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Improved Voltage Boundary with Model-Based Control Algorithm for Increased Torque in the Field Weakening Region of Induction Machines

Lookup NU author(s): Hamidreza Gashtil, Professor Volker Pickert, Dr Dave Atkinson, Dr Mohamed Dahidah, Professor Damian Giaouris

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This is the authors' accepted manuscript of an article that has been published in its final definitive form by IEEE, 2021.

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Abstract

At high speed, electric vehicles (EVs) have limited torque when powered by an induction machine (IM). In IM the high-speed region is called field weakening and the region is known for torque limitation. This paper proposes a control method that increases the torque without applying discontinuous-modulation techniques which is commonly used. A bespoke model-based voltage control method has been developed that enables reaching the hexagonal voltage reference trajectory for the field weakening region. So far, all model-based control methods are constrained by the inscribed voltage circle which lies within the hexagonal voltage boundary. This restriction limits the available inverter output voltage across the motor windings, which in turns restricts the output torque of the drive. To achieve the hexagonal voltage trajectory, this paper introduces a new calculation of the d-axis current for the entire speed range in field weakening region. This calculation is based on the hexagonal voltage boundary equations and the stator voltage vector position. This generates a new reference d-axis current that minimizes the difference between the hexagonal voltage boundary and its inscribed voltage circle. As a result, the proposed d-axis current maximizes the output torque and output power in the field weakening region. The proposed method is presented analytically. Simulation and experimentally validated results are presented to confirm its feasibility and effectiveness.

Publication metadata

Author(s): Gashtil H, Pickert V, Atkinson DJ, Dahidah MSA, Giaouris D

Publication type: Article

Publication status: Published

Journal: IEEE Transactions on Transportation Electrification

Year: 2021

Volume: 7

Issue: 3

Pages: 1600-1614

Print publication date: 01/09/2021

Online publication date: 04/01/2021

Acceptance date: 15/12/2020

Date deposited: 02/01/2021

ISSN (electronic): 2332-7782

Publisher: IEEE

URL: https://doi.org/10.1109/TTE.2020.3048306

DOI: 10.1109/TTE.2020.3048306

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