【作者】 毕广明；

【导师】 郑黎明；

【作者基本信息】 汕头大学 ， 机械电子工程， 2008， 硕士

【摘要】 本论文以感应电机(IM)和风力机(WT)为研究对象,运用MatLab/SimuLink工具对控制系统进行了建模和仿真。针对感应电机的直接转矩控制(DTC)存在的缺点,利用空间电压矢量调制(SVPWM)和无差拍(Dead-beat)控制改善电压矢量实现和参考电压矢量获取环节,运用自校正速度PI环节完成了直接转矩控制的优化;针对大型风力机的控制方法,分析了风力机控制系统组成结构和控制方法以及对部分部件的载荷影响,建立了控制模型并采用滤波器控制得出了初步结果。论文首先分析和介绍了风能和交流调速系统的发展概况,找出直接转矩控制和风力机载荷控制的发展情况。对感应电机结构及特点进行了分析,继而给出了感应电机在任意坐标系下的数学模型;深入探讨了直接转矩控制在感应电机上应用的理论基础,分析了电压矢量对电磁转矩和电机磁链的控制作用,给出了感应电机直接转矩控制原理结构框图;对于经典直接转矩控制的缺陷和无差拍控制的异步电机应用,提出了一种改进无差拍直接转矩控制策略的方法,磁链环节电压矢量经过简单计算得出,转矩环节电压矢量被有效的分解后由转矩PI控制器和转子转速与定子磁链乘积给出,指出转速与定子磁链乘积是保持电机转速和磁链为给定值的基础;基于梯度下降法的速度PI环节的自校正控制的在线增益调节优化了系统响应和转矩脉动控制。借助MatLab/SimuLink工具,对感应电机直接转矩控制系统各环节、SVPWM和速度PI自校正控制进行了仿真建模,实现了经典直接转矩控制和无差拍直接转矩控制仿真实验,得到了与理论分析一致的仿真实验结果。理论分析和仿真实验结果表明,在不影响动态性能的情况下,提高了系统速度响应、磁链轨迹、磁链和转矩跟踪的控制精度,有效地减小了磁链和转矩脉动,保持了良好的转矩动态响应,速度PI环节的效果明显。为设计基于空间电压矢量调制的感应电机直接转矩控制实际系统提供了有效的方法和工具。然后论文分析了大型风力机控制方法,主要为变速风力机的转矩控制。随着风力机的大型化和柔性化,控制方法在变速风力机运行过程对载荷的影响逐渐引起大家的重视。本文分析了风力机运行过程中的各个子系统的联系,建立了统一的变速风力机的控制模型,以传动系统和塔架的左右振动为主要研究对象。从经典控制方法出发,在最大风能捕获状态下利用滤波器实现转矩控制对传动结构和塔架左右振动的抑制效果。借助MatLab/SimuLink工具,完成了连续系统下的仿真建模,利用信号处理工具箱和控制要求设计了相应的滤波器。理论和仿真结果表明,转矩控制能够起到抑制振动的作用。更多还原

【Abstract】 The paper is subjected to induction motors (IMs) and wind turbines (WTs), implementing their control system models and simulation with Matlab/SimuLink. Aimed at drawbacks of direct torque control (DTC) for induction motors, it is considered that Space Vector Pulse Width Modulation (SVPWM) improve voltage vectors implementation, Dead-beat control strategy for reference voltage vectors and self-tuning PI controller for torque and flux ripple reduction. Then aimed at wind turbine control systems, the analysis of their structure and strategies and their influences on component mechanical loads is emphasized. We have basic simulation results for Control models and filter control theory applying on WTs.Firstly, wind energy and methods for speed control of induction motors is introduced, including DTC and wind turbine torque control typical approaches. Then IMs kinds and applications are presented. IMs dynamic model at any reference frame is obtained. Using the model, basics of DTC principle and IMs are considered. Voltage vectors influences on electronic torque and motors flux are showed. Classic DTC principle’s diagram is gained. To improve classic DTC drawbacks, the paper proposes an improved Dead-beat control strategy. Voltage vectors for torque are decomposed reasonably, while one for flux is implemented simply. Two parts of it are implemented by PI controller and the product of rotor speed and stator flux respectively. The product of motor speed and stator flux magnitude is essential for keeping motor speed and flux constant. Self-tuning PI speed controller reinforced responses deeply as gradient descent optimization to adjust gains automatically online. With Matlab/Simulink tools, it is modeled including every component of IMs DTC, SVPWM and self-tunging PI controller. As the simulation of classic DTC and New dead-beat control is finished, all results obtained prove above. Systems responses such as precision of speed, flux locus, flux or torque tracking and so on is improved. The reduction of torque and flux ripples presents clearly. The paper is good for designing actual IMs DTC application based on SVPWM.Secondly, control strategies for large wind turbine is introduced, most of them are variable speed WTs’torque control. As WTs’height and flexibility increase, studies on control strategies’affects on WTs mechanical loads become more and more important, especially for variable speed. According to the relations among all subsystems of WTs, a unified control model of variable speed WTs has been built including pitch control. The drive-train torsion and tower side-side vibration are main focus. Based on classic control strategy, filters are used for reduction while the rotor are tracking for optimal speed for energy capture. With Matlab/Simulink tools, the continuous model and filter design are completed simply. The theory and simulation results prove that WTs torque control can restrain vibration successfully.更多还原