电气专业毕设英文文献(格式已修改)

本科毕业设计外文文献及译文文献题目：Direct Torque Control of Induction Motors Utilizing Three-Level Voltage Source Inverters文献作者：Xavier del Toro Garcia, Antoni Arias, Marcel G. Jayne and Phil A. Witting文献来源：IEEE Trans. Ind. Electron, vol. 51，No. 4，pp. 744757发表日期：2004年8月班 级：姓 名： 学 号：指导教师：翻译日期：英文原文：Direct Torque Control of Induction Motors Utilizing Three-Level Voltage Source InvertersXavier del Toro Garcia, Antoni Arias, Marcel G. Jayne,and Phil A. WittingAbstractA new control strategy for induction motors based on direct torque control is presented which employs a three-level inverter instead of the standard two-level inverter. The controller is designed to achieve a torque ripple reduction by taking advantage of the increase in the number of inverter states available in a three-level inverter. The harmonic distortion in the stator currents and the switching frequency of the semi-conductor devices are also reduced in the new control system presented.Index TermsInduction motor drives, three-level converter, torque control.I. INTRODUCTIONThe standard voltage source inverter (VSI) traditionally used in electrical drive systems is the two-level VSI, which unfortunately has a number of inherent limitations. For example, the maximum voltage that can be supported by the semiconductor switching devices in the VSI limits the maximum value of dc-link voltage. Furthermore, the output voltages and currents from the VSI can contain high harmonic distortion. The output voltage waveforms can also contain large values of dV/dt, which contribute to the degradation of the machine windings insulation and bearings, and also produce considerable electromag-netic interference during operation. New multilevel VSI topologies,however, can considerably reduce many of these limitations 1.The most commonly used multilevel topology is the three-level neutral point clamped (NPC) VSI 2. This type of VSI has advantages over the standard two-level VSI, such as a greater number of levels in the output voltage waveforms, less harmonic distortion, and lower switching frequencies.Direct torque control (DTC) has emerged to become a possible alternative to the well-known vector control strategies for induction motor control systems 3, 4. Although considerable research has been made into the two-level topologies associated with this method of control, the amount of research carried out to date into DTC systems employing multilevel topologies is still rather limited. The major advantage of the three-level VSI topology when applied to DTC is the increase in the number of voltage vectors available. This means the number of possibilities in the vector selection process is greatly increased and leads to a more accurate control system, which can result in a reduction of the torque and flux ripples. This is of course achieved at the expense of an increase in the complexity of the vector selection process. Although several authors have recently proposed the implementation of DTC utilizing this higher-level topology, their approaches are based on the use of more complex vector selection tables combined with modulation techniques based on analytical methods which have machine parameter dependency 5 6. A different approach is a selection table based on the concept of virtual vectors 7. These new methods considerably increase the complexity of the control strategy when compared to the classical DTC system 3, and they cannot be extended to different multilevel topologies with a higher number of levels because of the table selection method adopted.Fig. 1. Schematic diagram of the new controller.This paper describes a controller based on DTC that can be applied to different multilevel VSI topologies. It avoids the use of hysteresis comparators and look-up tables, and it does not require the knowledge of the motor model in the control system except for the inherent estimator as in the classical DTC system.II. NEW CONTROLLERThe general structure of the new controller is shown in Fig. 1. This novel controller generates a reference stator voltage vector (us) in coordinates (us,us) according to the DTC basic principle, rather than using the VSI state look-up table as used in classical DTC. This approach adopted is close to the DTC with space vector modulation scheme with closed-loop ux and torque control, and stator ux oriented control 4. More recently, other similar methods based on the predictive torque control concept have appeared 8 9.The inputs to the controller are the stator ux error (es),the torque error (ee) and, additionally, the stator ux angular speed (B),which is obtained to incorporate the back electromotive force (BEMF) term to improve the torque response at different operating points. The reference voltage vector calculated by the controller can be synthesized using different techniques with different degrees of complexity, such as choosing the nearest vector available or using modulation techniques 911. This controller can be applied to any topology because the type of VSI only affects the way the reference voltage vector has to be synthesized.The controller is based on the principle that the desired decoupled control of the stator ux modulus and torque is achieved by the controller acting on the respective radial and tangential components of the stator ux vector (B). The variation of the stator ux vector is approximately proportional to the voltage vector applied to the motor. Therefore, when calculating the reference voltage vector (in xy coordinates xed to the stator ux vector), the tangential component (usy) will depend on the torque error (ee), whereas the radial component (usx) will depend on the stator ux error (eB). As can be seen in Fig. 1, two closed-loop proportional controllers are employed to generate the components of the reference voltage vector. Ks and Ke are the proportional gains of these controllers and have been tuned experimentally to achieve a minimum torque and ux ripple. Their initial values can be set to approximately the ratio between nominal stator voltage and nominal stator ux modulus for Ks, and the ratio between nominal stator voltage and nominal stator fluxFig. 2. Torque response characteristics for classical DTC with a two-levelVSI. Operating point: =7.4 Nm. m = 200 r/min. modulus for Ks, and the ratio between nominal stator voltage and nominal torque for Ke.It can be seen in Fig. 1 that a feedforward action that compensates the BEMF term is added to the output of the torque controller to calculate the tangential component of the reference voltage vector. The BEMF term is obtained by multiplying the nominal stator ux modulus (sn) and the stator ux angular speed (s), which is previously ltered by means of a low-pass lter.The reference vector in xy coordinates is then transformed to xed coordinates. The novel controller developed synthesizes the reference voltage by choosing the nearest VSI vector to the reference voltage vector. The nearest vector is found by means of calculating the minimum distance of the voltage vectors that can be delivered by the VSI to the reference voltage vector. This calculation involves evaluating the modulus of the difference between vectors. The complexity of the system presented is increased when compared to classical DTC due to the use of proportional controllers instead of hysteresis comparators, the xy to coordinate transformation and the method to nd the nearest vector. Finally, it should be noted that the balance of the neutral point voltage is one of the main issues associated with the control of the three-level NPC VSI 11. In the novel controller the balance is achieved by selecting the appropriate conguration among the redundant possibilities that exist for some of the vectors delivered by the VSI.III. EXPERIMENTAL RESULTSThe practical implementation of the new controller is based on a dSpace DS1103 board that performs the control tasks. This board contains a PowerPC and a DSP. A three-level NPC VSI utilizing IGBT devices is used to supply a 380/220-V four-pole 1.1-kW cage-rotor induction motor. The dc-link voltage employed is 200 V. Figs. 2 and3 show the steady-state torque responses at 200 r/min and nominal torque conditions (7.4 Nm) for the classical DTC strategy with a two-level VSI and the new control system employing a three-level VSI described in this paper, respectively. The sample time used was 100 s in both systems.To assess the performance of both systems, the torque standard deviation (e) is calculated for the torque ripple. Additionally, the ux standard deviation (s), the total harmonic distortion (THD) of the stator current THD_iS, and the mean switching frequency in the semiconductor devices (FSw) are calculated for both systems. From the experimental results shown in Figs. 2 and 3, it is apparent that the torque ripple for the new system utilizing a three-level VSI is considerably reduced. The resultFig. 3. Torque response characteristics for the new controller with a three-level VSI. Operating point: =7.4 Nm. m = 200 r/min.of the VSI switches in the proposed system are both reduced by more than 50%. The switching frequency is reduced due to the utilization of a three-level VSI. In this type of VSI, some transitions between the three possible states of a leg do not involve the commutation of all the switches.IV. CONCLUSIONA new controller based on the DTC principle is presented, and it is shown that the controller can be easily implemented in a three-level VSI drive system. The new controller does not involve the use of any motor model parameters, as in classical DTC, and therefore, the control system is more robust compared to other methods that incorporate motor parameters. The experimental results obtained for the new DTC scheme employing a three-level VSI illustrate a considerable reduction in torque ripple, ux ripple, harmonic distortion in the stato currents,and switching frequency when compared to existing classic DTCsystems utilizing the two-level VSI.REFERENCES1 J. Rodriguez, J. Lai, and F. Z. Peng, “Multilevel inverters: A survey of topologies, controls, and applications,” IEEE Trans. Ind. Electron.,vol. 49, no. 4, pp. 724738, Aug. 2002.2 A. Nabae, I. Takahashi, and H. Akagi, “A new neutral-point-clamped PWM inverter,” IEEE Trans. Ind. Appl., vol. IA-17, no. 5, pp. 518523,Sep./Oct. 1981.3 I. Takahashi and T. Noguchi, “A new quick-response and high-efciency control strategy of an induction motor,” IEEE Trans. Ind. Appl.,vol. IA-22, no. 5, pp. 820827, Sep./Oct. 1986.4 G. Buja and M. P. Kazmierkowski, “Direct torque control of PWM inverter-fed AC motorsA survey,” IEEE Trans. Ind. Electron., vol. 51,no. 4, pp. 744757, Aug. 2004.5 K.-B. Lee, J.-H. Song, I. Choy, and J.-Y. Yoo, “Torque ripple reduction in DTC of induction motor driven by three-level inverter with low switching frequency,” IEEE Trans. Power Electron., vol. 17, no. 2, pp. 255264,Mar. 2002.6 G. Brando and R. Rizzo, “An optimized algorithm for torque oscillation reduction in DTC-induction motor drives using 3-level NPC inverter,” in Proc. IEEE ISIE, Ajaccio, France, Jun. 2004, pp. 12151220.7 Z. Tan, Y. Li, and M. Li, “A direct torque control of induction motor based on three-level NPC inverter,” in Proc. IEEE PESC, Vancouver, BC, Canada, Jun. 2001, pp. 14351439.8 P. Correa, M. Pacas, and J. Rodrguez, “Predictive torque control for inverter-fed induction machines,” IEEE Trans. Ind. Electron., vol. 54,no. 2, pp. 10731079, Apr. 2007.9 M. Nemec, D. Nedeljkovic, and V. Ambroic, “Predictive torque control of induction machines using immediate ux control,” IEEE Trans. Ind. Electron., vol. 54, no. 4, pp. 20092017, Aug. 2007.10 A. K. Gupta and A. M. Khambadkone, “A space vector PWM scheme for multilevel inverters based on two-level space vector PWM,” IEEE Trans. Ind. Electron., vol. 53, no. 5, pp. 16311639, Oct. 2006.11 J. Pou et al., “Fast-processing modulation strategy for the neutral-point-clamped converter with total elimination of low-frequency voltage oscillations in the neutral point,” IEEE Trans. Ind. Electron., vol. 54, no. 4, pp. 22882294, Aug. 2007.中文译文：基于三电平电压型逆变器的异步电机的直接转矩控制摘要：一种基于直接转矩控制的电动机的新型控制方式，其采用了三电平逆变器，而非标准的两个电平逆变器。这种控制系统通过增加逆变器的数量亦即采用三电平逆变器，从而实现降低转矩波动的目的。在新的控制系统中，定子电流的高次谐波失真现象和半导体开关器件的开关频率也相应减少。关键词：异步电机驱动，三电平变换器，转矩控制。 一 绪 论标准电压源逆变器（VSI），传统上用在电机驱动系统的是双电平VSI，但是不幸的是其具有一些固有的局限性。举例来说，因为其最大电压即是半导体开关器件所能承受的最大电压，从而影响了其直流输出电压的品质。此外，从VSI输出的电压和电流，可能包含高次谐波，从而产生失真现象。而且输出的电压波形，还可能包含较大的dv/dt，即电压波动较大，这加速了电机绕组绝缘破坏和轴承的磨损，同时在操作中也会产生相当大的电磁干扰。本文所介绍的这种新型多层次的VSI的拓扑结构，可以很大程度上弥补这方面的不足。最常用的多层次拓扑结构，是三个级别中性点钳位（NPC）VSI。这种类型的VSI比标准的两个级别VSI更具有优势，如在控制输出电压波形，减少谐波失真等方面，同时在降低开关频率方面具有更好的表现。直接转矩控制（ DTC ）的出现已经可能替代著名的矢量控制策略成为新的主流感应电机控制系统。虽然在两个层次的拓扑结构及与此相关联的方法控制上已经有相当多的研究。大量的研究表明，迄今为止所研究的DTC系统，在运用于多层次的拓扑结构方面仍相当有限。利用3个级别的VSI拓扑结构的先进性在于，它适用于接受数目增加的电压矢量。这意味着，在载体的选择程序中有多种可能性，并且极大地增加控制系统的准确性。当然，这是在牺牲在复杂的载体选择过程减少扭矩和通量中抖动的增加。虽然经过几次的改进，最近作者又提出了利用这种更高层次的拓扑结构实施对接受数目增加的电压矢量，其办法是基于使用更复杂的载体选型表合并与调制技术为基础的分析方法，其中有机参数的依赖。图 1新型控制器示意图本文介绍了一种基于直接转矩控制的控制器，可以适用于不同的多电平逆变器拓扑。它避免了滞环比较器和查找表的使用，它不需要电机模型的知识控制系统中除了固有的估计在传统直接转矩控制系统。二 新型控制器 一般结构的新型控制器如图.1所示 ，这新型控制器生成一个参考定子电压矢量（ ）在 - 坐标系()根据有关DTC的基本原则， 而不是使用国家标准的查找表中使用的经典DTC。采用的这方法是对空间矢量接近 DTC有关闭-环流出和转力矩控制的调音方案和固定子流出定向控制。最近，其他类似根据预测转矩控制的方法已经出现。控制器的输入是定子流出误差 (), 转力矩误差 () 和定子熔化角速度 (),用以获得合并后面的电动