【作者】 周博；

【导师】 邓福军；

【作者基本信息】 大连交通大学 ， 电力电子与电力传动， 2011， 硕士

【摘要】 直接转矩控制(DTC)理论于20世纪80年代由德国学者M.Depenbrok和日本学者1.Takahashi针对异步电机提出。由于其具有控制结构简洁、转矩动态响应快、鲁棒性好等优点,目前发展十分迅速。但是,直接转矩控制系统低速运行时转速转矩脉动大,即低速性能差,这一弱点阻碍该控制法在技术上的良好实现。本文在介绍异步电机工作原理基础上分析传统直接转矩控制低速脉动的原因,并根据磁链观测不准和开关频率低这两大原因,提出一种模糊直接转矩控制新方案。该方案针对磁链观测不准问题,提出一种新的磁链观测器——改进的无PI调节器的自适应积分器,传统自适应积分器含PI调节器和非线性饱和环节,调试起来难度很大,为改变这一状况,本文在传统自适应积分器结构上做了适当的调整修改,去掉PI调节器且无非线性饱和环节；另一方面,新方案用模糊控制器代替传统的双阈值滞环控制器来选择最优空间电压矢量,把磁链转矩误差分区处理,避免传统帮帮控制中因对不同误差采取相同控制策略带来的转矩转速脉动,开关频率也将提高。在模糊直接转矩控制系统中,本文还根据圆形磁链扇区有一定对称性的特点定义了一个磁链角度映射,把整个360°区间都映射到第一扇区当做模糊输入量,该映射大大减少了模糊控制规则数量,提高了模糊推理速度。最后,本文采用Matlab软件中Simulink、SimPowersystem及Fuzzy Logic Toolbox三个工具箱对传统直接转矩控制系统和基于模糊控制的直接转矩控制系统进行低速建模仿真。仿真结果表明改进的磁链观测器没有直流偏移和初始相位问题,新方案能明显减小转矩脉动,稳定转速,且系统响应速度大大加快。这说明本文为提高直接转矩控制系统低速性能所做的工作是正确与合理的。更多还原

【Abstract】 Direct torque control (DTC) was first proposed by German scholar M.Depenbrok and Japanese scholar I.Takahashi for induction motor in the 1980s. Currently, it’s develops very rapidly because of the simple control structure, good torque dynamic response and good robustness. However, the torque ripples are large at a low speed, and this poor low-speed performance makes hard to achieve the method in reality.This paper analyzes the reasons of the torque ripples at a low speed base on introduce the operation principle for the induction motor, besides, propose a new scheme fuzzy direct torque control according to these reasons the inaccurate flux observe and low switching frequency. And in the new scheme a new flux observer is designed—modified adaptive integrator without PI controller to resolve the inaccurate problem. Traditional adaptive integrator within a PI regulator and the nonlinear saturation link, and it’s difficult to debug, this paper makes appropriate modifications to settle that problem—remove the PI regulator. On the other hand, the new scheme use fuzzy controller instead of the hysteresis controller to select the optimal space voltage vector, improve the switching frequency through to divide the torque error into different intervals and give different control voltages for each of them. In the fuzzy DTC system, a stator flux angle mapping technique which mapping the entire 360°range to the first sector has been defined to reduce the size of the rules base on the symmetric characteristics of the circular flux, so that the fuzzy reasoning speed increases greatly.Finally, the paper use Simulink toolbox, SimPowersystem toolbox and Fuzzy Logic Toolbox of Matlab software to build up the model of classic DTC system and fuzzy DTC system and simulation. The simulation results show that modified adaptive integrator is not having the issue of DC offset and the initial phase, the new strategy can significantly reduce the torque ripple and stabilize the speed, and the response of the fuzzy DTC is faster obviously. All this shows that the work in the paper for improving low-speed performance of DTC system is correct and reasonable.更多还原