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Space vector modulation and control of multilevel converters.

机译：空间矢量调制和多级转换器的控制。

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This dissertation is the result of the research and development of a power conditioning system for superconductive magnetic energy storage systems (SMES). The dominant challenge of this research was to develop a power conditioning system that can match slowly varying dc voltages and dc currents on the superconductive magnet side with the ac voltages and ac currents on the utility side. At the same time, the power conditioning system was required to provide a bidirectional power flow to the superconductive magnet.; The focus of this dissertation is a three-level diode-clamped dc/ac converter, which is a principle part of the power conditioning system. Accordingly, this dissertation deals with the space vector modulation (SVM) of three-level converters and introduces a computationally very efficient three-level SVM algorithm that is experimentally verified.; Furthermore, the proposed SVM algorithm is successfully generalized to allow equally efficient, real-time implementation of SVM to dc/ac converters with virtually any number of levels. The most important advantage of the proposed concept is that the number of instructions required to implement the algorithm is almost independent from the number of levels in a multilevel converter.; More on the side of the control of multilevel converters, particular attention in this dissertation is paid to the problem of charge balance in the split dc-link capacitors of three-level neutral-point-clamped converters. It is a known fact that although the charge balance in the neutral point (NP) can be maintained on a line cycle level, a significant third harmonic current flows into the NP for certain loading conditions, causing the neutral-point voltage ripple. The logical consequence of that ripple is the deteriorated quality of the output voltage waveforms as well as the increased voltage stress on the switching devices.; This was the motivation to more carefully explore the loading conditions that cause the imbalance, as well as to study the fundamental limitations of dc-link capacitor charge balancing algorithms. As part of this work, a new model of the neutral-point current in the rotating coordinate frame is developed as a tool for the investigation of theoretical limitations and in order to provide some insight into the problem. Additionally, the low-frequency ripple is quantified and guidelines are offered that can help determine the correct size for the dc-link capacitors.; Because the study of the neutral-point balance identified the loading conditions that (under some possible system constraints) cause an unavoidable neutral-point voltage ripple, a feed-forward type of control method is developed next. The proposed feed-forward algorithm can effectively prevent the neutral-point voltage ripple from creating distortions in the converter output voltage under all loading conditions and without causing additional disturbance in the neutral-point voltage. The feed-forward method is developed for a sine triangle as well as for the SVM type PWM algorithm.; The simulation results that include the full dynamic model of the converter and load system validate the feed-forward approach and prove that the feed-forward algorithm can effectively compensate for the effect of the neutral-point voltage ripple. The simulation results are then experimentally verified.
机译：本文是超导磁储能系统功率调节系统研究与开发的成果。这项研究的主要挑战是开发一种功率调节系统，该系统可以使超导磁体侧的缓慢变化的dc电压和dc电流与公用事业侧的ac电压和ac电流相匹配。同时，功率调节系统需要向超导磁体提供双向功率流。本文的重点是三电平二极管钳位的dc / ac转换器，这是功率调节系统的主要组成部分。因此，本文研究了三电平转换器的空间矢量调制（SVM），并介绍了一种计算效率非常高的三电平SVM算法，该算法经过实验验证。此外，成功地推广了所建议的SVM算法，以实现几乎任何数量级别的SVM到dc / ac转换器的同等高效，实时实施。提出的概念的最重要的优点是，实现算法所需的指令数量几乎与多级转换器中的级别数量无关。在多电平转换器的控制方面，本文特别关注三电平中性点钳位转换器的分离式直流母线电容器中的电荷平衡问题。众所周知的事实是，尽管中性点（NP）的电荷平衡可以维持在线路周期水平，但是对于某些负载条件，大量的三次谐波电流会流入NP，从而引起中性点电压纹波。这种纹波的逻辑后果是输出电压波形的质量下降以及开关器件上的电压应力增加。这是为了更仔细地研究导致不平衡的负载条件，以及研究直流链路电容器电荷平衡算法的基本局限性。作为这项工作的一部分，开发了一种新的旋转坐标系中的中性点电流模型，作为研究理论极限并为问题提供一些见识的工具。另外，对低频纹波进行了量化，并提供了指南，可以帮助确定直流链路电容器的正确尺寸。由于对中性点平衡的研究确定了（在某些可能的系统约束下）导致不可避免的中性点电压纹波的负载条件，因此下一步将开发一种前馈型控制方法。提出的前馈算法可以有效地防止中性点电压纹波在所有负载条件下在转换器输出电压中产生失真，而不会引起中性点电压的额外干扰。前馈方法是针对正弦三角形以及SVM型PWM算法而开发的。包含转换器和负载系统的完整动态模型的仿真结果验证了前馈方法，并证明了前馈算法可以有效补偿中性点电压纹波的影响。然后对仿真结果进行实验验证。

著录项

  • 作者

    Celanovic, Nikola.;

  • 作者单位

    Virginia Polytechnic Institute and State University.;

  • 授予单位 Virginia Polytechnic Institute and State University.;
  • 学科 Engineering Electronics and Electrical.
  • 学位 Ph.D.
  • 年度 2000
  • 页码 159 p.
  • 总页数 159
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 无线电电子学、电信技术;
  • 关键词

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