--The relationship between the two-individual current control and the vector space decomposition (VSD) control for a dual three-phase permanent magnet synchronous machine (PMSM) is investigated in this paper. It is found that the VSD control is more flexible on controlling the fundamental current in sub-plane and the fifth, seventh current harmonics in z 1 z 2 sub-plane with different PI gains, while the two-individual current control is comparable to the VSD control in having the same PI gains in the and z 1 z 2 subplanes. It is also found that the two-individual current control may have potential instability issues due to the mutual coupling between the two sets of three-phase windings. If the mutual coupling between the two sets is weak to some extent, then the two-individual current control could have the same dynamic performance as the VSD control without the stability issues. Experiments are conducted on a prototype dual three-phase PMSM to validate the theoretical analysis.Index Terms--double d-q synchronous frame current control, double-star motor, dual three-phase, instability, two-individual current control, VSD control.

© 2017. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works. Reproduced in accordance with the publisher's self-archiving policy.eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request.Abstract --A method for enhancing torque capability of a dual 3-phase permanent magnet synchronous machine (PMSM) based on conventional dual 3-phase drive system by injecting the fifth and seventh current harmonics without any hardware re-configuration is proposed in this paper. Compared with the third current harmonic injection which is commonly used to enhance torque capability of dual three-phase machine, the two isolated neutral points of each set of single 3-phase windings do not need to be re-connected to the middle point of dc-link capacitors or an additional power switching bridge to provide flowing path for zerosequence current. Further, no additional current sensors are required to obtain the feedback of zero-sequence current to regulate it effectively. For a prototype dual 3-phase PMSM, the average torque increases approximately by 9% at the cost of 0.56% increase in the 12th harmonic torque ripple. The effectiveness of the torque capability enhancement is confirmed by experiments.

--The relationship between the two-individual current control and the vector space decomposition (VSD) control for a dual three-phase permanent magnet synchronous machine (PMSM) is investigated in this paper. It is found that the VSD control is more flexible on controlling the fundamental current in sub-plane and the fifth, seventh current harmonics in z 1 z 2 sub-plane with different PI gains, while the two-individual current control is comparable to the VSD control in having the same PI gains in the and z 1 z 2 subplanes. It is also found that the two-individual current control may have potential instability issues due to the mutual coupling between the two sets of three-phase windings. If the mutual coupling between the two sets is weak to some extent, then the two-individual current control could have the same dynamic performance as the VSD control without the stability issues. Experiments are conducted on a prototype dual three-phase PMSM to validate the theoretical analysis.Index Terms--double d-q synchronous frame current control, double-star motor, dual three-phase, instability, two-individual current control, VSD control.

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This paper proposes an simplified instantaneous output power control to suppress the second harmonic DC bus voltage due to asymmetry in a three-phase PWM converter system without any sequential component decomposers. Normally, in the instantaneous output power control, the positive and negative output voltages and currents are required and they are usually decomposed by notch filters or dual second-order generalized integrals that are difficult to tune and complicated. While in the proposed method, the positive-sequence and negative-sequence currents are regulated by PI plus resonant (PI-R) controllers in dq-frame. Therefore, the sequential current decomposers can be avoided. Meanwhile, the positive and negative sequence output voltages, which are essential for calculating the positive-sequence and negative-sequence current references, are simply obtained from the outputs of the PI and resonant controllers, respectively. The proposed method is robust to any asymmetries and its effectiveness is verified on a prototype asymmetric three-phase permanent magnet synchronous generator (PMSG) system with inherent and externally added asymmetries.

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