【作者】 刘述喜；

【导师】 王明渝；

【作者基本信息】 重庆大学 ， 电气工程， 2010， 博士

【摘要】 与两电平逆变器相比,多电平逆变器具有输出电压更加接近正弦波、谐波含量少和输出电压跳变小等特点,非常适合于高压大容量交流变频调速系统。然而,作为一种新型电能变换技术,基于多电平逆变器供电的感应电动机的高性能调速控制在理论和实践中依然存在着大量值得研究和探讨的问题。三电平逆变器作为多电平逆变器的典型代表,具有拓扑结构相对简单、所用器件相对较少,可靠性高等特点。因此对以三电平拓扑结构为基础构成的高性能交流电机调速系统进行深入研究具有实际意义。本文以二极管箝位式三电平逆变器带电机负载为对象,对多电平逆变器的建模、PWM控制技术、直接转矩控制技术进行了全面的理论分析,并进行了仿真和实验研究。论文首先分析了多电平逆变器拓扑结构的发展和研究现状,讨论了交流调速的发展和直接转矩控制技术的特点,指出本文选题的目的和意义。详细论述了二极管箝位型三电平逆变器的拓扑结构和工作原理,在α、β静止坐标系下,建立了三电平逆变器供电的感应电动机为负载的统一数学模型,在此基础上建立了仿真系统,为全面分析三电平逆变器供电的、采用各种控制策略的电机调速系统奠定了基础。详细分析了三电平逆变器的脉宽调制模式的工作原理,包括载波形式的PWM控制技术和空间矢量脉宽调制技术,重点分析了空间电压矢量调制技术的实现方法。讨论了空间电压矢量调制模式下的中点电压波动的原因,建立了平均中点电流模型,为中点电压平衡控制提供了理论依据。对于上述各种PWM方法,均建立了仿真模型,仿真结果验证了其理论分析的正确性和方法的有效性。深入分析了三相感应电动机直接转矩控制的基本原理,探讨了一种改进型的基于电机数学模型直接推导的定子磁链估算方法。讨论了三电平逆变器直接转矩控制中的主要问题及其矢量选择方案。详细介绍了传统的三电平基于滞环调节的直接转矩控制系统方案,有单一矢量法和固定矢量合成法,但两者转矩脉动较大。为此,分析了基于数学模型的转矩和磁链的预测控制,提出一种基于预测控制的快速空间矢量调制方式的三电平直接转矩控制方法,转矩脉动减少,且有利于数字化实现。多电平电压型逆变器空间电压矢量多,采用传统的直接转矩控制,矢量选择比较复杂,且所选择的电压矢量作用时间通常为一个采样周期,因而转矩脉动相对较大。为此,提出了一种三电平模糊直接转矩控制策略,引入模糊逻辑后,将转矩和磁链误差进行分级,根据误差级别的大小选择需要的电压矢量。该方法既有效地抑制了磁链和转矩的脉动,又很好地保留和继承了传统直接转矩控制鲁棒性强的优点。以TMS320F2812 DSP为控制核心研制了一套二极管箝位式三电平逆变器实验平台。在此平台上完成了三电平SVPWM开环控制、基于快速空间矢量调制算法的三电平直接转矩预测控制、基于模糊逻辑的三电平逆变器直接转矩控制等相关实验研究,并给出了主要的实验结果和相应的结论。实验结果论证了本文理论分析的正确性和控制方法的有效性。更多还原

【Abstract】 Compared with two-level inverters, multilevel inverters have the following characteristics such as output voltage more close to sinusoidal wave, small harmonics and dv/dt. It’s suitable for high-voltage high-power variable speed system of AC motors. However, as a new energy converting technology, the control of machine based on multilevel inverters for high performance has still some problems that are worth to be researched and probed in theory and practices.As one of typical representatives of multilevel inverters, three-level inverter is of the simple topology, few devices and high reliability. The research has the actual significance on high performance AC variable speed system based on three-level inverter. Taking the diode clamped three-level inverter as the objective, and induction machine as the load, this thesis gives the theoretical study and analysis of the multilevel with induction machine in detail. The inverters modeling, the control technology of PWM, and direct torque control (DTC) technologies are studied. The simulation and experiment researches are performed.The thesis analyzes the development and research status of multi-level inverters firstly. Also the development of AC variable speed and the characteristic of direct torque control are discussed. Then the aim and significance for the research are demonstrated. The topology and operation principles of diode clamped three-level inverter are discussed, the mathematics model is built under theα,βtwo phase stationary coordinates, and based on the mathematics model the simulation system is built. All these lay the foundation of researching all kinds of control strategy of the induction machine supplied with three-level inverter.The operation principle of three-level inverter is analyzed for the pulse width modulation (PWM), including carrier-based PWM and space vector PWM (SVPWM). The realization method of SVPWM is mainly analyzed. The reason is also analyzed for the neutral-point voltage fluctuating. Neutral-point voltage model is built which provides the evidence to the control of neutral-point potential. For the above PWM methods, the simulation models are built. The simulation results verified the validity and feasibility of the theory analysis.This thesis discussed the principle of direct torque control of induction machine. An improved method of u-i integrator of stator flux-linkage observer is discussed. The problems of DTC in three-level inverters and the scheme of selecting vectors are analyzed. Then, conventional DTC based on hysteresis band including single vector and synthesized vectors are analyzed in detail. However, the torque ripple is large. Therefore, the precontrol of torque and flux-linkage is introduced, a new DTC algorithm based on precontrol of torque and fast space vector PWM is presented. The torque ripple is lower. It’s easy for digital implementation.Due to the large number of vectors for multilevel inverter, vector selecting is complicated when conventional DTC is applied to three-level inverter. The selected vector acts on a sample period. This will result into torque fluctuation. Therefore, a fuzzy DTC is presented. After introducing fuzzy logic, the error of torque and flux-linkage is divided into different grades. According to the grades, the desired vector is selected. This method not only reduces the ripple of torque and flux-linkage, but also keeps and inherits the advantage of conventional direct torque control. It has desired robust.Taking the DSP TMS320F2812 as the controller, the experiment platform for the diode clamped three-level inverter is established. The relative experiment researches were completed for the control of SVPWM and DTC control of torque precontrol and fuzzy logic. The main results and conclusions are given. The experimental results verified the theoretical analysis and the control strategies proposed in this thesis.更多还原