电气专业毕设英文文献格式已修改.docx

1、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

2、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 in

3、stead 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-c

4、onductor 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 numb

5、er 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 wavefo

6、rms 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.Th

7、e 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

8、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 da

9、te 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

10、 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 utilizin

11、g 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

12、. 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 n

13、ew 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

14、 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

15、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 ar

16、e 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

17、 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 synthesiz

18、ed.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

19、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 ca

20、n 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 s

21、et 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 K

22、s, 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

23、 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 t

24、he 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.

25、 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 p

26、oint 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 RESUL

27、TSThe 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

28、 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

29、 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 devi

30、ces (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 V

31、SI. 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 th

32、e 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 illustr