The pictures of probabilistic characteristic in both sides of impendence matching balance transformers are drawn , and probabilistic density figures are also given . the simulation model of shaoshan 4 electrical tractor is raised , at the same time facing the restriction of probabilistic method , the paper raised that using monte carlo simulation absorbed harmonics currents of the model of electrical tractor and simulated the superposition of low harmonics currents . through compared with real time data , the monte carlo simulation can be confirmed , and the breakthrough point of restriction of using probabilistic method is discussed 为了有效模拟机车在运行中所产生的谐波电流，本文在matlab的平台空间中建立了韶山4型电力机车的仿真模型，导入到matlab运算程序中，对低次谐波电流叠加进行模拟，从而证实了蒙特卡罗模拟法仍然是目前较为可靠可行的方法，同时讨论了在电牵引系统中针对低次多谐波源叠加使用基于中心极限定理的概率分析方法必须使用相关参数进行修正，即需要和电力机车的带电运行方式有机的结合在一起。
The study has completed the design of two - phase inverter and made up of the two - phase inverter - motor system for experimental use it is a variable frequency adjustable speed system with a open - loop control of rotational speed , which consists of voltage - controlled oscillator circulating assign device inverter circuit and two - phase induction motor a accurate mathematical model is set based on the whole system , and simulator program of dynamic and steady condition is established , which is used to calculate the dynamic and steady performance by kron and symmetrical coordinate converter by simulator calculation and experimental research with specific parameter of the system , a comparison is made between predicted and experimental characteristics , experimental measurements are shown to compare closely with corresponding theoretical result it is compared with some variable frequency adjus table speed system comprising inverter and single - phase induction motor from the system efficiency torque pulsation and the effect of two - phase inverter capacitance based on the conclusion , harmonic cancellation pulse width modulation control of a two - phase inverter - fed induction - motor drive system is researched , which cancelled the low harmonic and improve the system performance 通过对电机的kron变换和对称分量变换，建立了系统较精确的数学模型，编制了系统动态及稳态运行的仿真计算程序分别计算系统的动态和稳态性能。通过对系统的具体参数进行了仿真运算和实验研究，实验和仿真结果进行比较，说明实验和理论较为一致，并从系统效率、转矩脉动及两相逆变器电容的影响等方面与各种逆变器和单相异步电动机组成的变频调速系统加以比较。在此基础上，对两相逆变器供电-异步电动机系统使用谐波抑制pwm控制进行了研究，由于减少了低次谐波，改善了系统性能。
In the part of software the thesis presents an algorithm to eliminate the influence of the exist of low harmonic wave to the rate - of - rise protection in the short circuit current . by simulation , it is proved that the algorithm can meet the demand and the error is quite small 另外，考虑地铁馈线末端短路电流中低次谐波的存在，对电流上升率延时保护的影响，提出了一种采样数据谐波处理算法，通过利用labwindows / cvi仿真，证明该算法能有效除去谐波对保护的影响，且引起的误差很小。
