Research on modifying inverter controls in utility-scale renewables to emulate synchronous-generator voltages/currents under faults to retain existing protection infrastructure

研究修改公用事业规模可再生能源中的逆变器控制，以模拟故障下的同步发电机电压/电流，以保留现有的保护基础设施

• 批准号: 1936560
• 负责人: Ned Mohan
• 金额: $ 45.17万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1936560&HistoricalAwards=false
• 关键词: Research; modifying; inverter; controls; utility

For combating the climate crisis, generating electricity from renewable resources, such as wind and solar, is essential. These resources are economical primarily in large scales and are often located far away from the metropolitan areas, hence need transmission lines. Protective relays are installed on these transmission lines to detect faults caused either by lighting or other short circuits, and disconnect faulted lines. The existing protection equipment is designed for electricity that is generated in power plants using conventional sources such as coal and natural gas. However, this protection infrastructure will not work with the existing control methods used in renewables-based generation. With many states opting to move towards hundred-percent generation by renewables, all existing protective relays will need to be replaced. The objective of the proposed research is to allow the existing protection equipment, such as relays, to continue to be used even as the electricity generation transitions from conventional sources to renewables, by controlling the renewable-based generation such that it emulates the conventional generation in the event of a fault. This will avoid incurring the huge cost of the system-wide upgrade of the protection infrastructure. The proposed approach is based on first determining the type of fault that has occurred and then to take appropriate action such that the existing relays perform as they do in the case of conventional sources. This research will be a very important step in keeping the cost of renewables low in order to enhance their penetration into the utility grid. It will be transformative in advancing knowledge in the critical field of protecting the transmission infrastructure and becoming a norm used by hardware equipment manufacturers. This research is at the intersection of power electronics, power systems, and controls, and will be very educational for the next generation of power engineers.The objective of this proposal is to find a solution to the real and immediate need to enhance the integration of utility-scale renewables. Existing inverters of utility-scale renewable resources, such as PVs and wind, are controlled to generate balanced three-phase currents even during unbalanced faults. However, to operate, the commonly-used protection relays depend upon unbalanced currents that are generated, such as by the synchronous generators of conventional power plants during unbalanced faults. With the increasing penetration of such inverter-based resources, toward the goal of hundred-percent renewables, the existing protection schemes will not work. The proposed research is on injecting appropriate unbalanced current during faults so that the use of the existing transmission-protection infrastructure continues, without having to incur the huge cost of the system-wide upgrade of the protection infrastructure. The proposed approach is based on first identifying the type of fault that has occurred and then to inject the appropriate currents to make the relays operate, knowing only the inverter terminal voltages and the transformer-winding configuration. The proposed control scheme is based on emulating the time-tested behavior of conventional generators during faults, thus requiring no modifications in the existing protection infrastructure, i.e., the inverters operate based solely based on local measurements. This research will thoroughly investigate and develop the control scheme by software emulation and hardware verification. The research will also examine the impact of this control on the inverter components. The aim of the technology transfer is that the control scheme becomes a norm that can be mandated by transmission-system owners and independent power producers, who in turn, would require it of inverter manufacturers.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.

为了应对气候危机，利用风能和太阳能等可再生资源发电至关重要。这些资源主要在大规模时是经济的，并且通常远离大都市地区，因此需要输电线路。保护继电器安装在这些输电线路上，用于检测由闪电或其他短路引起的故障，并断开故障线路。现有的保护设备是针对使用煤炭和天然气等传统能源的发电厂所产生的电力而设计的。然而，这种保护基础设施无法与可再生能源发电中使用的现有控制方法一起使用。随着许多州选择实现百分百可再生能源发电，所有现有的保护继电器都需要更换。拟议研究的目标是，通过控制可再生能源发电，使其模仿传统发电方式，即使发电从传统能源过渡到可再生能源，也可以继续使用现有的保护设备（例如继电器）。发生故障时。这将避免产生全系统保护基础设施升级的巨额成本。所提出的方法首先确定已发生的故障类型，然后采取适当的措施，使现有继电器的性能与传统电源的情况一样。 这项研究将是保持可再生能源较低成本以提高其对公用电网的渗透率的非常重要的一步。它将在推进保护传输基础设施这一关键领域的知识方面产生革命性的影响，并成为硬件设备制造商使用的规范。 这项研究处于电力电子、电力系统和控制的交叉点，对于下一代电力工程师来说非常有教育意义。该提案的目的是找到一种解决方案，以满足增强电力电子、电力系统和控制集成的实际和紧迫需求。公用事业规模的可再生能源。即使在不平衡故障期间，公用事业规模可再生资源（例如光伏和风能）的现有逆变器也可被控制以产生平衡的三相电流。然而，常用的保护继电器的运行取决于所产生的不平衡电流，例如由传统发电厂的同步发电机在不平衡故障期间产生的不平衡电流。随着此类基于逆变器的资源的渗透率不断提高，为了实现百分百可再生能源的目标，现有的保护方案将不再有效。拟议的研究是在故障期间注入适当的不平衡电流，以便继续使用现有的传输保护基础设施，而不必承担保护基础设施的全系统升级的巨额成本。所提出的方法首先确定已发生的故障类型，然后注入适当的电流以使继电器工作，仅了解逆变器端子电压和变压器绕组配置。所提出的控制方案基于模拟传统发电机在故障期间经过时间考验的行为，因此不需要对现有保护基础设施进行修改，即逆变器仅基于本地测量进行操作。本研究将通过软件仿真和硬件验证来深入研究和开发控制方案。该研究还将研究这种控制对逆变器组件的影响。技术转让的目的是使控制方案成为输电系统所有者和独立电力生产商可以强制执行的规范，而后者反过来又要求逆变器制造商采用该控制方案。该奖项反映了 NSF 的法定使命，并被认为是值得的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来获得支持。