同步发电机空载电压波形的齿磁通计算

为了快速准确计算谐波励磁同步发电机和普通同步发电机的空载谐波电压，提出一种齿磁通法计算谐波电压。利用有限元法，仅计算转子在一个齿距内移动时不同位置处的定子各个齿的磁通，通过绕组与齿的关联关系得到定子绕组感应电动势。该方法考虑了磁路、凸极效应、饱和、绕组布置、齿槽效应以及斜槽的影响。谐波励磁同步发电机上的实验结果与计算结果的比较说明了方法的正确性。该方法计算准确，计算量小，计算速度快。     

Direct field orientation controller using the stator phase voltagethird harmonic

This paper presents the development and implementation of a direct field orientation controller (DFOC) for induction machines based on determination of the spatial position of the air gap flux from the third harmonic component of the stator phase voltages. The control utilizes spatial saturation harmonic components rotating at synchronous frequency that are generated in the air gap flux when the machine operates in a saturated condition. When the machine is wye connected, the sum of the three phase voltages results in a signal dominated by the third harmonic and a high frequency component due to the rotor slot ripple. It is shown that the third harmonic voltage component can be effectively used to estimate both amplitude and position of the air gap flux. Two methods for estimation of the air gap flux from the third harmonic voltage are discussed in the paper. A complete induction motor direct field orientation control is designed and implemented in the laboratory. Extensive experimental results showing the DFOC drive system performance are presented and discussed     

分段式Halbach阵列永磁同步电机非理想气隙磁场建模分析

Halbach阵列是一种特殊的永磁体充磁方式,可以提供理想的气隙磁密,且转子无需采用铁磁材料。由于定子开槽,永磁同步电机定转子气隙不均,气隙磁密谐波增加,产生齿槽转矩。本文利用子域模型法建立了分段式Halbach阵列永磁同步电机空载磁场解析模型。其解析模型计算结果与有限元结果相比,两者气隙磁密波形吻合较好。该解析模型为进一步研究电枢反应、齿槽转矩等性能奠定了基础。     

Sensorless field-orientation control of an induction machine byhigh-frequency signal injection

This paper describes a new scheme to find the rotor flux angle from stator voltages and currents by injecting high-frequency signal. The signal is not a rotating one, but a fluctuating one at a synchronous rotating reference frame with the fundamental stator frequency. When the estimated rotor flux angle coincides with the actual angle, the proposed method makes virtually no ripple torque, no vibration and less audible noise caused by the injected signal. The difference of impedances between the flux axis and the quadrature axis at high-frequency signal injection on the rotor flux angle is explained by the equivalent circuit equation of the induction machine. The difference is verified by experiments on the test motors at various testing conditions. The sensorless field-orientation algorithm is proposed, and the experimental results clarify the satisfactory operation of the algorithm with 150% load torque at zero stator frequency     

Modified direct torque control method for induction motor drives based on amplitude and angle control of stator flux

This paper proposes design and implementation of a direct torque controlled induction motor drive system. The method is based on control of separation between amplitude and angle of reference stator flux for determining reference stator voltage vector in generating PWM output voltage for induction motors. The objective is to reduce electromagnetic torque ripple and stator flux droop which result in a decrease in current distortion in steady-state condition. In addition, the proposed technique provides simplicity of a control system. The direct torque control is based on the relationship between instantaneous slip angular frequency and rotor angular frequency in adjustment of the reference stator flux angle. The amplitude of the reference stator flux is always kept constant at rated value. The system has been implemented to verify its capability such as torque and stator flux responses, stator phase current distortion both during dynamic and steady state with load variation, and low speed operation.     

Space-Vector State Model of Induction Machines Including Rotor Slotting Effects: Toward a New Category of Observers

This paper develops a new space-vector dynamic model of the induction machine, including stator and rotor slotting effects. With this approach, the slotting effect is considered only in the stator and rotor leakage variation. The model has been also rewritten in a space-vector state form useful for control applications, since it contains the information of the rotor position. This model works with both low- and high-frequency supplies, differently from most control models, including slotting effects, which usually model only the high-frequency behavior of the machine. The model has been implemented in numerical simulation and verified experimentally on three motors with the same stator and three different rotor configurations. Experimental results confirm the goodness of the model and are in accordance with the results in the literature.      

基于高频电压信号注入的永磁同步电机转子初始位置估计

提出了一种表面安装式永磁同步电机转子初始位置估计的方法。其原理是向定子绕组中注入脉动的高频电压信号,由于定子电感随转子位置q 而变化,因此绕组的高频电流响应信号中含有q 角的信息,但是该方法无法判断转子磁极的极性,因此在初步辨识出q 角的基础上再向d轴注入高频电压信号,并利用磁场饱和引起的电感量的变化来估计出转子的磁极极性。该方法不需要知道电机的精确参数,也不需要额外的硬件。介绍了实验系统的构成和参数,给出了实验结果,实验结果表明理论分析正确。     

Performance and torque-ripple characterization in induction motoradjustable-speed drives using time-stepping coupled finite-elementstate-space techniques

In this paper, the time-stepping coupled finite-element state-space (TSCFE-SS) model developed in an earlier companion paper is applied here for assessments of effects of machine geometry and magnetic circuit design modifications, and effects of pulsewidth modulation (PWM) carrier frequency on performance characteristics of induction motor drives. Namely, this has been accomplished through analysis of developed torque profile ripples and harmonic spectra of mid-air-gap radial flux density waveforms of the case-study motor. Furthermore, consequent effects of design modifications pertaining to geometry and/or magnetic circuit modifications and PWM carrier frequency on ohmic and iron core losses are investigated. The investigation has been performed on a case-study motor, which is a Y-connected single-layer three-phase two-pole 1.2-hp 208-V squirrel-cage induction motor with 24 stator slots and a cage with 34 rotor bars     

U型单相自起动永磁同步电机参数计算与起动特性分析

为了使U型单相永磁同步电机实现自起动,气隙采用非对称形式。文中基于二维有限元法对电机绕组电感、磁链和定位转矩进行了计算。在此基础上,针对所建立的动态数学模型,用龙格库塔法对空载起动过程进行了动态仿真计算,得到该电机电流、转矩和转速曲线。同时讨论了电源合闸角、转子初始相角、磁链和负载转矩对电机转速和旋转方向的影响。本文所论述的工作为该电机的进一步理论研究与优化设计奠定了基础。     

基于虚拟阻抗的双馈风力发电机高电压穿越控制策略

电网电压骤升故障会造成双馈感应发电机定子绕组中产生定子磁链的暂态直流分量,甚至引起比电网电压跌落更强的双馈发电机定、转子电流和电磁转矩的冲击。首先分析电网电压骤升下双馈发电机转子电流的电磁过渡过程,在变流器转子电流环中引入虚拟电阻控制,虽然能够有效抑制转子电流和电磁转矩的振荡,但是会引起转子电压过高和转子电流振荡过程加长,仅在低频部分具有抑制作用,因此本文引入虚拟电感,形成虚拟阻抗的改进控制策略,缩短了电网电压骤升时的转子振荡过程,并且对高频部分具有较强的抑制作用,提高了系统的高电压穿越性能。仿真和实验结果验证了所提控制策略的有效性和可行性。     

Compensation for parameter variation of induction motor improved torque control characteristics in low- and high-speed regions

In the vector control system using the slip frequency control method, the rotor resistance of an induction motor is used to calculate a slip frequency. Thus the change in temperature of the rotor resistance causes the deterioration of the torque control characteristic. This paper presents a new method of compensating for the rotor resistance change which is robust for the stator resistance change. A current control loop is composed of the λ-δ axes in which the λ axis is coincident to the stator current. In this method, the stator voltage error on the δ axis which is directly obtainable from this current control loop was used. The change in the stator voltage was able to be detected accurately, therefore the torque control accuracy was improved, particularly in the low-speed region. The experimental results of the current response and the compensation for the rotor resistance deviation also are shown. Moreover, although the mutual inductance has been treated as an invariable value, the value does change by a frequency and an exciting command. In this control method, an initial tuning of the equivalent mutual inductance was achieved by detecting the deviation component of the stator voltage on the δ axis at the no-load running condition. Furthermore, in the region with the constant power where the field weakening control was achieved, the excellent experimental results of the compensation for the deviation of the equivalent mutual inductance are shown.     

High torque induction motor with rotating magnets in the rotor

This paper describes a new type high torque induction motor which has the rotating magnets in the rotor. The motor basically consists of a usual stator, cylindrical rotor, and inner cylinder of which the surface is covered by a set of magnets. The rotor turns at somewhat less than synchronous speed. The inner cylinder with magnets can revolve freely against a rotor shaft. The magnets revolve synchronized by the rotating magnetic field induced by the stator current. The magnets make the flux in the rotor. Then we can expect torque increase by the increase of the flux. The results of magnetic field analysis indicate the flux is increased. In the experimental results of a test motor which is a 400 W prototype machine, we have obtained the torque increase by approximately 20 percent as anticipated in the magnetic field analysis. Moreover, test results show improvements of efficiency and power factor in the motor operations. The efficiency of the test motor is obtained as high as 10 percent at the rated output over those of a same size conventional induction motor. Although power factor of conventional induction motors is lagging at all times, the test motor can be operated with near unity, leading or lagging by adjusting the ac supplied source voltage.     

低转矩磁链脉动型电励磁同步电机直接转矩驱动系统的研究

电励磁同步电动机定子电感通常较小,转子阻尼绕组的存在使得电机暂态电感更小。若采用转矩及磁链滞环型直接转矩控制(基本DTC)策略电机电磁转矩及定子磁链脉动较大。针对电励磁同步电动机引入一种空间矢量调制型直接转矩控制(SVM-DTC)策略。它基于电励磁同步电动机中转矩角控制电磁转矩原理,利用空间电压矢量合成出最佳电压矢量实时补偿定子磁链矢量误差,以达到减小电动机在运行中电磁转矩及定子磁链脉动量之目的,同时又能基本维持开关频率恒定。仿真和实验结果证明,与基本DTC相比较,SVM-DTC电磁转矩和定子磁链脉动大幅度降低;电机起动电流峰值大大减小,稳态电流畸变较小;同时系统能够平稳地由恒转矩区过渡到弱磁区运行。     

电流源变频器供电异步电动机谐波电流的仿真与分析

根据梯形PWM技术的原理,通过仿真模型的建立来重点分析电流源变频器供电直流回路中的大电感和负载侧的并联电容对电动机的定子和转子的谐波电流、转矩和转速的影响。     

Observer-based direct field orientation: analysis and comparison ofalternative methods

This paper focuses on methods of achieving direct field orientation (DFO) of induction machines based on closed-loop, stator, and rotor flux observers which are well suited to both zero and very high-speed operation. Both observer topologies are dominated by a current model at zero and low speeds, and a voltage model at high speeds. Application of such rotor and stator flux observers to both stator and rotor direct field orientation is presented, including experimental results for three different methods. The influence which flux regulation has on parameter sensitivity of the complete DFO system is analyzed. A rotor-flux-regulated and -oriented system is shown to be sensitive to leakage inductance under high slip (i.e., field weakened) operation. Both a stator-flux-regulated and -oriented system and a stator-flux-regulated, rotor-flux-oriented system are shown to have reduced parameter sensitivity at high speeds. Unlike stator flux orientation using simple voltage integration stator flux models, excellent zero and low-speed operation of an observer-based stator-flux-oriented system is demonstrated     

直接转矩控制永磁同步发电机相位自校正型定子磁链观测器

直接转矩控制永磁同步发电具有电磁转矩和直流电压输出动态响应快等优点,但这些优点的实现需要准确的定子磁链。实际发电机参数在一定范围内随工作点变化而变化,这就要求定子磁链观测器对这些参数变化具有很强的鲁棒抑制特性。该文提出一种新型定子磁链观测器,该观测器借助有效磁链概念计算出转子磁极位置角观测值,基于此将定子磁链电压模型和电流模型联系起来,无需转子速度信息;为了进一步降低观测的定子磁链相位误差,将观测的定子电流矢量与实际定子电流矢量乘积结果送给PI调节器,利用PI输出值对转子位置角观测值进行校正。实验结果表明,采用该文提出的定子磁链观测器在无需转子速度及参数辨识情况下,对电机参数变化及模拟量采样误差具有很强的鲁棒抑制特性,可以获得准确的磁链观测值,实现电磁转矩和直流发电电压的快速而平稳控制。     

感应电动机系统的变结构反推控制研究

感应电动机系统的矢量控制为了进行电流(或电压)的3/2(或2/3)坐标变换需要进行转子转差或磁链角的计算，转子转差的计算容易受转子电阻变化的影响，而磁链角的直接计算容易受定子电阻变化的影响，因此避免转子转差或磁链角的计算对于感应电动机系统的控制是非常有意义的。文中把变结构反推控制运用于感应电动机系统的转矩和磁链控制，设计方法避开了转子转差或转子磁链角的计算，通过一定的坐标变换，基于定子侧的静止坐标系实现转矩和磁链的解耦控制。变结构反推控制设计能够实现快速的速度、转矩和磁链的渐近跟踪，同时系统控制器能够保证系统性能在电动机参数和外部负载变化时具有强的鲁棒性，通过Matlab仿真验证了系统设计的有效性和可行性。     

异步电机按定子磁场定向的转差频率控制

在分析现有转差频率控制方案优缺点的基础上，提出一种按定子磁场定向的转差频率控制方案。利用坐标变换和磁场定向原理，建立按定子磁场定向的异步电机数学模型。新系统通过定子电压直轴分量直接控制定子磁链的变化率；在转速通道中，电流调节器的输出作为转差频率，继承了标量型转差频率控制方案的优点。新系统的动态控制算法不依赖于转子电阻和电感参数。结果表明，新系统具有良好的静、动态性能和鲁性棒。     

Extending the optimization of the rotating transformer brushless excitation to all rectifier modes

Brushless excitation of a synchronous machine has a significant advantage: no slip-rings are necessary. The rotating transformer method is investigated: the excitation machine is a wound rotor induction machine with controllable voltage supply on the stator side. The synchronous machine is excited by a diode bridge, connected to the rotor of the excitation machine. The operation of the system is essentially determined by the commutation of the rotating diode bridge. It has different rectifier modes in such a configuration (possibly long commutation process caused by the variable, possibly lower voltage; larger commutation inductance). With justified simplifications, a model is derived to investigate the operation. The classical converter theory is applicable for the variable voltage, variable frequency supply of the diode bridge. Optimal operation considering the utilization of the excitation machine is introduced, developed and extended to all rectifier modes. The result is a matching rule for the parameters of the system, which can be satisfied by complex design of the system elements.     

Induction motor drive based on the stator flux vector control

This paper presents a new torque control algorithm for induction motors, based on the stator flux vector control. For each sampling period, the value of the stator voltage is calculated to keep the stator flux equal to the reference vector, while the stator flux reference vector is calculated to keep the rotor flux amplitude constant at all operating conditions. An improved stator and rotor flux estimation algorithm is proposed, enabling robust and stable operation of the drive, even at low speeds. The induction motor torque is manipulated by variations of the flux angular velocity, enabling drive operation with fixed switching frequency and ripple-free torque in the steady state. The performance of the proposed algorithm is tested through various experimental runs, proving good behavior of the drive in both transient and steady-state operating conditions.