A state observer for the permanent-magnet synchronous motor

An identity state observer for the permanent-magnet synchronous motor is derived which reconstructs the electrical and mechanical states of the motor from current and voltage measurements. The observer operates in the rotor frame and estimates direct and quadrature stator currents, rotor velocity, and rotor position. Since the rotor position is estimated, the rotor reference frame is approximated using the latest rotor position estimate. The motor dynamics and the transformation into the estimated rotor frame are nonlinear, and thus the observer and observer error dynamics are nonlinear. Therefore, stability is analyzed using a linearized error model. Simulations including realistic measurement disturbances are used to investigate the global stability and accuracy of the observer     

A novel technique for estimation and control of stator flux of a salient-pole PMSM in DTC method based on MTPF

A permanent-magnet synchronous machine (PMSM) can be controlled using the direct torque control (DTC) technique in three different ways, i.e., by controlling flux, reactive torque and rotor d-axis current. Frequently, the DTC technique controls the speed of the motor by controlling stator flux with the aim of obtaining an optimal torque. A varying flux, proportional to the torque, may be used instead of a fixed flux, resulting in a maximum torque per ampere or maximum torque per flux (MTPF). In this paper, a reference-flux-generating method is followed to achieve the MTPF. An approximate equation is then derived using numerical techniques in order to obtain the reference flux from the torque. This equation is then applied to the DTC control system in order to obtain the reference flux. The control scheme has been verified by simulation and tests on a salient-pole permanent-magnet synchronous motor.     

Sensorless speed control of nonsalient permanent-magnet synchronous motor using rotor-position-tracking PI controller

This paper presents a new velocity estimation strategy of a nonsalient permanent-magnet synchronous motor (PMSM) drive without a high-frequency signal injection or special pulsewidth-modulation (PWM) pattern. This approach is based on the d-axis current regulator output voltage of the drive system that has the information of rotor position error. Rotor velocity can be estimated through a rotor-position-tracking proportional-integral (PI) controller that controls the position error to zero. For zero and low-speed operation, the PI controller gains of rotor position tracking controller have a variable structure according to the estimated rotor velocity. In order to boost the bandwidth of the PI controller around zero speed, a loop recovery technique is applied to the control system. The proposed method only requires the flux linkage of the permanent magnet and is insensitive to parameter estimation error and variation. The designers can easily determine the possible operating range with a desired bandwidth and perform vector control even at low speeds. The experimental results show the satisfactory operation of the proposed sensorless algorithm under rated load conditions.     

Control and dynamics of constant-power-loss-based operation ofpermanent-magnet synchronous motor drive system

The operational envelope of electrical machines is limited by the maximum permissible power loss of the machine at any given speed. The control and dynamics of the permanent-magnet synchronous motor (PMSM) drive operating with a maximum power loss versus speed profile is proposed in this paper. The proposed operational strategy is modeled and analyzed. Its comparison to the conventional strategy of limiting current and power to rated values demonstrates the superiority of the proposed scheme. The implementation of the proposed strategy is developed. It is achieved with an outer power loss feedback control loop. This has the advantage of retrofitting the present PMSM drives with the least amount of software/hardware effort. The PMSM drives in this case then can use the existing controllers to implement any torque control criteria, such as constant torque angle, unity power factor, constant air-gap flux linkages, maximum torque per unit current, or maximum-efficiency operation. Experimental verification of the new operational strategy is provided. The concepts presented in this paper can be applied to all other types of motor drives     

An RMRAC Current Regulator for Permanent-Magnet Synchronous Motor Based on Statistical Model Interpretation

A new robust model reference adaptive control (RMRAC) scheme for the current regulation of a permanent-magnet synchronous motor (PMSM) is proposed in a synchronous frame, which is completely free from the control performance degradation caused by parameter uncertainties. The current regulator of the PMSM is the innermost loop of its electromechanical driving system and plays an important role in the control hierarchy. When the PMSM runs precisely at high speeds, the cross-coupling terms must be compensated for. In the proposed RMRAC, the input signal is composed of the control voltage obtained by the model reference adaptive control (MRAC) law and the output of the disturbance estimator. The gains of the feedforward and feedback controllers are estimated by the proposed modified gradient method, where the system disturbances are filtered out by the estimated current regulation error. A voltage corresponding to the estimated system disturbances is fed forward to the control input in order to filter out the disturbances. The proposed method compensates the cross-coupling terms in a synchronous current model regardless of parameter variations. It also shows a good real-time performance due to the simplicity of control structure. Through simulations and real experiments, the efficiency of the proposed method is verified.     

煤矿井下隔爆TCR型SVC散热问题设计

随着我国煤矿产量的不断提高,井下供电线路不断延伸,各种大功率电气设备也不断增多。传统的只在地面变电所进行无功补偿已经难以满足要求,研制适合井下使用的动态无功补偿设备势在必行。而大功率电力电子设备在煤矿井下含爆炸性气体、高湿度的特殊环境中应用,散热问题是一个亟待解决的关键技术。所以,研究井下用SVC的散热问题是十分必要的。本文介绍了目前各种散热技术,并结合实际设计出一套水循环冷却散热系统,在Fluent下进行了仿真验证。     

基于空间矢量调制的电励磁同步电动机DTC研究

本文将空间矢量调制型直接转矩控制(SVM-DTC)策略引入到同步电动机控制系统中,利用优化的空间矢量组合实现了转矩、磁链误差的精确补偿,同时保证了功率器件开关频率恒定。研究了基于改进电压模型的电励磁同步电动机定子磁链计算方法以及转子励磁控制方式。最后使用Matlab/Simulink环境对所使用的方法进行了仿真验证。     

Experimental nonlinear torque control of a permanent-magnetsynchronous motor using saliency

In this paper, a new nonlinear control strategy is proposed for a permanent-magnet salient-pole synchronous motor. This control strategy simultaneously achieves accurate torque control and copper losses minimization without recurring to an internal current loop nor to any feedforward compensation. It takes advantage of the rotor saliency by allowing the current (i_d) to have nonzero values. This, in turn, allows us to increase the power factor of the machine and to raise the maximum admissible torque. We apply input-output linearization techniques where the inputs are the stator voltages and the outputs are the torque and a judiciously chosen new output. This new output insures a well-defined relative degree and is linked to the copper losses in such a way that, when forced to zero, it leads to maximum machine efficiency. The performance of our nonlinear controller is demonstrated by a real-time implementation using a digital signal processor (DSP) chip on a permanent-magnet salient-pole synchronous motor with sinusoidal flux distribution. The results are compared to the ones obtained with a scheme which forces the i_d current to zero     

内置式永磁同步电机弱磁控制技术的研究

针对电动汽车所使用的内置式永磁同步电机在不同工况下的转速与转矩需求,基于内置式永磁同步电机标幺化数学模型,文中设计了在线计算法最大转矩电流比控制与电压反馈法弱磁控制相结合的控制策略,以便对电机进行弱磁控制。以一台2.8 kW永磁同步电机作为研究对象,使用MATLAB/Simulink对所设计控制策略进行了仿真研究,并搭建弱磁控制系统实验平台并进行验证。仿真及实验结果表明,该控制策略具有较好的鲁棒性与较快的转矩响应速度,可以满足电机不同工况下的转速转矩需求。     

Analysis of direct torque control in permanent magnet synchronousmotor drives

This paper describes an investigation of direct torque control (DTC) for permanent magnet synchronous motor (PMSM) drives. It is mathematically proven that the increase of electromagnetic torque in a permanent magnet motor is proportional to the increase of the angle between the stator and rotor flux linkages, and, therefore, the fast torque response can be obtained by adjusting the rotating speed of the stator flux linkage as fast as possible. It is also shown that the zero voltage vectors should not be used, and stator flux linkage should be kept moving with respect to the rotor flux linkage all the time. The implementation of DTC in the permanent magnet motor is discussed, and it is found that for DTC using available digital signal processors (DSPs), it is advantageous to have a motor with a high ratio of the rated stator flux linkage to stator voltage. The simulation results verify the proposed control and also show that the torque response under DTC is much faster than the one under current control     

Steady-State and Transient Performance Analysis for a Single-Phase Capacitor-Run Permanent-Magnet Motor With Skewed Rotor Slots

This paper presents a numerical analysis method to accurately predict the steady-state and transient performance of a single-phase capacitor-run permanent-magnet motor with skewed rotor slots. Two-dimensional time-stepping finite-element analysis has been used to successfully predict the steady-state and dynamic transient performance of the prototype motor by using a multislice model. The agreement between computed and measured results of the prototype motor validates the proposed analysis method. The maximum efficiency and minimum torque ripple versus the value of capacitance have been determined from the results of the steady-state synchronous performance analysis. The run-up response corresponding to skew pitch has been obtained from the results of the starting performance analysis.     

Online Stator and Rotor Resistance Estimation Scheme Using Artificial Neural Networks for Vector Controlled Speed Sensorless Induction Motor Drive

This paper presents a new method of online estimation for the stator and rotor resistances of the induction motor for speed sensorless indirect vector controlled drives, using artificial neural networks. The error between the rotor flux linkages based on a neural network model and a voltage model is back propagated to adjust the weights of the neural network model for the rotor resistance estimation. For the stator resistance estimation, the error between the measured stator current and the estimated stator current using neural network is back propagated to adjust the weights of the neural network. The rotor speed is synthesized from the induction motor state equations. The performance of the stator and rotor resistance estimators and torque and flux responses of the drive, together with these estimators, are investigated with the help of simulations for variations in the stator and rotor resistances from their nominal values. Both resistances are estimated experimentally, using the proposed neural network in a vector controlled induction motor drive. Data on tracking performances of these estimators are presented. With this speed sensorless approach, the rotor resistance estimation was made insensitive to the stator resistance variations both in simulation and experiment. The accuracy of the estimated speed achieved experimentally, without the speed sensor clearly demonstrates the reliable and high-performance operation of the drive     

DTFC-SVM motion-sensorless control of a PM-assisted reluctance synchronous machine as starter-alternator for hybrid electric vehicles

Permanent magnet-assisted reluctance synchronous machine (PM-RSM) starter alternator systems are credited with good performance for wide speed range in hybrid electric vehicles. This paper proposes a motion-sensorless motor/generator control of PM-RSM from zero speed up to maximum speed, using direct torque and flux control with space vector modulation. A quasioptimal stator flux reference with a flux versus torque functional is proposed. A stator flux observer in wide speed range uses combined voltage-current models for low speeds, and only the voltage model for medium to high speeds, both in proportional-integral closed loop. A novel rotor speed and position observer with a fusion strategy employs signal injection and only one D-module vector filter in stator reference for low speed, combined with a speed observer from the stator flux vector estimation-for medium-high speed. The proposed system is introduced piece by piece and then implemented on a dSpace 1103 control board with a 350-A metal-oxide-semiconductor field-effect transistor-pulse-width modulation converter connected to a 42-Vdc, 55-Ah battery, and a 140-Nm peak torque PM-RSM. Extensive experimental results from very low speed to high speed, regarding observers and drive responses, including artificial loading (motoring and generating), seem very encouraging for future starter-alternator systems.     

Torque Feedforward Control Technique for Permanent-Magnet Synchronous Motors

This paper proposes a torque control method for interior permanent-magnet (IPM) motors operating in a wide speed range requiring high torque/power accuracy and a fast dynamic response. Using the fact that the motor parameters are nonlinear and significantly vary with direct and quadrature current operating points, a new optimal operating plane is generated. This operating plane combines the maximum torque per ampere (MTPA) curve, current limit circle, and maximum torque per volt (MTPV) curve, voltage limitations, and torque calculation under the nonlinear parameter variations. As a result, new feedforward tables are generated, which make full use of measured motor parameters. The new torque and flux regulators built around the feedforward tables provide a fast dynamic response and accurate steady-state torque/power production. The proposed controller was implemented and successfully tested on a 105-kW IPM motor electric drive used in a fuel-cell vehicle program.      

Sensorless control of permanent-magnet synchronous motors using online parameter identification based on system identification theory

An online parameter identification method and sensorless control using identified parameters were realized in surface and interior permanent-magnet synchronous motors (SPMSMs and IPMSMs, respectively). As this method does not use rotor position or velocity to identify motor parameters, the identified parameters are not affected by position estimation error under sensorless control. The proposed method can be applied to all kinds of synchronous motors. The effectiveness of the proposed method was verified by experiments in both SPMSMs and IPMSMs.     

Performance of induction motor with free-rotating magnets insideits rotor

This paper presents a new induction motor that has free-rotating magnets inside a rotor. The magnets can revolve freely against the rotor with the shaft. In this motor, the airgap flux is provided by both rotating permanent magnets and the stator coil current. A prototype motor was fabricated by modifying the rotor of a conventional three-phase four-pole 400 W squirrel-cage induction motor. The experimental results of a prototype motor showed superior performance in comparison to conventional motors in terms of the power factor, efficiency and torque characteristics. The power factor can be controlled to be unity, leading or lagging by changing the supply frequency and/or source voltage. The efficiency of the motor, over a wide output power range, is remarkably higher than that of the same size conventional induction motor. A high torque can be obtained in a high speed area     

基于扰动观测器的内置式PMSM无传感器控制

针对两相静止坐标系下基于观测器进行IPMSM无传感器控制时存在电角度估算误差与交直轴电感和负载转矩耦合、电角度补偿复杂等问题,文中选择在同步旋转坐标系下采用电机原有电感参数进行IPMSM无传感器控制。通过建立PMSM 的矢量数学模型,对存在电角度估算误差时采用IPMSM原参数对反电动势估算的影响进行分析,分析结果验证了该方法的理论可行性。利用MATLSB/Simulink进行仿真,并进行了针对性实验。实验结果表明,文中所提算法无须电角度补偿,在扰动条件下仍能对电机转子位置和速度进行良好地跟踪。     

Problems associated with the direct torque control of an interior permanent-magnet synchronous motor drive and their remedies

This paper investigates problems associated with the implementation of a direct torque control (DTC) strategy for an interior permanent-magnet synchronous motor drive. The DTC technique is increasingly drawing attention because of elimination of current controllers and, hence, their inherent delays, and elimination of the rotor position sensor. The latter advantage perhaps is the main impetus for considering this new approach of torque control. Problems associated with this controller, namely, the offset in the current measurements, the stator resistance variation, and the requirement of initial rotor position are addressed in this paper. Ways of mitigating of these problems are also investigated in this paper. These are evaluated with modeling and experimental studies, results of which are also presented.     

A rotor position and speed observer for permanent-magnet motors with nonsinusoidal EMF waveform

A new nonlinear reduced-order observer to estimate the rotor speed and position for permanent-magnet motors, with arbitrary electromotive force (EMF) waveform, is presented. The proposed observer is suitable for the realization of a torque control with minimum torque ripple. In order to implement the observer, the EMF generated by the motor is first obtained experimentally offline. After that, it is approximated by a Fourier series in order to develop the model to be used in the online estimation. From the estimated EMF, rotor position and speed are calculated using the relationship between the EMF and the rotor variables. The proposal is validated with experimental results.     

Indirect torque control of switched reluctance motors using iterative learning control

This paper proposes the use of iterative learning control (ILC) in designing a torque controller for switched reluctance motors (SRMs). The demanded motor torque is first distributed among the phases using a torque-sharing function. Following that, the phase torque references are converted to phase current references by a torque-to-current converter and the inner current control loop tracks the phase current references. SRM torque is a highly nonlinear and coupled function of rotor position and phase current. Hence, the phase current references for a given demanded torque can not be obtained analytically. Assumption of linear magnetization characteristics results in an invertible torque function. However, the nominal phase current references obtained using this torque function will lead to some torque error as motor enters into magnetic saturation. For a constant demanded torque, the error in the phase current references will be periodic with rotor position. Hence, we propose to use ILC to add a compensation current to the nominal phase current references so that torque error is eliminated. Similarly, current tracking for the nonlinear and time-varying system is achieved by combining a simple P-type feedback controller with an ILC controller. The proposed scheme uses ILC to augment conventional feedback techniques and hence, has better dynamic performance than a scheme using only ILC. Experimental results of the proposed scheme for an 8/6 pole, 1-hp SRM show very good average as well as instantaneous torque control.