【作者】 赵峰；

【导师】 林湘宁；

【作者基本信息】 华中科技大学 ， 电力系统及其自动化， 2014， 博士

【摘要】 电网作为保障现代社会经济发展和安全稳定的重要基础设施,其安全问题一直受到高度的关注。近年来大停电事故的多次发生揭示了电网本身存在固有的安全隐患,极端自然灾害暴露了电网应对恶劣外部环境时的脆弱性,电网在蓄意攻击场景下的应对能力应当引起警惕。电网在“内忧外患”环境下的生存能力值得深思。现有的电网生存性评估或脆弱性评估理论已取得了许多成果但仍存在一些不完善的地方,如单纯从电网结构的角度考虑电网脆弱性而忽视了电网运行方式的影响,缺乏对于电网结构均衡性和脆弱性之间相互关联的深入分析和评价,少有从内因和外因相结合的角度对于电网正常运行方式下和电网扰动状态下的电网生存性的综合评判。为此,本文从电网完成基本电能传输任务能力的角度围绕电网在正常运行方式下和扰动状态下已存在和潜在的生存问题展开研究,建立了电网生存性评估指标体系评估方法及扰动源定位方法。完善了电网生存性评估的理论体系,为电网安全性评估提供了一个新的角度。所做的工作和所取得的主要成果归纳如下：提出了基于潮流追踪方法的电能传输路径解析方法,能够透过电网潮流的表面深入分析电能流动的深层特性,得到全网的“发电机-负荷”节点之间的所有电能传输路径,并基于电能传输路径分析定义了电气距离,克服了只依赖网络结构定义电气距离方法的缺陷,能够更全面地反映电网的电能传输特性。在此基础上构建了能够反映电网电能传输效率的畅通性评估指标及方法,并能够辨识出对电网电能传输中起枢纽作用的重要元件。考虑了电网关键节点与关键支路在空间尺度上的分布特征对也电网脆弱性的影响,提出了考虑多源扰动及电网自身结构均衡特性的电网脆弱性评估指标与评估方法。通过分析电网节点和支路在电能传输作用方面的分布差异提出电网结构的均衡度指标,定义了节点之间的空间距离和支路之间的空间距离,并提出了关键节点的空间分布均衡度和关键支路的空间分布均衡度。综合考虑元件失效对于电网整体传输性能的影响建立了电网对于关键元件的依赖度指标。分析了电网在随机失效和蓄意攻击2种模式下的脆弱性。建立了综合考虑电网畅通性、均衡性和脆弱性的电网生存性评估指标体系及评估方法研究,提出了基于层次分析法和改进灰色关联度法的生存性指标权重分层优选方法,将电网生存性各项指标综合形成一个有机整体。提出了基于电网生存性评估的电网规划方案方法。基于典型实际电网算例构建了4个规划方案,计算了各个规划方案的生存性各项指标,得出了每一个规划方案的生存性水平。算例分析表明电网畅通性与电网脆弱性之间既相互联系又存在着一定的矛盾,证明了电网生存性体系将畅通性和脆弱性结合考虑的必要性。针对威胁电网生存性的两类元件的典型失效场景,分别提出了相应的扰动源准确定位方法。针对传统的发电机过电压保护在发电机并列运行场景下的选择性和速动性不足问题,提出了发电机并列运行场景下过电压源辨识策略,既能够在发电机励磁系统失灵时快速切除故障发电机,又能够在系统甩负荷等外部因素下充分发挥发电机AVR的电压调节作用以保证系统电压水平的恢复。分析了现有行波故障定位方法截断误差来源并提出了行波故障定位校正方法,在低采样率能够显著减小最大故障定位误差,在高采样率下能够提升高精度故障定位结果出现的概率。所提出的两种扰动源定位方法能够为电网应对元件失效场景的生存能力提供重要的保障。更多还原

【Abstract】 As an important infrastructure to guarantee social and economic development, security issues of power systems have always been highly concerned. Occurrence of blackout accidents in recent years has revealed the inherent potential safety hazard of power grid itself. Extreme natural disasters exposed the vulnerability of the grid under extreme conditions. Coping capacity of power systems in deliberate attack scenarios should cause alarm. Power systems survivability in conditions of both domestic trouble and foreign invasion is worth thinking about.Existing power survivability assessment or vulnerability assessment theory has obtained many achievements but there are still some imperfections, such as most theory focus on one aspect of power grid vulnerability, lack of comprehensive evaluation of power grid in normal and disturbance conditions from the internal and external perspective. If a power transmission grid in normal operation mode is smooth, generally it has more hub of higher degree of nodes and branches. However, when a high degree of node or branch fails, the impact on power grid will be more serious, and will have much higher degree of vulnerability. To solve the survival problems of power systems under normal condition and disturbance, from the perspective of power transmission efficiency, this paper established power system survivability index system and its evaluation method as well as disturbance location scheme.Power transfer path analysis method is proposed based on power flow tracing, and is able to deep analyze power transfer characteristics through the surface of the power flow and obtain all power transmission paths between generator and load. On the basis of power transfer path analysis, power smoothness evaluation index and method is constructed to reflect grid electricity transmission efficiency. The proposed index is able to identify pivotal components in power transmission.Power system vulnerability index and its evaluation method are put forward with consideration of multi-disturbance and evenness of power grid structure. Power grid evenness index is proposed based on distribution differences of nodes and branches in power transfer process. Spatial distance between nodes and spatial distance between branches are respectively defined. Spatial distribution evenness index for key nodes and key branches are proposed. Considering comprehensive influence of component failure on power transfer, key component dependence index is established. Power system vulnerability is analyzed under random failures and deliberate attack.On the basis of smoothness, evenness and vulnerability index, power system survivability index and evaluation method is established. A combined weight hierarchical optimizing method based on analytic hierarchy process (AHP) and improved gray correlation method is proposed to solve and calculate index weights of the survivability index system.Power grid planning evaluation method based on power system survivability is proposed. Based on Southern Brazilian46-bus network, four planning cases are designed, and survivability level of each case is calculated. Case study indicates that there are some contradictions between the smoothness and vulnerability also proves the necessity of evaluating both smoothness and vulnerability.Against two typical component failure mode that threat power system survivability, the disturbance location method is proposed respectively. A novel criterion for exactly identifying the machine leading to overvoltage of the common bus among the machines working in parallel is developed, to overcome loss of selectivity of existing schemes in some cases. By mean of this scheme, the machine leading to the overvoltage of the common bus due to the exciter runaway can be discriminated and removed appropriately. In comparison, the overvoltage due to load shedding can be identified as the one due to the external reason. Then, the machines with healthy exciters will not be tripped incorrectly, which will allow the AVR operates appropriately to adjust the system voltage back to the normal level. Based on the analysis of truncated error, a universal wavefront positioning correction method on traveling-wave-based fault-location algorithms is proposed. The proposed correction method is able to control the location error within150m under a different sampling rate. The maximum error is reduced by order at a low sampling rate. In the case of a high sampling rate, the probability distributions of location error are improved significantly although the maximum error cannot be decreased significantly. The two disturbance location methods provide important foundation for power system survivability against typical component failures.更多还原