A Brushless, Doubly Fed Machine (BDFM) attempts to combine the advantages of conventional induction and synchronous types of electrical machines by its unique architecture. The validation of BDFM designs in an actual test environment requires the estimation of the BDFM model parameters from actual experimentation. Accurate values for the parameters are also required by controllers that will be used in the future with specific objectives in mind. This study deals with the design of an estimation scheme to evaluate the parameters for a BDFM, dynamic model. Experimental results are presented. Conventional, practical estimation schemes are based generally on a number of experiments carried out at different operating points, or are limited to estimating a few parameters. The thrust of this work is towards developing a technique that can evaluate all parameters of the BDFM model around the same operating point, and, with limited number of experiments. The parameter estimation scheme is developed with practical implementation in mind. The constraints of the experimental procedure are outlined. The validity of the estimation scheme has been established by tests on a laboratory prototype of the BDFM. / Graduation date: 1995

Basic operation, as well as successful development, of the Brush less Doubly-fed Machine (BDFM) has been documented, and research has turned from proof of concept and early development to the more practical direction of increased manufacturability to prove industrial viability. Previous research centered on using standard induction motor stators along with a manufactured BDFM rotor. The more recent efforts center around a ground up design of an optimized BDFM prototype system including a custom converter, a custom die-cast rotor, and a custom stator, all designed specifically for a BDFM system. This paper presents the design process involved in the development of the rotor and stator of a pre-production optimized 5 hp BDFM with a die-cast rotor, from the initial evaluation of the desired specifications to design, simulation, construction, and finally to testing. Using the results of the 5 hp BDFM design, a 15 hp BDFM was designed and manufactured, and the results of that effort are included in this paper as well. This complete process, from design to testing, enables a closed loop analysis of the design techniques and tools used; the successes of the design can be affirmed and the shortcomings identified and corrected. While the primary goal of this paper is to produce two successful BDFM prototypes, the secondary goal is to improve the BDFM design process. / Graduation date: 1998

This thesis presents the development of dynamic control strategies for the brushless doubly-fed machine (BDFM). A simple open-loop scalar controller is first investigated and its response is found to be oscillatory. Using the speed feedback signal, an improved closed loop scalar control algorithm is designed. Steady state performance is controlled by the magnitude of the BDFM control winding current. Simulation and experimental results demonstrate that the closed loop algorithm has a slow response and is suitable for low performance drive applications. A model reference adaptive control algorithm is investigated in simulation, attempting to improve the BDFM dynamic response and assure its robustness against system parameter variations. Further investigations reveal that the field orientation principle for conventional induction machines can be adapted for the BDFM. This enables the design of a rotor flux oriented control algorithm, based on a newly established synchronous reference frame model. Simulation results illustrate the algorithm's fast dynamic response and robustness against parameter variations. The verification of various control algorithms is carried out on a laboratory system consisting of an experimental BDFM, a power converter and associated control hardware. An Intel 80196Kr microprocessor is used to implement inverter switching and current regulation for the BDFM control winding. The rotor flux oriented control algorithm is implemented using an Intel 80960KB floating point microprocessor, achieving a control bandwidth in the kHz-order. Evaluation of a BDFM synchronous angle shows its significance in control design, and it is incorporated into the later control algorithm development in order to eliminate electric torque estimation. This simplifies control algorithm design and is verified experimentally. Consequently, the control algorithm for the BDFM can approach the simplicity of equivalent induction machine control techniques. / Graduation date: 1996

The continuing desire of industry to further improve process efficiency, through tighter control and energy conservation, has prompted users to pay closer attention to Adjustable Speed Drives (ASDs). The conventional ASDs consist of induction or synchronous motors controlled by power electronic controllers through the adjustment of supply frequency and line voltage. The drawback of these conventional ASDs lies in the high cost of the power electronic controllers which have the same rating as that of the machine itself. The Brush less Doubly-Fed Machine (BDFM) ASD has proven, both analytically and experimentally, to provide a cost effective and a wide range of precise speed control. The experimental BDFM prototypes built to date were designed and constructed individually based on designers' experience with self-cascaded machines. The success with these prototypes has promoted the idea of standardizing the design procedure for all future BDFMs. This thesis offers a general design procedure for the BDFM, which can serve as a first step in standardizing the manufacturing process of this machine. The procedure is presented in the form of a demonstration, by applying it to the design of a 60-hp, 600 to 900 r/min, 460-volts BDFM pump drive to replace the currently utilized conventional 60-hp wound rotor induction motor ASD. An ideal design, which determines machine details such as physical dimensions, slot specifics and conductor details based on conservative magnetic and electric loading assumptions, is one form of the design procedure. The other form, the practical design, involves utilizing a specified physical dimensions and slot details to determine the associated conductors' details and to insure the compliance of machine loadings with up-to-date industrial standards. In both procedures, the design will be made to satisfy, if not to exceed, the existing conventional drive performance. / Graduation date: 1994

This thesis covers the efforts of the design, analysis, characteristics, and construction of a Linear Brush less Doubly-Fed Machine (LBDFM), as well as the results of the investigations and comparison with its actual prototype. In recent years, attempts to develop new means of high-speed, efficient transportation have led to considerable world-wide interest in high-speed trains. This concern has generated interests in the linear induction motor which has been considered as one of the more appropriate propulsion systems for Super-High-Speed Trains (SHST). Research and experiments on linear induction motors are being actively pursued in a number of countries. Linear induction motors are generally applicable for the production of motion in a straight line, eliminating the need for gears and other mechanisms for conversion of rotational motion to linear motion. The idea of investigation and construction of the linear brushless doubly-fed motor was first propounded at Oregon State University, because of potential applications as Variable-Speed Transportation (VST) system. The perceived advantages of a LBDFM over other LIM's are significant reduction of cost and maintenance requirements. The cost of this machine itself is expected to be similar to that of a conventional LIM. However, it is believed that the rating of the power converter required for control of the traveling magnetic wave in the air gap is a fraction of the machine rating. The constructional design of the machine is such that the primary contains two 3-phase windings. One of these 3-phase systems is connected directly to the utility grid; the second 3-phase system, with a different number of poles, is connected to a power electronic converter which has the capability of providing adjustable frequency and amplitude of voltage or current. The speed of the traveling magnetic field can be varied simply by controlling the output frequency of the power electronic converter. The design of the actual machine is such that the two 3-phase systems laid in the primary of the machine are magnetically decoupled from each other because of the difference in pole number of the two systems, (e.g. 6-pole and 2-pole for the test prototype machine in our research lab). The other degree of freedom that this machine provides, is the operation of the machine under two distinct speeds by implementing the pole change technique. This mode of operation can give only discrete changes in speed, however, it provides efficient running at those speeds with a minimum of control mechanism. On the other hand, it is anticipated that the LBDFM with two actively fed windings will produce a continuously adjustable speed over a wide range. Hence, LBDFM will be superior if it can be designed to function effectively. / Graduation date: 1991

A brushless doubly-fed machine (BDFM) is a single-frame, self-cascaded induction machine capable of operating in both the induction and the synchronous modes. This thesis presents some important advances concerning dynamic modeling, simulation and analysis of the BDFM. Initially, a two-axis model and its associated parameters are developed and calculated. The development of the model is not subject to the commonly made assumption that the BDFM is electromagnetically equivalent to two wound rotor induction motors in cascade connection. Instead, the model is derived from a rigorous mathematical transformation of a detailed machine design model. This novel approach emphasizes not only the analysis of the machine performance in both dynamic and steady state conditions, but also the design aspects of the machine by correlating the machine performance with the actual machine parameters computed from machine geometry. Using the two-axis model, simulation of the machine dynamic performance in all conceivable modes of operation is carried out and the results are compared with test data available with good correlation. Steady state models, under certain assumptions, are derived based on the two-axis model. For the synchronous mode, motoring operation, a solution technique is developed and utilized to perform steady state performance analysis of the BDFM. Finally, stability analysis of the machine is examined using the linearized version of the two-axis model. Since the linearized two-axis model of the BDFM is time-varying, commonly used eigenvalue analysis techniques cannot be employed directly to investigate the stability characteristics of the machine. However, since the system matrix is a periodic function of time, the theory of Floquet is introduced so that the original linear time-varying system of equations are transformed into a set of equivalent system of equations with a constant system matrix. Eigenvalue analysis is then applied to analyze the stability of the BDFM system over a wide speed range. Predictions by the eigenvalue analysis are correlated with test data. The study concludes that the proposed two-axis model is a good representation of the BDFM for dynamics, steady state, stability investigations of the machine and further development of control strategies for the proposed BDFM system for adjustable speed drive and variable speed generation applications. / Graduation date: 1991

Thesis (M.S.) in Electrical Engineering--University of Maine, 2009. / Includes vita. Includes bibliographical references (leaf 49).

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 240-266). Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 151-164). Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 1996. / Includes bibliographical references.