【作者】 于洋；

【导师】 韩祯祥； 甘德强；

【作者基本信息】 浙江大学 ， 电力系统及其自动化， 2008， 博士

【摘要】 以超高压、长距离输电、大容量机组、大范围互联和大容量的区域间交换为显著特征的现代电力系统,其稳定性一旦遭受破坏,必将造成巨大的经济损失和灾难性的后果,致使电力系统安全稳定问题一直是研究的热点。近年来,国内外发生的多次严重大停电事故充分地暴露了大型互联电网的脆弱性,因此对大停电事故的原因、发展机理以及预防措施的研究愈发重要和迫切。为此,国内外学者做了大量研究工作并提出了多种连锁故障模型,如OPA、CASCADE及隐性故障等,但与系统的实际情况存在一定的偏差,各电气元件的动态特性、电气参量的时域动态过程等问题都尚未解决。本文针对这些问题提出了电力系统的动态连锁故障模型,并分析了电力系统连锁故障及其自组织临界性。在此方面,本文做了如下主要工作:1.提出了一种基于频率稳定性的电力系统连锁故障模型。该模型用以研究电力系统短期频率随机动态特性,考虑了机组频率保护、低频减载装置以及元件切除时间等随机因素,并基于蒙特卡罗模拟方法分别予以分析。仿真结果初步揭示了电力系统连锁故障中频率动态的统计特性,对比分析了一次调频、起始故障规模、旋转备用容量以及不同低频减载方案对频率动态过程和停电规模及其概率的影响。2.提出了一种基于交流潮流及长期动态仿真的连锁故障模型。该模型考虑了含发电机组及负荷的全系统动态行为,同时考虑了在动态过程中机组保护、低频/低压减载、变压器过励磁、线路过载/短路保护及解列等自动装置受随机因素的影响。该模型可以较为准确的模拟电力系统动态行为及连锁故障。以PSS/E软件为仿真平台采用蒙特卡罗方法对我国某省实际电网予以仿真,仿真结果证实了所提模型可以较为准确、有效地模拟系统连锁故障,并较真实地反映了该电网实际存在的问题,仿真结果的统计数据表明系统停电规模及其概率基本符合幂率特性。与以往结论不同,根据仿真结果发现了系统存在故障规模临界点,在临界点前后系统的幂率特性会发生变化,并指出了临界点对大停电预防的重要意义。3.根据所提的动态连锁故障模型,对电网的参数做了灵敏度分析。比较了不同的减载方案、减载原理、负荷构成、一次调频以及区外联络线传输功率等因素对系统的自组织临界性、临界点以及停电概率的影响,最后根据仿真结果对预防大停电所需采取的措施提出了一些建议。4.提出了不同孤岛反措下确定性的分布式电源最大准入容量计算方法。该模型考虑了机组频率和电压保护、低频减载、低压减载以及线路过载等约束条件,比较了不同的孤岛反措方案对最大准入容量的影响,为分析分布式电源对连锁故障的影响提供了一些理论基础。5.建立了计及分布式电源的动态连锁故障模型,研究了不同DG接入水平及孤岛反措对系统连锁故障及自组织临界性的影响,仿真结果表明停电概率随关闭主力机组且DG接入水平的增大而波动,并根据系统停电概率讨论了DG的最大准入容量,为确定适当的DG接入水平提供了新的方法和思路。更多还原

【Abstract】 The insecurity and instability problems will certainly cause enormous losses and catastrophic results for modern power systems with the feature of extra high voltage and long-distance transmission lines, large capacity generators, cross-regional inter-connections and huge inter-area power exchanges. Therefore, studies on the power system security and stability have been received much attention for a long time. Several blackouts in the past few years fully reveal the vulnerability of large inter-connection power system. It’s important and urgent to research on the reason, evolvement and preventive measures of blackouts. Many works have been done and some of cascading outage model, such as OPA, CASCADE and Hidden Failures were present by the researchers. However, these cascading outage models are imprecise and some factors, such as time-domain dynamic characteristic of electric components are not included. To solve these problems, dynamic cascading outage models are present in this thesis and self-organized criticality(SOC) of power system is analysed. Contributions are summarized as follows:1. A cascading outage model with its stochastic counterparts are present for cascading failure investigation. Stochastic factors associated with generator frequency relay, u.f. load shedding and breaker tripping time, etc. are explicitly modeled. Using a Monte Carlo simulation tool, the risk of frequency-induced cascading failures is assessed. The influences of relevant factors on statistic characteristic of power system cascading failures, such as frequency primary regulation, AGC (spinning reserve), the size of initial disturbance and u.f. load shedding schemes, are also analyzed. The results presented demonstrate interesting values of the model in identifying the factors that contribute to cascading failures and blackouts.2. A cascading outage model based on dynamic simulation has been developed and analyzed in this work together with its stochastic counterpart. The factors, such as stochastic characters of generator frequency/voltage protection, under-frequency/under-voltage protection, over-excitation, overload, short circuit and its tripping time, are considered. The model captures the fundamental dynamic characteristics of power system and its validity and accuracy for studying system cascading are confirmed based on PSS/E with Monte Carlo simulation. The results show the existence of the power law with critical points. When the critical point is exceeded, the outage size and its probability rise rapidly and the power law characteristic is changed. Critical points provide helpful information for blackout prevention.3. Based on dynamic cascading outage model, the influence of simulation parmaters, such as under-freqency/voltage load shedding, load components, primary regulation and tie-line power flow on power system SOC, critical points and blackouts probability is analysed. Some suggestions for blackout prevention is present hereby.4. The maximum penetration level of distributed generation under different anti-islanding methods is calculated using dynamic simulation. The frequency/voltage protection, under-frequency/volage load shedding and capacity constrains of transmission lines are fully consided. The influency of anti-landing methods on maximum peretration level of DG is discussed. These provide theoretical basis for analyzing the influence of DG on cascading outages.5. A cascading outages dynamic model with DG comprised is present. Influency of Different penetration levels of DG and aiti-landing methods on cascading outages and its SOC is analysed. The simulation results reveal that probability of blackout changes periodically with increasing of DG penetration level and main generator shutdown. The maximum penetration level of DG is discussed based on blackout probability.更多还原