【作者】 张兵；

【导师】 王政；

【作者基本信息】 东南大学 ， 电气工程， 2015， 硕士

【摘要】 本文首先重点介绍了三电平空间矢量调制策略(SVPWM)的实现步骤,仿真与实验结果表明：相对于两电平,三电平SVPWM调制策略采用了更复杂的空间矢量图,在单个区域内拥有了更多可用于合成的矢量,因此进一步细化了矢量的合成。由于流入直流侧母线电容中点的电流不为0,箝位型三电平逆变器存在着固有的母线电容电压波动问题或所谓的中点波动问题。为了深入研究母线电容电压的波动机理,论文分别建立了二极管箝位型三电平逆变器的开关模型、平均模型和同步旋转坐标系下的等效电路模型,并通过引入等效并联导纳和等效注入电流源概念得出了母线电容电压的稳态波动的解析表达式,随后解释了其暂态调节过程,以及叠加零序分量、带平衡因子的空间矢量调制策略及为母线电容并联均压电阻方法在控制母线电容电压波动方面的联系。不同于DNPC型结构,有源箝位(ANPC)型三电平拓扑结构中增加的两只箝位IGBT将传统0电平的输出电流路径扩充至4种,换流方式由原来的8种扩展至32种,这些新的换流方式可以通过控制箝位IGBT来加以选择,这为调节功率器件的损耗分布提供了控制自由度。本文从电流路径出发详细分析了有源箝位型三电平变换器中不同换流过程对器件损耗的影响,并将其划分为无源换流模式和有源换流模式两类,并建立了两种换流模式下各器件的导通损耗、开关损耗模型以及各器件间的导通损耗方差、开关损耗方差模型。结果表明,不同换流模式会对各器件的损耗以及各器件间的损耗方差产生影响,但是在变换器总的导通损耗、开关损耗、输出电压电流方面,它们却是一致的。在建立的模型的基础上,本文提出了一种基于损耗方差比较的损耗均衡策略。为了提高ANPC型三电平逆变系统的可靠性,本文分析了不同类型故障对逆变器输出电压及母线电容电压波动的影响,针对不同故障类型提出了相应的容错控制方案。针对故障重构后系统存在的母线电容电压波动问题建立了等效电路模型,给出了相应的波动控制方案,并提供了仿真和实验验证。更多还原

【Abstract】 An introduction of the procedure to realize space vector pulse width modulation (SVPWM) strategy is studied in this thesis firstly, results from the simulation and experiments has shown that:The SVPWM strategy has adopted an more complicated space vector diagram, and has more alternative vectors in one single area comparing with the two level inverter, thus refining the vector composing process.Because of the fact that the current flowing through the neutral point of the dc bus capacitor is not zero, neutral point clamped three level inverter has an intrinsic fluctuation problem in the bus capacitor voltage or the neutral point. In order to get an insight of the mechanism in bus capacitor voltage fluctuation, switching model, averaged model and equivalent circuit in synchronous rotating coordinate system were built in this thesis. Conceptions of equivalent parallel admittance and equivalent current source were introduced to find the mathematical expression of the bus capacitor voltage fluctuation. An explanation to the transient adjusting process, and the relationship of different bus capacitor voltage balance strategy, e.g. zero sequence injection, SVPWM with balance factor and parallel resistors, was given afterwards.Different from the DNPC structure, the two additional clamping IGBT in the active neutral point clamped (ANPC) topology extend the output current path of traditional O level to 4 types, and commutation types to 32 from 8. Because of the fact that these new commutation types were able to be chosen by control the clamping IGBTs, ANPC provides a possibility to control the distribution of power loss among the power devices. Beginning with descriptions of different current path, the effect of different commutation process on the power loss was analyzed in the ANPC three level inverter. Conception of passive commutation mode and active commutation mode was introduced to classify theses commutation process, conduction loss and switching loss model under the two types of commutation modes were built, variance was used to evaluate the unbalance degree of the power loss distribution. Results have shown that, different commutation modes will cause different loss distribution among power devices; however, they have the same effect on the total conduction loss, switch loss and output voltage waveform. Based on the model, a loss balance control strategy by comparing the loss variance was proposed.To improve the reliability of the ANPC three level inverter, the effect on the inverter output and the bus capacitor voltage fluctuation according to different types of fault was analyzed in this paper, corresponding fault tolerant solutions for each types of fault were proposed. In order to solve the bus capacitor fluctuation problem after fault reconstruction, equivalent circuit models were built; corresponding control strategies were given afterwards. Simulation and experiment were given to verify the validity.更多还原