| Author: | Jiang, Mingyuan |
| Title: | Design and optimization of multiport electrical machines and systems |
| Advisors: | Niu, Shuangxia (EEE) |
| Degree: | Ph.D. |
| Year: | 2024 |
| Subject: | Electric machinery Electric motors Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Electrical and Electronic Engineering |
| Pages: | xvi, 167 pages : color illustrations |
| Language: | English |
| Abstract: | Multiport electrical machines are widely utilized for energy distribution and combination, aiming to enhance overall efficiency, power factor, and speed/torque of transmission ports. These machines have gained increasing importance in transportation electrification and power generation due to their compact structure, design flexibility, and high efficiency. A comprehensive literature review is conducted, analyzing fundamental principles, advanced controlling strategies, and existing multiport topologies. The pros and cons of these topologies are evaluated, along with discussions on challenges and future trends. The review identifies two key research gaps: unsatisfactory torque performance and weaker flux controllability. To improve torque performance, a novel brushless dual-electrical-port dualÂ-mechanical-port machine (BLDDM) is proposed. This design incorporates high-order harmonic modulation, artificially enhancing the third-harmonic component of the airgap flux density in the inner airgap while maintaining the fundamental component in the outer airgap. Comparative analysis with conventional designs of the same dimensions demonstrates that the proposed BLDDM achieves a 50% higher back electromotive force (EMF) in the modulation winding and a 45.7% larger torque density. Experimental testing of a machine prototype validates the feasibility and advantages of the proposed design. For reducing energy consumption in control windings and enhancing overall efficiency in Variable Speed Constant Frequency (VSCF) applications, a novel brushless dual-electrical-port dual-mechanical-port doubly fed machine (BLDDÂ-DFM) is developed. This design incorporates high-order harmonic modulation, amplifying the third-harmonic component in the inner airgap of the magnetomotive force (MMF) while maintaining the fundamental component in the outer airgap. By employing high-order harmonic modulation, the slip ratio is reduced, resulting in energy savings. Finite element analysis and comparative studies confirm the effectiveness of the proposed design, and a prototype further validates its feasibility and advantages. To achieve improved flux weakening performance, a novel mechanical flux-weakening design for a spoke-type permanent magnet generator is proposed. This design allows effective adjustment of the total induced voltage and the amplitude of the back EMF vector sum by mechanically controlling the position of an adjustable modulator ring. Consequently, Variable Speed Constant Amplitude Voltage Control (VSCAVC) with a wide speed range can be achieved. Compared to the electrical flux weakening method, the mechanical approach offers easier operation without the risk of permanent magnet demagnetization. The proposed design is supported by an analytical model and operating principles, and performance analysis of different stator/rotor pole pair combinations using finite element methods demonstrates the characteristics of VSCAVC. Finally, a novel hybrid excitation consequent-pole contra-rotating machine with zero-sequence current excitation is introduced to enhance flux weakening ability. This design involves stator windings carrying both the DC field winding current and the AC armature current, resulting in a more compact machine. The flux can be weakened or enhanced without the risk of demagnetization by controlling the zero-sequence current excitation in the integrated winding. |
| Rights: | All rights reserved |
| Access: | open access |
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