Towards End-to-End Deep Learning Performance Analysis of Electric Motors

Convolutional Neural Networks (CNNs) and Deep Learning (DL) revolutionized numerous research fields including robotics, natural language processing, self-driving cars, healthcare, and others. However, DL is still relatively under-researched in physics and engineering. Recent works on DL-assisted analysis showed enormous potential of CNN applications in electrical engineering. This paper explores the possibility of developing an end-to-end DL analysis method to match or even surpass conventional analysis techniques such as finite element analysis (FEA) based on the ability of CNNs to predict the performance characteristics of electric machines. The required depth in CNN architecture is studied by comparing a simplistic CNN with three ResNet architectures. Studied CNNs show over 90% accuracy for an analysis conducted under a minute, whereas a FEA of comparable accuracy required 200 h. It is also shown that training CNNs to predict multidimensional outputs can improve CNN performance. Multidimensional output prediction with data-driven methods is further discussed in context of multiphysics analysis showing potential for developing analysis methods that might surpass FEA capabilities

Multifunctional Grid-Connected Voltage Source Inverter to Drive Induction Motor Operating With High-Inertia Load

This paper proposes a novel multifunctional topology for a grid-connected voltage source inverter to control the speed and power flow of a squirrel-cage induction motor. For high-inertia loads during startup, the issues faced include a large transient current and high heat generation. However, the solutions proposed by existing startup methods are inadequate. The topology presented in this study not only addresses the problems related to these methods, i.e., creating a smooth startup, but also presents a flexible alternative for power factor correction using capacitor banks. First, the proposed technique accelerates the motor smoothly to its operating point through the sinusoidal voltage provided by an inverter with an LC filter in its output. In the second step of the control method, after achieving stability in the desired operating point, a converter with an LC filter is assigned the task of power factor correction. Thus, the proposed topology achieves a smooth startup and unity power factor. It includes a new control strategy in which the rotor field-oriented control method is employed for the speed control mode. Finally, the validity of the proposed theory is verified

Linear Parameter-Varying and Fixed-Parameter H_∞-Based Control of a Bearingless Compressor

Bearingless machines have the potential to provide shorter rotors and achieve overall lower losses and higher energy densities than traditional technologies. However, levitation control has to overcome some further challenges. The aim of this work is to attain robust levitation in the presence of disturbances of various natures. To address dynamics dependent on varying speed, a linear parameter-varying (LPV) $H_{\infty }$ -based control of magnetic suspension is applied, where speed is the scheduled parameter. The model-based centralized position control uses inverse nonlinearity compensation and position estimation at actuator locations to decouple levitation and motoring as well as to linearize the plant model. Different control configurations and resulting performances are benchmarked from the application perspective. The tested controllers are synthesized according to the same weighting scheme. However, the control synthesis is achieved by using a Linear Matrix Inequality and a Riccati-based algorithm. A fixed-parameter $H_{\infty }$ controller and an LPV controller are evaluated against gain uncertainty. The performance of the controllers is studied based on frequency-domain analysis and time-domain simulations against accurate nonlinear plant models derived by Finite Element Modeling. Analytical results, supported by simulations with a detailed nonlinear plant model, together with selected experimental tests, assist the evaluation of the control performance of a 160 kW bearingless two-stage compressor prototype. The LPV controller demonstrates superior disturbance attenuation near the rotor bending modes and better handling of external disturbances at low frequencies. The compressors serve as part of a 500 kW high-temperature industrial heat pump

Cost-Effective Single-Inverter-Controlled Brushless Technique for Wound Rotor Synchronous Machines

This paper proposes a cost-effective brushless technique for wound rotor synchronous machines (WRSMs). The proposed technique involves a traditional current-controlled voltage source inverter that utilizes a simple hysteresis-controller-based current control scheme and supplies three-phase currents to the armature winding of the machine. The supplied armature currents inherently contain fundamental-harmonic and third-harmonic current components. These unique armature current waveforms were previously realized by using dual-inverter-controlled schemes achieved with and without thyristor switches to develop brushless WRSM topologies. The fundamental-harmonic current component is applied to develop the main stator field, whereas the third-harmonic component is employed to realize the harmonic magnetomotive force, which induces a back electromotive force (EMF) in the harmonic winding located at the rotor periphery. The induced harmonic EMF is rectified to deliver a DC current to the rotor field winding through a full-bridge diode rectifier to achieve brushless operation. The proposed cost-effective brushless technique for WRSMs is validated using 2-D finite element analysis employing JMAG-Designer 19.1 to investigate the electromagnetic and electromechanical behaviors of the machine. Furthermore, the proposed technique is employed in machine topologies with different pole/slot combinations for the armature winding to achieve better performance

Novel single inverter-controlled brushless wound field synchronous machine topology

This paper proposes a novel brushless excitation topology for a three-phase synchronous machine based on a customary current-controlled voltage source inverter (VSI). The inverter employs a simple hysteresis-controller-based current control scheme that enables it to inject a three-phase armature current to the stator winding which contains a dc offset. This dc offset generates an additional air gap magneto-motive force (MMF). On the rotor side, an additional harmonic winding is mounted to harness the harmonic power from the air gap flux. Since a third harmonic flux is generated in this type of topology, the machine structure is also modified to accommodate the third harmonic rotor winding to have a voltage induced as the rotor rotates at synchronous speed. Specifically, four-pole armature and field winding patterns are used, whereas the harmonic winding is configured for a twelve-pole pattern. A diode rectifier is also mounted on the rotor between the harmonic and field windings. Therefore, the generated voltage on the harmonic winding feeds the current to the field winding for excitation. A 2D-finite element analysis (FEA) in JMAG-Designer was carried out for performance evaluation and verification of the topology. The simulation results are consistent with the proposed theory. The topology could reduce the cost and stator winding volume compared to a conventional brushless machine, with good potential for various applications.National Research Foundation of Korea | Ref. 2016R1D1A1B01008058National Research Foundation of Korea | Ref. 2019H1D3A1A01102988Korea government Ministry of Trade, Industry and Energy | Ref. 2020403020009