无轴承异步电机解耦控制策略

针对2极转矩绕组和4极悬浮绕组构成的无轴承异步电机悬浮力耦合问题,利用悬浮绕组数学模型及其等效电路图,分析了转子感应电流对悬浮力控制的影响.在考虑悬浮绕组转子感应电流导致悬浮力耦合的基础上,研究了逆系统的悬浮解耦控制策略,构造了以悬浮绕组励磁电流为位移控制量的悬浮力控制模型.仿真及实验结果表明,该模型能实现悬浮力完全解耦,其控制器可以独立控制相对应的悬浮力,为无轴承全速范围悬浮控制提供借鉴.     

无轴承开关磁阻电机径向电磁力模型

针对现有无轴承开关磁阻电机数学模型忽略磁饱和或对磁饱和考虑不充分的不足,将麦克斯韦张量法和磁路分析法结合起来,提出了一种计算无轴承开关磁阻电机径向电磁力的方法.该方法考虑了电机运行过程中磁饱和以及转子的偏心位移,能够准确的描述电机径向电磁力的特性,为电机运行状态的离线分析和电机的设计提供了更为可靠的理论依据;该模型同时为无轴承开关磁阻电机电磁振动和噪声的预测与控制提供了理论依据.以一台实验样机为例,建立了考虑磁饱和的无轴承开关磁电机有限元分析模型.仿真结果证明了该解析模型的有效性.     

应用电流模型的无轴承异步电机悬浮控制

针对无轴承异步电机电枢绕组气隙磁链幅值和相位辨识问题,采用电流模型辩识电枢绕组气隙磁链;为了消除悬浮控制算法对气隙磁链相位的影响,应用预测控制实现电枢绕组气隙磁链控制相位零延迟.对无轴承电机径向悬浮力控制、基于电流模型的电枢绕组气隙磁链辩识算法以及气隙磁链相位预测进行研究;对样机在空载运行、3 000 r/min下恒速及1 000～3 000 r/min变速情况下进行悬浮控制实验.实验结果表明,电流模型法满足悬浮控制系统辨识电枢绕组气隙磁链的要求,相位角预测消除了控制延迟对气隙磁链相位的影响.     

无轴承薄片电机二维被动悬浮特性

为了研究无轴承薄片电机的被动悬浮特性,通过2D磁路分析的方法,建立了非永磁薄片电机的2D轴向悬浮力模型和回复力矩模型,并进行了有限元仿真验证。直接采用有限元分析的方法,得出了永磁薄片电机的被动悬浮力与电机各参量之间的关系。结果表明:电机的轴向悬浮力基本与轴向偏移、电机半径成线性关系,但与电机的轴向长度无明显关系,且气隙磁密越大悬浮力越大;电机的回复力矩随扭转角度增长而增长,电机的长径比较大、等效气隙较小时将难以产生回复力矩,回复力矩随着电机的轴向长度增加而增加,达到最大值后逐渐下降直至反向。     

单绕组磁悬浮开关磁阻电机的原理与解耦控制

针对瞬时悬浮力与瞬时转矩非线性、强耦合的特点,研究了一种新型单绕组磁悬浮开关磁阻电机的运行机理,提出瞬时悬浮力与平均转矩分相产生的双相导通解耦控制策略.构建单绕组磁悬浮开关磁阻电机相周期内悬浮力与转矩的全角度数学模型,基于悬浮力有效产生区间内平均转矩为零的特点,提出双相导通运行策略,并以提高悬浮力响应速度及电机动态运行性能为目标,给出了电流斩波幅值和关断角的优化控制方法.针对12/8极实验样机,开展相关的仿真与实验研究,结果表明了双相导通解耦控制策略的有效性与优越性,闭环系统具有良好的动静态性能.     

无轴承异步电机气隙磁场辨识方法与应用

针对无轴承异步电机电磁转矩与径向悬浮力这一强耦合的非线性复杂系统,依据转子磁场定向控制的特点,研制了转矩绕组采用转子磁场定向控制,径向悬浮控制所需的气隙磁场通过I-ω法适时辨识的控制系统.应用Matlab/Simulink建立了系统仿真模型.计算机仿真结果表明,实现了电磁转矩与径向悬浮力之间的完全解耦,具有良好的动、静态性能,验证了本文所提方案的有效性.     

无轴承电机轴向混合磁轴承自抗扰控制

为了实现无轴承电机轴向混合磁轴承的准确和稳定控制,依据自抗扰控制理论,设计了轴向混合磁轴承自抗扰控制系统,并给出其控制算法和控制结构。根据实验样机参数,利用MATLAB软件环境,构建了仿真系统,针对系统的阶跃响应、转子起浮、抗干扰能力等情况进行了仿真研究和性能分析。仿真试验结果表明,所设计的自抗扰控制系统具有精确度高、响应速度快、抗干扰能力强等特点,满足无轴承电机轴向混合磁轴承的高性能控制要求。     

三维有限元法求解无轴承开关磁阻电机电感

以一台12/8结构的无轴承开关磁阻电机为研究对象,选用不同未知量作为自由度,分别采用双标量磁位法、矢量磁位法和棱边有限元法对电机进行建模及计算,分析端部效应对电机磁场特性的影响;利用增强型能量增量法计算电机主、悬浮绕组的静态电感,研究无轴承开关磁阻电机的电感特性.通过与电感二维计算值和测量值的比较得到:无轴承开关磁阻电机端部效应严重,在不对齐位置处2D计算误差较大;棱边有限元法相对于另两种三维方法在求解高度非线性磁场问题时具有较高的计算精确度.     

无轴承永磁同步电机径向悬浮力动态解耦控制

针对无轴承永磁同步电机径向悬浮力之间存在的非线性、强耦合问题,提出基于神经网络逆系统方法的无轴承永磁同步电机径向悬浮力动态解耦控制策略.在分析无轴承永磁同步电机的工作原理和径向悬浮力产生机理的基础上,建立径向悬浮力的数学模型,并对该数学模型进行可逆性分析,证明此系统可逆.利用神经网络逆系统方法,将原来的非线性强耦合的多...     

Radial force and speed detection for improved magnetic suspension in bearingless motors

In this paper, radial forces and speeds are detected and used in negative feedback loops to enhance damping factors and response speed in bearingless induction motors. Radial forces and speeds are calculated from the detected radial force fluxes. Both radial force and torque generating fluxes are detected from search coil fluxes wound around stator teeth. The effectiveness on improving damping of radial positioning is shown both theoretically and experimentally.     

无轴承电机绕组轴线及控制系统刚度系数测定

针对无轴承电机悬浮控制系统模型中,两套绕组轴线坐标角度与模型刚度的确定均建立在一系列假设条件下,使实际数值与理论数值之间存在较大误差,且目前尚无对两套绕组轴线坐标关系及控制系统模型系数的精确测定方法,根据感应型无轴承电机气隙磁场的固有特性,建立了含两套绕组轴线坐标关系与转子偏心的磁悬浮力数学模型,提出了直接测定两套绕组轴线坐标关系及悬浮力模型系数的实验方法,精确测定出两套绕组坐标关系及控制系统的模型系数,可使无轴承电机实现精确控制.     

基于改进子域模型的双绕组无轴承磁通切换电机磁场解析计算

针对双绕组无轴承磁通切换永磁电机的复杂结构,通过建立一种改进的子域模型来分析电机电磁特性.对于悬浮绕组采用分布式双层绕组嵌放方式,提出了一种等效电流分析方法,将上、下层绕组电流等效为同一电流元.与传统子域模型中分布式双层绕组分析法相比,所提改进子域模型法可减少求解变量的个数,将未知参数矩阵从22阶简化到18阶,降低了磁...     

Control characteristics for quasi-optimal operation of switched reluctance motors

This paper presents the control characteristics of switched reluctance (SR) motors defined for the maximum efficiency of the motor or the motor–converter system and for the minimum ripple level of electromagnetic torque. Curves for control variables—switch-on and switch-off angles (or conduction angle) and average phase voltage—are obtained by computations from a simple mathematical model. This lumped-parameter model takes into account the magnetic saturation of the motor and the parameters of the power converter necessary to guarantee reliable results concerning power losses in the system. The investigations were carried out for two typical SRM with the number of teeth N_s/N_r=8/6 and 6/4 for a battery supply and for a 310-V rectifier supply. Time curves obtained from mathematical model and control characteristics resulting from numerous optimization computations were validated by thorough measurements performed on a special test rig.List of symbols D viscous friction damping, Nms - e_k back EMF in the kth winding, V - i_k current in the kth winding, A - J moment of inertia, kg/m² - L() phase winding's inductance in unsaturated state H - L(,i) phase winding's inductance considering saturation H - m number of phases - N_s/N_r number of teeth: stator/rotor - n rotational speed, 1/s - R phase winding's resistance, - R_i current measurement resistor value, - R_k total resistance in the kth phase circuit, - R_s resistance of a power source, - R_TDSat drain-source resistance of a transistor in the saturated state - r_D dynamic resistance of a diode, - T_e electromagnetic torque, Nm - T_l load torque, Nm - u_k voltage of the kth phase, V - U phase voltage RMS value, V - U_av phase voltage average value, V - _on switch-on angle, rad - _off switch-off angle, rad - _z=_on–_off conduction angle, rad - stroke angle of the motor, rad - _s efficiency of a motor - _u efficiency of a motor–converter system - rotor position angle, rad - (,i) saturation function of the winding's inductance - m_p level of the torque ripples, % - _r=2/N_r, rad rotor tooth pitch - _k rotor position angle reduced to the kth tooth-pitch, rad - (,i) flux linkage of a phase winding, Wb - angular velocity, rad/s - angular acceleration, rad/s²     

A new algorithm for sensorless operation of permanent magnet motors

In this paper, the authors propose and investigate a new algorithm for shaft position sensorless operation of permanent magnet motors, based on flux linkage and line current estimation. Measured line current and terminal voltage are used to estimate the flux linkage of the motor. The algorithm has a two current-loop structure, with the outer loop used to correct the position, and the inner loop utilised to correct the estimated flux linkage. The theoretical basis of the algorithm and individual definition of the system blocks is explained. Dependencies on motor parameters and measurement errors are discussed to show the effectiveness of the method using real data. As well as giving a detailed explanation of the new algorithm, the paper presents a wide range of computed and experimental results, demonstrating the reliability of the method even during acceleration of the motor from rest     

Transient and steady-state operation of induction motors with rotor asymmetries

Contents Steady-state analysis of induction motors with asymmetrical rotor impedances is presented by the application of the symmetrical-components method. New and general equivalent circuits are derived, and the analogy is pointed out between the equivalent circuits of this type of rotor asymmetries and other types. It is shown how the equivalent circuits can be extended for the case of transient operation when the rotor speed is constant.General state-variable equations are given for the calculation of transients. These can be easily solved by a digital computer using well known techniques.

---

Übersicht Das stationäre Verhalten von Asynchronmaschinen mit Unsymmetrien im Rotorkreis wird mit Hilfe symmetrischer Komponenten behandelt. Neue und allgemeine Ersatzstromkreise werden abgeleitet und die Analogie zwischen den Ersatzbildern für diese Art von Rotorasymmetrie und anderen Arten aufgezeigt.Ferner wird gezeigt, wie die Ersatzschaltbilder für den nichtstationären Betrieb bei konstanter Drehzahl erweitert werden können. Für die Berechnung des nichtstationären Verhaltens werden allgemeine Zustandsgleichungen angegeben, die mit bekannten Verfahren einfach auf Digitalrechnern gelöst werden können.

     

An air-gap-flux-oriented vector controller for stable operation ofbearingless induction motors

A bearingless induction machine has combined characteristics of an induction motor and magnetic bearings. It is known that the magnetic suspension of the rotor becomes unstable at overload operation, particularly in transient conditions. A novel air-gap-flux-oriented vector control scheme has been proposed to operate the bearingless induction motor during the high torque acceleration period. It has been found that there is an optimal flux orientation for complete decoupling in radial force generation. Test results in a laboratory bearingless induction motor validates the performance efficacy of proposed controller at overload conditions     

Extended high-speed operation via electronic winding-change method for AC motors

In many applications, it is often needed to extend the speed range of an electric motor. In permanent-magnet ac motors (PMAC), the maximum speed is limited by the available voltage for a given counter electromotive force value. The extension of the speed range can be achieved to some extent by using the field-weakening principle, resulting in constant-power characteristics, but is limited by machine parameters and inverter rating. In an induction-motor-based spindle drive for machine-tool applications, the wye/delta switchover method remains popular for extending the constant-power range without sacrificing the torque capability at higher speeds. Conventionally, the wye/delta method employs mechanical contactors that have limited life and are associated with dead time in the range of tens to hundreds of milliseconds due to mechanical constraints. Power-electronic versions of the contactors have been proposed, but they are rather complicated and involve many switching devices. This paper describes a novel and simple switching technique involving only two three-phase diode bridges and two insulated gate bipolar transistor (IGBT) switches to extend the speed range of ac machines (induction as well as permanent-magnet type). The proposed method requires a center tap to be placed in each phase of the motor with access to the ends and the center tap, making the motor a nine-lead machine. Test results carried out on a nonsalient-type PMAC motor and an induction motor are given to support the idea.     

Transient and steady-state operation of induction motors with general two-side asymmetry

Contents A new, general equivalent circuit is derived by using symmetrical-component theory for two-side asymmetrical three- and two-phase induction machines. The steady-state equivalent curcuit for the general three-phase case consists of controlled generators too, this is due to general asymmetry. All the elements of the equivalent circuit can be directly calculated from the known phase-coordinate stator and rotor components. The equivalent circuit is simplified for a two-side asymmetrical two-phase machine, realization is carried out with d, q components. As an extreme case, approximative the steady-state equivalent circuit is also derived for a single-phase machine with rotor asymmetry. The analogy is pointed out with the well known steady-state equivalent circuit of the single phase motor with symmetrical rotor. For the purpose of the direct measurement of an asymmetrical squirrel-cage induction motors' rotor currents, a model with external rotor is suggested. — For transient operation, a state-variable differential equation is derived by using Park-vector techniques, saturation of the main flux path is also present.

---

Übersicht In der vorliegenden Arbeit wurde die Diskussion des stationären Zustandes der dreiphasigen Asynchronmaschine mit asymmetrischer Vorschaltimpedanz in dem Statorkreis vorgeführt, mit der Anwendung der Theorie der symmetrischen Komponenten.Neue und allgemeine Ersatzschaltungen wurden abgeleitet, und es ist nachgewiesen, wie man diese auf den transienten Fall (mit konstanter Drehzahl) erstrecken kann.Auch auf den Fall der asymmetrischen Statorspannungen und Außenwiderständen sind Zustandsgleichungen gegeben.Neue Gleichungen wurden aufgestellt für den stationären Zustand der zweiphasigen asymmetrischen Asynchronmaschinen mit nicht orthogonaler Spulenanordnung mit der Applikation einer neuen, symmetrisierenden Transformation, und gleichzeitig auch neue Ersatzschaltung wurde abgeleitet. Gleichungen auch für den transienten Zustand sind gegeben.

     

Analysis of three-phase wound motors under unbalanced conditions

The analysis of three-phase wound motors with unbalanced supply voltages and unbalanced rotor-phase impedances is presented. The rotating field theory and coupling impedances approach are used in modelling the motor in the steady state. The effect of rotor skewing is considered. The relationships between stator and rotor quantities, in a general form, are obtained. The analysis is verified by comparison with the conventional equations for currents and torque.     

Effects of momentary voltage dips on the operation of induction andsynchronous motors

Simplified stability calculations of induction and synchronous motors on voltage dips are presented. The voltage dip withstand characteristics of induction and synchronous motors rated at the same horsepower and driving the same inertial loads are calculated. The motor characteristics influencing stability are: the type of motor selected (synchronous or induction); the pull-out torque of synchronous motors and the breakdown torque of induction motors; a constant excitation controller or an excitation boost on voltage dips for the synchronous motors; load and motor inertia; and load characteristics. Synchronous motors are not suitable for fast autoclosing or bus transfer, although these can be autoresynchronized. Transient torques and current surges must be considered when induction motors are connected for fast bus transfer. Due to varying power systems, motors and load characteristics, and much interaction between these, an analysis of avoiding a shutdown on voltage dips has to be performed on a case-by-case basis. This may include a computer-based study. The stiffness of the power system in relation to motor loads, the probable type of faults and fault clearance times, and motor protection and controls are some other concerns requiring an analysis in this context