An extended induction motor model for investigation of faulted machines and fault tolerant variable speed drives

Jasim, Omar (2010) An extended induction motor model for investigation of faulted machines and fault tolerant variable speed drives. PhD thesis, University of Nottingham.

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Abstract

High performance variable speed induction motor drives have been commercially available for industrial applications for many years. More recently they have been proposed for applications such as hybrid automotive drives, and some pump applications on more electric aircraft. These applications will require the drive to operate in the presence of faults i.e. they must be “Fault Tolerant” and be capable of “Fault Ride Through”. The aim of this project was therefore to investigate fault ride through control strategies for induction motor drives, particularly with respect to open circuit winding or power converter faults. Three objectives were identified and addressed to meet this aim.

a) A new simulation model for an induction motor was created which reflects both saturation and space harmonics effects within the drive under both symmetric (healthy) and asymmetric (faulted) conditions. The model has a relatively low computational requirement to allow it to be used in conjunction with the simulation of high performance control algorithms and power electronic equipment. For operation in both healthy and faulty conditions, comparisons show that the simulated saturation and space harmonic effects match those obtained from an experiment system. Therefore this model is a very useful tool for the development and optimisation of new control strategies for fault tolerant drive systems.

b) A novel on-line fault detection and diagnosis algorithm based on the measurement of the third harmonic component in the motor line currents has been proposed. The location of the open circuit fault is detected based on detecting a magnitude reduction for the third harmonic component of the current flowing to the motor terminals, and can be implemented in real time to give a fast response with little additional computational overhead.

c) A new open circuit fault tolerant control strategy has been designed for a delta connected induction machine suddenly affected by an open circuit winding fault. The fault ride through is achieved without any modification to either the power converter or the motor circuit. A novel feedforward compensation algorithm is introduced which considerably reduces the current and the torque ripple in the faulted drive motor. Two methods for controlling the neutral point voltage are also presented so that the available voltage capacity of the inverter is maximised in both normal and fault mode. For high speed operation, two different methods for field weakening control are presented, so that the available voltage capacity is maximized in both normal and fault mode.

This thesis describes the theoretical derivation of the new models and algorithms, and presents experimental results from a 4kW laboratory prototype to validate the proposals. The full fault tolerant system is experimentally demonstrated on a delta connected machine which suffers an open circuit winding fault. The improved motor performance under fault conditions is clearly seen.

Item Type:Thesis (PhD)
Supervisors:Sumner, M.
Gerada, C.
Faculties/Schools:UK Campuses > Faculty of Engineering > Department of Electrical and Electronic Engineering
ID Code:1285
Deposited By:Dr Omar Jasim
Deposited On:28 Sep 2010 14:52
Last Modified:19 Nov 2012 21:07

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