三电平逆变器直接转矩控制系统的研究

发布时间：2019-03-27 08:10

【摘要】：二极管中点钳位型(Neutral Point Clamped,NPC)三电平逆变器在高压大容量电机节能减排、降低硬件成本等方面有着显著优势而成为世界各国学者研究的热点。直接转矩控制技术((Direct Torque Control,DTC))作为电机的一种优良控制方法,将其与NPC三电平逆变器技术相结合运用到高压大容量电机上,具有重要的研究意义。本文以异步电机为负载,对二极管钳位型三电平DTC系统做了一些研究。首先,分析了异步电机和NPC三电平逆变器的数学模型,介绍了电压空间矢量对电机磁链与转矩的影响。其次,由于传统定子磁链观测器是开环系统,无法对定子磁链起到修正作用。针对此问题,采用了一种以定子磁链和定子电流为状态变量的闭环定子磁链观测器。再将此闭环观测器与速度辨识结合起来,取消传统速度传感器;然后介绍了一种简化的DTC系统方法。该方法不需要复杂的数学运算,直接在αβ坐标系下就能得到NPC三电平逆变器所需的电压空间矢量。最后,针对传统NPC三电平逆变器控制策略复杂及直流侧电容电压不平衡的问题,提出了一种简化的能够改善逆变器直流侧电容电压失衡的NPC三电平控制策略。该算法包括g-h坐标系的建立、参考电压矢量的转换、小扇区的重新划分、中点电位控制方法等部分。然后通过仿真实验对上述系统进行了验证。
[Abstract]:Diode midpoint clamp type (Neutral Point Clamped,NPC (three-level inverter) has obvious advantages in energy saving and emission reduction of high-voltage and large-capacity motor, reducing hardware cost and so on, so it has become the research hotspot of scholars all over the world. As an excellent control method of motor, direct torque control (Direct Torque Control,DTC) combined with NPC three-level inverter technology has important research significance in high-voltage and large-capacity motor. In this paper, a diode-clamped three-level DTC system with asynchronous motor as load is studied. Firstly, the mathematical models of asynchronous motor and NPC three-level inverter are analyzed, and the influence of voltage space vector on the flux and torque of the motor is introduced. Secondly, because the traditional stator flux observer is an open-loop system, the stator flux can not be modified. In order to solve this problem, a closed-loop stator flux observer with stator flux and stator current as state variables is adopted. Then the closed loop observer is combined with velocity identification to cancel the traditional velocity sensor, and then a simplified DTC system method is introduced. In this method, the voltage space vector of NPC three-level inverter can be obtained directly in 伪尾 coordinate system without complicated mathematical operation. Finally, aiming at the complex control strategy of the traditional NPC three-level inverter and the unbalanced capacitor voltage on the DC side, a simplified three-level control strategy of NPC, which can improve the capacitor voltage imbalance in the DC side of the inverter, is proposed. The algorithm consists of the establishment of the coordinate system, the conversion of the reference voltage vector, the re-partition of the small sectors, and the control method of the midpoint potential. Then the above-mentioned system is verified by simulation experiment.
【学位授予单位】：太原科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM464

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