【作者】 方晶；

【导师】 毛承雄； 陆继明；

【作者基本信息】 华中科技大学 ， 电力系统及其自动化， 2011， 博士

【摘要】 电力电子技术向着高电压、大功率方向的发展使得中性点箝位三电平高压变频器拓扑结构的优势越来越受到人们的重视,相关研究与应用也越来越多、越来越广。然而,受半导体材料的影响,电力电子器件的耐压始终有限,这不但限制了高压变频器过电压的承受能力,还增加了过电压保护设计的难度。针对该问题,本论文围绕高压变频器过电压保护和控制展开了研究。过电压产生原因的不同,其在高压变频器中的作用机理和表现形式也存在一定的差异。对各种过电压情况的具体分析,可以更清楚的了解到它们对高压变频器的影响,为高压变频器过电压保护设计提供良好的理论支持。结合广泛应用于电力系统过电压保护的氧化锌压敏电阻的特点,本论文认为它能作为中性点箝位三电平高压变频器过电压保护装置。为了解决单个电力电子器件耐压低和氧化锌压敏电阻残压高的问题,结合各种过电压的表现形式,本论文提出对高压变频器中最重要的逆变部分进行整体过电压保护的思想,通过对整个逆变部分的过电压保护,实现对高压变频器的过电压保护。根据三电平变频器开关状态,详细分析了逆变部分耐压情况,结合实际中性点箝位三电平高压变频器系统参数,进行了氧化锌压敏电阻选型计算。实验结果证明了选取的氧化锌压敏电阻满足理论分析参数要求,仿真结果证明了氧化锌压敏电阻能对中性点箝位三电平高压变频器过电压进行有效的保护。变频器是理想的电动机软启动装置,为了使电动机在顺利启动的同时过电流尽可能小,本论文对变频器的启动频率进行了详细推导计算。结合实际电动机参数的仿真结果证明了变频器启动频率计算的正确性。多相电动机可以实现低压大功率输出,为了对多相电动机驱动系统进行改进,本论文提出了一种无输入变压器多相电动机高压变频器拓扑结构。该多相电动机高压变频器无需移相变压器,减小了系统体积和成本,同时,由于结构的特点,大幅降低了电力电子器件耐压和功率要求。此外,相对于传统多相电动机高压变频器而言,更容易实现模块化设计,增强了系统的可移植性,易于实现系统冗余。为了配合该多相变频器,本论文还提出了独立定子绕组多相电动机结构。仿真结果和低压九相电动机样机实验都证明了无输入变压器多相电动机高压变频器拓扑结构和独立定子绕组多相电动机结构的正确性和可行性。结合独立定子绕组九相电动机结构特点,进行了详细的谐波磁势分析,推导出谐波磁势的详细表达式。在此基础上,对考虑空间谐波磁势影响的谐波电磁转矩进行分析,推导出其详细表达式。为多相电动机设计和多相变频器控制优化提供了理论依据。更多还原

【Abstract】 The advantages of Neutral Point Clamped (NPC) three-level high voltage motor drives are more and more outstanding for the improvement of power electronics towards high voltage and high power. There are a lot of researches and applications of NPC motor drives. But the withstand voltage of power electronic device is still finite, which not only limits the overvoltage tolerant capability, but also presents challenges on overvoltage protection. To solve the problem, this dissertation researches on overvoltage protection and control of high voltage motor drives.For the different causes of overvoltage, the effects and behaviors are also different in the high voltage motor drives. Detailed analysis of each causes of overvoltage can make the effects more clearly and give strong theoretical support for overvoltage protection design of high voltage motor drives. Considering the characteristics of ZnO varistor which is widely used in power system overvoltage protection, this dissertation chooses it as the overvoltage protection device for NPC three-level high voltage motor drives.To solve the problem of low withstand voltage of single power electronic device and high residual voltage of ZnO varistor, this paper presents a method by protecting the inverter part of high voltage motor drives based on analysis of each kind of overvoltage. If the inverter part is not overvoltage, the whole system is not overvoltage either. The withstand voltage is detailed analysis based on switch states of three-level motor drives. Calculations of how to choose the ZnO varistors is given based on practical project parameters. Experimental results show that the designed ZnO varistors meet the theoretical analysis quite well. Simulation results proved that the designed ZnO varistors can protect NPC three-level high voltage motor drives from overvoltage effectively.Motor drives are ideal starting device for motors. The calculation of motor drives starting frequency is given to satisfy the starting requirement of motors and reduce the starting current. Simulation results based on practical motor parameters proved that the calculation of starting frequency is correct.Multiphase motors have a lot of advantages include low voltage input and high power output. This paper presents a novel topology of multiphase motor drives. It is not need the phase-shifting transformer, which reduces the system volume. In addition, the withstand voltage and power requirements of power electronic device is significantly reduced. Moreover, comparing with the traditional multiphase motor drives, it is easy to implement modularization and redundancy, and enhance system transplant. Simulation results and low voltage nine-phase motor drives experimental results are both proved that the novel topology of multiphase motor drives is correct and feasibility.Detailed calculation of harmonic magnetomotive force based on nine-phase motor is given. Furthermore, considering space harmonic magnetomotive force effects, harmonic electromagnetic torque has been analyzed. The detailed expression of harmonic electromagnetic torque has been give. It can be the theoretical support for multiphase motor design and multiphase motor drives control strategy optimization.更多还原