Fixed-switching-frequency DTC control for PM synchronous machine with minimum torque ripples

In this paper, fixed-frequency direct torque control (DTC) of a permanent magnet synchronous motor (PMSM) is presented. In this method, the stator voltage vector is generated according to the increase stator flux components in the stationary frame ( , ). A control algorithm based on predictive control to reduce the effect of the computing time on the stator flux vector position is also presented. The implementation of this method in the case of a PMSM, which is done without hysteresis regulators, is simple and does not require any filter. Simulation and experimental results show that the proposed method reduces the torque ripple while achieving a good dynamic response.     

Uncontrolled generator operation of interior PM synchronousmachines following high-speed inverter shutdown

Interior permanent magnet (IPM) synchronous machine drives are vulnerable to a special fault mode when gating is suddenly removed from the inverter switches during high-speed operation. The resulting IPM machine operation as a generator in combination with an uncontrolled rectifier must be properly understood and accounted for in the machine design to avoid damage to either the machine or inverter. An approximate closed-form solution is derived in this paper which relates the resulting machine phase current (and torque) to the IPM machine parameters, the DC-link voltage and the rotor speed. The resulting operating characteristics are particularly interesting for IPM machines that have been designed with inductance saliency ratios greater than 2 (i.e., high-saliency machines). The validity of the approximate solution is confirmed using dynamic simulation results, and the implications of these results for the machine designer seeking to minimize or eliminate the impact of this undesired operating mode are thoroughly discussed     

Basic principle and design criteria of axial-flux PM machineshaving counterrotating rotors

Axial-flux PM machines are particularly suitable for application in electrical drives devoted to ship propulsion, since they allow the elimination of the large-power gearbox used in conventional systems. In consideration of that, this paper deals with a novel slotless axial-flux PM machine topology which is characterized by the synchronous counterrotation of the two machine rotors. Such a new machine topology can find application in the direct driving of two counterrotating propellers, which may be used in ship propulsion systems to recover energy from the rotational flow of the main propeller slip stream. In this case, the use of an axial-flux machine having counter-rotating rotors allows an improvement in terms of weight and efficiency, since the epicyclic gear otherwise required for the motion reversal can be avoided. The paper discusses the stator winding arrangement which allows the opposite motion of the machine rotors and reports experimental results taken from a small-size machine prototype     

Axial flux interior PM synchronous motor: parameters identification and steady-state performance measurements

This paper presents different measurement and identification approaches applied to a nonconventional permanent-magnet (PM) synchronous machine, namely, the novel axial flux interior PM (AFIPM) synchronous motor. The nonconventional geometry of the AFIPM motor requires a dedicated discussion on the parameter identification subject. In the paper, the standstill frequency-response test and the standstill time-response test on the AFIPM prototype are presented. On the basis of these tests, the d- and q-axes circuit parameters are chosen. To confirm the validity of the standstill tests, the load tests have also been performed. Furthermore, the load tests provide some preliminary AFIPM machine performance results and additional information on the saturation phenomena. The d- and q-axes equivalent circuits parameters obtained by the performed measurements are analyzed and compared. Finally, the most appropriate AFIPM machine model is selected.     

表贴式高速永磁电机多场耦合转子设计

针对高速永磁电机转子设计同时受机械强度和电磁性能限制,参数选取困难的问题,基于机械强度设计、电磁设计以及转子动力学设计理论,采用有限元法,提出一套完整的基于多物理场耦合的高速永磁电机转子优化设计方法。综合考虑材料各向异性、离心力以及温度影响,分析了典型护套转子的机械强度变化规律;结合电磁性能要求,确定了最小护套厚度和永磁体厚度,并对三种护套转子的动力学特性进行分析。仿真结果表明,对于大功率高速永磁电机,比较适合采用表贴式的转子结构,而且碳纤维护套转子较其他转子具有更好的机械和转子动力学特性;通过多场耦合的设计方法得到的转子结构能够同时兼顾机械、电磁以及转子动力学特性的要求。     

Initial rotor position estimation of an interior permanent-magnet synchronous machine using carrier-frequency injection methods

This work presents a method using carrier-frequency injection to estimate the initial rotor position and magnetic polarity for an interior permanent-magnet synchronous machine. A nonsaturating inductance model of the machine provides no information about the polarity of the rotor magnet because the position observer based on this model is locally stable at both poles. To distinguish the polarity of the rotor magnet, the magnetic saturation effect can be used. The Taylor series can be used to describe the nonlinear magnetic saturation relationship between the current and the flux linkage in the d-axis rotor reference frame. The second-order term produces the second harmonic component of the carrier frequency, and the sign of its coefficient identifies the polarity of the rotor magnet being tracked. Both simulation and experimental results show good response of the position observer at several rotor electrical positions using either a rotating vector in the stationary reference frame or a oscillating vector in the estimated rotor reference frame.     

Enhanced current control of high-speed PM machine drives throughthe use of flux controllers

This paper compares various types of current controllers, including a novel method based on flux control. A proportional integral (PI) control method is used initially, to control the current in a high-speed permanent-magnet synchronous machine. The performance of this simple PI loop is presented, Various improvements to the PI controller are investigated, and the change in performance examined. A new current control scheme based on a flux-linkage model of the machine is introduced. The performance of the model-based control is demonstrated and compared with the performance of the PI current controller. Factors affecting the accuracy of the model-based control are given. By incorporating these factors into the model, the performance of the flux controller is further enhanced     

Optimum design of a multilayer interior permanent magnet synchronous motor using reluctance torque

The report analyzes the results of experiments done with an inverter drive interior permanent‐magnet (IPM) motor. We examine results of both FEM (finite element method) simulation and experiments using a prototype motor with identical conditions set for stator and magnet volume. The results indicated that with magnets implanted inside the rotor, the values for the d‐axis inductance of the motor remained roughly the same, unaffected by the shape or number of layers. However, the q‐axis inductance exhibited significant change. This research report compares an IPM motor having two layers of permanent magnets with a motor having a single layer. The dual layer shows a 30% or greater increase in torque using the same current. These results indicate that this motor is especially effective for such applications as robots, plant machinery, compressor motors, and electric vehicles. © 1999 Scripta Technica, Electr Eng Jpn, 127(1): 64–72, 1999     

A saturating lumped-parameter model for an interior PM synchronousmachine

This paper presents a lumped-parameter magnetic model for an interior permanent-magnet synchronous machine. The model accounts for the effects of saturation through a nonlinear reluctance-element network used to estimate the q-axis inductance. The magnetic model is used to calculate inductance and torque in the presence of saturation. Furthermore, these calculations are compared to those from finite-element analysis with good agreement     

High-performance PM synchronous motor drive for an electricalscooter

In this paper, the design of a full electrical system for an electrical scooter is presented. The paper explains the design choices that have been made to satisfy the typical main requirements for an electrical vehicle. According to them, an interior permanent-magnet synchronous motor has been incorporated in a drive able to control the motor both in the constant-torque (constant-flux) and in the constant-volt-ampere (flux-weakening) regions. Experimental results carried out on a system prototype are also included in the paper     

内置式永磁同步电机转子初始位置估计方法

针对无位置传感器永磁同步电机控制系统起动运行困难的问题,提出一种基于混合信号注入的内置式永磁同步电机改进转子磁极初始位置估计方法.采用注入高频旋转电压信号的方法检测磁极位置,设计一种通过PI跟踪观测器对所构建磁极位置误差信号进行控制的方案,当误差调节至零时将获得磁极位置初判值,降低了算法的复杂性.以磁极位置初判值为矢量角,往定子绕组注入2个方向相反的脉冲电压矢量,通过比较直轴电流大小可以简单、有效地判断出磁极极性,实现对位置初判值进行校正,从而获得转子初始位置估计值.应用所提出的估计方法对一台22kW内置式永磁同步电机进行实验,得到转子位置电角度平均估计误差为4.6°.     

A synchronous machine model for unbalanced analyses

This paper presents a new asymmetrical model of synchronous generators for power system transient stability simulations. The symmetrical component method has been used traditionally in the analysis of unbalanced faults in power systems. This is mainly because the synchronous generators, which play an important role in the power system, can be easily treated by the method. However, when analyzing a system that has elements with asymmetrical impedance, it may not be easy to use the symmetrical component method. In such cases, the simulations can be easily executed by using the phase coordinate method. However, there are few papers that derive a phase coordinate model of synchronous machines. This paper analyzes synchronous generators under asymmetrical conditions in detail by using the symmetrical component method, then derives a model of synchronous generators for the phase coordinate method. © 1997 Scripta Technica, Inc. Electr Eng Jpn 119(2): 46–59, 1997     

A novel direct torque control for interior permanent-magnet synchronous machine drive with low ripple in torque and flux-a speed-sensorless approach

A novel direct torque control (DTC) scheme for an interior permanent magnet synchronous machine (IPMSM) is proposed in this paper, which features low torque and flux ripple and almost fixed switching frequency. The torque and flux ripples have been significantly reduced compared with those of the basic DTC reported in the literature. A speed estimation scheme is integrated with the proposed DTC scheme in order to achieve a fully sensorless high-performance IPMSM drive.     

Magnet design and motor performances of a double‐layer interior permanent magnet synchronous motor

In this paper we discuss the results of our investigation of the interior permanent magnet synchronous motor (IPM), with permanent magnets embedded in the rotor, and particularly the double‐layer IPM synchronous motor, which has two layers of magnets embedded in the rotor, layered in the radial direction. For this investigation, we studied the arrangement of permanent magnets both through simulation and by experiments with a prototype. The results concerning the form of the magnets clearly show the advantages of the reverse arc configuration, which makes it possible to increase the surface area creating magnetic flux. We further determined that to maximize both the q‐axis flux and the flux of the permanent magnets, the optimum width of the q‐axis flux path between the magnets for the motor investigated here is 2 mm. The results also clearly show that chamfering the ends of magnets is effective in achieving better utilization of the q‐axis flux.© 1999 Scripta Technica, Electr Eng Jpn, 128(1): 62–69, 1999     

嵌入式永磁同步电机自适应在线参数辨识

针对嵌入式永磁同步电机参数辨识问题,提出一种自适应在线参数辨识方法,可在同一模型中对定子电阻、d轴电感、q轴电感和永磁体磁链进行辨识.该方法基于模型参考自适应系统,在同步旋转d-q坐标系下,构造出q轴电流自适应观测器,利用q轴电流观测误差,借助Lyapunov超稳定理论建立参数的辨识模型并推导出待辨识参数的自适应律,保证了特定条件下系统的稳定性和辨识参数的收敛性,解决了参数在线辨识算法的鲁棒性差、算法复杂等问题.仿真和实验结果表明,辨识参数能够在较短的时间内收敛到真实值附近,并且具有较小的误差.     

Multistage axial-flux PM machine for wheel direct drive

The design of direct-drive wheel motors must comply with diameter restrictions due to housing the motor in a wheel rim and allow the achievement of very high torque density and overload capability. Slotless axial-flux permanent magnet machines (AFPMs) prove to be the best candidate for application in electric vehicles as direct-drive wheel motors, as in comparison with conventional machines they allow designs with higher compactness, lightness and efficiency. The paper presents a newly conceived AFPM which has a multistage structure and a water-cooled ironless stator. In the proposed new topology of the machine, the space formerly occupied by the toroidal core becomes a water duct, which removes heat directly from the interior surface of the stator winding. The high efficiency of the machine cooling arrangement allows long-term 100% overload operation and great reduction of the machine weight. The multistage structure of the machine is suited to overcome the restriction on the machine diameter and meet the torque required at the wheel shaft. The paper gives guidelines for the design of a multistage AFPM with water-cooled ironless stator, and describes characteristics of a two-stage prototype machine rated 215 Nm, 1100 RPM     

Design considerations for fractional-slot winding configurations of synchronous machines

This paper presents some design considerations for synchronous machines characterized by a fractional number of slots per pole per phase. The main advantage of this configuration is a smooth torque, which is due to the elimination of periodicity between slots and poles. A second advantage is a higher fault-tolerant capability, making the machine able to work even in faulty conditions. However, the fractional-slot configuration presents a high content of MMF harmonics that may cause an unbalanced saturation and thus an unbearable torque ripple. A method to design fractional-slot machines is illustrated in this paper, including double-layer and single-layer windings. The analytical computation is extended to determine the harmonics of MMF distribution. Their effect is highlighted in isotropic as well as anisotropic machines. Finally, some considerations are reported to avoid unsuitable configurations.     

Improved lyapunov function for synchronous machine transient stability study

Contents The transient stability of a synchronous machine is analysed by utilizing Lyapunov's direct method. Lyapunov functions of Lur'e-type are developed, which include the effects of first and second-order speed governor. The used Lyapunov functions have been developed essentially by a systematic procedure based on the nonlinear control theory, Kalman's transformation and the second Lyapunov theorem. The paper evaluates the maximum region of asymptotic stability in the state-plane of a swinging synchronous machine while the computed critical clearing times are compared with those obtained by numerical integration. A numerical example is given.

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Verbesserte Lyapunovsche Funktion zur Untersuchung der transienten Stabilität von Synchronmaschienen

Übersicht Die transiente Stabilität einer Synchronmaschine wird mittels des Lyapunov'schen Direktverfahrens untersucht. Es werden Lyapunov'sche Funktionen Lur'scher Art entwickelt, die die Folgen des Geschwindigkeitsreglers erster und zweiter Ordnung beibehalten. Die benutzten Lyapunov'schen Funktionen sind im wesentlichen nach einer systematischen Prozedur auf der Grundlage der Theorie der nichtlinearen Kontrolle, der Kalman'schen Transformation und des zweiten Lyapunov'schen Ansatzes entwickelt worden. Es ist Ziel dieser Veröffentlichung, die Frage zu beantworten, was der größte Bereich der asymptotischen Stabilität auf der Zustandsebene einer schwingenden Synchronmaschine ist. Die berechneten kritischen Fehlerlöschzeiten werden mit denen verglichen, die durch numerische Integration erhalten werden. Es wird ein numerisches Beispiel angegeben.

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List of principal symbols E internal voltage of generator - E voltage of infinite bus - x _d transient reactance of generator - x _l reactance of each of the two transmission lines - ₀ 2f _o ,f _o=50 Hz - angle betweenE andE - ₀ , ₀ before and after-fault respectively steady-state value of - x _o x ₁₂+x _d - x ₁₂ total reactance between generator terminals and infinite bus - M inertia constant of generator - K _d mechanical damping coefficient - P _i instantaneous input power to generator - P _o post-fault steady-state input to generator - K _g the loop gain of the governing system - T _g equivalent time constant of governor - T _h time constant of the prime mover - V(x) Lyapunov function - V _mx critical maximum value ofV(x) - t _cl clearing time - t _er critical time