Subharmonics and chaos in switched reluctance motor drives

In this paper, the investigation of the nonlinear dynamics of an adjustable-speed switched reluctance motor (SRM) drive with voltage pulse width modulation (PWM) regulation is carried out. Nonlinear iterative mappings based on both nonlinear and approximately linear flux linkage models are derived, hence the corresponding subharmonic and chaotic behaviors are analyzed. Although both flux linkage models can produce similar results, the nonlinear one offers the merit of accuracy but with the sacrifice of computational time. Moreover, the bifurcation diagrams show that the system generally exhibits a period-doubling route to chaos     

Performance optimization in switched reluctance motor drives with online commutation angle control

The problem of performance optimization in current controlled switched reluctance motor (SRM) drives is investigated. Two controllers are proposed that determine the optimal turn-on and turn-off angles, respectively, for improving motor efficiency and torque ripple. The suggested controllers are simple, do not affect the complexity of the drive, and are easily implemented since the knowledge of torque-angle-current characteristics or magnetization curves is not required. The proposed control scheme is demonstrated on a prototype experimental system.     

开关磁阻调速电动机运行实例分析

对开关磁阻电动机调速系统的组成、工作原理、使用情况和节能效果进行了总结分析。     

Maximum efficiency in single-pulse controlled switched reluctance motor drives

The problem of choosing the firing angles for accomplishing maximum efficiency in single-pulse controlled switched reluctance motor drives is investigated. The suggested method is based on the optimal control of flux-linkage, through the firing angles, according to load torque requirements and depending on rotor speed. A controller that determines online the optimal turn-on and turn-off angles is proposed. The suggested controller does not affect the complexity of the drive and it is easily implemented, since knowledge of magnetization curves is not required. Moreover, it provides smooth transition between optimal single-pulse and pulse width modulation (PWM) current control modes and thus, optimal performance of the switched reluctance motor drive is attained over the entire speed range. Simulation and experimental results are presented to validate the resulting improvements of the proposed control scheme.     

Simulation of switched reluctance motor drives using two-dimensional bicubic spline

In this paper, a novel simulation algorithm of switched reluctance motor drives is presented. With the proposed algorithm the two-dimensional (2-D) bicubic spline interpolation is used to describe the nonlinear magnetic characteristics in switched reluctance motors. The corresponding computational method of 2-D bicubic spline function is described in detail. The simulation results are also compared with and validated by experimental data. Compared with conventional techniques, the presented simulation algorithm is more accurate even though it requires relatively little information on the magnetic characteristics of the motor.     

Performance analysis of PV pumping systems using switched reluctance motor drives

A PV pumping system using switched reluctance motor (SRM) is thoroughly investigated in this work. This motor is supplied by a d.c. voltage through a simple switching circuit. This drive circuit is much simpler than the normal d.c./a.c. inverter required to supply the induction motor. The efficiency of this motor is considerably higher than that of the equivalent d.c. or induction motors. In addition, because of the simple construction, SRM is cheaper than these conventional drives. Because of the above advantages of the SRM, the proposed system has higher efficiency and lower cost as compared with other systems.A design example is studied in detail to explore the advantages of PV pumping systems based on this new drive. The study of the performance of the proposed system showed that the operating efficiency of the motor is about 85% during most of its working time. The matching efficiency between the PV array and the proposed system approaches 95%. The major part of the losses takes place in the pump and the riser pipes, this loss represents one-third of the total available energy.     

Analysis of the waveform-detection technique for indirectroto-position sensing of switched reluctance motor drives

A sensing technique that monitors rotor-position indirectly by monitoring the phase current waveform is evaluated. Computer simulations showing the effects of back-EMF on phase current rise and fall-times are presented. A control circuit for current-waveform-based rotor-position detection has been implemented using hard-wired digital circuits. Torque-speed and system efficiency characteristics resulting from the application of the method to a 4 kW, four-phase SR motor with IGBT drive are also presented     

一种改进的四相开关磁阻电机直接转矩控制

开关磁阻电机转矩脉动大的问题限制了其应用,将交流电机的直接转矩控制方法应用于开关磁阻电机中。分析了直接转矩控制原理及电压矢量建立原则,利用MATLAB构建了变磁链的开关磁阻电机直接转矩调速系统模型,有效抑制了转矩脉动,并针对电机启动过程中定子电流脉冲大的问题,提出了将电流斩波与直接转矩控制方式相结合的方法,通过合理选择控制参数,使转矩脉动幅度在10%以内,同时将电流脉冲减小到原来的1/3,提高了电机的动态及稳态性能。     

A novel multilayer switched reluctance motor

The switched reluctance motor is a simple and robust machine, which has found application over wide power and speed ranges in different shapes and geometries. This paper introduces a new configuration for a high starting torque switched reluctance motor (SRM). This configuration allows more space for coil windings in small size motors with a high number of stator and rotor poles. It also presents a centrifugal switch mounted on the motor shaft for a sudden advancement of current-pulses relative to rotor position after reaching a preset motor speed in order to develop higher torque at starting. To evaluate the motor performance, two types of analysis, namely numerical techniques and an experimental study have been utilized. In the numerical analysis, due to the highly nonlinear nature of the motor, a finite element analysis is employed, and for the experimental study, a prototype motor has been built and tested. Finally, the prototype motor is compared with a conventional SRM of the same size. The calculated results compare favorably with the test results. In comparison with the conventional SRM, the proposed motor in this paper seems to be very promising     

Iterative learning-based high-performance current controller for switched reluctance motors

Switched reluctance motors (SRMs) are being considered for variable speed drive applications due to their simple construction and fault-tolerant power-electronic converter configuration. However, inherent torque ripple and the consequent vibration and acoustic noise act against their cause. Most researchers have proposed a cascaded torque control structure for its well-known advantages. In a cascaded control structure, accurate torque control requires accurate current tracking by the inner current controller. As SRM operates in magnetic saturation, the system is highly nonlinear from the control point of view. Developing an accurate current tracking controller for such a nonlinear system is a big challenge. Additionally, the controller should be robust to model inaccuracy, as SRM modeling is very tedious and prone to error. In this paper, we have reviewed various current controllers reported in the literature and discussed their merits and demerits. Subsequently, we have proposed and implemented a novel high-performance current controller based on iterative learning, which shows improved current tracking without the need for an accurate model. Experimental results provided for a 1-hp, 8/6-pole SRM, demonstrate the effectiveness of our proposed scheme.     

Electromagnetic modeling and control of switched reluctance motor using finite elements

This paper considered the implementation of a current control method for switched reluctance motors (SRMs) and presented a novel approach to the accurate online modeling of a three phase 6/4 SRM drive. A three phase 6/4 SRM is given theoretical calculation of inductance of the SRM model. The SRM was then tested in a Matlab/Simulink environment and numerically analyzed by using nonlinear 2D look-up tables created from its calculated flux linkage and static torque data. The simulation studied the hysteresis and voltage control strategies. The ideal waveform of stator current under the voltage-current condition and improved shape of rotor were proposed.     

Charge and discharge control of a switched reluctance motor based flywheel

根据开关磁阻电机的特性建立了储能飞轮的数学模型,采用Matlab/Simulink仿真分析了系统最大允许电流和电机开断角对系统控制性能的影响。设计了系统充放电控制方式,仿真结果表明,采用电流斩波与角度位置相结合的速度电流双闭环控制方式进行充电控制,采用电流斩波控制的电压电流双闭环控制方式进行放电控制,系统充放电过程具有响应速度快、稳态精度高的特点。最后通过仿真验证了开关磁阻式储能飞轮用作不间断电源的可行性。     

An improved analytical model for the switched reluctance motor

In analytical modeling of the switched reluctance (SR) machine, current is often chosen as the state variable, although flux-linkage provides a simpler and more efficient choice. Furthermore, it is typically the case that mutual inductance is neglected. In this paper, a new analytic formulation is presented that uses flux-linkage as the state variable and in which mutual coupling between phases is also represented. In addition, the paper presents an approach to determining the parameters of the flux-linkage curves of the machine that result in a better fit with measured laboratory data. Using the proposed approach, the simulated machine performance for a 12/8 SR motor is shown to compare favorably with experimental results measured in the laboratory.     

An efficiency-optimization controller for induction motor drives

When working close to their nominal operating point, induction motors are high-efficiency machines. However, at low load, efficiency is greatly reduced when magnetization flux is maintained at nominal value. Therefore, it is necessary to adjust the flux level according to the load, so as to decrease iron and copper losses. This paper deals with a field-oriented scheme for induction motor drives leading to efficiency optimization. It is based on optimal power factor tracking by adjusting magnetization current component with to respect the torque current component. Simulation results are presented to highlight the feasibility and validity of the proposed method     

Asymmetrical switched reluctance motor for a wide constant power range

In this paper the systematic approach to the design of a asymmetrical three-phase switched reluctance motor (SRM) with wide constant power range is described. It is shown that the SRM configuration with an unequal number of turns per phases may provide a wider constant power range than a corresponding symmetrical one. If the stator pole widths are unequal, the constant power range may be further extended. In these considerations, the maximal volt-ampere characteristics of the power converter are kept on the same level. The results are obtained using a suitable SRM model whose validity has been experimentally verified. The experimental results for the referent symmetrical SRM drive and asymmetrical one with an unequal number of turns per phase are also presented.     

A simple nonlinear model of the switched reluctance motor

The paper presents a simple nonlinear model of the switched reluctance motor (SRM) which requires a minimum of precalculated or measured input data. Therefore, it is convenient for use in earlier stage of SRM design in order to minimize time for finding optimal configuration. Moreover, it is shown that this model produces accurate torque shape for given current, and accurate flux linkage-current relationships. This also provides reliable results in dynamic regime. The simulation and experimental results are compared for available three-phase 6/4 motor     

Hopf bifurcation and chaos in synchronous reluctance motor drives

This paper first presents the occurrence of Hopf bifurcation and chaos in a practical synchronous reluctance motor drive system. Based on the derived nonlinear system equation, the bifurcation analysis shows that the system loses stability via Hopf bifurcation when the d-axis component of its three-phase motor voltages loses its control. Moreover, the corresponding Lyapunov exponent calculation further proves the existence of chaos. Finally, computer simulations and experimental results are used to support the theoretical analysis.     

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 e...     

Intelligent tuning of commutation for maximum torque capability of a switched reluctance motor

Since the winding current and inductance profiles of a switched reluctance motor (SRM) are far from ideal, its torque generating characteristics are quite ambiguous and difficult to optimize quantitatively. In this paper, the intelligent commutation tuning control to improve the torque generating performance of an SRM is presented. First, the effect of the commutation instant on the torque characteristics of a singly excited SRM is observed. Then accordingly, an intelligent method of commutation tuning is developed to improve the torque generating capability. In making the tuning, the minimization of the motor drawn line current is employed as a performance index to equivalently yield maximum torque per ampere (TPA). Finally, the circuit implementation of the developed tuning scheme is carried out. The appropriate commutation makes the motor draw minimum current under any load condition. It follows that the motor conversion efficiency is also improved. In addition, owing to the increased torque generating capability, the tracking and regulation speed control performances are also improved. Some experimental results are provided to demonstrate the effectiveness of the proposed control scheme.