Collaborative Research: Innovative Approaches for Robust and Reliable Operation of Voltage Source Converters in Critical Conditions of Emerging Grids

合作研究：新兴电网关键条件下电压源变换器稳健可靠运行的创新方法并网电压源变换器越来越多地应用于能源领域，例如用于分布式能源与电网的互联。转换器的功能不佳的瞬间可能导致局部和系统级问题。例如，南加州1,200兆瓦故障引起的太阳能光伏资源中断的原因是逆变器控制系统中采用的锁相环功能错误。现场数据还显示，由于电网电压谐波和常规公用事业自有电容器开关事故造成的部分或全部发电损耗，光伏逆变器运行不稳定。在具有挑战性的条件下，精确和鲁棒的频率估计、电压同步和电流生成等功能对于保持分布式资源高渗透的电网的可靠性至关重要。这项研究已经确定了1)电网的弱点，2)电网电压畸变，以及3)电网电压和频率干扰，作为广泛描述的主要关键电网条件。因此，本文建议1)研究这些条件对逆变器功能的影响，2)综合创新和有效的解决方案。提出的研究投资于开发模块化，实用和高效的解决方案，充分集成转换器组件，并最大限度地减少损害多目标系统完整性的苛刻组件。项目成果将提高未来电网关键工况下逆变器响应的质量和强度，并将导致1)提高电力系统可靠性，2)改善其电能质量，3)增加其逆变器承载能力。这将加强公共电力交付服务，赋予相关能源行业权力，并在各种教育和研究团体之间建立新的联系。该项目将刺激和维持多元化学生的跨学科培训，特别是在密西西比州立大学和佐治亚南方大学参加STEM项目的代表性不足的少数民族，并改善广泛的STEM课程。本研究将建立理论，以有效地制定并网变流器的组成部分之间的相互作用，如锁相环和控制器，以及变流器和宿主电网之间的相互作用。有效的建模、分析和控制过程将被开发出来，以实现变流器与弱、污染和扰动电网条件的鲁棒集成。锁相环、最优鲁棒控制、信号和发生器仿真理论被用来将变换器元件牢固地结合在一起，并以最优的方式设计它们。该项目的方法是充分集成和优化转换器组件，而不添加冗余和不连接的组件，这些组件可能会损害这个多面和高耦合工程系统的其他方面。特别是，将部署和结合最新的锁相环先进模型和最新的最优控制设计方法，将锁相环完全集成到变换器的整个控制系统中，并以最优和鲁棒的方式设计整个控制系统。高保真功率-硬件在环测试将用于检验所提出方法的实用性和有效性。通过全组件集成，减少振荡和不稳定性，拟议的项目将增加给定电网的逆变器托管容量，以及其可靠性和电能质量。该项目还将加强这些多个领域的基础知识（即锁相环，最优和稳健控制以及信号），以应用于将可再生资源整合到二十一世纪的电力和能源系统中的关键问题。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。

Collaborative Research: Innovative Approaches for Robust and Reliable Operation of Voltage Source Converters in Critical Conditions of Emerging GridsGrid-connected voltage source converters are increasingly deployed in the energy sector, e.g. for the interconnection of distributed energy resources to the power grid. An instant of the converter's poor functionality can cause local and system level problems. For example, the cause of the 1,200 MW fault-induced solar photovoltaic resource interruption in Southern California is identified in erroneous functioning of the phase-locked loop employed in the inverter control system. The field data also show an unstable operation of photovoltaic inverters caused by grid voltage harmonics and partial or full generation loss caused by routine utility-owned capacitor switching incidents. Functions such as accurate and robust frequency estimation, voltage synchronization, and current generation during challenging conditions are crucial to maintaining the reliability of a power grid with high penetration of distributed resources. This research has identified 1) grid weakness, 2) grid voltage distortions, and 3) grid voltage and frequency disturbances, as broadly describing the major critical grid conditions. Thus, it proposes to 1) investigate the impacts of these conditions on the inverter functions, and 2) to synthesize Innovative and Effective Solutions. The proposed research invests in developing Modular, Practical and Efficient solutions that fully integrate the converter components and minimize demanding components that compromise the integrity of this multi-objective system. The project results will advance the quality and strength of inverter responses during critical conditions of future grids and will lead to the 1) improvement in the power system reliability, 2) improvement in its power quality, and 3) increase in its inverter hosting capacity. This will enhance the public power delivery services, empower the related energy industry, and develop new ties among various education and research communities. The project will stimulate and sustain the cross-disciplinary training of diversified students, particularly the underrepresented minorities enrolled in STEM programs at Mississippi State University and Georgia Southern University, and improve the broad STEM curricula. This research will establish theories to effectively formulate interactions among components of a grid-connected converter such as its phase-locked loop and its controller and between the converter and its hosting power network. Effective modeling, analysis and control processes will be developed for robust integration of the converter to the weak, polluted, and disturbed grid conditions. The phase-locked loop, optimal and robust controls, signals, and generator emulation theories are used to solidly tie the converter components together and design them in an optimal way. The project's approach is to fully integrate and optimize the converter components without adding redundant and disjoint components which may compromise other aspects of this multi-faceted and highly coupled engineering system. Particularly, recent advanced models of the phase-locked loops and recent optimal control design approaches will be deployed and joined to fully integrate the phase-locked loop into the entire control system of the converter and to design the entire control system in an optimal and robust way. High-fidelity power-hardware-in-the-loop testing will be used to examine the practicality and effectiveness of the proposed methods. Through full components integration leading to reduced oscillations and instabilities, the proposed project will increase the inverter hosting capacity of a given power grid, as well as its reliability and power quality. The project will also enhance the fundamental knowledge in those multiple fields (i.e. the phase-locked loops, optimal and robust controls, and signals) as applied to the crucial problems of integrating renewable resources to the power and energy system of our twenty-first century.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.