【作者】 于绚；

【导师】 李斌；

【作者基本信息】 天津大学 ， 电力系统及其自动化， 2010， 硕士

【摘要】 基于可再生能源的分布式发电系统是解决世界能源短缺和环境污染的重要途径,也是促进电力工业变革的契机。为协调大电网与分布式电源间的矛盾,充分发掘分布式能源为电网和用户所带来的价值和效益等,微网作为可再生能源并网发电规模化应用的有效途径得到了世界各国的高度重视。微网中分布式电源的存在,使电网从单向供电的模式向大量使用受端分布式发电设备的多源多向模式转变。微网作为一个集电源与负荷一体的系统,有两种运行方式:并网运行和孤网运行。如何在这两种运行方式下切换,即何时并网、何时解列,就成了微网能否稳定运行、减少扰动的一个关键问题。本文研究了微网解列的条件和判定。在大电网中,失步解列是防止电网崩溃的最后一道防线,误解列造成的影响和损失都很大,因此一定要保证失步判别的可靠性;但在微电网中,失步解列是微网解列的重要组成部分,除此之外,很多其他情况也需要解列微网,例如外部故障和非计划孤岛运行等。系统失步解列和微网失步解列在解列影响上的巨大区别,导致了其在要求上的差异,这也使得传统失步解列方案在微网失步解列中不能完全适用,微网失步解列中更注重快速动作,而系统失步解列更注重可靠性。本文分析了失步和振荡情况下测量阻抗、功率、阻抗角、视在阻抗角、U cos(?)等电气量的变化特征,研究了各种判定方式在微网失步解列判别中的适用性。在此基础上,本文利用模糊数学理论,综合考虑了电压、频率、视在阻抗角、U cos(?)的幅值及其变化率特征,提出了微网的综合失步解列方案,并利用仿真数据对其进行了验证。更多还原

【Abstract】 Distributed generation based on renewable energy can relieve the shortage of energy and environmental pollution problems all over the world, consequently promote the power industry. But there are also some cooperant problems between large power grids and distributed generators. To exert the effect and benefit of distributed generator, and simplify the connection of distributed generator, micro-grid operation appeared and be highlighted for special attention.The existence of generators in micro-grid power systems makes the power flow changed from unidirectional to multidirectional. As a whole system of power source and load, micro grid has two operation modes: connection and islanding. To reduce the disturbance of large power system and maintain the stability of micro-grid, how and when to switch micro grid operation between connection and islanding becomes a key issue. This paper is about the out-of-step disconnection of micro-network. The out-of-step disconnection is the last ditch to prevent power system breakdown in traditional large power system, so it must operate based on out-of-step sure, or there would be a lot of load lost for misoperation. But the influence of misoperation of micro-grid is not as important as that in large power system. Out-of step is only one of the disconnection conditions of micro-grid. The requirement different of out-of-step operation between HV power system and micro-grid makes the traditional out-of-step judgment methods not entirely suitable in micro-grid.This paper analyzes some parameters’characteristic and variation when swing or out-of-step occurs, and their applicability in micro-grid out-of-step disconnection. These parameters contain impedance, P and Q, impedance angle, power angle and U cos(?). Based on these analyses, this paper gives an out-of-step algorithm using fuzzy logic. This algorithm combines voltage, frequency, power angle and their changing rate, and algorithm tests show that this new algorithm is more time saving and reliable.更多还原