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河南理工大学外文文献翻译 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 744 757 发表日期 2004 年 8 月 班 级 姓 名 学 号 指导教师 翻译日期 河南理工大学外文文献翻译 英文原文 Direct Torque Control of Induction Motors Utilizing Three Level Voltage Source Inverters Xavier del Toro Garcia Antoni Arias Marcel G Jayne and Phil A Witting Abstract A 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 Terms Induction motor drives three level converter torque control I INTRODUCTION The 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 河南理工大学外文文献翻译 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 河南理工大学外文文献翻译 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 CONTROLLER The general structure of the new controller is shown in Fig 1 This novel controller generates a reference stator voltage vector u s in coordinates us us according to the DTC basic principle rather than 河南理工大学外文文献翻译 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 fl ux and torque control and stator fl 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 fl ux error e s the torque error e e and additionally the stator fl 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 9 11 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 fl ux modulus and torque is achieved by the controller acting on the respective radial and tangential components of the stator fl ux vector B The variation of the stator fl ux vector is approximately proportional to the voltage vector applied to the motor Therefore when calculating the reference voltage vector in x y coordinates fi xed to the stator fl ux vector the tangential component u sy will depend on the torque error e e whereas the radial component u sx will depend on the stator fl ux error e B As can be seen in Fig 1 two closed loop proportional controllers are employed to generate the components of the reference voltage vector K s and K e are the proportional gains of these controllers and have been tuned experimentally to achieve a minimum torque and fl ux ripple Their initial values can be set to approximately the 河南理工大学外文文献翻译 ratio between nominal stator voltage and nominal stator fl ux modulus for K s and the ratio between nominal stator voltage and nominal stator flux Fig 2 Torque response characteristics for classical DTC with a two level VSI Operating point 7 4 Nm m 200 r min modulus for K s and the ratio between nominal stator voltage and nominal torque for K e 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 fl ux modulus sn and the stator fl ux angular speed s which is previously fi ltered by means of a low pass fi lter The reference vector in x y coordinates is then transformed to fi 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 河南理工大学外文文献翻译 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 x y to coordinate transformation and the method to fi 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 confi guration among the redundant possibilities that exist for some of the vectors delivered by the VSI III EXPERIMENTAL RESULTS The 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 fl 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 河南理工大学外文文献翻译 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 result Fig 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 CONCLUSION A 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 河南理工大学外文文献翻译 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 fl ux ripple harmonic distortion in the stato currents and switching frequency when compared to existing classic DTCsystems utilizing the two level VSI 河南理工大学外文文献翻译 REFERENCES 1 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 724 738 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 518 523 Sep Oct 1981 3 I Takahashi and T Noguchi A new quick response and high effi ciency control strategy of an induction motor IEEE Trans Ind Appl vol IA 22 no 5 pp 820 827 Sep Oct 1986 4 G Buja and M P Kazmierkowski Direct torque control of PWM inverter fed AC motors A survey IEEE Trans Ind Electron vol 51 no 4 pp 744 757 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 255 264 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 1215 1220 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 1435 1439 8 P Correa M Pacas and J Rodr guez Predictive torque control for inverter fed induction machines IEEE Trans Ind Electron vol 54 no 2 pp 1073 1079 Apr 2007 河南理工大学外文文献翻译 9 M Nemec D Nedeljkovic and V Ambroic Predictive torque control of induction machines using immediate fl ux control IEEE Trans Ind Electron vol 54 no 4 pp 2009 2017 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 1631 1639 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 2288 2294 Aug 2007 河南理工大学外文文献翻译 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 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 河南理工大学外文文献翻译 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 河南理工大学外文文献翻译 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 s usus 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 ee ee 熔化角速度 用以获得合并后面的电动势 BEMF 在不同的营运 s 点来改善转力矩回应 参考电压矢量计算像是选择最接近的载体提 供或使用调制技术 由控制器可合成采用不同技术与不同程度的复 杂性 参考电压矢量计算 控制器可应用于任何拓扑 因为所有类型 仅仅影