Speed/Torque Ripple Reduction of High-Speed Permanent Magnet Starters/Generators With Low Inductance for More Electric Aircraft Applications

With the electrification trend of future aircraft, high-speed permanent magnet starters/generators (PMSs/Gs) will potentially be widely used in onboard generation systems due to their high power density and high efficiency. However, the per-unit reactance of such high-speed machines is normally designed to be very low due to limited onboard power supply voltage and large electrical power demand, which can result in large current ripples in the machine and thus large torque ripples especially when the machine is fed with a semiconductor-based inverter of a lower switching frequency. The torque ripples may further lead to speed oscillation and generate severe vibrations and noises that are harmful to the mechanical system and human beings around. In this article, a speed/torque ripple reduction method for high-speed PMS/Gs with a low inductance is proposed to improve their performance within a wide speed range. An active damping technique is applied to the speed loop to increase the anti-disturbance capability and generate a smoother reference for the current loop, whereas an adaptive output voltage saturation limit is utilized for the current loop to limit the peak value of current to prevent overcurrent and torque spikes. The parameter tuning criteria are derived through a thorough analysis. Finally, the proposed method is validated on a high-speed PMS/G with an inductance of 99
$\mu \text{H}$
. The results show that the speed ripples and torque ripples are reduced by over 50% within a speed range of 2–14 krpm.