面向机车牵引的感应电机传动技术研究

【作者】 王瑞；

【导师】 赵金；

【作者基本信息】 华中科技大学 ， 控制科学与工程， 2012， 博士

【摘要】 轨道交通的安全稳定运行关系到人们生活、工作及社会经济发展,提供安全、快捷、舒适的旅行始终是铁路运输的宗旨。在机车牵引交流传动系统中,牵引变流器作为核心动力部件,其正常工作与否将直接关系到整个传动系统、乃至全车安全可靠运行的成败,开展机车牵引变流器故障容错研究具有重要的现实意义。矢量控制和直接转矩控制在机车牵引中已经得到了广泛应用,然而两种控制方案依赖于电机参数,开展电机参数辨识的研究对于提高牵引控制系统性能具有重要的作用。面对牵引变流器大功率低开关频率的特点,为了在充分利用开关频率的同时降低输出谐波对系统性能的影响,同步调制策略将是牵引变流器在一定调制频率下的必然选择。为此,本文以提高在途机车运行的安全性以及控制系统的性能为目的,以牵引变流器逆变侧故障容错,电机参数辨识,同步调制为主要内容展开系统深入研究。针对牵引变流器逆变侧某只功率管故障,本文研究将该桥臂与对应电机相断开,使电机处于单相容错运行状态。基于双旋转磁场理论以及对称分量法,推导给出了电机单相运行下的等效电路,指出正常运行时的开环控制策略同样适用于单相容错运行,但带载能力大大降低并且缺乏自启动能力。根据电流的特点,推导了单相运行下电机的动态数学模型以及双闭环控制策略,指出电机存在两倍供电频率的转矩脉动,对于是否需要在速度环设置相应的低通滤波器来滤除该转矩脉动则需要根据系统惯量大小酌情而定。针对牵引变流器逆变侧某只功率管故障,本文研究将该桥臂对应的电机相端点接至直流母线中点,利用剩余两个桥臂完成对电机线电压的调制,使电机三相容错运行。由于只有四只功率管,导致基本电压空间矢量中没有零矢量。为了对零矢量进行合成,继而给出了两种开关序列,利用双傅里叶积分分析,对这两种开关序列的谐波铜耗进行了分析比较,指出两者的谐波铜耗相差近三倍。由于电机一相端点接入了直流母线中点,使得上下两只电容不停地充放电。在三相电流对称的前提下,推导了电容电压的波动表达式。这种充放电的不对称,甚至会导致上下两只电容电压向相反方向漂移。针对电容电压波动,提出了简单易行的调制策略来抵消这种波动所造成的影响。针对电容电压漂移,分别从调制策略和开关状态两个角度分析提出了简单可靠的漂移抑制方案,提高了系统运行的可靠性。针对d轴电压模型和无功功率模型中参数与其实际值间偏差对电机转子时间常数辨识结果的影响。本文对这两种模型的参数敏感性问题进行了详细的分析,推导给出了辨识偏差与各参数偏差间的关系式。指出d轴电压模型低速时受定子电阻变化的影响较大,但受互感变化的影响较小,而无功功率模型则切好相反。基于此,提出将d轴电压模型和无功功率模型相结合组成混合辨识模型,在不同的运行工况下,通过调节两个模型误差函数的权重,充分利用各自的优点。针对牵引变流器低开关频率的特点,基于FFT分析给出了两种同步调制对称方式的数学模型。在给出关于开关角度计算的超越方程的基础上,将这一求解问题转化为带约束的单目标优化问题,并利用序列二次规划法(SQP)对这一问题进行了求解。根据解曲线的特点,采用拟合的方法对曲线进行了分段多项式拟合,以便于实际工程实现。以TMS320LF2407A为控制芯片搭建了小功率物理实验平台,开展了三相感应电机单相容错以及三相容错两种控制方案的物理实验,实验结果验证了本文两种容错方案的正确性和可行性。更多还原

【Abstract】 The safe operation of rail transit is directly related to people’s life, work and social development. Safe, quick, comfortable travel is always the tenet of railway transportation. In locomotive traction AC drive systems, traction converter as the key power component, its safe operation is directly related to the reliable operation of the whole system. The research on the fault tolerance of traction converter therefore has important practical significance. With the wide application of vector control and direct torque control in locomotive traction, motor parameter identification will no doubt improve the dynamic property of the traction system. In order to realize the full utilization of power converter switching frequency and reduce the influence of harmonics on the system performance, the synchronous modulation seems to be an inevitable choice with the rise of the modulating frequency. As a consequence, for the reliable operation and better control performance, the inverter fault tolerance, motor parameter identification and synchronous modulation in locomotive traction are studied in detail in this dissertation.The single phase fault tolerance operation, in which the fault bridge is disconnected from the motor terminal, is studied under the fault of traction converter. Based on the double revolving field theory and method of symmetrical component, the corresponding equivalent circuit is derived, and it is pointed out that the motor can still working under traditional open loop control method, but with low loading capacity and no self-starting ability. The dynamic mathematical model of motor under this single phase operation is derived and the corresponding double closed loop control method is also presented. For the existence of torque pulsation, whether to set the low pass filter in the speed loop or not is dependent on the system inertia.The three phase fault tolerance scheme is discussed in detail, in which the motor terminal corresponding to the fault bridge is connected to the middle point of dc-link and the motor line-to-line voltages can be modulated as a result. In order to synthesize the zero voltage space vector which does not exist in this topology, two switching sequences are proposed and the resulting almost three times difference in harmonic copper losses is presented using double Fourier integral analysis. Because of the middle point connection with the motor terminal, the upper and lower capacitor voltage will fluctuate, even drift in opposite direction. The fluctuation is formulated providing that three phase currents are symmetrical. The effect of the fluctuation can be neutralized by compensation to modulating waveform. The drifting can be solved by modulation strategy and certain switching state two different perspectives, the reliable operation is therefore improved.In the procedure of rotor time constant identification with d axis voltage and reactive power two models, any parameter difference between the one used in the models and that in the motor will cause the wrong identification result. The detailed parameter sensitivity formulations of the two models are derived, pointing out that two models have opposite sensitivity to stator resistance and mutual inductance. Therefore, two models are combined as one mixed model to fully utilize their own advantage by adjusting weight factor at different conditions.Based on the FFT analysis, two synchronous modulation models with different symmetric form are presented. On the basis of transcendental equation solved for switching angles, the formulation is converted to one single objective optimization problem with certain constraints. The problem is solved using sequential quadratic programming. The piecewise polynomial fitting is adopted to the solved results for more easily practical implementation.The low power physical experiment platform is set up with TMS320LF2407A as the main controller. The single phase and three phase fault tolerance schemes are tested respectively. The results validate the correctness and feasibility of two schemes.更多还原