Design and initial testing of a high speed 45 kW switched reluctance drive for aerospace application

This paper presents innovative research towards the development of a 45 kW high speed switched reluctance drive as an alternative starter-generator for future aero-engines. To perform such a function the machine had to be designed with a very wide constant power-speed range. During engine-start/motoring mode, a peak torque demand of 54 Nm at 8 krpm was met, whilst in generating mode, 19.2-32 krpm, the machine was designed to deliver a constant power of 45 kW. The key enabling feature of the design lies in the novel rotor structure developed so as to allow for such a wide speed range. The results presented, are those measured during the initial testing phase and validate the system design and performance in the low-speed region with the machine operated in starting-mode. The measured machine power density is at 9.8 kW/ltr, whilst the global system efficiency is at 82%

Intelligent Control of Switched Reluctance Motor for Electrical Vehicle Applications with Different Controller

تستخدم محركات المعاوقي المفتاحي لإنتاج الكثير من  عزم الدوران والتي تعمل عند التشبع المغناطيسي العالي. وبالنظر إلى التشبع المغناطيسي العالي، فإن العلاقة بين تيار الطور، وموقع الدوار هي علاقة غير خطية. لذلك فان  الضجيج، الاضطرابات، وعزم القصور الذاتي  عند  التحميل يمكن أن يكون لها جميعا تأثير سلبي على أداء المحرك المعاوقي المفتاحي. في هذه الدراسة تم تطوير وحدة التحكم الانزلاقي. وقد استخدم وحدة التحكم الانزلاقي في تنظيم السرع على مدى واسع  بما في ذلك المحرك المعاوقي المفتاحي في السرع العالية والسرع الواطئة وتقارن هذه الدراسة وحدة التحكم الانزلاقي مع وحدة التحكم التناسبي المتكامل التفاضلي في المحرك المعاوقي المفتاحي ذو 4/6 اقطاب باستعمال  الطرق الامثل للتحكم . ومقارنة  سرعة الجزء الدوار مع السرعة المضبوطة .فان وحدة التحكم الانزلاقي المتسارع هو الافضل من حيث الاداء والمتانة في  تطبيق السيارات الكهربائية  تبعا لنظام السيمولنك المستخدم Switched reluctance motors (SRM) are used to produce a lot of torque when they are operating at high magnetic saturation. Due to the high magnetic saturation, the relationship between phase current, rotor position, and the flux linkage of SRM is nonlinear. Noise, disturbances, and inertia of load torque can all have a negative impact on the SRM driver system's speed controller performance. In this study, the SRM driver system's sliding mode controller was developed .The sliding mode controller( SMC) speed controller was used to regulate speeds of the SRM throughout a wide range speeds, including high and low speeds. This study compares (SMC) with a modified reaching law and a Proportional Integral Divertive Control (PID) controller for a 6/4 pole SRM using an optimization technique for switching controllers. Furthermore, the rotor speed was simulated and compared to the reference speed. The Exponential Sliding Mode Controller (ExpSMC) is the best in terms of performance and robustness for an electric vehicle application, depending on a simulation of an established test bench using the two controllers

Geometric Parameter Optimization of Switched Reluctance Machines for Renewable Energy Applications using Finite Element Analysis

The choice of SRM design depends on the specific application and performance requirements. Factors such as power output, torque characteristics, and efficiency will all influence the choice of SRM design. To find an optimal geometry, it is therefore necessary to determine the effect of each parameter such as rotor pole angle, stator pole angle, stator external diameter, rotor diameter, air gap length, rotor yoke, stator yoke and shaft diameter on the machine performance. For this reason, this paper discusses a comparative study of the geometric parameters influence on SRM performance. The analysis is performed by finite element simulations based on the variation of rotor inclination, air gap length, stator and rotor polar arc variations of three machine topologies such as the three-phase 12/8 SRM, three-phase 6/4 SRM and four-phase 8/6 SRM. For a reliable comparison, these machines must have the same basic dimensions (stator outer diameter, rotor outer diameter and length) and operate in the same magnetic circuit saturation. Graphical and numerical results of torque and magnetic flux for three SRM topologies are highlighted. The presented study aims to provide reliable results on the dimensions to be adjusted for various applications

A modified neutral-point balancing space vector modulation technique for three-level neutral point clamped converters in high speed drives

This paper describes a high performance neutral point voltage balancing technique for a Neutral point clamped (NPC) Converter. Conventional neutral point voltage balancing methods do not function well under low power factor, low pulse ratio and near-unity modulation index operation conditions. These conditions are essentially dominant operation conditions for aircraft starter/generator systems. This paper introduces an alternative space vector modulation technique for three-level NPC converters in an aircraft starter generator system. The selection of voltage space vectors is optimized for high modulation index and low power factor operation. Disturbances caused by low pulse ratio is also compensated. The proposed method maintains neutral point voltage balance and ripple minimization over the full range of operating conditions. The paper also provides a detailed analysis into the sources of neutral point voltage imbalances and ripples in high speed drives with deep flux weakening. Simulation results obtained from a Simulink/PLECS model and experimental results obtained from a 45kVA, 32krpm aircraft starter generator test rig proves the proposed method eliminates the neutral point voltage imbalance and significantly reduces the neutral point voltage ripple

Dual-Pulse Mode Control of a High-Speed Doubly Salient Electromagnetic Machine for Loss Reduction and Speed Range Extension

In this paper, a dual-pulse mode control of a high-speed doubly salient electromagnetic machine (DSEM) for efficiency improvement over a wide speed range is investigated and implemented. The dual-pulse mode control method and operation principle are introduced. The influence of excitation angles and field current on the operation performance is analyzed by finite element method (FEM) based on the back-electromotive force (EMF) and inductance characteristics. The loss distribution for various speed and load torque requirement is attained, and the control parameters are optimized. The excitation angle can reduce the back-EMF at high speed through transformer-EMF and flux-weakening armature reaction. A prototype of 12/8-pole DSEM drive system is developed and dual-pulse mode control in high-speed operation under low DC-link voltage is implemented. Both the simulated and measured results show that the torque capacity of the DSEM is improved and the loss is reduced over a wide speed range

Comparative evaluation for an improved direct instantaneous torque control strategy of switched reluctance motor drives for electric vehicles

Due to the expected increase in the electric vehicles (EVs) sales and hence the increase of the price of rare-earth permanent magnets, the switched reluctance motors (SRMs) are gaining increasing research interest currently and in the future. The SRMs offer numerous advantages regarding their structure and converter topologies. However, they suffer from the high torque ripple and complex control algorithms. This paper presents an improved direct instantaneous torque control (DITC) strategy of SRMs for EVs. The improved DITC can fulfill the vehicle requirements. It involves a simple online torque estimator and a torque error compensator. The turn-on angle is defined analytically to achieve wide speed operation and maximum torque per ampere (MTPA) production. Moreover, the turn-off angles are optimized for minimum torque ripples and the highest efficiency. In addition, this paper provides a detailed comparison between the proposed DITC and the most applicable torque control techniques of SRMs for EVs, including indirect instantaneous torque control (IITC), using torque sharing function (TSF) strategy and average torque control (ATC). The results show the superior performance of the proposed DITC because it has the lowest torque ripples, the highest torque tor current ratio, and the best efficiency over the low and medium speed ranges. Moreover, the comparison shows the advantages of each control technique over the range of speed control. It provides a very clear overview to develop a universal control technique of SRM for EVs by merging two or more control techniques

Optimal Advance Angle for Aided Maximum-Speed-Node Design of Switched Reluctance Machines

In the design processes of Switched Reluctance Machines that operate in wide constant power speed ranges, the maximum power available at maximum speed must be evaluated for every machine candidate. This is critical to ensure compliance with the power requirement. Important parameters to include in the design routine include the duration of the energizing period and the advance of the turn-on instant (i.e. advance angle). The latter is highly related to the machine geometry and is usually evaluated through time-consuming finite-element based iterative methods. In this paper, a simple, yet novel analytical model is proposed to cater for the torque-maximising advance angle in a closed-form analytical expression, directly from the machine geometry. The goal is to provide a non-iterative design tool that speeds up the design process. Successful validations against finite element analyses and experimental results on an SR machine prototype are reported. The main outcome of this paper is shown by the improvement in computation time, without any significant loss of accuracy

Multi-objective torque control of switched reluctance machine

PhD ThesisThe recent growing interest in Switched Reluctance Drives (SRD) is due to the electrification of many products in industries including electric/hybrid electric vehicles, more-electric aircrafts, white-goods, and healthcare, in which the Switched Reluctance Machine (SRM) has potential prospects in satisfying the respective requirements of these applications. Its main merits are robust structure, suitability for harsh environments, fault-tolerance, low cost, and ability to operate over a wide speed range. Nevertheless, the SRM has limitations such as large torque ripple, high acoustic noise, and low torque density. This research focuses on the torque control of the SRD with the objectives of achieving zero torque error, minimal torque ripple, high reliability and robustness, and lower size, weight, and cost of implementation. Direct Torque Control and Direct Instantaneous Torque Control are the most common methods used to obtain desired torque characteristics including optimal torque density and minimized torque ripple in SRD. However, these torque control methods, compared to conventional hysteresis current control, require the use of power devices with a higher rating of about 150% to achieve the desired superior performance. These requirements add extra cost, conduction loss, and stress on the drive’s semiconductors and machine winding. To overcome these drawbacks, a simple and intuitive torque control method based on a novel adaptive quasi sliding mode control is developed in this study. The proposed torque control approach is designed considering the findings of an investigation performed in this thesis of the existing widely used control techniques for SRD based on information flow complexity. A test rig comprising a magnet assisted SRM driven by an asymmetric converter is constructed to validate the proposed torque control method and to compare its performance with that of direct instantaneous torque control, and current hysteresis control methods. The simulation and experimental results show that the proposed torque control reduces the torque ripple over a wide speed range without demanding a high current and/or a high switching frequency. In addition, It has been shown that the proposed method is superior to current hysteresis control method in the sensorless operation of the machine. Furthermore, the sensorless performance of the proposed method is investigated with the lower component count R-Dump converter. The simulation results have also demonstrated the excellent controller response using the standard R-Dump converter and also with its novel version developed in this thesis that needs only one current sensor

Double stator switched reluctance machine with mutual coupled windings

Ph. D. ThesisThis thesis describes the development of a four-phase double-stator switched-reluctance motor (DSSRM) with mutually coupled windings. This machine, which has a topology that combines features of both the mutually coupled and double-stator switched-reluctance motor, will be shown to have the potential to offer improved torque productivity under the same ohmic loss limitation; though experimental mechanical and thermal confirmation remains to be completed. It is widely thought that the electrification of vehicle traction will be an essential element in the automotive industry in the next decade. An eventual sales ban on diesel and petrol vehicles has recently been reported to be planned by several industrial countries. Even disregarding these political declarations, which could only be considered as expectation rather than strict policy, the spread of hybrid powertrain technology and the continuous fall of Li-ion battery prices will effectively motivate an increasing number of automotive manufacturers to participate in this revolution. Since the cost of rare-earth materials is expected to continuously rise and the mining of these resources has left an enormous impact on the environment, the development of a high-performance SRM as an alternative to a permanent magnet synchronous machine (PMSM) is worthy and necessary. In addition to the enhancement of electromagnetic performance, this thesis discusses the mechanical properties and rotor structure of the DSSRM. The rotor support, which holds the rotor segments together, should be strictly of non-conducting material to prevent significant eddy current loss. Since most materials struggle to offer a compatible stiffness to steel, methods have been investigated to meet the challenge of designing a rotor support able to endure the centrifugal force of rotor segments during high-speed spinning. Thermal issues pose another challenge for this prototype but simulations indicate that the DSSRM could have better cooling capability than the conventional SRM configuration. A prototype was built and compared with a 12/16 segmental-rotor SRM, previously developed at Newcastle University. The results indicated that the prototype machine gave a promising torque performance with a relatively low copper loss