Abstract
In order to achieve a more sustainable and greener future, electrification in the transportation sector has become a trending topic for the past decade, including electric vehicle (EV), electric ship propulsion system and electric aircraft (MEA) and etc. Permanent magnet synchronous electrical machine (PMSM) is chosen to be a key component within these propulsion systems for its high-power density and efficiency that allows a compact design. On this basis, PMSM with more than 3 phases not only possesses the similar characteristics, but also has the inherent fault-tolerant capability owing to its extra “degree of freedom”. Therefore, multi-phase PMSM represents a promising solution for these safety-critical applications with better reliability and robustness. In particular, dual three-phase PMSM (DT-PMSM) with asymmetrical winding set has been widely studied and investigated for its great torque quality with low torque ripple, and simple implementation with 2 conventional 3-phase inverters.In this thesis, the fault-tolerant control (FTC) of DT-PMSM, with both isolated (2N) and connected neutral points (1N), is studied and investigated when it is under the single open-circuit fault (OCF). The novel FTC scheme of full-torque-operation-range minimum loss (FTOR-ML) is proposed to mitigate the additional copper loss, which combines the merit of the conventional scheme of minimum loss (ML) and maximum torque (MT). The entire torque operation range (TOR) of MT is achieved with minimum copper loss. The analytical solution of FTOR-ML is derived in this thesis for both winding configurations.
Furthermore, TOR of both winding configurations are extended in the proposed extended-TOR with minimum ripple (ETOR-MR) scheme, by 2nd-order harmonic current injection into the synchronous DQ subspace. In the case of 2N, the proposed algorithm has improved the TOR from 57.74% to 78.85% of rated torque in the single OCF condition; for 1N, 69.94% of TOR has been increased to 80.07%. Throughout the extended range, although torque ripple is inevitably induced, it is kept at the minimum level by the proposed algorithm, and at the same time sinusoidal current waveform is guaranteed in each healthy phases to eliminate any undesired losses due to harmonics current. The analytical solution of the proposed algorithm is derived for 2N while look-up tables are needed for 1N during implementation.
A test bench with a 12-kW DT-PMSM is setup to validate the proposed control schemes and verify the optimised result obtained by the proposed optimisation algorithm.
| Date of Award | 26 Jun 2024 |
|---|---|
| Original language | English |
| Awarding Institution |
|
| Supervisor | Xiaoze Pei (Supervisor), Chris Brace (Supervisor) & Richard Burke (Supervisor) |