Research On Double-stator Axial Flux Switched Reluctance Motor Drive System

Electric vehicles’ limited range and drive motor’s restricted installation space have led to a trend toward lightweight,miniaturized,and highly efficient drive motors.Therefore,increasing the torque/power density and operation efficiency of switched reluctance motors over a wide speed range has become a hot research topic.Axial flux switched reluctance motor(AFSRM)has the advantages of short axial length,large air gap area,and high torque density,and it has potential applications in the field of electric vehicle drive motors.In recent years,with the improvement of industrial level and processing technology,AFSRM has gradually regained people’s attention.Besides,with the balanced axial electromagnetic force and the large heat-dissipation area,the double stator AFSRM structure is considered the most promising research target among the AFSRM structures.At the same time,due to the inherent double stator configuration,the double stator AFSRM structure could switch between the winding series and the parallel mode online flexibly.The motor can operate in the series mode to achieve high torque operation at low-speed region and operate in the parallel mode to extend the speed range.The online reconfiguration of these two modes allows the motor drive system to combine the advantages,enabling efficient operation over a wide range of drive systems.This thesis aims to increase the torque density of switched reluctance motors and improve their operating efficiency over a wide speed range.Hence,it takes the perspective of the novel magnetic circuit design and the presentation of a new power converter and focuses on the design and optimization of the new double-stator AFSRM structure and the design and control of the new reconfigurable winding power converter topology as critical technologies.The main elements of the research are summarized as follows:Firstly,a new double-stator AFSRM structure with single-tooth concentrated winding configuration is proposed by novel magnetic circuit design.The torque/power expressions and the design flow are derived.Then,the initial structural parameters are designed,and the effect of these parameters on the static torque performance of the motor is investigated using the single-parameter scanning method.In addition,the more significant parameters are optimized with the Taguchi orthogonal experiment algorithm to improve the average torque while reducing torque ripple.An experimental prototype is fabricated according to the final structure parameters,and the experimental platform is established.The experimental results show that the proposed motor structure achieves a shorter axial length,smaller axial electromagnetic force,a larger change rate of magnetoresistance,a larger maximum and minimum inductance difference value and higher torque density.To further shorten the magnetic circuit,a double-stator AFSRM structure with full-pitched winding configuration is proposed.The operation principle is investigated,and the design flow is presented.A multi-layered and multi-objective optimization method is developed for a large number of dimensional parameters.The optimization variables are divided into high-sensitivity and low-sensitivity parameters separately using the sensitivity analysis method.For the high-sensitivity parameters,a response surface combined with the genetic algorithm is employed for optimization,while for the low-sensitivity parameters,the Taguchi orthogonal method is applied.An experimental prototype is machined and the results indicates that the structure obtaines a high maximum minimum inductance difference value and improves torque output capability.The proposed multi-layered and multi-objective optimization method achieves simultaneous improvement of the three optimization objectives.Hence,the performance of the two novel motor structures is compared with that of the double-stator AFSRM structure with the conventional concentrated winding configuration,and the effect of different winding configurations on the performance of the double-stator AFSRM is discussed and investigated.Besides,the mechanism of the new motor structure to enhance the torque output capability is explored.Due to the inherent double stator configuration of the new motor structure,the left and right stator disks are completely symmetrical.The winding coils can be connected in both series and parallel and have the ability to changeover between the two connection modes online.To combine the advantages of the two modes,a novel three-legs reconfigurable winding power converter is presented.The two typical modes and six operation states are investigated,and the mode-selection criteria are presented.Furthermore,the experimental platform based on the three-legs reconfigurable winding converter is constructed.The experimental results indicate that the proposed converter achieves stable operation in both the series and parallel modes,and improves the operating efficiency in a wide-speed range.To enhance the performance of the reconfigurable winding converter,a novel three-switches power converter is proposed using discrete IGBT devices without the anti-parallel diode as the mode-switching switches.The two typical modes and six operation states are analyzed.Besides,a phase-by-phase current-to-zero switching control method is proposed.Meanwhile,an adaptive fuzzy logical control strategy is presented by introducing a mode factor to address the shortcomings of the traditional PI speed regulator,which is hard to meet the requirements due to changes in motor parameters caused by mode switching.Furthermore,the experimental platform based on the three-switches reconfigurable winding converter is established.The results suggest that the presented power converter achieves online stable switching of the motor in both the series and parallel modes.Besides,the proposed mode changeover strategies achieve the low speed fluctuation operation of the drive system.