基于滑模控制的异步电机直接转矩控制技术研究

发布时间：2018-07-16 19:02

【摘要】：在交流传动领域中,直接转矩控制(DTC)技术具备简单的结构、良好的动态性能,且涉及的电机参数少等优点,是继矢量控制之后另一种具有宽广应用前景的交流调速策略,因而受到了普遍的关注。然而,传统直接转矩控制系统存在转矩与磁链脉动大、开关频率不恒定、电机参数变动或外界摄动时系统鲁棒性低等问题限制其运用。滑模变结构控制是一种非线性控制方法,具有“滑动模态”可以进行设计,对系统参数的变化及外界扰动具有较强的鲁棒性的优点。因此本文以抑制转矩与磁链脉动、保持开关频率恒定为出发点,将滑模变结构控制策略用于异步电机的DTC系统中。本文首先给出了异步电机的数学模型、阐述了异步电机DTC的基本原理、剖析了传统DTC转矩脉动的根本原因。其次,运用了滑模变结构理论,研究了以转矩误差与磁链误差作为状态变量实现对传统DTC转矩与磁链脉动的抑制方案。然后,针对滑模变结构控制自身的抖振问题,采用了一种改进型趋近律方法,并以二阶系统为对象设计了基于改进型趋近律滑模变结构控制器,与基于等速趋近律的滑模控制器进行对比分析。接着,设计了基于转矩与磁链滑模变结构的异步电机DTC系统,其主要思路是利用新设计的转矩与磁链滑模控制器来取代传统DTC中的滞环调节器,采用频率恒定的空间矢量脉宽调制(SVPWM)技术代替电压开关矢量选择表进行电源逆变控制。最后在以上研究的基础上用Matlab/Simulink搭建了基于转矩与磁链滑模变结构的异步电机SVM-DTC系统的仿真模型。仿真结果表明,该系统与传统DTC系统相比,转矩脉动率由原来的75%减少到9.4%,相对减少了 87.47%,定子磁链轨迹更近似圆形轨迹且脉动也得到有效抑制,逆变器开关频率近似恒定的同时,系统对参数变化和外部干扰表现出较强的鲁棒性。
[Abstract]:In the field of AC transmission, direct torque control (DTC) technology has the advantages of simple structure, good dynamic performance and less motor parameters. It is another kind of AC speed regulation strategy with broad application prospect after vector control. As a result, it has received widespread attention. However, the traditional direct torque control system has many problems, such as large torque and flux ripple, unsteady switching frequency, low robustness of the system when the motor parameters change or outside perturbation, and so on. Sliding mode variable structure control is a nonlinear control method, which can be designed by sliding mode, and has strong robustness to the variation of system parameters and external disturbances. Therefore, in order to restrain the torque and flux ripple and keep the switching frequency constant, the sliding mode variable structure control strategy is applied to the DTC system of asynchronous motor. In this paper, the mathematical model of asynchronous motor is given, the basic principle of DTC is expounded, and the fundamental reason of traditional DTC torque ripple is analyzed. Secondly, the sliding mode variable structure theory is used to study the scheme of restraining the traditional DTC torque and flux ripple by using torque error and flux error as state variables. Then, for the chattering problem of sliding mode variable structure control, an improved approach law method is adopted, and a sliding mode variable structure controller based on the improved approach law is designed for the second order system. It is compared with the sliding mode controller based on the constant velocity approach law. Then, the DTC system of asynchronous motor based on torque and flux chain sliding mode variable structure is designed. The main idea is to replace the traditional hysteresis regulator with the new designed torque and flux chain sliding mode controller. The frequency constant space vector pulse width modulation (SVPWM) technique is used to control the inverter instead of the voltage switch vector selector. Finally, the simulation model of SVM-DTC system based on torque and flux chain sliding mode variable structure is built by Matlab / Simulink. The simulation results show that compared with the traditional DTC system, the torque ripple rate of the system is reduced from 75% to 9.4%, and the stator flux path is more similar to the circular path and the ripple is effectively suppressed. While the switching frequency of the inverter is approximately constant, the system is robust to the variation of parameters and external interference.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP273;TM343

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