High-performance decoupling control techniques for various rotatingfield machines

This paper presents a comparative study of different field-oriented rotating-field machines, including squirrel cage induction machines, series-connected wound rotor induction machines, and synchronous machines. Evaluation of various field-oriented rotating-field machines for high-performance applications is presented. The concept of torque linearization and decoupling control is studied and compared for the various field-oriented motors. Computer simulations, experimental results and space phasor diagrams are employed to illustrate the dynamics of decoupling control for the various field-oriented-control (FOC) systems. The control complexity and parameter sensitivity of various FOC drive motors are compared     

A New PWM Strategy Based on a 24-Sector Vector Space Decomposition for a Six-Phase VSI-Fed Dual Stator Induction Motor

This paper presents a new space vector pulsewidth modulation (SVPWM) technique for the control of a six-phase voltage source inverter (VSI)-fed dual stator induction machines (DSIM). A DSIM is an induction machine which has two sets of three-phase stator windings spatially shifted by 30 electrical degrees and fed by two three-phase VSIs. Despite their advantage of power segmentation, these machines are characterized by large zero sequence harmonic currents, and in particular those of order 6 k plusmn 1, which are due to the mutual cancellation between the two stator windings. The proposed SVPWM scheme, while easy to implement digitally, reduces significantly these extra stator harmonic currents. Experimental results, collected from a 15 kW prototype machine controlled by a digital signal processor, are presented and discussed.     

一种有效的大规模数据的分类方法

本文提出了一种基于自组织特征映射神经网络(SOM)和支撑矢量机(SVM)相结合的复杂模式的大规模数据的分类方法.该方法首先利用自组织特征映射神经网络对待识目标进行聚类,然后应用支撑矢量机方法对其进行分类识别.通过对复杂异或(XOR)分类问题,以及实际的Iris和Appendicitis数据分类问题等的分类实验,且与仅用支撑矢量机的分类方法比较,结果表明,本文提出的方法对复杂模式的大规模数据的分类识别问题具有较好的效果,且训练时间大幅度减小.     

对比分析法在“电机学”课程教学中的应用

本文针对"电机学"课程性质,通过分析学生在课程学习中存在的问题,提出对比分析法在课程学习中的应用。该方法有助于培养学生对电机基本理论的理解能力,并且能够提高学生分析问题、解决问题的能力。这种方法贯穿课程学习的始末,在直流电机、变压器、异步机和同步机这四类通用电机中都能用到。实践证明,这种教学方法的应用能达到较好的教学效果。     

Performance Analysis of Aluminum- and Copper-Rotor Induction Generators Considering Skin and Thermal Effects

Recent progress in wind-power generation has led to the use of grid-connected and self-excited induction generators (SEIGs). Aluminum has been the common conductor material for squirrel-cage induction machines for a long time, largely because of low cost and ease of manufacturing. Recent developments in materials engineering have brought forth copper-rotor induction machines with promising results. In these machines, skin effect as well as temperature effect on the machine equivalent-circuit parameters during operation are expected to play an important role in the evaluation of induction-machine performance. In this paper, a qualitative performance analysis of aluminum- and copper-rotor SEIGs considering the skin and thermal effects has been presented theoretically and experimentally.     

基于反电动势估计的异步电动机离散直接转矩控制方法

本文介绍了一种基于反电动势估计的异步电动机离散直接转矩控制方法（DTDTC），利用这种方法可以实现对电磁转矩和定子磁链模值的精确控制，在实现过程中，只需要知道少量的电动机参数一定子电阻和定子漏感，因而，这种控制方法对电动机参数变化具有较强的鲁捧性。另外，详细分析了计算延迟对系统性能的影响，在此基础上，对基本DTDTC控制方法进行了改进。最后，对这种控制方法进行了实验验证，实验试验结果表明了这种控制方法的有效性。     

Dynamic emulation of mechanical loads using a vector-controlledinduction motor-generator set

This paper addresses the problem of electronic emulation of both linear and nonlinear mechanical loads using a vector-controlled induction machine dynamometer. It is shown that a basic emulation scheme where the dynamometer torque demand is derived from the inverse dynamics of the emulated load is not generally viable, especially if the emulated load is part of a closed-loop speed control system. A new feedforward speed-tracking control scheme for the dynamometer is presented, which preserves the load dynamics and allows for emulation of a large class of nonlinear loads. An experimental rig is described using vector-controlled induction machines as the drive motor and dynamometer, and experimental results showing excellent emulation of both linear and nonlinear load dynamics are presented     

On-line rotor cage monitoring of inverter-fed induction machines bymeans of an improved method

This paper suggests a fault-detection technique to monitor defects such as cracked rotor bars in induction machines. It has been introduced as the Vienna monitoring method. Rotor bar faults cause an asymmetric magnetic flux pattern in the air gap. Thus, the current phasor (or voltage phasor at current-controlled machines), flux phasor and air-gap torque differ from those of an ideal symmetric machine. The Vienna monitoring method compares the outputs of a reference model, which represents an ideal machine, to a measurement model. Observing the deviations of these two models makes it possible to detect and even locate rotor faults. It can be applied to inverter-fed machines as no frequency analysis is used. The method is verified by online experimental results from a DSP-controlled IGBT inverter drive. The findings match the outcomes of a detailed machine simulation. Air-gap flux density evaluation by a measurement coil system proves both the excellent sensitivity and fault location ability of the proposed scheme     

Variable flux control of permanent magnet synchronous motor drivesfor constant torque operation

In this paper, a small signal model of permanent magnet synchronous machines is developed which includes both components of torque, i.e., magnet torque and reluctance torque. The effects of flux variations on the torque are analyzed by the use of the developed model. The off-line torque compensation method proposed for induction machines is then adapted to permanent magnet motor drives to achieve a constant torque, variable flux operation of the drives. A sensitivity analysis is performed to show that the off-line method is influenced considerably by machine parameter variations. Therefore the concept of forced compensation is introduced and an on-line torque compensation controller is proposed. Simulation results are presented to show the effectiveness of the proposed controller. An experimental vector controlled permanent magnet motor drive including the on-line torque compensation controller is implemented based on a TMS320C31 DSP to evaluate the method. The experimental results also confirm a desirable variable flux control of the motor drive under constant torque operation     

Magnetising method for speed sensorless controlled induction motordrives

In speed-sensorless controlled standard induction machine drives a start without torque is only possible if the rotor speed of the demagnetised machines is known. A new method is proposed, which allows a fast and accurate identification of the rotor speed of demagnetised machines without a speed or position sensor     

Control systems for induction machines with magnetic saturation

Extensions of field-oriented control methods for induction machines, accounting for magnetic saturation, are developed. The new methods are based on a nonlinear π model for the saturated machine. This model is a more accurate representation of the saturation phenomena in the machine than are most previous models, and it is shown to also facilitate development of control algorithms. Observers for estimating rotor flux are also discussed. Experimental results verifying operation of one proposed control method are presented     

Torque calculations of current-source induction machines using the1-2-0 coordinate system

The authors extend the use of the classical induction motor equations obtained through the 1-2-0 coordinate system to cover situations with nonsinusoidal, chopped current sources. Detailed analysis is demonstrated through the widely used six-pulse, current-source-inverter-fed induction machines. The derivations of two different types of analytical torque equation (time-domain and frequency-domain series equations) are given. Their results are compared with each other and with results obtained from extensive air-gap and shaft torque measurements. The only difference in results between the frequency- and time-domain methods is that the voltage pulse corresponding to the switching is not included in the time-domain method; however, a voltage spike, as indicated by the frequency-domain-series method, would be expected at each switching point because of the rapid change of flux linkage. Test results agree with calculated results     

Sensorless control of induction Machines at zero and low frequency using zero sequence currents

This paper considers both flux and rotor position estimations for sensorless control of delta-connected cage induction machines (IMs) at low and zero frequency operation. The variation of leakage inductance due to either saturation or rotor slotting is tracked by measuring the derivative of the zero sequence current in response to the application of appropriate voltage test vectors. The method requires only a single extra sensor. It requires access to machine phase windings and is appropriate for integrated-type induction motor drives. Both a closed-slot and an open-slot machine is used to demonstrate rotor flux and rotor position tracking, respectively. Experimental results are presented showing sensorless torque control and sensorless speed and position control at low and zero frequencies.     

异步电机无速度传感器控制技术研究现状与展望

异步电机无速度传感器控制技术已经成为近年的研究热点，转速估计是异步电机无速度传感器控制技术的核心问题，本文对各种常见的异步电机转速估计方法进行了评价，指出了各方法的优、缺点及其适用场合，展望了今后研究的热点方向。预测了无速度传感器控制技术可能的发展方向。     

Axial flux machines drives: a new viable solution for electric cars

For electric car propulsion systems, the wheel motor is an application that requires the electrical machine has shape flexibility, compactness, robustness, high efficiency, and high torque. Axial flux machines are an interesting solution, where the motor is directly coupled to, or inside, the drive wheels. In this paper, axial flux induction and synchronous machines as wheel motor applications are presented and some considerations for each motor type are drawn by the authors. The structure with two rotors seems to be a very promising solution for both induction and synchronous machines. In the induction motor case, the two rotors can rotate at different speeds, thus the motor can act as a mechanical differential. The axial flux permanent magnet motor with two rotors is very compact and can be integrated inside the wheel     

基于Q-Learning的虚拟机动态伸缩算法

针对大规模云环境中业务量变化时平台服务质量和资源消耗的问题,提出一种基于Q-Learning的虚拟机扩容/缩容决策算法。将该问题转换为马尔科夫决策模型,为了在业务平台服务质量和资源消耗之间取得较好的平衡,智能体根据平台当前状态计算出最佳策略,执行决策并转到下一状态。仿真结果表明,该算法可根据业务量的变化实时作出伸缩决策,并提供最合适的虚拟机资源以满足业务需求,且能提高平台的稳定性。     

Optimization of automated high-speed modular placement machinesusing knowledge-based systems

This paper introduces an optimizer for a new family of modular, multistation, walking beam, high-speed chip mounters. The objective is to optimize the machines in a manner that would streamline the use of nozzles and part feeder mechanisms and at the same time increase throughput. The optimization of these machines is a large NP-complete problem, and therefore, a heuristic search method is needed to solve the problem in reasonable time. Four knowledge-based systems are introduced to solve this problem. These systems were designed to emulate human experts, who have optimized these types of machines manually. Benchmarks were performed for 18 industrial test cases. The results show that overall, the knowledge-based systems outperformed software supplied by the vendor of the machine in both feeder slot savings and throughput. This performance represents a key improvement, and a prototype system has been implemented in our industrial partner's factory     

Determination of converter control algorithms for brushlessdoubly-fed induction motor drives using Floquet and Lyapunov techniques

This paper presents a method of analyzing the stability of brushless doubly-fed machines (BDFM) in the synchronous mode of operation. Unlike the stability analysis of conventional induction and synchronous machines for which the linearized state equations are time-invariant, the linearized state equations of the BDFM are time-varying and, consequently, their eigenvalue analysis cannot be performed directly. However, since the system matrix of the linearized equations is a periodic function of time, the generalized theory of Floquet can be applied to transform the time-varying system of equations into an equivalent set of equations with a constant system matrix. Eigenvalue analysis can then be employed to analyze the stability characteristics of given equilibrium points. Investigation into the stability of a proof-of-concept BDFM in the synchronous mode of operation using the transformed linearized model shows good correlation between theoretical and experimental results. In addition, the possibility of designing a BDFM drive with inherent open-loop stability over the entire speed range is demonstrated. Finally, under stable steady state synchronous operation, power converter control methods are discussed and it is shown that scalar control methodologies similar to those for induction motor drives can be applied to the BDFM     

PI and fuzzy estimators for tuning the stator resistance in directtorque control of induction machines

Direct torque control (DTC) of induction machines uses the stator resistance of the machine for estimation of the stator flux. Variations of stator resistance due to changes in temperature or frequency make the operation of DTC difficult at low speeds. A method for the estimation of changes in stator resistance during the operation of the machine is presented. The estimation method is implemented using proportional-integral (PI) control and fuzzy logic control schemes. The estimators observe the machine stator current vector to detect the changes in stator resistance. The performance of the two methods are compared using simulation and experimental results. Results obtained have shown improvement in DTC at low speeds