CPS: Medium: Coupled cAscade Modeling, Prevention, and Recovery (CAMPR): When Graph Theory meets Trajectory Sensitivity

本文的研究重点是电能网络物理系统（CPS）的级联故障，这是我国的关键基础设施。级联故障是指一个或几个部件的故障导致互联系统的大范围故障，是电网停电的主要原因。此类故障的机制非常复杂，因为它以耦合的方式涉及电网的物理层（例如发电机、传输线等）和网络层（例如通信和控制元件）。这是一个需要调查的非常重要的问题，因为连锁故障可能会使我们的经济损失数十亿美元。该项目以整体的视角来控制电力CPS中的级联故障。所提出的研究有两个紧密耦合的推力区域。推力1旨在准确理解级联故障机制及其预防，而推力2则侧重于故障位置不确定的停电后的恢复。利用轨迹灵敏度理论和图论来发展对能量CPS级联故障的基本理解，这可以应用于物理系统本质上是动态的，并且物理系统和网络系统中的故障传播是耦合的其他CPS。所提出的预防性控制策略可以保护关键基础设施免受大规模故障的影响，并提供更高的弹性，而所提出的恢复策略适用于由级联、自然灾害或其他事件引起的停电后，这将减少关键基础设施的停机时间。为了支持扩大妇女参与计算机活动的倡议，拟议的研究将被纳入宾夕法尼亚州立大学EECS学院提供的为期一周的夏令营。关于这项研究的演讲将在2019年的夏令营中进行一周，然后将在2020年和2021年提供以这项研究为主题的课程为重点的夏令营。提出的研究有两个关键目标：(a)准确理解级联故障机制及其预防，(b)在故障位置和预算约束不确定的情况下制定停电后的恢复计划。文献中用于研究级联传播的电网准稳态模型对停电后期的结果不准确，而完全动态模型对于大规模统计分析是不切实际的。为解决这一问题，提出了一种“时间混合”模型和一种“时空混合”模型，利用轨迹灵敏度理论分别在系统级和组件级量化网格的应力，并适当地从QSS模型切换到动态模型。接下来，为相互依赖的电网和通信系统开发了一个统一的基于图形的模型，该模型考虑了传统的监控和数据采集（SCADA）系统以及现代广域监测、保护和控制（WAMPAC）系统的几个特殊功能，以及它们为CPS提供的可观察性和可控性。在此基础上，提出了一种稳定约束的级联预防补救措施方案。最后，在存在预算约束和故障不确定性的情况下，提出了一种利用混合电网模型和统一通信网络模型的渐进式评估和恢复方法。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The proposed research focuses on cascading failures in electrical energy cyber-physical systems (CPS), which is a critical infrastructure of our nation. Cascading failures, where the failure of one or few components causes a wide-spread failure of the interconnected system, is a major cause of blackouts in power grids. The mechanism of such failures is highly complex as it involves the physical layer of the grid (e.g. generators, transmission lines, etc.) and the cyber layer (e.g. communication and control elements) in a coupled manner. This is a very important problem to investigate as cascading failures can cost our economy billions of dollars. This project takes a holistic view at taming cascading failures in electrical energy CPS. The proposed research has two tightly coupled thrust areas. Thrust 1 aims at an accurate understanding of the cascading failure mechanism and its prevention, while Thrust 2 focuses on recovery following blackouts under uncertainty of failure locations. Theory of trajectory sensitivity and graph theory are leveraged to develop a fundamental understanding of cascading failures in energy CPS, which can be applied to other CPSs where the physical system is dynamic in nature and the failure propagation in the physical system and the cyber system are coupled. The proposed preventive control strategy can protect critical infrastructures from large-scale failures and facilitate higher resiliency, whereas the proposed recovery strategy is applicable in the aftermath of a blackout caused by cascades, natural disasters, or other events, which will reduce downtime of the critical infrastructure. In support of the Broadening Participation in Computing initiative among women, the proposed research will be integrated into the one-week summer camps offered by the School of EECS at Penn State. Presentations about this research will be given to high school girls over the course of one week in the 2019 camps, and then camps focused on curriculum on the topic of this research will be offered in 2020 and 2021.The proposed research has two key objectives (a) develop an accurate understanding of the cascading failure mechanism and its prevention, and (b) develop a recovery plan following blackouts under uncertainty of failure locations and budget constraints. The quasi-steady-state (QSS) model of power grid used in literature for studying cascade propagation produces inaccurate results towards the later stages of blackouts, whereas a fully dynamic model is impractical for large-scale statistical analyses. To solve this, a 'temporally hybrid' and a 'spatio-temporally hybrid' model are proposed, which quantify the stress of the grid at the systems level and the component level, respectively, using trajectory sensitivity theory, and appropriately switch from the QSS to the dynamic model. Next, a unified graph-based model for interdependent power grid and communication systems is developed, which takes into account several special features of the legacy Supervisory Control and Data Acquisition (SCADA) system along with the modern Wide-Area Monitoring, Protection, and Controls (WAMPAC) system, and the observability and controllability they provide for the CPS. Furthermore, a stability-constrained remedial action scheme for cascade prevention is proposed. Finally, a new approach for progressive assessment and recovery, which leverages the hybrid power grid models and the unified communication network model, is proposed in the presence of budget constraints and failure uncertainties.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.