模块化多电平逆变器控制策略研究

发布时间：2018-04-28 09:28

  本文选题：模块化多电平逆变器 + 电容电压平衡控制　； 参考：《中国矿业大学》2014年硕士论文

【摘要】：近年来，电力电子技术在高压大功率领域的应用日益广泛，在高压功率开关器件技术没有本质突破的前提下，利用中压功率器件的多电平逆变器是解决高压大功率变换的最好选择。同时，随着新能源技术及轻型直流输电系统的发展，一种新型电压源型多电平逆变器拓扑结构：模块化多电平逆变器（ModularMultilevel Converter, MMC）因其具有模块化程度高、易于拓展，输出电压谐波特性好，等效开关频率高等优点而受到日益广泛的关注。目前，国内外针对MMC的学术研究相对较少，亟待对其进行深入研究。 本文详细分析了模块化多电平逆变器的拓扑及其工作原理，建立了MMC的数学模型，为逆变器的控制策略分析奠定了基础。在模块化多电平逆变器中，直流母线提供的电流必须通过子模块的悬浮电容输出至负载，因此电容电压会出现一定的波动。大量悬浮电容的电压平衡控制是保证系统稳定可靠工作的前提条件，，本文从逆变器桥臂的功率脉动与能量脉动的角度对影响子模块电容电压波动的因素进行了深入分析，为本文电压平衡控制策略的提出提供了理论依据。 为解决传统载波层叠PWM技术中MMC子模块开关频率不一致的问题，本文将循环虚拟映射的概念应用于模块化多电平逆变器，在载波层叠PWM调制技术中建立虚拟子模块和实际子模块之间的无差别循环映射关系；在此基础上，本文提出了基于载波层叠PWM技术的选择性循环虚拟映射（Selective Virtual LoopMapping, SVLM）电压平衡控制方法，该方法不需要将子模块按照电压值大小排序，使其适用于模块化多电平逆变器子模块数目众多的场合，也不需要向调制波上叠加额外的控制分量，谐波性能好，并且该方法具有很强的动态调节能力。仿真结果显示，该方法能够很好地平衡能量在MMC的子模块电容之间的分配，有效地平衡电容电压及抑制环流，整个系统具有良好的动静态特性。 在五电平模块化多电平变换器的实验平台上对本文提出的电压平衡控制方法进行了实验验证，为MMC的推广应用提供了实验依据。
[Abstract]:In recent years, power electronics technology has been widely used in the field of high voltage and high power. Multilevel inverter with medium-voltage power device is the best choice to solve high-voltage and high-power conversion. At the same time, with the development of new energy technology and light DC transmission system, a new type of voltage source multilevel inverter topology: modular multilevel inverter (MMCT) is easy to expand because of its high modularization degree. More and more attention has been paid to the advantages of good harmonic characteristics of output voltage and high equivalent switching frequency. At present, there are relatively few academic researches on MMC at home and abroad. In this paper, the topology and working principle of the modular multilevel inverter are analyzed in detail, and the mathematical model of MMC is established, which lays a foundation for the analysis of the control strategy of the inverter. In the modularized multilevel inverter, the current provided by DC bus must be output to the load through the suspension capacitance of the submodule, so the capacitance voltage will fluctuate to a certain extent. Voltage balance control of a large number of suspended capacitors is a prerequisite to ensure the stability and reliability of the system. In this paper, the factors affecting the voltage fluctuation of submodules are deeply analyzed from the angle of power pulsation and energy pulsation of the bridge arm of the inverter. It provides a theoretical basis for the voltage balance control strategy in this paper. In order to solve the problem of inconsistent switching frequency of MMC submodule in traditional carrier stacked PWM technology, the concept of cyclic virtual mapping is applied to modularized multilevel inverter in this paper. In the carrier stacked PWM modulation technology, the non-differential cyclic mapping relationship between the virtual submodule and the actual sub-module is established, and on this basis, In this paper, a selective Virtual Loop Mapping (SVLM) voltage balance control method based on carrier stacked PWM technology is proposed. The method is suitable for the multi-level inverter with a large number of modules, and it does not need to add additional control components to the modulation wave. The harmonic performance is good, and the method has a strong dynamic adjustment ability. The simulation results show that this method can balance the energy distribution among the submodule capacitors of MMC effectively balance the capacitance voltage and suppress the circulation. The whole system has good dynamic and static characteristics. The voltage balance control method proposed in this paper is experimentally verified on the experimental platform of the five-level modular multilevel converter, which provides the experimental basis for the popularization and application of MMC.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM464

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本文编号：1814706