A dynamic magnetic equivalent circuit model for design and control of wound rotor synchronous machines

Xiaoqi Wang, Purdue University

Abstract

Recently, a new magnetic equivalent circuit (MEC) model was developed to support automated multi-objective design of wound-rotor synchronous machines (WRSMs). In this research, the MEC model and its application have been enhanced. Initial enhancement has focused on using the MEC model to explore machine design and control as a unified problem. Excitation strategies for optimal steady-state performance have been developed. The optimization is implemented in two phases. First, stator and field excitation at rated power is obtained as part of a WRSM design in which the objectives are to minimize machine mass and loss. Second, a map between current and torque is generated using a single-objective optimization in which core, resistive, and switch conduction loss are minimized. Optimal as well as sub-optimal and traditional controls are studied and compared. An interesting result is that a relatively straightforward field-oriented control is consistent with a desire for mass/loss reduction and control simplicity. The applicability of the excitation to systems in which prime mover angular velocity varies and is (un)controllable is considered, as well as its impact on machine design. A second contribution has been the derivation of a mesh-based dynamic MEC model for WRSMs. As part of this effort, a reluctance network has been derived to model flux distribution around damper bar openings. The reluctance network is applicable to a user-defined damper bar pattern, which enables the study of optimal damper bar placement. In addition, Faraday's law is applied to establish a state model in which stator, field, and damper winding flux linkages are selected as state variables. The resulting coupled MEC/state model is solved to obtain transient machine dynamics, including damper bar currents. In addition, skew of the rotor pole is incorporated using a multi-slices model. The proposed dynamic model opens new paths for exploration. Perhaps most significantly, it enables rigorous design of coupled synchronous machine/diode rectifier systems, which are used in numerous applications, but are often designed using rules of tradition created prior to the availability of efficient numerical simulation.^

Degree

Ph.D.

Advisors

Steve Pekarek, Purdue University.

Subject Area

Engineering, Mechanical|Physics, Electricity and Magnetism

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