ensure observability based on network topology, are sufficient. However for instability prediction, it is very essential that the PMUs are located such that important/vulnerable buses are also directly monitored. In this thesis a method for optimal placement of PMUs, considering the vulnerable buses is developed. This method serves two purposes viz., identifying optimal locations for PMU (planning stage), and identifying the set PMUs to be closely monitored for instability prediction. The major issue is to identify the key buses when the angular and voltage stability prediction is taken into account. Integer Linear Programming technique with equality and inequality constraints is used to find out the optimal placement set. Further, various aspects of including the Phasor Measurements in state estimation algorithms are addressed. Studies are carried out on various sample test systems, an IEEE 30-bus system and real life Indian southern grid equivalents of 24-bus system, 72-bus system and 205-bus system.