NPC型三相三电平逆变器系统研究

发布时间：2019-06-09 18:23

【摘要】：大功率电力电子设备广泛应用于电力、交通等许多领域,多电平拓扑结构结合新型大容量开关器件、优良的控制方法是大功率电力电子设备的发展方向。其中,二极管中点钳位(Neutral-Point Clamped)型三电平逆变器由于其较为简单的结构和控制、较高的性价比,成为目前应用较广的多电平变换器之一。文章首先介绍几种不同拓扑结构的多电平变换器的研究现状以及研究热点;随后详细分析三电平的不同的空间矢量调制算法的优劣。与两电平相比,三电平拥有更多的矢量,实现SVPWM的途径随之增多,何种实现方法准确度高、计算量小、处理速度快、占用处理芯片内存小等问题值得深入分析;本文研究对象为地铁辅助变流器,因此对输出波形质量要求很高,需要具备很高的稳态精度,很好的动态性能,要求在频繁的突加、突减负载时,系统仍然能够稳定运行。针对该要求,本文提出一种基于离散域的PI+状态反馈的控制策略;针对离散域的负载电流前馈解耦通道复杂难求,本文详细分析控制器的作用机理,据此提出一种新型求解负载电流前馈传递函数的方法,仿真和实验结果证明该控制方法不仅使系统稳态精度高,而且动态性能也能满足要求。最后根据NPC型三相三电平逆变器带异步电机开环控制系统的低频震荡现象,分析异步电机容易低频振荡的机理,指出NPC型三相三电平逆变器在控制性能良好的情况下,死区是引起异步电机低频振荡的主要原因,据此提出一种新型死区补偿策略来改善此现象。
[Abstract]:High-power electronic equipment is widely used in many fields such as power, transportation and so on. Multi-level topology combined with new large-capacity switching devices, excellent control method is the development direction of high-power electronic equipment. Among them, diode midpoint clamp (Neutral-Point Clamped) three-level inverter has become one of the most widely used multilevel converters because of its simple structure and control and high performance-price ratio. In this paper, the research status and research hotspots of several multilevel converters with different topologies are introduced, and then the advantages and disadvantages of different space vector modulation algorithms for three-level are analyzed in detail. Compared with the two levels, the three levels have more vectors, and the ways to realize SVPWM are increased. The problems such as high accuracy, small computation, fast processing speed and small memory occupation of the processing chip are worthy of in-depth analysis. The research object of this paper is subway auxiliary converter, so the quality of output waveform is very high, it needs to have high steady-state accuracy and good dynamic performance, and the system can still run stably when the load is suddenly added and suddenly reduced. In order to meet this requirement, a control strategy based on discrete domain PI state feedback is proposed in this paper. In view of the complexity and difficulty of load current feedforward decoupling channel in discrete domain, the action mechanism of the controller is analyzed in detail, and a new method for solving load current feedforward transfer function is proposed. The simulation and experimental results show that the control method not only makes the steady-state accuracy of the system high, but also meets the requirements of dynamic performance. Finally, according to the low frequency vibration phenomenon of NPC three-phase three-level inverter with asynchronous motor open-loop control system, the mechanism of easy low-frequency oscillation of asynchronous motor is analyzed, and it is pointed out that the NPC three-phase three-level inverter has good control performance. Dead time is the main cause of low frequency oscillation of asynchronous motor. Based on this, a new dead time compensation strategy is proposed to improve this phenomenon.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM464

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