【作者】 丁凯；

【导师】 邹云屏；

【作者基本信息】 华中科技大学 ， 电气工程， 2004， 博士

【摘要】 近年来,在高压大功率应用领域多电平功率变换技术得到了广泛的关注,成为电力电子领域中学者研究的热点。大量新型的电路拓扑和相应调制策略的产生,使多电平技术得到了飞速的发展。本文在对传统多电平逆变器拓扑进行分析的基础上,重点对混合多电平逆变器拓扑及其相关调制方法进行研究。 本文对多电平逆变器的主电路拓扑结构如二极管钳位多电平逆变器、飞跃电容多电平逆变器、级联多电平逆变器以及广义多电平逆变器等进行概述。并对常见的几种多电平调制方法如多电平消谐波 PWM 方法、空间矢量方法、优化阶梯波宽度法、相移 SPWM方法进行了分析综述。 本文首次对混合多电平拓扑及混合调制方法的概念进行了定义。对定义范围内的一些混合拓扑结构的发展情况进行了描述,研究了不同混合拓扑及相关调制方法,并对这些多电平拓扑存在的一些相关问题进行了分析。 在单相二极管钳位 5 电平逆变器的基础上,本文分析研究了基于单相二极管钳位 5电平逆变器的一种级联型拓扑结构,这种拓扑结构的思想是将多个单相二极管钳位 5 电平逆变单元串接起来,其输出的电压是通过合成每个二极管钳位逆变器的输出电压而形成的。在这种拓扑结构中由于每个功率单元采用的是二极管钳位 5 电平逆变器,那么在输出相同等级电压时所需的功率单元个数比传统级联型要少很多。 首次提出了一种新型的混合二极管钳位级联多电平逆变器。本文在对传统的级联多电平,传统混合级联多电平以及二级管钳位级联逆变器研究的基础上提出了一种新型混合二极管钳位级联多电平逆变器。新型逆变器是将具有不同直流母线电压的多个二极管钳位多电平逆变器进行级联,输出电压是将这些逆变器的输出电压进行相加而合成的。根据新型逆变器的特点,提出了一种适用于此拓扑的新型混合调制策略。本文对两单元混合级联的具体示例进行了详细分析,并说明这种新型的拓扑不存在高压模块输出过多基波电压的情况。文中将拓扑结构中混合级联的模块个数推广到了 N,并进行了讨论。 为了进一步简化单相二极管钳位多电平拓扑,本文对一种新型单相不对称 5 电平逆变器进行了研究,这种新型逆变器是通过将半桥二极管钳位逆变器和传统两电平半桥逆变器共享同一直流母线而获得的。针对这种新型的拓扑结构,本文分析了一种方波合成与单极性三角载波 PWM 技术相结合的调制方法,在这种调制方法下,新型逆变器允许开关速度较快的器件和耐压值较高的器件工作在一起。文中将这种逆变器与其它五种单相 5 电平逆变器进行了分析比较,并对新型的单相 5 电平不对称逆变电路进行了实验验证。 首次提出了一种新型混合不对称级联型逆变器。本文根据单相不对称 5 电平逆变器 I<WP=6>华 中 科 技 大 学 博 士 学 位 论 文可以用较少的器件输出较多电平的特点,研究了将单相不对称 5 电平逆变器与传统全桥逆变器进行级联、多个单相不对称 5 电平逆变器自身进行级联的一些新型混合不对称级联型拓扑。并针对此类拓扑结构的特点,分别提出了两种新型的混合不对称调制方法。文中对新型拓扑进行了实验验证。在对本文提出的多种混合调制方法进行归纳总结的基础上,首次提出了适用于多电平逆变器的新型混合调制技术及其分析方法。这种新型混合调制技术是以传统级联型逆变器为研究基础,适用于级联型或者其它一些类型的多电平逆变器。新型混合调制技术的基本思想是在级联多电平逆变器中用最少或者较少的单元来输出高频 PWM 波形,其余单元输出低频阶梯波,从而使逆变器的合成输出电压达到全 PWM 调制。本文首次利用幅值条件和电平条件对这种新型调制策略进行了理论分析和推导,并以文中所研究的内容为实例进行分析,给出了应用这种调制技术的一般方法和设计步骤。更多还原

【Abstract】 In recent years, multilevel converters have presented an important development to reachhigher power with increasing voltage levels. The research on the multilevel inverter has beenreceiving wide attention, and becoming hot point in power electronics. Based on traditionalmultilevel topologies, this paper focus on topologies and modulation methods for hybridmultilevel inverters, and a lot of innovation are made. Hybrid multilevel topologies and hybrid modulation methods are firstly defined in thisdissertation. According to the range of the definition, several hybrid topologies and controlmethods are given, analysis of problems for the hybrid topologies are carried out. . Diode-clamp cascaded multilevel inverter based on single-phase 5-level diode-clampinverter is presented. The multilevel waveform is synthesized by adding of each converteroutput voltage. A novel hybrid diode-clamp cascade multilevel converter is firstly put forward. Thenew concept of the converter is based on connection of multiple diode-clamp convertermodules with different dc bus voltages. A new hybrid PWM method is also proposed. Adetailed example is given, and a general discussion of N-cell HDCMC is presented.Experiment validation is also carried out. An asymmetric 5-level inverter is developed in which a half-bridge diode-clampinverter and a conventional half-bridge inverter are connected to a common split-capacitorpower supply. Analysis of a control technique for the inverter, which incorporatessquare-wave synthesis in conjunction with unipolar triangle carried-based PWM method, isincluded. Under the proposed control technique, the new configuration permits faster devicesand high voltage devices operating in synergism. Comparison with five other single-phase5-level inverters is presented in this paper. In order to verify the proposed approach, asingle-phase 5-level asymmetric inverter was constructed and experimental results areprovided. Novel hybrid asymmetric inverters are firstly proposed. Based on asymmetric 5-levelinverter, this paper proposed a new hybrid asymmetric 9-level inverter in which anasymmetric 5-level inverter and an H-bridge inverter with equal dc bus voltage are seriesconnected to form an inverter phase leg. This paper also presents a hybrid asymmetric cascadeinverter based on the connection of multiple asymmetric 5-level inverters. New hybridasymmetric control techniques for the two inverters are proposed. Output spectral analysis iscarried out, experiment validations are provided. III<WP=8>华 中 科 技 大 学 博 士 学 位 论 文 On the base of many hybrid modulation methods proposed in this paper, a generalizedhybrid modulation method and analytical method are firstly given. The derivation of hybridmodulation technique is based on traditional cascaded inverter. The novel concept of themodulation method is to output full PWM waveform by using the least or fewer modules tooutput high frequency PWM waveform, while other modules only need to output lowfrequency stepped-waveforms. Theoretical analysis and derivation based on amplitudecondition and level condition are firstly given. Design procedure of the methods and examplesare presented.更多还原