【作者】 张瑞；

【导师】 高赟；

【作者基本信息】 西安科技大学 ， 控制理论与控制工程， 2013， 硕士

【摘要】 在交流调速中,直接转矩控制以思想新颖、结构简单、控制手段直接和动态特性优良的特点成为了该领域的研究热点。其基本思想是通过电压控制定子磁链,达到直接控制转矩的目的,从而实现转速的控制和调节。本文从异步电机数学模型出发,系统阐述了异步电机直接转矩控制的基本原理,详细分析空间电压矢量与定子磁链、电动机转矩的关系。根据定子磁链的不同控制策略,首先介绍传统的六边形磁链轨迹直接转矩控制的原理和结构,并在Matlab/Simulink的仿真平台上建立其仿真模型。通过仿真研究得出六边形DTC磁链开关频率低,低速域内转矩脉动大。为了克服六边形磁链控制中的转矩脉动等问题,引入圆形磁链轨迹DTC,建立模型并仿真。仿真结果表明圆形DTC转矩脉动小,磁链轨迹光滑,但磁链开关频率较高。根据两种控制方法在低高速域内不同的控制性能,建立低速域采用圆形磁链控制,且高速域切换到六边形磁链控制的全速范围内直接转矩控制系统,并进行仿真分析,结果表明在全速范围两模型之间过渡平滑,速度响应及时,且有效降低磁链开关频率针对传统直接转矩控制中开关频率不恒定、磁链和转矩脉动相对较大的问题,研究了将空间矢量脉宽调制技术(SVPWM)与DTC相结合的一种基于空间矢量调制技术的改进策略(SVM-DTC)。该方案用PI控制器取代传统直接转矩控制中的滞环控制器,并用SVPWM代替电压矢量开关表来控制逆变器。通过对SVM-DTC策略进行Matlab/Simulink建模和仿真,结果表明该策略可以有效减少转矩脉动。本文在李亚普诺夫稳定性理论基础上设计速度自适应全阶磁链观测器,并构造基于此速度辨识法的无速度传感器直接转矩控制系统。并通过仿真得出该方法可以对速度进行准确跟踪,实现转速辨识。更多还原

【Abstract】 In the field of AC machines control, Direct Torque Control (DTC) has become a focuswhich has many advantages such as new control method, simple structure, direct controlmeans and fast torque response. The basic idea of DTC is to control the motor torque directlythrough the voltage that acts on the stator flux, so as to control and regulate the rotationalspeed of the motor.This paper described the DTC basic theory of asynchronous motor systematically frommathematical model of asynchronous motor and analyzed the relationship of space voltagevector and stator flux, motor torque. According to different control strategies based on thestator flux, this article intruducs the principle and stucture of the the hexagonal flux trajectoryfirstly. Based on the simulation software Matlab/Simulink, the models of the hexagonalflux trajectory DTC are build. The results are obtained through simulation studies that it haslow flux switching frequency with large torque ripple especially in the low speed range. Inorder to improve the performance of the hexagonal flux DTC at low-speed, a circular fluxstajectory is analyzed and the simulation model of circular flux trajectory control DTC isbuild. It can be seen from the simulation result that the torque ripple is smaller with smothflux path, but the flux switching frequency is much high. Based on the two different controlmethods with their own control performance at low or high speed range, a model of full speedrange is build which uses circular flux control methods at low speed range and switches tohexagonal flux control at high range. The simulation studies show that these two models cancomplete the conversion smothly and reduce the switching frequecy of the flux effectively.In order to solve the problems of variable switching frequency and large flux and torqueripple, an advanced strategy (SVM-DTC) by combining the space vector pulse widthmodulation (SVPWM) and DTC together is researched. The hysteresis controller and voltagevector switching table are respectively replaced by PI controller and SVPWM method. The simulation research is done on the Matlab platform.The results show that the SVM-DTCstrategy can reduce the torque ripple and improve the tanditional DTC performance.An observer of full-order flux based on Layapunov stability theory is designed in orderto indentify the motor speed.The simulation model of speed sensorless DTC is build. It canbe seen from the simulation results that this method can track the speed accurately andcomplete the speed identification.更多还原