【作者】 符晓；

【导师】 伍小杰；

【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】 在矿井提升、机车牵引等中高压大功率应用中,三电平交流变频调速驱动的电励磁同步电动机被广泛使用。为减小三电平变频器的开关损耗,提高其输出功率,需降低PWM变换器的开关频率;但随之带来输出谐波增加、动态性能下降等问题,传统控制方法不再适用。本课题针对三电平高压变频器驱动电励磁同步电机时,降低开关频率所引起的输出电流谐波畸变率增大、调速系统动态性能下降等问题进行系统建模及控制算法的研究。首先,描述了本文研究所针对的电励磁同步电动机三电平变频调速系统的特点,分析了二极管中点箝位式(neutral point clamped,NPC)三电平PWM逆变器的开关特性,并介绍了所设计、使用的50kW同步电机实验装置。借助滑动傅立叶变换(sliding discrete fourier transform, sDFT)提取感应电压的基波成分,设计了一种基于sDFT的同步电机转子初始位置角检测方法。其次,介绍了低开关频率下使用的PWM方法。给出了在低调制度下使用的线电压坐标系SVPWM和高调制度下使用的分段同步优化PWM方法,并提出了在开关频率的上限为500Hz的情况下,PWM分段同步调制方案的选取原则,及它们的数字实现方法。最后,提出了在低调制度区使用的平衡因子控制法和在高调制区使用的调整小矢量作用顺序的三电平变频器的中点电位平衡控制策略。利用复矢量信号流图对PWM变换环节进行建模,在对电流内环控制系统零极点图分析的基础上,提出了一种新颖的复矢量电流调节器。该调节器能有效改善降低开关频率造成的电流耦合现象,且具有较好的动稳态性能。对低开关频率下的PWM逆变器进行了复矢量建模,给出了电励磁同步电机的复矢量信号流图;接着分析常规PI调节器和带前馈补偿的PI调节器在低开关频率下的不足之处,然后基于零极点图分析进行了复矢量电流调节器的设计,并进行了实验验证。在对电励磁同步电机磁链观测原理分析的基础上,提出了电流模型与电压模型的过渡方法。随着控制性能要求的提高,电流测量误差对电励磁同步电动机控制性能的影响愈加显著。本文采用谐振式观测器对实际的电流测量误差进行补偿;为了消除残余误差,采用了带残余误差补偿器的纯积分磁链观测器以精确观测磁链。使用优化的PWM方法无法通过采样直接获得基波电流,而低通滤波器在提取基波分量的同时造成相位滞后、幅值衰减,难以满足系统高性能调速要求。为改善这一问题,本文在对电励磁同步电机进行复矢量和矩阵相结合的建模基础上,结合现代控制理论的观测器原理,针对电励磁同步电机,设计了一种新颖的基于不同坐标系的混合定子基波电流观测器。该混合基波观测器能在低开关频率下实现定子基波电流的快速观测,并具有良好的动态跟踪性能。最后研究了低开关频率下基于定子磁链轨迹跟踪的优化PWM开关角实时调整策略,解决了动态调速过程中使用离线计算的优化PWM模式引起的开关角紊乱、装置过流等问题。提出了低开关频率下电励磁同步电机的完整的控制方案,并进行了实验验证。实验结果验证了所提出控制方法的有效性。该论文有图83幅,表5个,参考文献231篇。更多还原

【Abstract】 The three-level ac variable frequency converter fed electrical excited synchronous machine is in increasing demand for numerous medium-voltage high power industrial applications such as mining hoist and locomotive traction. The operation of the PWM converter should be kept at low switching frequency so as to restrain the dynamic losses of the three-level converter and improve its output power. Problems due to low switching frequency are studied in this paper, with system modeling and control strategies for solving the problems.First, the feathers of the three-level variable frequency converter fed electrical excited synchronous machine are described. The pulse width modulation (PWM) methods at low switching frequency are introduced. The complex state signal flow graph is used for modeling the PWM conversion part. With the analysis of zero-pole graph of the current control inner loop, a novel complex state current regulator is proposed. It can effectively reduce the cross coupling of the current control loop caused by low switching frequency, while realize high dynamic and steady performance at the same time are proposed.Based on the analysis of the flux observation principles of the electrical excited synchronous machine,the transition method between the current model and voltage model is proposed. A simple resonant type observer to compensate current measurement errors for the pure-integration-based flux estimation is proposed. The technique further contains a residual error compensator to eliminate miscellaneous residual error of the integrator. A novel hybrid fundamental current observer at different coordinates for the electrically excited synchronous machine is designed based on the observer theory and the complex vector model. This kind of hybrid observer can extract the fundamental component of the stator current instantaneously as well as the perfect performance of dynamic tracking. Finally, a real-time switching angle adjustment strategy of optimal PWM based on stator flux trajectory control at low switching frequency is proposed. Problems caused by using the offline calculated optimal PWM patterns at the dynamic speed control, such as switching angle disorder and equipment overcurrent trip are solved by this method.There are 83 figures, 5 tables and 231 references in this dissertation.更多还原