Collaborative Research: Large-Signal Stability Analysis and Enhancement of Converter-Dominated DC Microgrid

题目：合作研究：变换器主导的直流微电网大信号稳定性分析与增强虽然直流微电网具有许多众所周知的优势（例如，更简单、更高效、更紧凑的电力转换系统以及更少的电缆铜消耗），但独特的直流电气特性，如直接P-V耦合（即，即使很小的负载/发电变化也可能导致电压闪变和设备故障）和低系统惯性（即，极少的过载能力），对电网的稳定性构成了巨大的挑战。小信号稳定只能保证系统在平衡点处的稳定，而稳定域的真正边界无法确定；因此，当系统有较大的扰动时，在确保稳定性方面存在很大的限制。现有文献中的大信号分析工具要么适用范围有限，要么理论基础不严谨。因此，迫切需要建立一个以变流器为主导的直流微电网大信号稳定性分析的基础知识库和一个全面的直流电网稳定性设计指南。该项目的研究成果直接有助于我国在微电网和分布式能源越来越多的情况下保持高可靠性和高弹性电力的总体目标。拟议的教育和推广研究计划将(i)将该项目的理论框架、整理的数据集和测试平台纳入密歇根大学迪尔伯恩分校和德克萨斯大学奥斯汀分校的现有课程；（ii）促进K-12学生对STEM的兴趣；（iii）通过公共访问网站、顶级会议和期刊出版物以及各种媒体在公共领域传播所有项目材料、过程、设计和结果；（iv）通过创建对微电网有社会意义的项目，为代表性不足的本科生提供丰富的研究机会。本项目的目标是：(a)采取严格的步骤，推导出具有多个分布式能源和恒定功率负载的直流微电网的大信号全局稳定性的充分标准，这仍然是一个未解决的难题，因为传统的小信号稳定性分析不适用于发生大干扰时的变流器主导的电力系统，如故障，脉冲功率负载或负载切换；(b)研究一种系统的方法，以理论上合理但易于实施的方式改善变流器主导的直流微电网的全局渐近稳定性，最终弥合三个传统上脱节的领域之间的技术差距：控制理论，电力系统和电力电子。拟议的项目旨在通过利用pi的专业知识（例如，电力系统，电力电子，优化，控制理论和机器学习）的范围和深度来实现这一目标。提出的研究将在以下方面具有智力优势：(1)为理解100%恒功率负载渗透和基于变流器的分布式能源的无惯性直流微电网的大信号稳定性准则提供基础知识基础；(2)稳定感知变流器，以理论上合理且易于实现的方式共同提高变流器主导的直流微电网的全局渐近稳定性；(3)用严格的数学方法和安全的学习算法估计具有多平衡点的一般动态系统（即直流微电网）的吸引区域；(4)一个电源-硬件在环测试平台，允许创新的稳定感知转换器的概念验证原型的动态交互。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。

Title: Collaborative Research: Large-Signal Stability Analysis and Enhancement of Converter-Dominated DC MicrogridAbstract: While DC microgrids have many well-understood advantages (e.g., simpler, more efficient and compact power conversion system as well as less copper consumption in the cables), the unique DC electric characteristics, such as direct P-V coupling (i.e., even a small load/generation change can lead to voltage flickers and equipment malfunctions) and low system inertia (i.e., very little overload capacity), pose great challenges to grid stability. Small-signal stability can only ensure the stability of the system at the equilibrium point, but the true boundary of the stability domain cannot be determined; hence there are major limitations in securing stability when the system has large disturbances. Existing large-signal analysis tools in the literature have either limited applicable ranges or non-rigorous theoretical foundations. Therefore, there is an urgent need to develop a fundamental knowledge base of large-signal stability analysis in converter-dominated DC microgrids and a comprehensive design guideline for DC grid stability. The research findings of this project directly contribute to the overall goal in our country to maintain high reliability and resilience electricity with more and more microgrids and distributed energy sources. The proposed education and outreach research plan will (i) incorporate theoretical frameworks, curated data sets, and testbed from this project into the existing curriculum at both the University of Michigan-Dearborn and the University of Texas at Austin; (ii) promote K-12 students’ interest in STEM; (iii) disseminate all project materials, processes, designs and results in the public domain via public-access websites, top-ranking conference and journal publications and in diverse media; and (iv) provide rich research opportunities to under-represented undergraduates by creating societally meaningful projects on microgrids.The goal of this project is to (a) take a rigorous step toward deriving the sufficient criteria for large-signal global stability in DC microgrids with multiple distributed energy sources and constant power loads, which is still an unsolved puzzle because traditional small-signal stability analysis does not apply to converter-dominated power systems when a large disturbance occurs, such as a fault, a pulse power load, or load switching; and (b) investigate a systematic methodology to improve the global asymptotic stability of a converter-dominated DC microgrid in a theoretically sound yet easy-to-implement manner, ultimately bridging the technology gap between three traditionally disjointed areas: control theory, power systems, and power electronics. The proposed project aims to fulfill this goal by leveraging the range and depth of the PIs’ expertise (e.g., power systems, power electronics, optimization, control theory, and machine learning). The proposed research will have intellectual merits in the following areas: (1) a fundamental knowledge base to understand the large-signal stability criteria of inertia-less DC microgrids with 100% penetration of constant power loads and converter-based distributed energy sources; (2) a stability-aware converter to collectively improve the global asymptotic stability of converter-dominated DC microgrids in a theoretically sound yet easy-to-implement manner; (3) rigorous mathematical methods and safe learning algorithms for estimating the region of attraction of a general dynamic system (i.e., a DC microgrid) with multiple equilibria; and (4) a power-hardware-in-the-loop testbed allowing for dynamic interactions of the proof-of-concept prototypes of innovative stability-aware converters.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.