Control and optimization of three-phase grid-connected converters for aircraft ground powering systems

Abstract

Power electronics interfaced facilities connected to medium and low voltage distribution networks could lead to drastic changes in power system dynamics, causing some weak grid characteristics, such as high grid impedance, low short circuit capacity, and rich grid background harmonics. The three-phase grid-connected converters, as a common power interface, becomes an emerging topics in research. However, the occurrence of sampling, and delay in digital control systems pose an effect on the traditional energy conversion systems, damaging the control performance or even triggering instability. Besides, the switching pattern, especially the cross-talk of converters with multiple different operating frequencies leads to a defective background harmonic environment.
In this work, three-phase AC/DC converters for an aircraft ground powering system are the major research object. Such system features variable AC frequency and a high proportion of power electronic devices, representing a typical scenario of the weak grid caused by transportation electrification. The small-signal model of the system is built and verified by experimental results. On this basis, digital Smith predictor-based control scheme is utilized to reduce the cross-coupling phenomenon introduced by the varied fundamental to sampling frequency ratio. Further, a heuristic optimization algorithm-based control scheme is proposed to optimize the voltage harmonics through regulating the switching pattern of the converters. By tackling the aforementioned problems in the illustrative electrical power distribution system, stability, power quality and reliability can be enhanced without extra hardware investments. Theoretical analysis and methodologies adopted also provide a benchmark for controlling and optimizing weak grids for other applications.

Date of Award	20 Aug 2025
Original language	English
Awarding Institution	University of Nottingham
Supervisor	Giampaolo Buticchi (Supervisor), Sandro Guenter (Supervisor), Nadia Tan (Supervisor) & Patrick Wheeler (Supervisor)