牵引供电系统负序电流分析及其对策..doc

摘 要 目前我国电气化铁道采用单相工频交流制，使用电力系统三相中的两相分别通过供电臂向电力机车供电，造成电压三相不平衡，对系统和其他负荷产生影响。因此，正确建立电气化铁道牵引供电系统的仿真模型，并研究电气化铁道牵引供电系统产生的负序分量，对于解决和改善供电系统负序问题具有重要实际意义。 牵引变电所的牵引负荷随时间变化剧烈，负序容量大，功率因数较低，还释放大量的谐波。利用并联补偿综合解决负序、无功的补偿(必要时还要兼顾谐波)，是提高动力指标和经济效益的有力手段。为使并联补偿得到综合的和最有效的利用，应从整个系统的观点出发，把牵引供电系统(通过牵引变压器)与电力系统联系起来，提出并联补偿的最住分布方式。 首先本文结合牵引供电系统的特点，通过Simulink仿真建立牵引供电系统基本仿真模型，接着根据负序电流的特点，提出新型的检测方法。然后根据不同牵引变压器（Scott、YNd11、阻抗匹配平衡变压器等）的特点，对其进行三相不平衡度进行特性分析，对牵引变压器的选型具有参考价值。 最后建立了牵引电力系统中并联补偿分析、计算的通用模型，计算出负序电流的一般表达式，以及全负序相量图的应用范围。提出改善负序的方法，包括采用特殊接线的牵引变压器、牵引变电所的换相连接、并联补偿等。并且重点研究牵引变电所的并联补偿，然后以YNd11接线牵引变电所为例对其进行负序功率补偿，通过计算和Simulink仿真验证其正确性。根据负载的不同情况提出两种不同的并联补偿分布方式，仿真波形结果验证了并联补偿对降低负序的作用。 关键词：电力机车;牵引系统;不平衡度;负序电流;并联补偿 ABSTRACT At present our electrified railway use single-phase industrial frequency alternating current system ,it use two of the three-phase in the power system to supply power to the electric locomotive through the power-supply arm,then it cause a voltage unbalanced three-phase. So, establishing a simulation model of proper electric iron traction system correctly seems important and researching the negative sequence components that produced in the electric iron traction system in power supply system also has important practical significance to reduce the negative sequence of power supply system. The tractions load of traction substation changes over time，has large capacity of negative sequence, low power factor, also release a lot of harmonic. Using parallel compensation for negative sequence and reactive power compensation (when necessary even give attention to the harmonic), which is a perfect method to improve the dynamic index and economic benefit. In oder to make use of the parallel compensation effectively and comprehensively, we should make a point of view from the whole system, connecting the traction power supply system (through the traction transformer) and power system, come up with a best distribution mode for the parallel compensation. According to the electric tractio