电网不平衡时模块化多电平换流器的控制研究

发布时间：2018-01-16 07:02

本文关键词：电网不平衡时模块化多电平换流器的控制研究　出处：《合肥工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：近年来,随着电力电子技术的发展,高压大功率电力电子设备被广泛应用于电力系统中的柔性交流输电、高压直流输电、静止无功补偿等场合,其能够有效地提高系统电能质量和输配电系统效率。随着新能源的快速发展,柔性直流输电技术将会在我国未来电网的发展中起到十分关键的作用。在柔性直流输电工程中,多电平换流器由于其输出波形谐波含量低、功率器件电压应力低等优点,被越来越多地应用于高压大功率领域中。在众多多电平拓扑中,模块化多电平拓扑(MMC)由于具有模块化易扩展、良好的冗余特性、输出谐波低、功率器件开关频率低等优点,使之成为近年来的研究热点。本文首先对MMC的拓扑结构及工作原理进行了分析,分析推导了MMC正常工作时上下桥臂电压,输出交流电压及上下桥臂电流,环流和交流输出电流之间的关系。对目前常用的调制策略、电容电压平衡技术做了全面的阐述,详细分析了载波层叠PWM调制、载波移相PWM调制和NLM调制等MMC调制策略,并构造了桥臂能量和控制器及桥臂能量差控制器来控制子模块电容电压的平衡。本文接着研究了电网不平衡条件下MMC的控制策略。对三相MMC的一相建立了等效电路模型并进行了数学分析,分析了电网不平衡时MMC的工作特性,然后研究了电网不平衡时MMC的控制策略,主要对比分析了三种控制方法：基于dq同步旋转坐标系的控制方法、基于PR调节器的控制方法、基于准PR调节器的控制方法,并搭建了MATLAB/Simulink仿真模型进行验证。最后设计并搭建了基于分层思想的三相MMC实验平台,具体包括：MMC硬件系统设计和软件控制系统设计。其中硬件系统设计包括主电路设计及主控制器(DSP)、桥臂控制器(FPGA)、子模块控制器(CPLD)的设计,DSP、FPGA、 CPLD构成了MMC的三层控制系统。软件控制系统设计包括上述三层控制器的软件设计。在此实验平台的基础上,进行了基于直接调制法和子模块电容电压排序法的开环实验,实验结果表明了方案的可行性。
[Abstract]:In recent years, with the development of power electronics technology, high-voltage high-power power electronic equipment is widely used in the power system of flexible AC transmission, high-voltage direct current transmission, static reactive power compensation and other occasions. It can effectively improve the system power quality and transmission and distribution system efficiency. With the rapid development of new energy. Flexible direct current transmission technology will play a very important role in the future development of power grid in China. In the flexible direct current transmission project, the multilevel converter has low harmonic content due to its output waveform. Power devices with low voltage stress are more and more used in high-voltage and high-power fields. Among many multilevel topologies, modularized multilevel topology (MMCs) is easy to expand because of its modularization. Good redundancy, low output harmonics and low switching frequency of power devices make it a hot research topic in recent years. Firstly, the topology and working principle of MMC are analyzed in this paper. The relationship between upper and lower arm voltage, output AC voltage, upper and lower arm current, circulation and AC output current during normal operation of MMC is analyzed and deduced. The capacitive voltage balance technology is described in detail, and the strategies of carrier stacked PWM modulation, carrier phase-shifted PWM modulation and NLM modulation are analyzed in detail. The bridge arm energy and controller and the bridge arm energy difference controller are constructed to control the capacitor voltage balance of the submodule. Then, the control strategy of MMC under the unbalanced power grid is studied. The one-phase construction of the three-phase MMC is established. The equivalent circuit model and mathematical analysis are carried out. This paper analyzes the working characteristics of MMC when the power network is unbalanced, and then studies the control strategy of MMC when the power network is unbalanced. Three control methods are compared and analyzed: the control method based on DQ synchronous rotating coordinate system. The control method based on PR regulator and the control method based on quasi-PR regulator. Finally, a three-phase MMC experimental platform based on layered theory is designed and built. The hardware system design includes the main circuit design and the main controller DSPG, the bridge arm controller and the FPGA. the hardware system design includes the hardware system design and the software control system design of the MMC, including the main circuit design and the main controller DSPG, the bridge arm controller. The design of submodule controller (CPLD) is based on DSP FPGA. CPLD is the three-layer control system of MMC. The software control system design includes the software design of the three-layer controller mentioned above. On the basis of this experimental platform. The open loop experiment based on direct modulation method and capacitor voltage sort method of sub-module is carried out. The experimental results show the feasibility of the scheme.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM46

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