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

合作研究：在新兴电网的关键条件下稳健可靠地运行电压型变流器的创新方法并网的电压型变流器越来越多地部署在能源部门，例如用于分布式能源与电网的互联。转换器功能不佳的瞬间可能会导致本地和系统级别的问题。例如，南加州1,200兆瓦故障导致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运行错误。现场数据还显示，由于电网电压谐波和常规电力公司电容器投切事件导致的部分或全部发电损失，光伏逆变器运行不稳定。在分布式资源渗透率较高的情况下，准确而稳健的频率估计、电压同步和挑战条件下的电流产生等功能对于维持电网的可靠性至关重要。这项研究确定了1)电网薄弱，2)电网电压失真，3)电网电压和频率扰动，概括地描述了主要的关键电网条件。因此，它建议1)调查这些条件对逆变器功能的影响，以及2)综合创新和有效的解决方案。拟议的研究投资于开发模块化、实用和高效的解决方案，以完全集成转换器组件，并将危及该多目标系统完整性的要求最低的组件降至最低。该项目的成果将提高逆变器在未来电网关键条件下的响应质量和强度，并将导致1)电力系统可靠性的提高，2)电能质量的改善，3)逆变器承载能力的增加。这将增强公共电力输送服务，为相关能源行业提供动力，并在各个教育和研究社区之间发展新的联系。该项目将刺激和维持对多样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课程的代表性不足的少数族裔，并改进广泛的STEM课程。这项研究将为有效地描述并网变流器的锁相环和控制器以及变流器与其所在电网之间的相互作用奠定理论基础。将开发有效的建模、分析和控制过程，以便将变流器稳健地集成到弱、污染和扰动的电网条件下。锁相环、最优和稳健控制、信号和发电机仿真理论被用来将变流器部件牢固地联系在一起，并以最佳方式进行设计。该项目的方法是完全集成和优化转换器组件，而不增加冗余和分离的组件，这可能会影响这个多方面和高度耦合的工程系统的其他方面。特别是，最新的先进锁相环模型和最新的最优控制设计方法将被应用和加入，以将锁相环完全集成到变流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-硬件在环测试将被用来检验所提出方法的实用性和有效性。通过全面集成组件，减少振荡和不稳定，拟议的项目将提高特定电网的逆变器承载能力，以及其可靠性和电能质量。该项目还将加强应用于将可再生资源整合到我们21世纪的电力和能源系统的关键问题的多个领域的基础知识(即锁相环、最优和稳健控制以及信号)。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.