【作者】 景巍；

【导师】 谭国俊；

【作者基本信息】 中国矿业大学 ， 电力电子与电力传动， 2011， 博士

【摘要】 大功率变频器采用多电平技术可有效地降低变频器输出电压的谐波成分，改善其输出性能。然而随着电平数的增多，变频器中的功率器件会大幅度增加，同时对其控制器也提出了更高的要求。因此，无论是从实用性还是控制复杂性方面，三电平变频器都具有较强的竞争优势。变频器随着其容量的不断提升，功率器件的损耗也急剧增加，散热问题已成为大功率三电平变频器研发过程中的关键问题之一。现场应用表明，散热性能的好坏直接影响到变频器的可靠性以及使用寿命，恶劣的情况下甚至能直接导致功率器件的损坏。变频器的发热主要是由功率器件的损耗引起的，同时功率器件本身又对温度非常敏感，温度的变化会影响功率器件的导通和关断特性，从而影响变频器的工作性能，因此准确地分析功率器件的损耗特性可优化变频器的散热设计，保障变频器的稳定可靠运行。作为功率器件损耗研究的基础，本文对三电平变频器常用的载波比较正弦脉宽调制（SPWM）和空间矢量脉宽调制（SVPWM）进行了分析，阐明了两种调制方法下输出电压的谐波特性，并分析了两者之间的本质关系。在功率器件损耗计算时，SVPWM的等效调制函数可近似采用正弦波注入三次谐波的方法。在分析了中点钳位型（NPC）三电平变频器在不同负载工况下功率器件的工作特性的基础上，根据功率器件的损耗模型提出了一套考虑结温效应的功率器件损耗计算方法，采用热阻等效电路模型计算了功率器件的结温，并分析了功率器件的损耗和结温随调制度和负载阻抗角的变化规律。针对NPC三电平变频器功率器件损耗和结温不平衡的缺陷，分析了有源钳位型（ANPC）三电平变频器的工作原理，通过对冗余零电压状态下不同电流通路的合理选择可实现功率器件损耗和结温平衡。在分析了已有调整策略的基础上提出了一种改进PWM方法，可实现功率器件最优结温平衡。同时在分析了ANPC三电平变频器不同负载工况下功率器件工作特性的基础上，提出了考虑结温效应的功率器件损耗计算方法。在分析了ANPC三电平变频器功率器件开路和短路状态的基础上，利用零电压状态冗余的优势，提出了ANPC三电平变频器单个功率器件开路或短路故障状态下的容错运行控制方法。为了验证容错控制方法的可行性，提出了容错控制下功率器件的损耗计算方法。更多还原

【Abstract】 The device’s losses increase dramatically with the expanded capability of three level converters and the heat dissipation issue has become one of the key problems during the converter developing process. Industrial application indicates that the heat dissipation system affects the converter’s reliability and life time directly and some of the power devices could be damaged immediately with a worse heat dissipation system. It is commonly known that the devices are very sensitive to the heat which is generally caused by the losses. The variations of device’s junction temperature affect the conduction and switching characteristics and thus the converter’s performance as well. So it is very important to get the precise device’s losses since the loss information could optimize the heat dissipation system which guarantees the converter’s stable and reliable operation.Firstly, as the basis for the loss research, the commonly used carrier based sinusoidal pulse width modulation (SPWM) and space vector pulse width modulation (SVPWM) were analyzed. Secondly, power device’s operation principles of neutral point clamped (NPC) three level in different load conditions were analyzed. Based on the loss model of the devices, the loss calculation method which took the junction temperature effect into consideration was proposed. Thirdly, Point to NPC three level converter power device’s loss and junction temperature unbalance problem, the operating principle of active NPC (ANPC) three level was analyzed. Based on the analysis of on hand modulation strategies, an improved PWM method was proposed which has better junction temperature balance ability. Finally, taking the advantage of redundancy zero voltage output states, the fault tolerant operation control method of ANPC three level converter under single device open circuit or short circuit fault was proposed. Furthermore, the loss calculation method under fault tolerant operation was also proposed to evaluate the feasibility of the control method.更多还原