【作者】 文晓燕；

【导师】 郑琼林；

【作者基本信息】 北京交通大学 ， 电力系统及其自动化， 2012， 博士

【摘要】 摘要：一方面,社会生活和经济发展对交通运输能力的要求不断提高,列车运行速度越来越高,另一方面人们越来越重视列车乘坐舒适性,这就要求列车控制在起动、制动等各个运行过程中做到既快又稳。同时,能源和环境问题是全球化重要课题,而列车牵引电机功率非常大,所以效率优化对于列车牵引电机控制具有重要意义。为此,本文针对列车起动、制停过程等低速运行工况下牵引电机优化控制问题进行了研究。首先,本文分析了列车运行性能与牵引电机控制之间的关系,从而明确如何改进电机控制才能提高列车运行性能。具体来说,列车运行舒适度主要受牵引力／制动力曲线影响；平稳制动、准确停车要依靠先进的制动技术；而提高牵引电机运行效率是实现节能减排的重要途径之一。在此基础上,本文对提高牵引电机控制精度的关键技术及现有研究成果进行了总结和讨论。接着,本文根据列车运行要求对牵引电机控制器进行了优化设计,主要包括牵引力曲线优化设计、制动力优化设计和效率优化控制3个部分。(a)牵引力曲线优化设计：根据列车起动过程快速性和舒适度两方面的要求,本文采用脉冲基3次多项式S曲线作为牵引力曲线,根据列车速度实时计算牵引力参考值,并且进行列车运行阻力计算误差校正。(b)制动力优化设计：在对比各种列车制动方式优缺点的基础上,论文选择再生电制动作为主要制动方式；列车制停过程制动力参考值计算方法与起动过程相似；此外,论文还讨论了行车制动和驻车制动之间的切换配合问题。(c)效率优化控制：矢量控制方式下,根据电机工作点调整励磁电流和转矩电流、合理分配电机的铁损和铜损可以提高其运行效率。在此过程中,等效铁损电阻计算是重要一环,只有准确估算出铁损电阻效率优化控制才能发挥出应有效果。由于牵引电机测速编码器分辨率比较低,列车低速运行时速度测量采样率进一步降低容易导致磁场定向准确度下降。为了提高电机低速运行时磁场定向准确度,本文对磁链观测器做了进一步研究,在分析各种磁链观测器模型特点的基础上,提出了一种改进电压型磁链观测器。电压模型磁链观测器精度主要受反电动势零漂、定子电阻误差和定子电压计算误差影响,本文围绕反电动势零漂和定子电阻误差的辨识和校正对电压型磁链观测器做了改进。根据磁链观测结果直流分量与反电动势零漂之间的关系,以磁链观测值直流分量作为反馈进行反电动势零漂估计和校正,通过闭环控制达到去零漂的效果。在分析定子电阻误差对磁链观测影响的基础上,本文构造了一个以两相同步旋转坐标系下电流分量为自变量、能够反映定子电阻误差大小和符号的变量,通过闭环控制使该中间变量趋近于0从而消除定子电阻误差。针对列车速度测量编码器分辨率低的实际情况,论文提出了一种连续中断T法速度测量方法：利用DSP捕获单元检测编码器脉冲上升沿和下降沿(双沿检测),通过软件方法实现每次捕获都触发捕获中断并在中断子程序中进行速度计算,从而提高速度采样率、减小测速时间延迟；同时,通过合理计算方法规避了编码器非50%占空比对双沿检测速度测量的影响。该方法能够最大程度地利用编码器脉冲的有效信息,而且不需要增加或改动硬件设施,只需合理设置和使用DSP捕获单元即可实现。对有两路输出脉冲的编码器而言,采用这种测速方式后测速延时比通常方法减小一半,电机低速运行动态性能和稳态性能有明显提高。目前,大多数交流牵引列车制停过程中会在速度较低时从电制动切换为空气制动,空气制动方式虽然可靠但缺点也很明显,如精确控制难度大,制动盘磨损、定期更换增加人力、财力成本,并且制动盘粉尘、噪音也会造成环境污染。如果能够完全利用电制动实现列车制停、空气制动仅作为驻车制动,就能很好地解决这些问题。电制动制停的关键在于低速区制动力输出能力、制停过程平稳和列车到达零速时电制动、空气制动的平滑切换。因为列车质量和系统惯性非常大,所以列车速度变化缓慢,可以认为速度是连续变化的。根据这一特点和魏尔斯特拉斯(Weierstrass)定理,本文利用多项式曲线拟合进行列车速度估算,并且采用最小二乘法确定多项式系数进一步提高拟合和估算精度。仿真结果表明根据曲线拟合估算值进行零速判断更加准确。本论文研究内容的相关实验在交流传动互馈试验系统上进行,所以本文还对试验系统稳定性进行了分析,主要包括试验系统主电路结构稳定性和电机控制扰动对系统稳定性的影响两部分。在分析试验系统主电路结构稳定性时,假设逆变器-电机处于理想控制,并把它们等效为一个由直流电压和电机工作点决定的受控电流源,进而利用小信号模型分析系统参数对稳定性的影响。然后,通过理论推导得到逆变器直流母线电压/电流变化量与电机控制扰动之间的传递函数,根据各传递函数的频率特性分析了电机控制扰动对直流母线电压/电流的影响。理论分析和实验验结果都表明直流母线电感越大、阻尼电阻越小、直流母线电容越小、电机速度越低、直流母线电压越低、负载转矩越大,系统稳定性越差。图93幅,表3个,参考文献104篇。更多还原

【Abstract】 ABSTRACT:Society and economy development require stronger transportation ability, so locomotive need higher speed and start-up/brake quickly to raise average velocity. Meanwhile, people need ride comfort, which implies locomotive speed should be regulated stably especially during start-up/brake process. There is a conflict between these two demands. Furthermore, energy and environment problem are global important issues, thus efficiency optimization is very meaningful for so large power AC traction motor. To overcome these problems, this thesis researches optimization control strategy of low speed operation and associated technical points.First of all, this thesis analyzes relationship between locomotive operation performance and traction motor control, which is useful for making sure how to optimize motor control. Specifically speaking, ride comfort is mainly determined by traction/braking force curve and their control accuracy; steady deceleration and accurate position shut down depends on braking technique; and motor efficiency optimization is one of the most important methods for low cost operation. Based on the analysis, this thesis discusses key techniques for high performance motor control, sums up existent research and studies remaining problems.Then, this thesis proposes a traction motor optimization controller, which includes three parts:traction force curve optimization, braking force optimization and motor efficiency optimization.(a) Traction force curve optimization:To realize quick and comfort start-up, pulse template polynomial S-curve is used for traction force reference calculation, and locomotive operation resistance force calculation error is corrected.(b) Braking force optimization:Among many kinds of braking force, regenerative electric brake is chosen. Braking force reference calculation is similar to traction force. During braking, motor controller detects running speed, estimates remaining time for shut down, and sends signal to air braking system in ahead for staying brake.(c) Efficiency optimization is realized through assigning copper loss and iron loss by adjusting magnetizing current and torque current in vector control system. And equivalent iron loss resistance estimation is very important for efficiency optimization control.Flux orientation is realized by integrating stator angle frequency in indirect vector control system, but orientation accuracy would deteriorate when traction motor operates in low speed area because of speed measurement sampling frequency decrease. After comparing several kinds of flux model, this thesis proposes an improved voltage model flux observer. The main demerits of voltage model are DC offset in EMF and stator resistance error, because they will result in magnitude and phase error in estimation. Here, a new kind of EMF drift and motor stator resistance error estimator is proposed, with which the errors can be estimated and compensated online.Generally, speed encoder mounted on locomotive has low resolution, so this thesis proposes a consecutive interrupt T-method for speed measurement. Both up-edge and down-edge are captured for speed calculation and every capture generates an interrupt request by setting DSP capture unit with software. Besides, speed calculation uses a smart method to evade encoder pulse duty coherence error. With this method, speed measurement time delay decreases obviously. What’s more, this method does not need any hardware modification; it is realized by rational DSP configuration in software. Motor control performance in low speed area is improved evidently with this method.At present, most vehicles mount multi kinds of braking force, and electric braking would be cut off when speed is low, leaving air-braking only until locomotive stops. Air-braking is dependable, but it results in too much human and financial cost, noise and dust. Pure electric brake is very meaningful, while the problem is how to improve motor control performance and zero speed detection during braking down. Based on large inertia and mass of locomotive, traction motor speed could be considered as continuous, so polynomial curve fitting is reasonable. With least-squares polynomial estimation results, both zero speed detection and motor control performance can be improved.At last, this thesis does research on test-bed stability. The analysis is achieved by two steps. First step:assume induction motor is under ideal control, and DC bus stability is analyzed with small signal model of test-bed. Second step:transfer functions between motor variables disturbance and DC bus voltage/current displacement are derived. With frequency characteristic of these transfer functions, test-bed stability is compared with ordinary AC-DC-AC driving system, and oscillation phenomena during experiment have a rational theory explanation.更多还原