交流微网保护策略研究

发布时间：2018-05-02 23:33

本文选题：分布式电源 + Park变换　；参考：《华北电力大学》2017年硕士论文

【摘要】：微网作为分布式电源与负荷的有效组网方式,凭借着其对分布式电源的高效利用,以及能够在并网和孤岛两种运行方式下无缝切换等优势而被广泛接受。微网作为控制单元虽然有着易于控制和管理的优点,但是其灵活的运行方式以及复杂的电源故障特点均给现有的保护配置提出了新的挑战,使传统的配电网保护不再具有适用性,因此需要设计新的保护方案。本文围绕此问题进行深入研究,完成的主要工作和成果如下:(1)分析了由逆变型分布式电源组成的微网的故障特性。以三个保护区组成的微网模型作为研究对象,分别在并网和孤岛两种运行方式下进行了故障仿真,深入分析了微网故障特性,为后续工作的开展奠定了基础。(2)研究了基于Park变换的低电压保护方案。为适应微网在孤岛运行方式下故障电流小的特征,利用故障时电压降落作为保护的依据,从而提高了保护的可靠性。该保护方案利用Park变换,把三相电压上的扰动量转换为dq轴的直流量,从而更好地描述故障扰动量。同时,对保护原理进行了理论分析,设定扰动量的阈值实现保护的动作。(3)对基于Park变换的低电压保护方案进行改进,进一步考虑了保护之间的配合以及动作的快速性,提出了一种基于低电压反时限微网保护方案。通过之前的故障特性分析,提出了保护动作方程,阐述了保护的原理。为实现保护之间的配合,对保护上下级之间的配合进行了整定。针对含有旋转式电源的微网,提出了依靠故障选相改进保护的设想;考虑到接地时过渡电阻问题,提出了利用电抗比例系数改进保护的猜想。(4)最后,本文在MATLAB/Simulink平台上搭建了微网系统,对所提方案进行有效性验证。分别对不同故障类型和不同故障点进行仿真,结果表明在并网和孤岛两种运行方式下,基于低电压反时限保护方案能够很好地切除各种故障,并且上下级保护之间能够有效的配合,解决了过流保护无法适应微网故障特性的问题。
[Abstract]:As an effective way of constructing distributed power supply and load, microgrid has been widely accepted because of its advantages of efficient utilization of distributed power supply and seamless switching between grid-connected and islanding operation modes. As a control unit, microgrid has the advantages of easy control and management, but its flexible operation mode and complex power failure characteristics pose new challenges to the existing protection configuration. Traditional distribution network protection is no longer applicable, so it is necessary to design a new protection scheme. The main work and results of this paper are as follows: 1) the fault characteristics of microgrid composed of inverter distributed power supply are analyzed. Taking the microgrid model composed of three protected areas as the research object, the fault simulation is carried out under the two operation modes of grid-connected and isolated island, and the fault characteristics of microgrid are deeply analyzed. A low voltage protection scheme based on Park transform is studied. In order to adapt to the characteristics of the microgrid with small fault current under the isolated island operation mode, the voltage drop during the fault is used as the basis of the protection, thus the reliability of the protection is improved. The Park transform is used to convert the disturbance on the three-phase voltage to the direct current of the dq-axis, which can better describe the disturbance of the fault. At the same time, the theory of protection is analyzed theoretically, and the protection scheme based on Park transform is improved by setting the threshold value of disturbance quantity to realize the protection. The cooperation between the protection and the rapidity of the action are further considered. A low voltage inverse-time microgrid protection scheme is proposed. Through the analysis of fault characteristics before, the protection action equation is put forward and the principle of protection is expounded. In order to realize the cooperation between the protection, the cooperation between the upper and lower levels of the protection is adjusted. Aiming at the microgrid with rotary power supply, the assumption of improving the protection by fault phase selection is put forward, and the conjecture of using reactance proportional coefficient to improve the protection is put forward considering the problem of transition resistance in grounding. In this paper, a microgrid system is built on MATLAB/Simulink platform, and the validity of the proposed scheme is verified. The simulation results of different fault types and different fault points show that under the two operation modes of grid-connected and islanding, the low-voltage inverse time-limited protection scheme can remove all kinds of faults well. The overcurrent protection can not adapt to the fault characteristics of microgrid.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM77;TM727

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