配电变压器负序电流动态抑制方法及实验研究

发布时间：2018-07-17 18:04

【摘要】：大量电力电子装置和动态非线性不平衡负荷（如电弧炉、电气化铁路、电焊机等）在电力系统中的广泛使用，使得配电变压器长期处于三相不平衡运行和严重谐波污染状态，导致电网中谐波和负序电流较高，造成损耗增加、保护误动等多种危害，严重威胁了电力系统的安全运行。本文分析了负序电流产生机理，针对负序电流的危害，分析了其各种影响因素，进而研制了一套配电变压器负序电流动态抑制系统，该系统不仅可有效抑制三相不平衡电流引起的负序电流，也能有效减小谐波电流对负序电流的影响，同时在提高功率因数的基础上降低配电变压器损耗，实现有效提高电力系统运行安全性和稳定性的目标。本文主要研究工作如下： ①分析了配电变压器负序电流产生机理及影响因素，在此基础上提出了一种配电变压器负序电流动态抑制方法，利用这一方法结合系统稳定运行条件，构建了负序电流动态抑制方法仿真实验模型，仿真实验结果表明三相不平衡电流和谐波电流是负序电流的主要影响因素，进而验证了负序电流动态抑制方法的有效性和可行性。 ②结合配电变压器实际工程环境，研制了配电变压器负序电流动态抑制系统，该系统按功能分为三相不平衡电流治理部分和谐波电流滤除部分。采用全电容器补偿方式进行了三相不平衡电流治理部分硬件模块设计，包括电参量采集单元设计、中央控制单元设计及电容器柜框架组建和补偿电容器等级分组等；结合现有的APF装置并考虑消除无功耦合现象进行了谐波电流滤除部分的设计，保证了系统整体的良好协同运行。 ③编写了系统现场端和服务器端软件程序，保证了系统的安全稳定运行，且有助于工作人员远程监控配电变压器运行状态。其中现场端软件主要包括现场端数据提取与识别子程序、无功调节量快速计算及电容器组投切控制子程序和GPRS无线通讯子程序等；同时，基于VC++2010编译软件和MySQL5.0数据库软件，编写了服务器端后台数据监测软件，动态了解现场端实时运行参数信息。 ④基于提出的负序电流动态抑制方法及构建的配电变压器负序电流动态抑制系统，分别于实验室和现场两种环境中进行了实验。在实验室平台条件下，运行结果表明该系统在无谐波电流存在时可有效抑制三相不平衡电流引起的负序电流；在现场挂网实验中，该系统不仅能有效抑制三相不平衡电流引起的负序电流，而且能有效降低谐波电流对负序电流的影响，并能提高功率因数和降低配电变压器附加损耗，，达到了各项预定目标。
[Abstract]:A large number of power electronic devices and dynamic nonlinear unbalanced load (such as electric arc furnace, electrified railway, welding machine, etc.) are widely used in power system, which makes the distribution transformer in the state of three-phase unbalanced operation and serious harmonic pollution for a long time. It leads to higher harmonic and negative sequence current in the power network, resulting in increased losses, protection misoperation and other hazards, which seriously threaten the safe operation of power system. In this paper, the mechanism of negative sequence current is analyzed, and the influence factors of negative sequence current are analyzed, and a dynamic suppression system of negative sequence current of distribution transformer is developed. The system not only can effectively suppress the negative sequence current caused by the three-phase unbalanced current, but also can effectively reduce the influence of harmonic current on the negative sequence current. At the same time, the loss of distribution transformer can be reduced on the basis of increasing the power factor. To achieve the goal of effectively improving the security and stability of power system operation. The main research work of this paper is as follows: 1 the mechanism and influencing factors of negative sequence current of distribution transformer are analyzed, and a dynamic suppression method of negative sequence current of distribution transformer is proposed. The simulation model of the negative sequence current dynamic suppression method is constructed by using this method combined with the stable operating conditions of the system. The simulation results show that the three-phase unbalanced current and harmonic current are the main influencing factors of the negative sequence current. Furthermore, the validity and feasibility of the negative sequence current dynamic suppression method are verified. 2 combined with the actual engineering environment of the distribution transformer, the negative sequence current dynamic suppression system of the distribution transformer is developed. The system is divided into three-phase unbalanced current control and harmonic current filtering according to its function. The hardware module of three-phase unbalanced current control is designed by using full capacitor compensation mode, including the design of electrical parameter acquisition unit, the design of central control unit, the construction of capacitor cabinet frame and the compensation of capacitor grade grouping, etc. Combined with the existing APF device and considering the elimination of reactive power coupling, the harmonic current filtering part is designed to ensure the good cooperative operation of the whole system. It ensures the safe and stable operation of the system and helps the staff to remotely monitor the operation state of the distribution transformer. The software in the field mainly includes the subroutine of data extraction and identification, the quick calculation of reactive power regulation, the switching control program of capacitor bank and the wireless communication subroutine of GPRS, etc. At the same time, it is based on VC 2010 compiler software and MySQL 5.0 database software. The background data monitoring software of the server is written to dynamically understand the real-time operation parameter information of the field end. 4 based on the proposed negative sequence current dynamic suppression method and the construction of the distribution transformer negative sequence current dynamic suppression system, Experiments were carried out in both laboratory and field environments. Under the condition of the laboratory platform, the operation results show that the system can effectively suppress the negative sequence current caused by the three-phase unbalanced current without harmonic current, and in the field experiment, The system not only can effectively suppress the negative sequence current caused by the three-phase unbalanced current, but also can effectively reduce the influence of harmonic current on the negative sequence current, and can improve the power factor and reduce the additional loss of the distribution transformer.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM421

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