Model predictive current control of switched reluctance motor with inductance auto-calibration

The thesis is composed of three papers, which investigate the application of Model Predictive Controller (MPC) for current control of Switched Reluctance Motor (SRM). Since the conventional hysteresis current control method is not suitable for high power SRM drive system with low inductance and limited switching frequency, MPC is a promising alternative approach for this application. The proposed MPC can cope with the measurement noise as well as uncertainties within the machine inductance profile. In the first paper, a MPC current control method for Double-Stator Switched Reluctance Motor (DSSRM) drives is presented. A direct adaptive estimator is incorporated to follow the inductance variations in a DSSRM. In the second paper, the Linear Quadratic (LQ) form and dynamic programming recursion for MPC are analyzed, afterwards the unconstrained MPC solution for stochastic SRM model is derived. The Kalman filter is employed to reduce the variance of measurement noises. Based on Recursive Linear-Square (RLS) estimation, the inductance profile is calibrated dynamically. In the third paper, a simplified recursive MPC current control algorithm for SRM is applied for embedded implementation. A novel auto-calibration method for inductance surface estimation is developed to improve current control performance of SRM drive in statistic terms. --Abstract, page iv

Development of methods, algorithms and software for optimal design of switched reluctance drives

The aim of this thesis is to estimate the perspectives of integrated switched reluctance drives (I-SRDs), i.e. reluctance machines integrated with converters. It is assumed that such drive series can be manufactured in the power range of 0.75...7.5 kW and speed ranges of 300...3000 rpm and 600...6000 rpm for applications like pumps, fans, conveyors, compressors, extruders and mixers. Based on the performed research and design work it is stated that the new drives have to be developed according to their applications, which determine objective functions and constraints, and that the best possible design should be found as a solution of a synthesis task. Sizing equations are not applied at all. The approach used in the thesis is based on the virtual prototyping concept, i.e. the new I-SRD series is designed in a virtual environment. Therefore, mathematical models and the ways to verify them have to be elaborated. The concepts of multidisciplinary and multilevel modeling are applied. The multidisciplinary model is a combination of interconnected electromagnetic, thermal and noise models. The multilevel concept is the approach when different elements of the drive are described using different languages, i.e. on different levels. Several original solutions are introduced, like the electromagnetic model comprising SIMULINK block-diagrams and MATLAB script, expressions for the correction of the flux linkage due to end-effects, an original equivalent circuit for thermal analysis, which allows using a very simple and fast method to solve the circuit, together with the concept of a multi-layer equivalent cylinder for modeling the motor winding. For verification of the multidisciplinary model a database of test results has been collected using both testing of several reluctance machines in the laboratory and analyzing of test results published by other researchers. After verification the model can be considered as a virtual prototype and can be used in the synthesis process. Several methods of solving the synthesis task were tested. The method, proved to be best suited for solving this task in the proposed form, is the genetic algorithm in the vector form with alphabetic encoding. The genetic algorithm should be coupled with the experimental design method or with the Monte-Carlo method

High Performance Switched Reluctance Drives

PhD ThesisThe fully-pitched winding arrangement is one of the most radical changes in the design of doubly-salient reluctance motors in recent times. By replacing conventional shortpitched windings with fully-pitched windings, the resulting machine has a strong and position dependant mutual coupling between phases. The major torque producing mechanism is due to changes in mutual inductance with rotor position. This enables the windings to be better utilised, and with correct selection of excitation all phases can contribute useful torque all of the time. The increased winding utilisation requires a lower MMF per phase in comparison with a short-pitch wound machine with a single phase excited. Given a suitable winding configuration and machine dimensions, the copper losses for a given torque can be significantly lower than an equivalent conventional switched reluctance machine. Operation of a three phase fully-pitched winding switched reluctance machine has been studied theoretically, in simulation and experimentally. The experimental drive comprises of a D132 frame 12:8 machine, IGBT power converter and DSP controller. Operation with unipolar phase currents has been investigated over a wide speed range and performance compared with a conventional switched reluctance machine. Bipolar operation with several different excitation patterns has been investigated. Unipolar operation gives the largest torque/speed envelope with a simple controller, although bipolar modes can equal this with a more complex controller. Results show that for equal RMS phase current the average torque produced by four different modes of excitation are approximately equal. However, there is a large difference in the torque ripple and acoustic noise performance of each mode. Current control in switched reluctance machines is complicated by the non-linear nature of the load. By controlling flux-linkage rather than current a linear load model can be used. A discrete time 'dead-beat' flux-linkage controller has been implemented which gives superior phase current control performance to other types of controller with the same sample interval. A new method of constant torque operation based on 'flux ramps' has been proposed. This method gives predictable performance and enables constant torque operation over a wide speed range. A Genetic Algorithm has been shown to be very effective when applied to the problem of optimising the 'flux ramps' for minimum torque ripple. A speed controller has been implemented which makes use of the Genetic Algorithm optimised flux ramps to give smooth torque over a wide speed range.Royal Societ

High-Performance Control of Switched Reluctance Motors

A general high bandwidth, low ripple, instantaneous torque control strategy with a variable field-angle for extended constant-power speed range is presented. The strategy is based on the SR motor's electromagnetic characteristics measured at the motor terminals and is the nearest functional equivalent to AC vector control for this type of machine. Low torque ripple and high bandwidth are achieved over a wide range of speeds and a constant power range of 3:1. The proposed controller, which is applicable to most SR motors, is found to reduce the torque ripple by a factor of 5 in comparison with conventional square-wave current operation, and has been operated over a speed range of 1:6000

A new converter topology for high-speed high-starting-torque three-phase switched reluctance motor drive system

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Switched reluctance motor (SRM) has become a competitive selection for many applications of electric machine drive systems recently due to its relative simple construction and its robustness. The advantages of those motors are high reliability, easy maintenance and good performance. The absence of permanent magnets and windings in rotor gives possibility to achieve very high speeds (over 10000 rpm) and turned SRM into perfect solution for operation in hard conditions like presence of vibrations or impacts. Such simple mechanical structure greatly reduces its price. Due to these features, SRM drives are used more and more into aerospace, automotive and home applications. The major drawbacks of the SRM are the complicated algorithm to control it due to the high degree of nonlinearity, also the SRM has always to be electronically commutated and the need of a shaft position sensor to detect the shaft position, the other limitations are strong torque ripple and acoustic noise effects

Multi-Objective Optimization of the Switched Reluctance Motor for Improved Performance in a Heavy Hybrid Electric Vehicle Application

The goal of this research is to improve the performance of the switched reluctanc

Optimisation de la Conception du Moteur Synchrone à Excitation Hybride pour Véhicules Électriques à Haut Performance

Since 1970, the ever-growing concerns of human community for the life-threatening environmental changes have pushed the policy makers to decarbonize those sectors with high energy demands, including the transportation industry. Optimal designs of Electric Vehicles (EVs) can contribute to today’s exigent car market, and take the leading role for future sustainable transportation of human and goods. At the heart of electromechanical energy conversion lays the electrical machines, which have attracted lots of interests and efforts for efficiency increase and cost reduction. In this thesis, a methodology is proposed and implemented to design and optimize the cost and efficiency of a Hybrid Excitation Synchronous Machine (HESM) for a given vehicle and a desired driving cycle. Hybridization in the excitation system can combine the favorable qualities of high-torque at low-speed with superior overloading capability, exceptional flux weakening and extended Constant Power Speed Range (CPSR), high efficiency, and flexible controllability in motoring and generation modes. With HESM technology, we can also shift from the rare-earth magnets towards the cheap ferrite magnets and guaranty the supply for motor industry. The designed HESM in this work responds to three requirements of the vehicle, namely, the maximum cruising speed, acceleration time, and gradeability, with the least or null overdesign in the drivetrain. At the same time, it will have the maximum global efficiency over the driving cycle, and the minimum cost for the material. The optimization is conducted at either of the component and system levels. The optimization at component-level is developed based on the Non-dominated Sorting Genetic Algorithm-II (NSGA-II). A new formulation for the objective functions is proposed, which deals with the design optimization and cost minimization, simultaneously. To maximize the efficiency, a system-level search is conducted to find the optimum HESM with the highest global efficiency over a given driving cycle. Due to the 3D direction of magnetic flux in the selected HESM topology, the Finite Element Analysis (FEA) was very time- and process-consuming. To be able to evaluate the objective functions during the optimization, a new model has been developed based on a 3D Magnetic Equivalent Circuit (MEC) network. This model predicts well the non-linearity of magnetic materials, as compared with the FEA simulations. At last, the final optimized HESM is evaluated by the virtue of FEA technique.Depuis 1970, les préoccupations de l’humanité envers les changements climatiques ont poussé les chercheurs à faire des études approfondies pour optimiser les machines électriques pour avoir des véhicules électriques plus performants et moins énergivores. La conception optimale de véhicules électriques (EV) peut contribuer pour un marché automobile plus exigeant et jouer un rôle principal pour le futur du transport durable des biens et des personnes. Les machines électriques se trouvent au cœur de la conversion d'énergie électromécanique, qui ont suscité beaucoup d'intérêts et d’efforts pour augmenter leur rendement et réduire leur coût. Cette thèse propose une méthodologie et une mise en œuvre pour minimiser le coût et maximiser l’efficacité d’une machine synchrone à excitation hybride (HESM) pour un véhicule donné et un cycle de conduite sélectionné. L'hybridation du système d’excitation peut combiner les qualités favorables comme un couple élevé à basse vitesse avec une capacité de surcharge supérieure, un défluxage exceptionnelle et une plage de vitesse prolongée de puissance constante (CPSR), une efficacité élevée et une contrôlabilité flexible dans les modes de traction et de freinage régénératif. Avec la technologie HESM, nous pouvons également passer des aimants de terres rares aux aimants en ferrite bon marché, et garantir l’approvisionnement pour l’industrie automobile. Le HESM conçu dans ce travail répond à trois exigences du véhicule : la vitesse de croisière maximale, le temps d’accélération et la capacité de monter une pente, avec un surdimensionnement minimal ou nulle de la chaîne de traction. Une optimisation multiniveau avec une interaction entre la vision composant et la vision système est proposée et validée. L’optimisation au niveau du composant est développée sur la base de l’algorithme génétique de tri non dominé (NSGA-II). Une nouvelle formulation pour les fonctions objectives est proposée pour l’optimisation simultanée de la conception de la machine et de la minimisation de son coût. Après avoir optimisés onze HESM au niveau du composant, pour maximiser l’efficacité, une optimisation au niveau du système est réalisée pour trouver le HESM optimal avec le plus haut rendement global sur le cycle de conduite donné. Une validation de la conception finale de la HESM présente un meilleur rendement global sur le cycle de conduite de 18,65% en relation à une machine synchrone à excitation séparée équivalente et 15,8% en relation à une à aiment permanent. En raison de la direction 3D du flux magnétique dans la topologie HESM sélectionnée, l’analyse par éléments finis (FEA) prenait beaucoup de temps et de ressources computationnelles. Afin d’évaluer les fonctions objectives lors de l’optimisation, un nouveau modèle a été développé basé sur un réseau de circuits magnétiques équivalents 3D (MEC). Ce modèle prédit bien la non-linéarité des matériaux magnétiques, par rapport aux simulations FEA. Enfin, le HESM optimisé final est évalué grâce à la technique FEA

Novel Bearingless Switched Reluctance Motor with Wide Flat Inductance Region to Simplify the Control of Torque and Levitation Force

In conventional 12/8 bearingless switched reluctance motors (BSRMs), the generation and control of torque and levitation forces are always coupled and interacted, which increases the complexity of the current control algorithm. In this paper, a novel BSRM with 12 stator poles and 4 rotor poles is proposed to simplify the control of torque and levitation, which has wide flat inductance region. Through allocating the generation of torque and levitation forces to different inductance regions of each phase, the levitation control can be similar as that of magnetic bearings, and the torque control can adopt the methods of conventional switched reluctance motors, e.g. current chopping control and angle position control. Accordingly, the current control algorithm of proposed BSRM becomes very easy and flexible. Extensive experiments were completed to verify the demonstrated performance of proposed motor