Ensuring Resilient Operation of the Future Power System with High Levels of Renewables using Switched Mode Devices

近年来，电力系统迅速引入了新型发电和新型负荷。这些新组件中的许多都通过由嵌入式数字信号处理器控制的电力电子转换器与电网连接。这种变流器的行为与传统电网中占主导地位的机电机械和无源设备截然不同。电力电子接口器件调节时间快，数字信号处理器编程灵活，具有较强的整体可控性。根据程序设置，它们可以在各种不同的动态模式下运行。此外，在电网中出现了各种新的复杂混合动力学，其机理尚不清楚。本提案旨在分析这些新的动态，并提供工程设计指南，以提供系统范围的性能保证。随着电力电子变流器数量的迅速增加，可再生资源和负载与电网中更传统的设备相互连接，产生了新的复杂混合动力学。在本项目中，引入了一个集理论框架，并提出了一个特征集的概念来解释现代电力系统的开关行为，标记离散事件和综合模式。在此原则下，将基于被动性的屏障证书框架以数学程序的形式构建，计算相应模式的特征集，从而建立监管级综合。利用变换器的可控性，利用控制Lyapunov-barrier函数设计辅助控制，降低了传统反馈控制器的保守性，扩大了特征集，提供了全系统的性能保证。模式综合和控制目标是确保状态在安全范围内运行，即在运行约束内运行。主要研究任务包括：(a)建立适当的数学基础来估计具有期望性质的安全区域，即估计误差和算法收敛性；(b)设计保持属性的反馈控制器以满足系统要求；(c)将设计的控制器和现有的非线性控制器（主要是死带和饱和）集成在一起，形成一个综合的混合闭环系统设计；(d)在连接网络的集中、分散或分布式结构下，综合不同来源之间的多种模式；(e)通过在无限维连续空间和模型约简的有限和离散近似框架中所需的正性证书的替代程序实现来解决可扩展性问题。

In recent years, electric power systems have seen a rapid introduction of both new types of generation and loads. Many of these new components interface to the grid through power electronic converters that are controlled by embedded digital signal processors. Such converters have a very different behavior than the electromechanical machines and passive devices that have been predominant in the traditional grid. Power electronic interfaced devices have greater overall controllability because of their fast regulating time and the flexible programming of digital signal processors. Depending on the program settings, they can operate under a variety of different dynamic modes. Moreover, a variety of new complex hybrid dynamics have arisen in the power grid whose mechanisms are poorly understood. This proposal seeks to analyze these new dynamics and provide engineering design guidelines that can provide system-wide performance guarantees.Due to a rapid increase of power electronic converters interfaced renewable resources and loads interconnected with the more traditional devices in the power grid, new complex hybrid dynamics have arisen. In this project, a set-theoretic framework is introduced and a feature set concept is proposed to explain switching behavior, label discrete events and synthesize modes for modern power systems. Under this principle, a passivity-based barrier certificate framework is formulated as a mathematical program to compute the feature sets of corresponding modes such that the supervisory level synthesis can be established. Moreover by taking advantage of converter controllability, a control Lyapunov-barrier function is employed to design a supplementary control to reduce the conservatism of traditional feedback controllers, enlarge the feature sets and provide system-wide performance guarantees. The mode synthesis and control objective is to ensure states operate within a safe range, i.e., within operational constraints. The main research tasks include: (a) establishing the proper mathematical foundation to estimate safe regions with desired properties, namely, estimate the errors and algorithm convergence; (b) design property-preserving feedback controllers to meet system requirements; (c) integrate designed controllers and existing controllers with nonlinearities (primarily, deadband and saturation) to form a comprehensive hybrid closed-loop system design; (d) synthesize multiple modes among different sources under a centralized, decentralized or distributed structure for a connected network; and (e) address scalability issues through alternative program realization of positivity certificates required in the framework of finite and discrete approximations of infinite dimensional continuous space and model reductions.