Title:  Multi-Objective Design, Optimization, And Condition Monitoring of High-Performance Electric Machines For Electric Propulsion

Committee:

Dr. Thomas Habetler, ECE, Chair , Advisor

Dr. Lukas Graber, ECE

Dr. Daniel Molzahn, ECE

Dr. Lijun He, GE Corporate Research

Dr. Yan Wang, ME

Abstract:

The objective of the proposed research is to develop methods for the multi-objective design, optimization, and condition monitoring of electric machines, so as to generate the optimal designs and improve machine robustness for traction applications. In particular, the selected high-performance electric machines are the switched reluctance machines (SRM) with simple and robust structure, and the interior permanent magnet (IPM) machines with high torque density and efficiency. For SRMs, an active current profiling technique integrated multi-objective analytical design and optimization is proposed to generate the optimal designs in terms of the multiple performance indices, which is proved to be accurate and time-saving, especially for a large search space with multiple prime design variables. The proposed scheme offers machine designers accurate, handy and convenient initial designs, which can be further verified or fine-tuned by FEA if necessary. The optimization process is further developed with advanced machine learning algorithms to accelerate the search process and facilitate the final decision making process with the t-SNE visualization algorithm. To monitor the demagnetization properties of the closed-loop direct torque controlled (DTC) IPMSMs, a nonintrusive high-frequency flux injection based PM temperature estimation method is proposed by analyzing the PM electrical high-frequency resistance, which is a byproduct of the eddy current loss induced by the applied high-frequency magnetic field. The developed IPM machine model results in practical ways to excite a proper amount of high-frequency current into the stator windings, which leads to a simple, accurate, and non-intrusive permanent magnet thermal monitoring scheme for DTC-controlled IPM machines. The demagnetization properties of the IPM machine under the most commonly observed stator inter-turn short circuit fault is also systematically investigated, thereby offering machine designers handy information in evaluating the demagnetization fault-tolerant capabilities of the IPM design candidates.