【作者】 徐萌；

【导师】 邹贵彬； 袁文广；

【作者基本信息】 山东大学 ， 电气工程（专业学位）， 2017， 硕士

【摘要】 一种由分布式电源、储能装置、智能化用户与可控负荷、监控和保护装置构成的新型供电系统,即"微电网",成为了解决配电网分布式电源高度渗透的重要途径。然而,微电网运行方式灵活多变,且内部分布式电源以逆变型电源为主,给传统配电网保护原理带来了严峻的考验。微电网拓扑结构复杂多样,上级电网馈线保护、并网点保护、微电网内部元件保护间的合理配合也成为了微电网保护研究的难点之一。对此,本文以微电网并网点保护与微电网馈线保护为对象开展研究,论文的主要工作与取得的成果如下所述。(1)在逆变型分布式电源故障特征的研究基础上,分别分析了传统保护原理中功率方向元件与正序故障分量方向元件在含逆变型电源配电网中的适用性,为微电网并网点保护及内部馈线保护原理的研究提供理论基础。(2)根据故障隔离策略对并网点开关动作行为的要求,利用不同故障情形下的延时环节实现并网点保护与上级电网馈线保护、微电网内部馈线保护、并网运行规范要求间的逻辑配合。利用并网点故障前后正序功率方向与正序电流幅值变化,提出了一种并网点处新型故障方向判别方法,并设计了过电流保护、低电压保护作为辅助判据,解决了三相金属性短路故障时的方向判别死区问题。(3)借鉴电流差动保护原理思想,基于微电网馈线区内外故障时正序差动阻抗的幅值差异,提出了一种适用于微电网馈线故障特征的正序阻抗差动保护原理。为进一步改善保护性能,有效应对分支负荷的影响,构造了带制动特性的动作判据。针对区内三相金属性短路故障时保护存在的死区问题,利用故障时正序阻抗与正序电流幅值特征构造了辅助判据。与传统电流差动保护相比,所提方法无需两端数据同步采样,对通信要求较低。以智能测控终端为平台,设计了保护软件流程,开发了面向工程实际的正序阻抗差动保护装置。软件仿真与装置测试结果均验证了保护原理的有效性。(4)基于不同故障类型下微电网馈线保护安装处各故障相能量函数的特征分析,提出了一种基于故障超前相的能量方向纵联保护方法。构造了幅值辅助判据以克服区内分支负荷投切的影响,研究了正序分量控制的逆变型分布式电源接入情形下保护原理的适应性。仿真结果表明,保护原理能够正确识别故障方向,并能躲过负荷投切的影响,且具有一定的抗过渡电阻的能力。更多还原

【Abstract】 A novel power supply system consisting of distributed generations,storage devices,smart consumers and controllable load,control and protection devices,namely’microgrid’,has become an important method of solving problems raised by the high penetration of distributed generations into distribution network.However,the flexibility of operation modes of microgrid with inverter-based distributed generations presents a severe challenge to traditional distribution network protection principles.Besides,the complex structure of microgrid,the reasonable cooradintion of main-grid feeder protection,grid-connection point protection and internal component protection of microgrid becomes one of the problems related to microgrid protection.This paper focuses on grid-connected point protection and internal feeder protection of microgrid.Firstly,based on the fault characteristic analysis of inverter-based distributed generation,the feasibilities of widely-used traditional power direction elment and positive sequence fault component direction element are studied respectively to proposetheoretical basis to grid-connected point protection and internal feeder protection of microgrid.According to requirements of fault isolation strategy for operation behaviors of grid-connected point switch,logical coordination of main-grid feeder preotction,internal feeder protection and paralleling opearation standard of microgrid is achieved by different time-delay segments in various fault cases.The variations of positive sequence power direction and positive sequence current amplitude at grid-connected point are utilized to construct a novel fault direction identification method.To solve its dead zone problem in three-phase short circuit fault case,over-current protection and low-voltage protection are designed as auxilliary criterions.Using current differential protection for reference,the amplitudes of the defined positive sequence differential impedance for the internal and external fault are analyzed,and a novel positive sequence differential impedance protection principle is proposed based on the impedance amplitude difference.To improve the performance,an operation criterion with braking characteristic is constructed to overcome the adverse effects of load branch.An auxiliary criterion based on the amplitude of positive sequence impedance and current is constructed for internal three-phase short circuit faults without transition resistance.Compared with traditional current differential protection,the proposed protection strategy has no need for synchronization measurement.Using the intelligent measurement and control terminals as a platform,protection software process is designed and a set of positive sequence impedance differential proection device faced to engineering application is developed.The feasibility of protection scheme is verified by simulation and device test results.On the basic of the various characteristics of energy function of each phase for different fault types at protection location of mircogrid feeder,amodified pilot protection method based on leading phase energy directionis proposed.An amplitude supplementary criterion to overcome effects of load switching is constructed and the adaptability of the proposed method in the presentence of inverter-based distributed generations is analysed.Simulation results show that the proposed scheme is able to identify fault directions and its performance is not only immune to the load change but resistant to transition resistance to some extent.更多还原