This thesis presents the design and analysis of specialised control systems for switched reluctance (SR) and permanent magnet (PM) machines in vehicular electric applications. Control systems for operation in motoring and power generation are considered for both the types of machines. The SR machine operation considered in this thesis is mainly focused towards the application of aero-engine starter/generators. The control designs for PM machines are formulated considering general fault-tolerant and isolated multiphase PM machines which can be applied in the majority of safety-critical vehicular power and propulsion applications. The SR motoring mode presented in this thesis considers the control design for operation from zero speed to a high speed range, while SR generation mode is confined to the high speed range, such as for the requirements of aero-engine starter/generator operation. This thesis investigates applied control methods for both single-pulse and chopping modes of operation. Classical excitation control versus peak current control and the introduction of a zero-voltage interval are compared for SR motor operation. Optimized excitation control versus two classical forms of excitation control are developed and compared for SR generator operation. Studies include simulation of a 12/8 250kW machine and experimental work on a 6/4 300W machine. The PM motoring and power generation considered in this thesis focuses on a special class of PM machines and drives which are specifically designed for fault-tolerant operation. Optimized control strategies for the operation of PM machines with the parallel H-bridge per-phase converter architecture are investigated. Mathematical modelling of the machine and drive with a consideration of harmonics is presented. The developed control methods are then evaluated by means of finite-element model based simulations of a 125kW five phase surface PM rotor machine and an interior PM rotor machine.

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Switched reluctance motor(SRM)drives are favored in many industrial applications because of their cost advantage and ruggedness. However, the torque ripple and bus current ripple of SRM restrict its application range  compared with traditional AC and DC motors due to the doubly salient pole structure and the highly non-linear coupling between torque, rotor position and phase current. As a result of the torque ripple on the shaft, unwilling large acoustic noises are generated. The large current ripple at the DC bus input requires large electrolytic capacitors for attenuation. However, electrolytic capacitors are of low reliability, which will reduce the duration of the control system. Because of these disadvantages, the acceptance of SRM by the industry, especially in servo-type applications which require stationary torque at low speed, is quite slow. In order to obtain high quality control, there have been many efforts in developing techniques for torque ripple attenuation. Primarily, two approaches are used to give a smooth torque. One is to improve the magnetic design, the other is to use sophisticated control techniques. Some torque control techniques have been proved to obtain a relatively good performance by simulations and experimental results. This thesis gives an alternative torque ripple minimization technique. Simulations and Experiments are conducted to show the effectiveness of this new control scheme. Under this new control scheme, the current controller are much easier to be designed under high speed application, which could be an advantage of it. First, the SRM operating principle is presented. The torque of SRM is produced by the tendency of its moveable part shifting to a position where the inductance of the exited winding is maximized. The torque ripple origin is discussed in terms of both magnetization and control. The torque ripple is produced during phase commutation interval because the phase current cannot rise from zero to the nominal value instantaneously due to the existence of the phase inductance. Second, a new torque control scheme is proposed. The new torque control of SRM is split into two cascade sub-tasks. At first, a current reference for ripple free torque is determined. Then a current controller is designed to regulate the current in the stator winding to reference value. Simulations are conducted to verify the effective of this torque control scheme in both ideal 'sinusoidal' SRM and a 'Pseudo-Sinusoidal' SRM. Finally, a motor drive control system is built to implement the new control scheme. The motor is tested under different speeds to see the torque ripple produced in different speed ranges. As a conclusion, the new control algorithm for constant torque and damped input bus current ripple is investigated. The advantages of this new torque control method are listed in the paper. Simulation and experimental results show the effectiveness of this new control method. / Master of Science

Model predictive control (MPC) for switched reluctance machine (SRM) drives is studied in this thesis. The objective is to highlight the benefits of implementing MPC to overcome the main drawbacks of SRMs and position them as an attractive alternative among electrical drives. A comprehensive literature review of MPC for SRM is presented, detailing its current trends as an application still at an early stage. The different features of MPC are highlighted and paired with the most challenging and promising control objectives of SRMs. A vision of future research trends and applications of MPC-driven SRMs is proposed, thus drawing a road-map of future projects, barriers to overcome and potential developments. Several important applications can take advantage of the improved features that SRM can get with MPC, especially from the possibility of defining a unified control technique with the flexibility to adapt to different system requirements. The most important cluster for SRM drives is the high- and ultrahigh-speed operative regions where conventional machines cannot work efficiently. SRMs with MPC can complement then the existing demand for electrical drives with high performance under challenging conditions. Three techniques based on the finite control set model predictive control (FCS-MPC) approach are developed out of the proposed road-map. The first one defines a virtual-flux current tracking technique that improves the existing ones in operating at different speeds and more than one quadrant operation. The method is validated for low- and high- power SRMs in simulations and diverse types of current waveform, making it easy to adapt to existing current shaping techniques. It is also validated experimentally for different operating conditions and robustness against parameter variation. The second technique proposed a predictive torque control that bases its model on static-maps, thus avoiding complex analytical expressions. It improves its estimation through a Kalman filter. The third technique uses a virtual-flux predictive torque control, similar to the first technique for current tracking. The techniques are validated at a wide speed range, thus evidencing superiority in performance without modification on the control structure. / Thesis / Doctor of Philosophy (PhD)

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The thermal management of electric machines is investigated with the application of techniques to a Switched Reluctance Machine and a high-speed Switched Reluctance Machine. Two novel concepts for said management of a Switched Reluctance Machine are proposed and developed: Inter-Laminate Cooling and a Continuous Toroidal Winding. The Inter-Laminate Cooling concept is developed with application to an iron core inductor which serves as a proxy for the electric machine. The experimental results confirmed the capability of the method, expressed by the effectiveness, which defines the performance measure of the applied cooling method; a concept which itself is equally applicable to other cooling methods that may be applied to any electric machine. The effectiveness also describes the gain in allowable input power to the machine which is realized to reach the same thermal limit versus the case without Inter-Laminate Cooling. The Inter-Laminate Cooling was not applied in experimental test to a Switched Reluctance Machine due to the present economic and fabrication limitations. The Continuous Toroidal Winding concept, originally conceived to permit the consideration of a fluid capillary core type of winding to enhance machine cooling, is developed to allow for peripheral cooling of the machine windings and end windings. The Continuous Toroidal Winding version of the Switched Reluctance Machine is investigated for both its thermal and electrical performance in the context of a machine that is equivalent electromagnetically to its conventional counterpart. The Continuous Toroidal Winding Switched Reluctance Machine was found to perform thermally as tested, in a manner superior to that of the conventional machine where the Toroidal machine was simulated and researched at an equivalent level of operation to the conventional machine. The electrical performance of the Toroidal Switched Reluctance Machine although supportive of the simulation analysis used to develop the machine, was not fully conclusive. This may have been due to problematic iron cores used in the construction of the experimental machines. The application of the Inter-Laminate Cooling method to a Switched Reluctance Machine is considered on an analytical basis for the special case of a High Speed Switched Reluctance Machine and found to be of net positive benefit as the machine’s iron losses are dominant over its copper losses. Application of the Inter-Laminate Cooling method to a lower speed machine, whilst beneficial, is not sufficient to significantly impact the temperature of the machine’s windings such that it would offset the loss of specific torque and power. As such, Inter-Laminate Cooling is only applicable where the net benefit is positive overall; in that the gain in input power realized is sufficient to overcome the loss of specific power and torque which will occur due to the increased machine volume. The “effectiveness” and “gain” approach for the evaluation of cooling methods applied to electric machines is a concept which should be adopted to aid in the comparative understanding of the performance of myriad different cooling methods being applied to electric machines both in research and practice, of which there is only minimal understanding. / Thesis / Doctor of Philosophy (PhD)

Switched reluctance motor has features like robust structure, low cost, and wide speed extension range over conventional induction and synchronous motors. These features make it a promising choice for many applications from electric vehicle to aerospace industry. However, due to its silent structure, the characteristics of switched reluctance motor are highly nonlinear. The nonlinearity makes it difficult to control and results in degraded performance such as high torque ripple and acoustic noise compared with conventional induction machine or synchronous machine. New power converters and control methods have to be developed to improve its performance. In order to reduce the current ripple and torque ripple, a novel three-level converter for switched reluctance motor is proposed. The operation modes and modulation method are presented in detail. Simulation and experimental results show that compared to conventional two-level converter, the proposed three-level converter is able to reduce current ripple, torque ripple and acoustic noise significantly without increasing cost. A fast and accurate current controller is essential for the torque control of switched reluctance motor. An adaptive current controller for the three-level converter is developed to avoid the performance degradation caused by manufacture inconsistency. This controller has the ability to adjust its parameters according to the specific motor it drives. Fast dynamic and high accuracy could be achieved through parameter adaption. In order to reduce the cost, and compete with the well-developed sensorless brushless DC and induction motor drive system, a new position sensorless control method for switched reluctance motor is proposed. This method is effective under both low speed operation and high speed operation. It can start with heavy load. It does not have to align the machine before start up as what is needed for many sensorless brushless DC drive systems. The proposed converter and control methods are all verified by simulation and experimental results. / Thesis / Doctor of Philosophy (PhD)

With the unstable cost and supply of rare earth materials used in permanent magnet electric machines, many alternative machine types are being studied which are suitable for different applications. The focus of this thesis is the design of a novel 6/14 switched reluctance machine which can be fitted in a residential heating, ventilation, and air-conditioning (HVAC) application based on measured performance characteristics of an existing surface mount permanent-magnet synchronous (SMPS) machine. Residential electric motor applications are reviewed and in particular - furnace blower motor appliances. The fundamentals of switched reluctance machines are discussed, including the mechanism, operation, and control strategy. A SMPS motor which is commercially available for retrofitting into residential HVAC systems is analyzed to find its performance characteristics through disassembly, inspection, and dynamometer bench testing. The design of a novel 6/14 SRM optimization process is outlined to investigate the effect of changing the geometry values within the motor on the performance characteristics, while keeping within the size constraints of the original motor. A novel 6/14 SRM design is presented which is capable of achieving the target goals in the desired operating conditions. Further suitability testing is performed in terms of thermal analysis of the motor in the peak and continuous operating condition and mechanical stress analysis of the rotor under various rotational speeds. The full CAD assembly of the motor is designed including components from the original SMPS motor to allow for fitting in the same HVAC application. / Thesis / Master of Applied Science (MASc) / With the unstable cost and supply of rare earth materials used in permanent magnet electric motors, many alternative machine types are being studied which are suitable for different applications. The focus of this thesis is the design of a novel 6/14 switched reluctance machine which can be fitted in a residential heating, ventilation, and air-conditioning (HVAC) application based on measured performance characteristics of an existing surface mount permanent-magnet synchronous (SMPS) machine. Switched reluctance machines have a number of benefits over permanent magnet machines including that they do not have permanent magnets, are less sensitive to high heat scenarios, have lower manufacturing costs, are more robust, and are generally capable of higher operating speeds. Residential electric motor applications are reviewed and in particular - furnace blower motor appliances. The fundamentals of switched reluctance machines are discussed, including the mechanism, operation, and control strategy. A SMPS motor which is commercially available for retrofitting into residential furnace systems is analyzed to find its performance characteristics through disassembly, inspection, and dynamometer bench testing. The design of a novel 6/14 SRM optimization process is outlined to investigate the effect of changing the geometry values within the motor on the performance characteristics, while keeping within the size constraints of the original motor. A novel 6/14 SRM design is presented which is capable of achieving the target goals in the desired operating conditions. Further suitability testing is performed in terms of thermal analysis of the motor in the peak and continuous operating condition and mechanical stress analysis of the rotor under various rotational speeds. The full 3D CAD assembly model of the motor is designed including components from the original SMPS motor to allow for fitting in the same HVAC application.

Switched reluctance machines (SRMs) have recently attracted more interest in many applications due to the volatile prices of rare-earth permanent magnets (PMs) used in permanent magnet synchronous machines (PMSMs). They also have rugged construction and can operate at high speeds and high temperatures. However, acoustic noise and high torque ripples, in addition to the relatively low torque density, present significant challenges. Geometry and topology optimization are applied to overcome these challenges and enable SRMs to compete with PMSMs. Key geometric design parameters are optimized to minimize various objective functions within geometry optimization. On the other hand, the material distribution in a particular design space within the machine domain may be optimized using topology optimization. We discuss how these techniques are applied to optimize the geometries and topologies of SRMs to enhance machine performance. As optimizing the machine geometry and material distribution at the design phase is of substantial significance, this work offers a comprehensive literature review on the current state of the art and the possible trends in the optimization techniques of SRMs. The thesis also reviews different configurations of SRMs and stochastic and deterministic optimization techniques utilized in optimizing different configurations of the machine. This thesis introduces a new ON/OFF optimization method based on the line search method to overcome the limitations of the conventional annealing-based ON/OFF optimization. The proposed method shows a faster convergence to optimal solutions than the conventional annealing-based ON/OFF method. The thesis also compares the performance of the generative optimization and the topology optimization of a 6/14 switched reluctance machine with the proposed method and the conventional method. The two methods are applied to two different design domains of the machine for topology and generative optimization and the results are compared to the results of the annealing-based ON/OFF method. The results show the effectiveness of the newly proposed method. A new technique has been introduced in this thesis for reducing the time of calculating stator radial force density waves of switched reluctance machines (SRMs). The method is based on the finite element (FE) simulation of a fraction of an electrical cycle. The new approach shows that a significant time reduction is achieved as compared to the time required for stator radial force density calculation based on the one mechanical cycle simulation method. As the switched reluctance motors introduce new challenges in aspects such as acoustic noise, vibrations, and torque ripples, the method introduced in this helps reduce the time of the optimization process of switched reluctance machines in the design stage to improve the machine performance. The proposed method is applied to radial flux switched reluctance machines. Three different SRMs configurations were used to show the effectiveness of this technique in different force components with minimal error as compared to the benchmark method based on the FE simulation of one mechanical cycle. / Dissertation / Doctor of Philosophy (PhD)

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