【作者】 李骏；

【导师】 彭方正； 钱照明；

【作者基本信息】 浙江大学 ， 电力电子与电力传动， 2006， 硕士

【摘要】 近年来,多电平变流器作为高压大功率变流技术的一个研究热点,在中高压变频调速、柔性交流输电系统等领域得到了广泛应用。 本文首先在第一章中对高压大功率变流技术研究现状进行了回顾,并对与多电平变流技术紧密相关的电力电子功率器件、数字控制技术的发展情况做了介绍;第二章对目前多电平变流器的电路拓扑和控制策略进行了总结,并将各自的优缺点和应用场合加以分析、比较。 第三章详细讨论了通用DSP数字控制平台的开发方案,本文对三电平逆变器系统的数字控制实现均基于此控制平台完成。 第四章针对二极管箝位(NPC)三电平逆变器,详细研究了载波PWM控制策略。分析和比较了不同载波PWM方法的优缺点,同时讨论了中点电位不平衡的原因及控制中点电位平衡的方法。基于分析的结果,提出了一种新的载波PWM控制方法,并详细讨论了这种方法的原理,仿真及DSP数字实现。该方法根据控制自由度的概念,通过对载波以及调制波控制自由度的合理组合,具有以下优点:1)在低调制度下,输出线电压的谐波特性(THD)远远优于传统的载波PWM控制方法,在高调制度下,输出线电压的谐波特性(THD)与传统的载波PWM控制方法相当;2)提高了直流电压利用率;3)很好的实现了中点电位平衡。仿真和实验结果验证了这种方法的有效性。 第五章针对二极管箝位(NPC)三电平逆变器,详细研究了SVPWM控制策略。分析了三电平SVPWM控制方法的原理,并讨论了一种新的开关序列排序方式,这种排序方式使得参考电压矢量在旋转过程中,开关状态切换严格符合开关序列排序原则。此外,讨论了基本电压矢量对中点电位的影响,并通过检测直流母线侧电压、负载电流,利用时间控制常数来平衡中点电位,讨论了仿真与DSP数字实现的方法。仿真和实验结果验证了这种方法的正确性。 最后对本文的研究工作进行了总结,并对将来的研究方向进行了展望。更多还原

【Abstract】 During recent years, multilevel converters, which have drawn tremendous interests as a high voltage high power conversion technology, have been widely used in medium to high voltage adjustable speed drives and Flexible AC Transmission Systems (FACTS) etc.The status quo of the development of the high voltage high power conversion technology is summarized in chapter 1 and two interrelating technology developments - power switching devices and digital control technology, are introduced. In chapter 2, the topologies of multilevel converters and control schemes are summarized. Moreover, their advantages, disadvantages and application fields are also analyzed and compared.In chapter 3, the development of a universal DSP digital control platform is discussed, which is the base of implementing digital control for the developed three-level NPC inverter in our lab.In chapter 4, the principle of carrier-based PWM control schemes for the three-level NPC inverter is discussed. The advantages and disadvantages of different carrier-based PWM methods are analyzed and compared. The problem of neutral-point voltage unbalance and the methods to solve this problem are discussed. A novel carrier-based PWM method utilizing control freedom degree (CFD) is proposed. The principle, simulation and DSP implementation of the method are discussed in detail. Compared with the traditional carrier-based PWM method, the novel method shows better harmonic characteristic under low modulation indices, while under a high modulation index, the harmonic characteristic of the novel method is almost the same as that of the traditional method. It also shows that the new PWM method has a higher dc-link voltage utilization ratio and better neutral-point balance capability. Simulation and experimental results verify the effectiveness of the proposed method.In chapter 5, the principle of SVPWM control scheme for the three-level NPC inverter is discussed. An optimized switching sequence is discussed. Using thissequence, the change of switching status firmly conforms to the principles of switching sequence assignment in SVPWM during the process of voltage vector rotation. The influence of the voltage vectors on neutral-point voltage is discussed. Using the information of dc-link voltages and load currents, the neutral-point voltage is balanced by introducing a time-control coefficient. The simulation and DSP implementation of SVPWM are discussed. The validity of the proposed method is verified by simulation and experimental results.In the last chapter, the research work of this thesis is summarized and the future research tasks are given.更多还原