Review of Three-phase Soft Switching Inverters and Challenges for Motor Drives

For electric vehicles (EVs),it is necessary to improve endurance mileage by improving the efficiency.There exists a trend towards increasing the system voltage and switching frequency,contributing to improve charging speed and power density.However,this trend poses significant challenges for high-voltage and high-frequency motor controllers,which are plagued by increased switching losses and pronounced switching oscillations as consequences of hard switching.The deployment of soft switching technology presents a viable solution to mitigate these issues.This paper reviews the applications of soft switching technologies for three-phase inverters and classifies them based on distinct characteristics.For each type of inverter,the advantages and disadvantages are evaluated.Then,the paper introduces the research progress and control methods of soft switching inverters (SSIs).Moreover,it presents a comparative analysis among the conventional hard switching inverters (HSIs),an active clamping resonant DC link inverter (ACRDCLI) and an auxiliary resonant commuted pole inverter (ARCPI).Finally,the problems and prospects of soft switching technology applied to motor controllers for EVs are put forward.

Model-free Speed Control of Single-phase Flux Switching Motor with an Asymmetrical Rotor

This paper proposes and implements a model-free open-loop iterative learning control(ILC)strategy to realize the speed control of the single-phase flux switching motor(FSM)with an asymmetrical rotor.Base on the proposed winding control method,the asymmetrical rotor enables the motor to generate continuous positive torque for positive rotation,and relatively small resistance torque for negative rotation.An initial iteration coefficient and variable iteration coefficient optimized scheme was proposed based on the characteristics of the hardware circuit,thereby forming the model-free strategy.A series of prototype experiments was carried out.Experimental results verify the effectiveness and practicability of the proposed ILC strategy.

Optimized Power Factor Correction for High Speed Switched Reluctance Motor

The Power Factor Correction(PFC)in Switched Reluctance(SR)motor is discussed in this article.The SR motors are applicable for multiple applications like electric vehicles,wind mills,machineries etc.The doubly salient structure of SR motor causes the occurrence of torque ripples,which affects the power factor of the motor.To improve the power quality,the power factor has to be corrected and the ripples have to be minimized.In order to achieve these objectives,a novel power factor correction(PFC)method is proposed in this work.Here,the conventional Diode Bridge Rectifier(DBR)is replaced by a Bridgeless Hybrid Resonant(HR)converter,which assists in improvising the output in a wider range.The converter is chosen because of having variety of beneficial measures including high gain.The converter’s output is fed to the SR motor by means of an asymmetric Bridge Resonant(BR)converter.The proposed converter operates in continuous mode of conduction with the switching frequency of 10 KHz.A hysteresis current controller and Proportional Integral(PI)controller are utilized for reducing the harmonics in the source current along with the regulation of output voltage.In addition,the speed control of SR motor is accomplished by means of the Whale Optimization Algorithm(WOA)assisted PI controller.The proposed methodology is effective for the control of unity power factor,torque and current ripples.The Total Harmonic Distortion(THD)of the source current is also minimized,which suits the standard of International Electrotechnical Comission IEC 61000-3-2.By this methodology,the power factor of 0.99 is achieved with 97%efficiency and 3.92%THD.The proposed methodology is validated in simulation by MATLAB and in hardware by FPGA Spartan 6E.

An Analytic Method of Segmented PWM Duty Cycle for Switched Reluctance Motor

In view of the large current peak and torque ripple in the actual current chopping control of switched reluctance motor,a segmented PWM duty cycle analysis method of switched reluctance motor based on current chopping control is proposed in this paper.The method realizes the control of the winding current by adjusting the average voltage of the two ends of the winding in one cycle through the PWM duty cycle.At the same time,according to the inductance linear model,the conduction phase is divided into a small inductance region and an inductance rising region,and the analytical formulas of PWM duty cycle in the two regions are deduced respectively.Finally,through matlab/simulink simulation and motor platform experiment,the current chopping control is compared with the segmented PWM duty cycle analysis method in this paper.Simulation and experimental results show that the segmented PWM duty cycle analysis method can effectively reduce the current peak and torque ripple,and has high practical application value.

Electromagnetic Design of a Switched Reluctance Motor With Segmental Rotors and Full-pitch Windings

整距绕组分块转子开关磁阻电机具有高速运行时低风（油）阻和低铁心损耗等优点，特别适合用于航天航空驱动系统。根据整距绕组分块转子开关磁阻电机的基本工作原理，结合输出功率与平均转矩的关系，将绕组电流等效为方波，推导出了整距绕组分块转子开关磁阻电机的主体尺寸计算公式；基于电机定转子未对齐位置和对齐位置的电磁特性，以及整距绕组分块转子开关磁阻电机的电磁特点，确定了定、转子极弧系数选取的规则；同时分析了绕组匝数等主要尺寸的选取的规则；最后，基于上述方法优化设计了一台实验样机，并通过有限元仿真及实验验证了整距绕组分块转子开关磁阻电机的电磁设计方法的正确性。

A CONTROL STRATEGY OF SWITCHED RELUCTANCE MOTOR FOR ELECTRIC VEHICLE APPLICATION

A control strategy of switched reluctance motor (SRM)for electric vehicle applications is proposed. In electric vehicle application, the switched reluctance motor is a good choice with its flexible control method, compactness, robustness, high efficiency and high starting torque. In this paper, the control strategy of motoring and regenerative braking for electric vehicle application is presented. Computer simulations are employed to analyze the steady state behavior of SRM propulsion system. Experimental results in electric motorcycle are provided to demonstrate the validity of SRM propulsion system.

Mode switching control strategy of dual motors coupled driving on electric vehicles

Based on analyzing the structure and working principle on electric vehicles （EVs） with dual motors coupled by planetarY gears, the control strategy of mode switching was proposed. The power interruption problem on EVs with automatic mechanical transmission （AMT） shifting was resolved. Based on the speed-torque characteristics of the planetary gears and the principle of the auxiliary motor＇ s zero speed braking, control features of mode switching were introduced. The mode shifting between the main motor mode and dual motors coupled driving were studied. Matlab/Simulink was adopted as a platform to develop the simulation model of EVs with dual motors drive system and 3 gears AMT. Simulation results demonstrated that the power interruption of dual motors drive system was solved during mode switching. The power requirements of EVs were satisfied, too.

Accurate Torque Modeling With PSO-Based Recursive Robust LSSVR for a Segmented-Rotor Switched Reluctance Motor

In order to improve the reliability in torque calculation of SRM,an accurate nonlinear torque model regresses by recursive robust least squares support vector regression(RR-LSSVR)is proposed in this paper.The model is in terms of a segmented-rotor switched reluctance motor(SSRM).The characteristics of the SSRM is introduced to show its nonlinear characteristics both in magnetic and torque.Then,its mathematic model is established,and an accurate inductance measurement method and a torque calculation method are presented.After this,the principle of the RR-LSSVR and why it can adjust weights according to errors are described.The model used the RR-LSSVR algorithm shows an outstanding capability in accuracy and quickness compared with other algorithms.Finally,to further validate the accuracy of the proposed model in practical application,simulation and experiment are designed based on a 16/10 SSRM.

Optimal design of linear switched reluctance motor for sea wave power generation

The switchless reluctance motor’s non-permanent magnet structure design ensures its high reliability in the marine environment;thus,it is a feasible solution for the generator of a sea wave power generation system.However,the corresponding thrust density and efficiency remain insufficient.This study focused on a new type of flat linear switched reluctance motor(LSRM),using the finite element software to establish a structural model,and optimized the design with the goal of improving the efficiency and energy density.The entropy method was adopted for sensitivity stratification to objectively select weights to avoid the influence of subjectively selected different proportional weights on the optimization results.Based on the entropy method,the sensitivity of different structural parameters was stratified,and the simulated annealing algorithm,response surface method,and single parameter scanning method were combined for optimization.Finally,the optimal structural size parameters of the motor were determined.Based on the two-dimensional finite element method,to simulate the electromagnetic performance of the reluctance motor under different operating conditions,such as thrust,loss,and efficiency,changes in motor performance before and after optimization were compared to verify the high power generation efficiency and energy density of the optimized linear motor.

A New Switching Sequences of SVPWM for Six-Phase Induction Motor with Features of Reduced Switching Losses

In this paper,new SVPWM switching sequences for six-phase asymmetrical induction motor drives are derived with the aim to reduce inverter’s switching losses.Total three switching sequences are introduced in this paper.These sequences are derived such that the phases get continuously clamped when a current of the phases is around its peak magnitude and hence reduced switching losses are recorded.The comparative performances of these modulation techniques are studied with two existing switching sequences.Simulation,analytical and experimental results are presented.Based on these results,it is found that new switching sequences reduce switching losses effectively in dual three phase inverters.

Design andtwo-objective simultaneous optimization of torque controller for switched reluctance motor in electric vehicle

In order to reduce the torque ripple,increase the average torque and optimize the drive performance of the switched reluctance motor (SRM),the nonlinear dynamic model of SRM is established in the MATLAB /Simulink environment.The effects of the turn-on and turn-off angles are investigated by the simulation results of the dynamic model,and the function is made among the rotor speed,turn-on angle and turn-off angle.To optimize the torque dynamic performance,the two-objective simultaneous optimization function is proposed by two weight factors.And the optimized turn-on and turn-off angles as functions of rotor speed are developed by using the simultaneous optimization method.Then the optimized torque controller is designed based on the optimized turn-on and turn-off angles.The simulation results show that the optimized torque controller designed in this paper can effectively reduce the torque ripple and increase the average torque,and optimize the torque dynamic performance of the SRM.

Winding Inductance and Performance Prediction of a Switched Reluctance Motor with an Exterior-rotor Considering the Magnetic Saturation

This paper deals with an analytical method to effectively calculate the inductance of an exterior-rotor switched reluctance motor(SRM),which evaluates the winding inductance of both the active section and the end section,accounting for the influence of core saturation.According to the inductance calculated by the analytical model,the flux linkage table and torque table can be established,and the steady state performance such as phase current,flux linkage,copper loss and core loss can be predicted.Effectiveness of this method is verified by the finite element method as well as by experimental results of a 12/8 SRM prototype.

Two Different Role Division Control Strategies for Torque and Axial Force of Conical Bearingless Switched Reluctance Motor

Although the five-degree-of-freedom magnetic levitation system composed of two conical bearingless switched reluctance motors(CBSRMs)owns the simplest structure,the torque and levitation forces are coupled greatly.Therefore,it is difficult to make the rotor rotate and be fully levitated simultaneously.To solve this problem,two different role division control strategies are proposed in this paper,i.e.individual role division and mutual role division control strategies.The difference between them is the selection of motor which controls the torque or the axial force.In order to understand the characteristics of control variables,the principle and mathematical model of CBSRM are introduced.After that,two control strategies are explained in detail.To verify the demonstrated performance,the simulations are completed with MATLAB/Simulink.

Hybrid Excitation Flux Switching Motor with Permanent Magnet Placed at Middle of Field Coil Slots and High Filling Factor Windings

Design and experimental studies on a hybrid excitation flux switching motor as a traction motor for hybrid electric vehicles drive are presented.A stator body of the motor consists of not only laminated silicon-iron electromagnetic steel and three-phase armature windings,but also both of field excitation coils and permanent magnets working together as a variable field magnetomotive force source.On the other hand,a rotor is composed of just laminated silicon-iron electromagnetic steel with salient poles like switched reluctance motor.To bring out the best in drive performances of the hybrid excitation flux switching motor as a variable flux motor for the application,each material adopted for the stator and rotor body should be designed properly in terms of motor efficiency,maximum torque and power densities and so forth.As some of them,in this paper,thinner silicon-iron electromagnetic steel sheet and permanent magnets with high remanent and low amount of Dysprosium used are applied for achieving higher motor efficiency.Moreover,all coils wound flatwise and edgewise using rectangular wires are introduced to realizing high filling factor for reduced copper losses.Experimental tests using a 60kW prototype of the motor demonstrates the designed motor has good motor efficiency under frequent operating points expected for the target vehicle drive.

Initial Rotor Position Detection of 12/10 Flux-switching Permanent Magnet Motors

电机转子初始位置检测的精度直接决定其启动运行时的性能。针对12/10极永磁磁通切换型电机,在验证其凸极性的基础上,采用注入脉振高频信号实现转子初始位置估计。通过对传统高频脉振正弦电压信号注入的分析,研究了基于高频方波或三角波的注入方法,再利用电流差值调制或直接信号调制方法得到位置误差信号,同时根据磁路的饱和效应,通过对d轴电流过零点时间差值的累加,实现了磁极方向辨识。分析了位置误差信号的系数与初始位置检测收敛性的关系。通过实验验证了所提方法的正确性和可行性。

Design and Analysis of Asymmetric Rotor Pole Type Bearingless Switched Reluctance Motor

Bearingless switched reluctance motor(BSRM) not only combines the merits of bearingless motor(BM) and switched reluctance motor(SRM), but also decreases the vibration and acoustic noise of SRM, so it could be a strong candidate for high-speed driving fields. Under the circumstances, a 12/14 BSRM with hybrid stator pole has been proposed due to its high output torque density and excellent decoupling characteristics between torque and suspension force. However, this motor has torque dead-zone, which leads to problems of self-start at some rotor positions and large torque ripple during normal operation. To solve the existing problems in the 12/14 type, an asymmetric rotor pole type BSRM is proposed. The structure and design process of the proposed motor is presented in detail. The characteristics of the proposed motor is analyzed and compared with that of the 12/14 type. Furthermore, prototype of the proposed structure is designed, manufactured and experimented. Finally, simulation and test results are illustrated and analyzed to prove the validity of the proposed structure.

Comparative Investigation of Torque-ripple Suppression Control Strategies Based on Torque-sharing Function for Switched Reluctance Motor

Torque ripple is an inherent property of switched reluctance motor(SRM),which seriously affects the control performance and application of the motor.This paper proposes two torque ripple suppression control strategies based on torque-sharing function(TSF).According to the symmetry characteristics of the flux linkage and rotor position curve family,a fourth-order Fourier series is used to fit the SRM flux linkage analytical model.The coefficient of each harmonic term of the flux linkage model is a function related to current,expressed by a sixth-order polynomial.The torque analytical formula can be derived from the flux linkage model.The torque error is calculated via the identified torque model and is compensated through TSF controller in order to reduce torque ripple.The torque model can also be used to establish the torque loop to achieve accurate tracking of the TSF reference torque to reduce torque ripple.Digital simulation was conducted,followed by the implementation on a SRM test bench using a 28335DSP as the master control chip.The experimental results are consistent with the simulation results,and indicate the effectiveness of the proposed schemes.

Switched Reluctance Motor: Research Trends and Overview

There has been a growing interest in switched reluctance motor(SRM)ever since the development of thyristor in 1956.The most appealing feature of SRM which attracts researchers over these years is its simple structure that incorporates concentrated windings on the stator poles and plain laminations of ferromagnetic material as a rotor.Due to this attributes,advances are being made rapidly with the consideration that SRM can be used as an alternative to DC motors and permanent magnet motors.The objective of this paper is to present an overview of the recent developments and a prediction of possible future advancements in SR Drives.Brief history,importance,innovations in structure and control,along with practical application examples are all discussed here to give a more in-depth comprehension of the motor.

Performance Prediction of Switched Reluctance Motor using Improved Generalized Regression Neural Networks for Design Optimization

Since practical mathematical model for the design optimization of switched reluctance motor(SRM)is difficult to derive because of the strong nonlinearity,precise prediction of electromagnetic characteristics is of great importance during the optimization procedure.In this paper,an improved generalized regression neural network(GRNN)optimized by fruit fly optimization algorithm(FOA)is proposed for the modeling of SRM that represent the relationship of torque ripple and efficiency with the optimization variables,stator pole arc,rotor pole arc and rotor yoke height.Finite element parametric analysis technology is used to obtain the sample data for GRNN training and verification.Comprehensive comparisons and analysis among back propagation neural network(BPNN),radial basis function neural network(RBFNN),extreme learning machine(ELM)and GRNN is made to test the effectiveness and superiority of FOA-GRNN.

Research on DTC System with Variable Flux for Switched Reluctance Motor

When switched reluctance motor(SRM)is in the status of the traditional direct torque control(DTC)system,due to the high saturation nonlinearity of the electromagnetic relationships of switched reluctance motors,the torque ripple and the stator phase current are larger.In order to resolve the above problems,through the analysis and deduction for SRM flux model and the influence of characteristics of flux and speed on torque ripple,this paper presents a variable-flux control strategy with the three closed-loop structure based on the critical flux supersaturated speed.And a DTC system of SRM with variable flux and three closed-loop is built up in Matlab/simulink.Moreover,the DSP hardware experiment platform based on the TMS320F2812 is established to validate the performance of the improved algorithm.The simulation and experimental results show that the new scheme has an obvious effect on torque ripple reduction,and the three-phase stator current is obviously reduced,which greatly reduces the stator winding copper consumption during the operation of SRM.Moreover,the improved system has good system stability.