基于SVPWM的交流电机矢量控制毕业设计外文翻译.doc

哈尔滨工业大学本科毕业论文（设计）翻译资料 本科毕业论文（设计）翻译资料论文题目交流电机矢量控制及仿真 班 级 姓 名 院（系）汽车工程学院 导 师 - 15 -基于SVPWM的交流电机矢量控制摘要为了解决大转矩脉动和谐波电流，低直流总线电压的问题，提出了一种新的控制策略。对交流感应电动机通过使用空间电压脉冲宽度调制，使静态和动态性能改善。本文基于SVPWM建立了系统仿真实验模式来验证系统控制方式的有效性。结果表明，它可以减少电流脉动和转矩脉动，提高直流总线电压的利用率。这意味着基于SVPWM控制策略可以有效地提高交流感应电机的伺服系统的动态和静态性能。关键词：空间电压矢量；PWM；交流感应电机；矢量控制第 1 章 简介早期的电动驱动器、直流电机，由于其优秀的静态和动态性能广泛应用于工业生产。1960年代后期,交流电动机由于其优势，如低成本、高可靠性和强大的环境适应性等,逐渐取代了直流电机在工业领域的应用。在1970年代前期，德国学者Felix Blaschke因为交流传动系统优良的转矩控制特性和显著的动态性能提出了矢量控制、矢量控制技术。目前，随着网络和电力电子设备和数字控制技术的发展，在电力驱动系统中，特别是定向矢量控制系统，交流传动逐步取代直流传动。电动机转子矢量控制是通过模仿直流控制方式的技术并且通过转子磁场定向和协调转换实现的速度和流量解耦，从而实现直流拖动性能指标和完全取代直流传动系统。电机控制集电机统一理论，机电能量转换和坐标转换理论于一体。基于转子磁场定位理论，定子电流分解成磁通电流分量和转矩电流分量，从而实现类似励磁直流电机磁场的解耦方式和转矩控制。矢量控制的以下三种调制方法:磁滞回线调制实现方法简单， 但大波形谐波表现不佳。正弦脉宽调制(SPWM)主要是使逆变器输出电压接近正弦波并且使基波分量尽可能大，谐波分量尽可能小，但其抑制谐波的能力是有限的，导致电机过热和转矩脉动的高谐波仍然可以生成。上面的两个矢量控制调制方法已经广泛应用于矢量控制系统中，但直流电压利用率仍然很低并且有较大的转矩脉动。SVPWM调制与传统SPWM比较，可以显著降低谐波输出电压，电动机谐波损失以及减少转矩脉动，同时它也有高电压利用率,可以显著改善控制性能。由于结构简单，可靠性高，性能优异，耐用，承载电流能力大,易于维护,低成本等。异步电动机已广泛应用于各种各样的传输系统。本文矢量控制使用SVPWM调制技术，控制异步电动机获得恒定的振幅并且获得旋转磁场，控制过程中，逆变器和电机是作为一个整体。理想的磁通量作为基准，当三相交流电机输入对称正弦电压，有效磁通矢量是通过使用不同的逆变器的开关模式生成的近似参考圆。为了提高交流感应电动机驱动系统有效的动态和静态性能，调制技术控制逆变器跟踪圆形旋转磁场，转子定向矢量控制方式是通过使用一系列的坐标变换实现解耦并控制定子电流励磁分量和转矩分量，这样的感应电动机作为一个直流电机控制。第 2 章 交流感应电机矢量控制模型矢量控制是电机矢量关系轴系旋转坐标的转换，为了实现实时控制电动机转矩，气隙磁场定向的定子磁场或转子磁场形成固定坐标系统。速度控制系统采用的矢量控制方法不仅具有速度范围的直流电机控制，但也可以控制转矩，因此它可以获得良好类似于直流电机的动态特性。本文采用转子磁场定向矢量控制策略，实现了一个完整的解耦的系统。该系统控制方法实现简单，控制精度高，控制块图所示： 图1转子磁场定向矢量控制总体框图三相交流电动机三相定子电流通过Clarke变换得到，然后经过Park变换，使直轴坐标系下的沿着转子磁通的方向得到励磁电流分量和转矩电流分量。对于三相交流电动机，他们分别是相当于励磁电流和转矩电流直流电机。因此可以根据直流电机的控制方法通过控制d轴和q轴的，来控制三相交流感应电动机。三相异步电机变频调速控制系统是一个高阶、多变量耦合和非线性的复杂系统。我们很难直接构建其动态结构设计和控制。但直流电动机是相对简单的，它是一个单一变量的自然耦合和线性数学模型。直流电机系统特征：直流励磁电流产生主磁场,然后主要磁场是一个稳定的直流磁场。在几何中性线刷时,电枢磁场和主磁场在垂直空间自然分离。电枢电流和励磁电流位于不同的循环并且各自独立。 在一定条件下，直流电机系统只有一个输入/输出变量电枢电压/速度，因此它可以被描述为一个输入/输出二阶系统。图2直流电机控制图的动态结构直流电机的动态结构控制图如图2所示。其中分别是电枢电流和负载电流；分别为晶闸管整流单元延迟时间，拖动系统的机电时间常数和电枢回路电磁时间常数；E 反电动势；R是电枢电阻；输入电压是由晶闸管整流输出，然后与负反馈修正后的直流电机的电压相加。直流电机具有上述优点,我们可以首先执行坐标变换来建立异步电动机的数学模型， 然后分别对相当于直流电机的结构励磁电流和转矩电流进行分析。矢量控制有三个坐标系统:ABC三相静止坐标系、两相旋转坐标系和两相静止坐标系统。从三相静止ABC坐标系到两相静止坐标系转换叫Clarke变换,相反叫Clarke逆变换;从两相静止坐标系到两相旋转坐标系称为Park转换、相反称为Park逆变换。矢量控制系统生产相同的旋转磁通标准，它使三相定子静止坐标系的交流电流感应电动机相当于直流电流电机的同步旋转坐标系，这样可以通过解耦控制磁通和转矩电流,从而可以获得和直流电机类似的控制效果。(1)Clarke变换三相异步电动机绕组的等值转换为两个在空间互相垂直的固定绕组，其结构如图3所示，当三相静止坐标系到两相静止坐标系时，气隙基本合成磁势不变，功率是恒定的，我们可以获得相电压、相电流的两相电机和相当于倍相电压、相电流有效值的三相电机，目前有以下前后转换关系：图3 三相ABC定子坐标系到两相静止坐标系转换图转换公式： （1）变换矩阵： （2）进行逆变换时的逆矩阵： （3）(2)Park变换图4 异步电动机的绕组模型图4是异步电动机的绕组模型，当整个坐标系以同步旋转速度旋转时，合成磁势也跟着旋转，它相当于一个旋转磁势，使旋转磁势等于ABC坐标系和坐标系下的磁势,所以异步电动机坐标系下模型相当于ABC坐标系和坐标系下的模型。为了坐标系和两相静止坐标系的相互转换,我们得出两相静止坐标系和旋转坐标系如图5所示。图5 两相静止坐标系和两相旋转坐标系从上面的图中,，根据轴同步旋转的角速度以及双轴角的变化随着时间的推移，我们可以得到以下公式： （4）转换成矩阵形式： （5）转换矩阵： （6）相应的逆矩阵： （7）Vector Control Based on SVPWM for ACIMAbstractTo solve the large torque ripple and current harmonics, low DC bus voltage problems, a new control strategy is proposed for AC induction motor by using space vector pulse width modulation, so that the static and dynamic performance are improved. The system simulation experiment mode was established based on SVPWM to verify the effectiveness of the system control mode. It is showed that it can reduce the current ripple and torque ripple, improve the utilization of DC bus voltage. It means that the control strategy based SVPWM can improve dynamic and static performance effectively for the ACIM servo system.Index TermsSpace voltage vector; PWM; ACIM; Vector controlI. INTRODUCTIONIn the early stages of electric drives, DC motor because of its excellent static and dynamic performance are widely used in industrial production, however, from the late 1960s, AC motor advantages, such as low-cost, high reliability and strong environmental adaptability and so on, gradually replace the DC motor in the field of industrial applications. Since the same time, in the early 1970s, since German scholar Felix Blaschke put forward vector control, vector control technology because of its superior torque control characteristics, the AC drive system dynamic performance has been significantly improved. At present, with the development of the high power electronic devices and digital control technology, in the electric drive system, AC drive gradually replacing the DC drive, specifically rotor field oriented vector control system, the vector control technology by imitating the control mode of the DC motor, through the rotor field oriented and coordinate transformation to achieve the speed and flux of decoupling, which can achieve the DC drag performance indicators and replace the DC drive system completely1.Vector control integrated motor unified theory,electromechanical energy conversion and coordinate transformation theory. Based on the rotor magnetic field orientation, the stator current is decomposed into the flux current component and the torque current component to achieve similar excited DC motor mode decoupling of the magnetic field and torque control. Vector control has the following three modulation methods: hysteresis loop modulation method is simple to implement, but large waveform harmonics, poor performance. Classic sinusoidal pulse width modulation (SPWM) is mainly to make the inverter output voltage as close to sinusoidal as possible, the fundamental component is as large as possible, and the harmonic components is as small as possible, but its ability to suppress harmonic is limited, the high harmonic still can be generated, which caused overheating of the motor and the torque ripple. The above two vector control modulation methods have been widely used in the vector control system, but the DC voltage utilization is still low and it has large pulsation. The SVPWM modulation is compared with the conventional SPWM, which can significantly reduce the harmonic content of the output voltage of the inverter and the motor harmonic losses, and reduce the torque ripple; meanwhile it also has high voltage utilization, and can significantly improve the control performance 2-4.Because of the simple structure, high reliability, excellent performance, durable, large over-current capacity, easy maintenance, low cost and so on, asynchronous motor has been widely used in a variety of transmission systems. In the paper, vector control was combined with SVPWM modulation technology to control asynchronous motors to obtain constant amplitude circular rotating magnetic field, in the control process, the inverter and the motor was as a whole, the ideal flux in the AC motor was as a benchmark when three-phase symmetric sinusoidal voltage supply to the motor, the effective flux vector which was generated by using different switching modes of the inverter to approximate the reference circle. The modulation technology control Inverter by tracking the circular rotating field. In order to improve the dynamic and static performance effectively of the AC induction motor drive system, the rotor field oriented vector control mode was adopted by using a series of coordinate transformation to achieve decoupling control of excitation component and torque component in the stator current, so that the induction motor can be controlled as a DC motor 5,6 .II. AC INDUCTION MOTOR VECTOR CONTROL MODELThe vector control is the motor vector relation transformated to the rotating coordinate shafting which is orientated by air-gap magnetic field, the stator magnetic field or the rotor magnetic field form stationary coordinate system, in order to achieve real-time control of the motor torque. Speed control system which adopted vector control method not only has the speed range of the DC motor, but also can control its torque, thus it can obtain good dynamic characteristics similar to a DC motor7,8. This paper adopted the rotor field oriented vector control strategy, it implemented a complete decoupling of the system, the control method achieved simply and had high control accuracy, its control block diagram was shown: Figure1. Rotor field oriented vector control overall block diagramThree-phase AC motor three-phase stator currents i A, iB ,iC through Clark transformation get ia , ib , then ia , ib through Park transformation and make D-axis along the direction of the rotor flux can get the exciting current component id and torque current component iq of the three-phase AC motor, they are respectively equivalent to the excitation current and the torque current of the DC motor. So can through control id and iq and according to the DC motor control method to control three-phase AC induction motor. The three-phase asynchronous motor VVVF control system is a higher order, the multivariable coupling and nonlinear complex system, we are difficult to directly build its dynamic structure to design and control. But DC motor is relatively simple, it is a single variable, the natural coupling and linear mathematical model.DC motor system characteristics 9: DC excitation current generated the main magnetic field, and then the main magnetic field is a stable DC magnetic field. When the brush in the geometric neutral line, the armature magnetic fields and the primary magnetic field is vertical and natural decoupled in the space. Armature current and excitation current is located in the different loops, and independent. DC motor system has only one input / output variable - armature voltage / speed, so it can be described as a single Input / output second order system under certain conditions. Figure 2. The dynamic structure of the DC motor control diagramThe dynamic structure control diagram of the DC motor is shown in figure 2, of which I d , I d1 was the armature current and load current respectively; T s , T m , T 1 were respectively thyristor rectifier unit delay time, drag system electromechanical time constant and armature loop electromagnetic time constant; E is back-EMF; R is the armature resistance; input voltage ct U was rectified by the thyristor output do U , and then fed to the DC motor after corrected with the negative feedback voltage.As the DC motor having the above advantages, we can firstly perform coordinate transformation to the mathematical model of asynchronous motor, and respectively conduct independent control to the excitation current and the torque current and is equivalent to the structure of the DC motor to be analyzed. Vector control change has three coordinate systems: three-phase ABC stationary coordinate system, the rotated two-phase dq coordinate system and the stationary two-phase ab coordinate system. From the stationary three-phase ABC coordinate system to the two-phase stationary coordinate system transformation called Clarke transformation, and on the contrary called Clarke inverse transformation; from the stationary twophase ab coordinate system to the rotated two-phase dq coordinate system called Park transformation, and on the contrary called Park inverse transformation. Vector control system producing the same rotating flux as criterion, it makes the stator AC current in the stationary three-phase coordinate system of induction motor be equivalent to DC current in the synchronous rotating coordinate system, so that the flux and torque current can be decoupled to controlling respectively, and the DC motor control effect can be obtained.A. Clarke TransformationThe three-phase still winding of asynchronous motors equivalently converted to two mutually perpendicular ab stationary winding in space ,its structure diagram is shown in Figure 3, when the three phase stationary coordinate system to the two-phase stationary coordinate system , air gap fundamental synthesis mmf unchanged, that power is constant ,we can obtain phase voltage, phase current of the two-phase motor is equivalent to times phase voltage, phase current RMS of the three-phase motor, the current have the following relationship before and after transformation.Figure