【作者】 周丹丹；

【导师】 钱雪军；

【作者基本信息】 同济大学 ， 电力系统及其自动化， 2008， 硕士

【摘要】 电力牵引负荷作为大功率单相整流负荷,其电流具有很大的随机性和不对称性,是一种严重的干扰性负荷,对电力系统的安全带来了严重的影响。本文首先分析了铁道牵引供电系统存在的问题,讨论了基于有源滤波器技术的一种牵引供电系统的平衡变换方案,以综合解决铁道牵引供电系统上三相负载不平衡、无功和谐波等问题。针对目前广泛采用的斯科特变压器,从有源滤波器与供电系统的连接关系、有源滤波器采用的变流器的电路形式等方面,提出了适用于三相平衡变换的牵引供电系统的有源滤波器方案。本文简要介绍了有源滤波器的基本原理和现有电路结构。以电压型变流器构成的单个并联型有源滤波器为研究对象,全面考察了现有有源滤波器指令电流的生成方法,提出了一种从畸变和不对称电源电压中提取基波正序电压的快捷方法,基于这种方法构造了指令电流的生成策略。同时,详细的分析和研究了定边带控制方式和基于三角波调制的PWM控制等方式,根据工程实践要求,提出了一种状态优化的定边带宽度控制策略,在满足电流跟踪精度的条件下,大幅度降低了开关元件的频率。通过分析平衡变换方案参数设计的总体要求,找到了有源滤波器各参数之间的关系式,提出了有源滤波器主电路参数设计的方法。根据电气化铁道牵引供电系统的特点,在PSCAD/EMTDC下建立了包含平衡变换系统的仿真模型,对平衡变换系统进行了较全面深入的研究。所得到的仿真实验的结果证实了系统结构、控制策略及参数计算方法的正确性和可行性。更多还原

【Abstract】 As a large power single phase rectified load, the electric traction load has many disadvantages like heavy distortion, acute fluctuation and severe asymmetry. The safe and economic operation of power systems is badly influenced. A novel power supply system for railway traction is presented in this paper, where the active power filters (APF) is utilized to eliminate the disadvantages of the system that is widely adopted at present. By compensating the negative, reactive and harmonic current simultaneously, the proposed system can avoid deteriorating the problem of the power quality.In corresponding to the asymmetrical transformers that is used in the traction supply system, one scheme is developed to realize the proposed balance electrical system (BED). The structure of APF suitable for implementing the BED is proposed, on a survey of the existing topology of the passive, active and hybrid filters, and the current, voltage, multi-level and cascade converters.An evaluation on most of methods proposed by other publication for generating the reference current/voltage is done in the paper, and the characteristic and applicability of these methods are analyzed. A high-speed and simple reference generating method is suggested, which can extract the positive sequence voltage from the asymmetrical, distorted source voltage, and the reference current can be generated by utilizing this voltage. Meanwhile, PWM control mode based on the triangular-wave modulation and set sideband control mode are analyzed and researched in detail. According to the practical requirements, a state optimal vector control strategy in which the correlation among the legs is harnessed is developed, leading to the result of low switching frequency, higher switching efficiency and accuracy.Through analyzing the general requirements on the design parameters of the BED, the relationship of the APF parameters is found, and the design method of the main circuit of APF is proposed. In corresponding to the features of the electrified railway traction power supply system, a traction power System Simulation model with BED is established in the PSCAD/EMTDC environment. Comprehensive research is done on the reactive power compensation and harmonic characteristics of the BED, and the correctness and feasibility of the system structure, control strategy and parameter calculation method are confirmed by the simulation results obtained.更多还原