基于PWM控制三相直流变换器的研究

发布时间：2018-10-09 14:00

【摘要】：随着分布式发电技术的发展和直流用电设备的增多，直流微网成为近年来的研究热点之一。单向和双向直流变换器占据了直流微网中功率变换单元的大部分，因而研究高效率、高功率密度、高可靠性和低成本的直流变换器对提高直流微网性能具有重要的意义。随着用电设备功率等级的提高，传统的单相直流变换器面临着器件电流应力较高的问题，而采用三相直流变换器成为解决该问题的主要途径之一。本文主要研究内容即是直流微网中单向和双向运行的三相直流变换器。首先，本文提出了一种通过传统不对称PWM控制，采用Y-Δ连接变压器的三倍流整流三相全桥直流变换器。该变换器应用于直流微网360V高压母线向48V低压母线传递能量的场合。本文分析了该变换器的工作原理，讨论了桥臂上管和下管实现ZVS的差异，并从磁性元件和功率器件的应力、实现软开关的负载范围等角度与采用Δ-Δ型变压器的该变换器、移相全桥变换器作了对比，结果表明本文提出的变换器能降低开关器件的电流应力、且具有更宽范围的ZVS负载范围。其次，本文针对该三相直流变换器，提出了一种新型PWM控制方式，使得变换器能够双向运行，有效占空比范围得以拓宽，且可以提升1倍的电压变比，因而可以减小变压器匝比以降低漏感，特别适合于直流微网中高压直流母线与储能单元之间的高电压变比、能量双向流动的功率变换场合。新型PWM控制方式下该变换器具有两种工作模式，本文从器件应力、损耗分析等方面进行了对比，，给出了该变换器的设计准则。最后，针对本文提出的两种控制方式下的三相直流变换器，分别设计了一台2kW的原理样机进行实验验证。实验结果表明，该变换器采用传统PWM方式控制时，可以实现所有开关管的ZVS，输出电流纹波脉动大大减小；采用新型PWM方式控制时，该变换器可以提高1倍电压变比，能量可以双向流动。
[Abstract]:With the development of distributed generation technology and the increase of DC power equipment, DC microgrid has become one of the research hotspots in recent years. Unidirectional and bidirectional DC / DC converters account for the majority of power conversion units in DC microgrids, so it is important to study high efficiency, high power density, high reliability and low cost DC / DC converters for improving DC microgrid performance. With the improvement of power level of electrical equipment, the traditional single-phase DC / DC converter is faced with the problem of high current stress of the device, and the adoption of three-phase DC / DC converter is one of the main ways to solve this problem. The main research content of this paper is three-phase DC-DC converter in DC micro-grid running in one-way and two-way. Firstly, this paper presents a three-phase full-bridge DC / DC converter with triple-current rectifier using Y- 螖 connected transformer through traditional asymmetric PWM control. The converter is used to transfer energy from 360V high voltage bus to 48V low voltage bus. In this paper, the working principle of the converter is analyzed, the difference between the upper tube of the bridge arm and the lower tube in realizing ZVS is discussed. From the angle of the stress of the magnetic element and power device, the load range of the soft switch and the converter using 螖-螖 type transformer, the converter is discussed. The results show that the proposed converter can reduce the current stress of switching devices and has a wider range of ZVS loads. Secondly, a new type of PWM control method is proposed for the three-phase DC / DC converter, which enables the converter to operate in both directions, widen the effective duty cycle range, and increase the voltage change ratio by twice. Therefore, the turn ratio of transformer can be reduced to reduce leakage inductance, which is especially suitable for the high voltage ratio between HVDC bus and energy storage unit in DC microgrid, and for the power conversion of bidirectional energy flow. The converter has two operating modes under the new PWM control mode. In this paper, the design criteria of the converter are compared in terms of device stress and loss analysis. Finally, an experimental prototype of 2kW is designed for the three phase DC / DC converter with two control modes proposed in this paper. The experimental results show that the ripple of the ZVS, output current can be greatly reduced when the converter is controlled by traditional PWM mode, and the voltage variation ratio of the converter can be increased by 1 times when the converter is controlled by a new PWM mode. Energy can flow in both directions.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM46

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