模块化多电平变换器控制策略研究

发布时间：2018-01-17 23:00

本文关键词：模块化多电平变换器控制策略研究　出处：《中国矿业大学》2015年硕士论文　论文类型：学位论文

【摘要】：模块化多电平变换器(Modular Multilevel Converter,MMC)因其具有公共直流母线的模块化拓扑结构的特点而被广泛应用于高压直流输电、电能质量治理以及电气传动等领域,因此对MMC及其控制策略的研究有着理论和工程意义。本文主要对MMC的相关控制策略进行研究,包括调制策略、子模块电容电压控制策略、内部环流抑制策略,本文还设计研制了一台MMC五电平的实验样机,并对本文采用的控制策略进行实验验证。介绍了MMC拓扑结构与常见的子模块结构,建立了MMC数学模型,研究了MMC运行控制规律;论述了适用于MMC的调制策略,分析了各种载波调制以及最近电平逼近调制的实现方法;重点研究和分析了输出相电压分别为五电平、九电平时载波移相调制的区别以及脉冲移相代替载波移相的可行性。从桥臂能量脉动变化规律入手,分析子模块电容电压波动规律,推导电容选取的原则;结合MMC拓扑结构和工作原理,研究了一种利用自身直流母线对悬浮电容预充电的方法;对传统排序法进行改进,采用一种基于双保持因子及排序电压上下限的优化排序法,在保证各子模块电容电压均衡的前提下有效降低开关器件的开关频率。分析了环流形成机理、环流的性质与作用;从桥臂功率脉动的角度出发分析了影响二倍频环流幅值的因素,推导了桥臂电感选取公式;研究了基于模块变动选择法的环流抑制策略,并将其与优化排序算法相结合,达到抑制环流、均衡电容电压、降低开关频率的目的。从主回路和控制系统两个角度研制了一台五电平MMC实验样机,主回路设计包括主要器件参数设计与选型,控制系统设计包括控制系统架构设计和程序设计;在所研制的MMC实验样机上对基于模块变动选择算法和优化排序算法的控制策略进行实验验证,实验结果表明该控制策略可以均衡子模块电容电压、降低开关频率、有效减小环流幅值,验证了上述控制策略的可行性与正确性。
[Abstract]:Modular multilevel converter with Modular Multilevel Converter. MMC) is widely used in HVDC transmission, power quality control and electrical transmission due to its modular topology of common DC bus. Therefore, the study of MMC and its control strategy has theoretical and engineering significance. This paper mainly studies the related control strategies of MMC, including modulation strategy, submodule capacitive voltage control strategy. In this paper, an experimental prototype of MMC five-level is designed and developed, and the control strategy used in this paper is verified experimentally. The topology of MMC and the common sub-module structure are introduced. The mathematical model of MMC is established and the control law of MMC is studied. The modulation strategies suitable for MMC are discussed, and the realization methods of various carrier modulation and nearest level approach modulation are analyzed. The emphasis is put on the study and analysis of the difference of the output phase voltage being five levels, the difference of the nine-electric carrier phase shift modulation and the feasibility of the pulse phase shifting instead of the carrier phase shift, starting with the variation law of the bridge arm energy pulsation. The rule of capacitance voltage fluctuation of submodule is analyzed, and the principle of capacitance selection is deduced. Based on the topology and working principle of MMC, a method of precharging levitation capacitor using DC bus is studied. The traditional sorting method is improved and an optimal sorting method based on the double hold factor and the upper and lower bound of the sort voltage is adopted. The switching frequency of the switch device is reduced effectively on the premise of ensuring the capacitor voltage equalization of each sub-module. The forming mechanism of the circulation and the nature and function of the circulation are analyzed. From the angle of the power pulsation of the bridge arm, the factors affecting the amplitude of the second harmonic circulation are analyzed, and the formula for selecting the inductance of the bridge arm is derived. The circulation suppression strategy based on modular variable selection method is studied and combined with the optimal sorting algorithm to suppress the circulation and equalize the capacitance voltage. In order to reduce the switching frequency, a five-level MMC experimental prototype is developed from the view of main circuit and control system. The main circuit design includes the design and selection of main device parameters. Control system design includes control system architecture design and program design. The experimental results show that the control strategy based on modular variable selection algorithm and optimal sorting algorithm can equalize the capacitance voltage of the sub-module on the developed MMC experimental prototype. The feasibility and correctness of the control strategy are verified by reducing the switching frequency and effectively reducing the circulation amplitude.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM46

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