【作者】 李玉军；

【导师】 王明渝；

【作者基本信息】 重庆大学 ， 电气工程， 2008， 硕士

【摘要】 多电平逆变器是近年来电力电子领域中高压大功率应用场合研究的一个热点,多电平逆变器技术是一种通过改进变换器自身拓扑结构来实现高压大功率输出的新型变换器,它无需升降压变压器和均压电路。由于输出电压电平数的增加,使得输出波形具有输出谐波小,每个开关器件所承受的电压应力较小。因此在中高压变频调速、交流柔性输电系统等领域得到了广泛的关注。本文针对三电平逆变器,对其控制方法进行了研究。对目前多电平逆变器的电路拓扑和控制方法进行了总结,并将各自的优缺点和应用场合加以分析、比较。针对二极管钳位型三电平逆变器,对其结构、工作原理进行了详细讨论。多电平逆变器的PWM控制技术是多电平逆变器研究中一个相当关键的技术,它与多电平逆变器拓扑结构的提出是同生的,因为它不仅决定多电平逆变器的实现与否,而且对多电平逆变器的电压输出波形质量、系统损耗的减小与效率的提高都有直接的影响。合适的PWM控制方式保证系统高性能和高效率的运行。多电平逆变器的PWM控制方法主要有两类:载波调制法和空间电压矢量调制法(SVPWM)。针对二极管钳位型逆变器,详细研究了SVPWM控制策略。在分析传统三电平SVPWM控制原理和技术特点的基础上,引入一种60°坐标系SVPWM快速算法。同时讨论了中点电位不平衡的原因以及中点电位平衡的方法。研究了两种三电平逆变器异步电机矢量控制系统的方案。一种是基于三电平中点钳位(NPC)逆变器的零序分量注入型异步电机矢量控制方案,另一种是基于SVPWM控制三电平异步电机矢量控制系统。前一种方法中,使用快速电流控制的直接转子磁链定向矢量控制模式,异步电机由三电平NPC逆变器供电,逆变器控制采用开关优化PWM算法。后一种方法中,逆变器控制采用60°坐标系SVPWM算法。仿真结果表明,两种方法在三电平逆变器供电的感应电动机上有效地实现了矢量控制,并且具有很好的性能。最后,设计一台三电平逆变器系统实验装置。实验装置包括三电平逆变器主电路,DSP2812控制板,驱动保护电路和辅助电源。编写控制系统软件程序,在样机上进行了实验研究。更多还原

【Abstract】 Recently, multi-level inverters have been widely studied in high power level application with high voltage output. As one new type of converter, multi-level converter provides high power output through changing circuit topology, without step up and step down transformer, and equalization circuit. The waveform of the line-to-line voltages is composed of multi-voltage levels, which leads to lower THD and lower switching voltage stress. So this technique has been widely concerned in applications such as medium voltage drive and flexible ac transmission system. The three-level inverter and its control strategy are studied in this paper.The topologies of multilevel inverter and control methods are summarized. Moreover, their advantages, disadvantages and application fields are also analyzed and compared. The structure and principle of three-level NPC inverter are analyzed in detail.PWM control technique is one of the key techniques for multi-level inverter .It is proposed in the same time with multi-level inverter topology. The PWM technique not only determines the performance of inverter, but also affects the quality of the output voltage waveform, the loss and the efficiency of the system directly. Proper PWM control method ensures operation with high performance and high efficiency. There are two main types of PWM control method, which are carrier-based PWM method and SVPWM method.SVPWM control schemes for the three-level NPC inverter are discussed in detail. Based on analyzing the control principle and technique characteristic of tradition SVPWM, one fast SVM algorithm based on 60°coordinate are introduced, which can get the three nearest vectors around the reference vector and their dwelling time easily. The reasons of neutral-point voltage unbalance and the methods of solving this problem are discussed.Two vector control schemes of an induction machine using three-level neutral point clamped (NPC) inverter are studied. One is zero-sequence component imposed three-level vector control system of induction machine. The other is three-level inverter vector control system based on SVPWM algorithm. In the former system, the direct rotor-flux-oriented control of induction machine supplied by a voltage-source inverter with fast current control is employed. The switching frequency optimal PWM (SFOPWM) method is used for the control of a three-level inverter with imposing zero-sequence component. In the latter system, The inverter is controlled by SVPWM algorithm based on 60°coordinate. Results from computer simulation show the good performance of the three-level inverter fed drive with vector control.In the end, three-level inverter experiment equipments are designed, which conclude main circuit of three-level inverter, DSP2812 control board, drive and protect circuit and auxiliary power. The program of control system is programmed, and the control strategy is tested by doing experiments.更多还原