Ms. Jiayue Zhou

PhD Candidate

Tsinghua University

Efforts in high-speed electric machines are fueled by the urgent need for energy-efficient and environmentally friendly propulsion systems. Researchers have dedicated significant attention to advancing high-speed permanent magnet machines, driven by the critical goals of optimizing power density, efficiency, and reliability. However, substantial challenges persist in key areas such as robust position sensing, high-performance current control, particularly at low switching-to-fundamental frequency ratios (SFFRs) and accurate evaluation of the machine performance.

Accurate rotor position data stands as a cornerstone for effective control strategies, with variable reluctance resolvers (VRR) offering outstanding robustness. Nevertheless, their efficacy diminishes at high speeds due to inherent excitation frequency constraints. To overcome this hurdle, I propose a hybrid excitation scheme for VRR. This innovative approach promises a comprehensive solution capable of addressing the entire speed range, including ultra-high-speed operations.

In the design realm of high-speed permanent magnet machines, the impact of the pulse width modulation (PWM) effect induced by inverters cannot be overstated. This phenomenon triggers high-order current ripple, particularly prominent at low SFFRs, resulting in efficiency reduction and excessive heat generation. I advocate for the development of a precise analytical model tailored for predicting PWM-induced current ripple in PM machines at low SFFRs, integrating cross-saturation effects.

Moreover, existing methodologies for current control of high-speed machines under low SFFRs often fall short in achieving both high dynamic performance and robustness. I introduce a novel deadbeat predictive current control method. Leveraging multisampling techniques and precise discrete models, this novel control strategy demonstrates effectiveness even at extremely low SFFRs, ensuring optimal performance in ultra-high-speed scenarios.

In summary, research in high-speed electric machines is driven by the urgent need for lightweight, efficient, and reliable propulsion systems. To achieve this vision, continuous advancements in materials, design, and control strategies are indispensable.