Jussi Karttunen CURRENT HARMONIC COMPENSATION IN DUAL THREE - PHASE PERMANENT MAGNET SYNCHRONOUS MACHINES

Jussi Karttunen Current Harmonic Compensation in Dual Three-Phase Permanent Magnet Synchronous Machines Lappeenranta 2017 80 pages Acta Universitatis Lappeenrantaensis 751 Diss. Lappeenranta University of Technology ISBN 978-952-335-097-7, ISBN 978-952-335-098-4 (PDF) ISSN-L 1456-4491, ISSN 1456-4491 Dual three-phase electric machines can bring significant benefits over conventional threephase machines in many applications. Although increasing the phase number of the electric machine can deliver significant advantages, it also introduces problems with stator current harmonics. In dual three-phase machines, even a small voltage excitation of certain frequency components can produce significant corresponding stator current harmonics. Current harmonics cause adverse effects such as additional losses, which degrade the efficiency of the machine. Thus, the target is usually to eliminate the harmonics. The established solution to eliminate current harmonics is to use some current harmonic compensation method. In the literature, a variety of methods have been suggested for the purpose. The objective of this doctoral dissertation is to show that in addition to the traditional methods, an inverse-based current harmonic controller can be effectively used to eliminate stator current harmonics in dual three-phase machines. Further, it is demonstrated that, compared with the traditional methods, the inverse-based structure of the proposed controller is very advantageous in the theoretical analysis. Another novel approach for harmonic compensation is obtained by recognizing that the current harmonics can be modelled as caused by a lumped disturbance signal. Hence, it is possible to use a disturbance-observer-based control to eliminate the current harmonics. The results show that the disturbance observer provides a high-performance alternative to the conventional harmonic compensation solutions. The well-known current harmonic compensation methods reported in the literature and the new approaches developed in this doctoral dissertation are extensively compared in terms of stability and performance. A detailed theoretical analysis of the methods is given by using a modern multi-input multi-output technique based on a structured singular value analysis. In addition, the performance of the methods is studied with experimental results. The main contribution of this dissertation is to establish the most favourable current harmonic compensation method for dual three-phase permanent magnet synchronous machines. All in all, the results show that the current harmonics can be eliminated robustly and efficiently with the right type and parameters of the harmonic compensation.