P37.116: HVDC Converter Stations and Flexible Alternating Current Transmission System (FACTS) Devices

Novel Concepts for DC Circuit Breakers and DC-DC Transformers: In previous years, a new, innovative tri-pole concept was developed to maximize the power transfer capability of ac-to-dc line conversions. Another new concept—transformerless voltage source converters—was studied, and the results were documented. The operational challenges of dc grids and the requirements for dc circuit breakers and dc-dc transformers were studied in 2016. In 2017, new VSC concepts on full-bridge modular multilevel converters and cascaded converters (half-bridge and full-bridge modules in the same converter) were studied. In 2018, compact dc converter stations were studied using simulations. In 2019, single-arm modular multilevel converter concepts were studied, and a prototype of the new concepts in a lab environment was developed in 2020. In 2020, a novel VSC concept with dc fault-current-blocking capability was studied, and prototype development in a lab environment was performed in 2021. In 2022, the state of the art of dc circuit breakers—including hybrid-type (mechanical plus solid state) breakers and dc-dc transformers—was documented. In 2025, different possible VSC topologies such as alternate arm converter for fault current limiting will be documented. In addition, new dc circuit breaker concepts and dc-dc transformer concepts will be explored in future years. Other new VSC concepts are being identified and developed. Some of these new concepts might be demonstrated at utility sites using supplemental funding. The study of each topic is prioritized with guidance from the members and the industry.

Best Practices for Operation, Maintenance, and Refurbishment for Life Extension of FACTS Controllers – SVC and STATCOM Life Extension Guidelines: This task systematically identifies needs in the operation, maintenance, and replacement of FACTS controllers. Initially, utilities with existing FACTS controllers might be surveyed to understand the existing maintenance and operation practices, and their needs documented and prioritized. Based on the survey results, best practices for operation and maintenance as well as replacement strategies may be developed. Plug-and-play components, which are vendor-independent, are necessary to facilitate upgrades of FACTS controllers. The requirements for plug-and-play components and potential components that could be plug-and-play may also be identified. Life extension guidelines for FACTS controllers—such as SVC, static synchronous compensator (STATCOM), static synchronous series compensator (SSSC), and unified power flow controller (UPFC)—will be developed in future years.

Performance and Cost Comparison of FACTS Controllers: In 2018, utility surveys were conducted to understand the operation and maintenance of some of the FACTS controllers, and the best practices were documented. In 2019, FACTS valve cooling system life assessment studies were conducted with utility surveys using practical applications. In 2019, novel control strategies were developed to operate a STATCOM as an active filter to absorb system harmonics. In 2020, a comparative study on the performance and costs of thyristor-controlled series capacitors (TCSCs) and SSSCs was started; it was completed in 2021. Comparison of the performance and costs of other FACTS controllers—such as SVC, STATCOM, and synchronous condensers—was started in 2021 and completed in 2022. In 2023, EPRI compared the performance and costs of UPFCs, interline power flow controllers (IPFCs), and other FACTS controllers. In 2024, the application of STATCOM with energy storage was studied and documented. A FACTS Application Guide, which includes all FACTS controllers, was developed in 2024. Several case studies will be developed with different FACTS device applications for power grids, including renewable applications in 2025 and beyond.

HVDC & FACTS Technology Watch Newsletter: To foster new opportunities in the HVDC and FACTS areas and disseminate technical developments in a timely manner, HVDC & FACTS Technology Watch is published annually. The newsletter reports on current and new HVDC and FACTS installations around the world as well as the latest developments in HVDC and FACTS technologies.

HVDC & FACTS Conference and Workshop: An HVDC & FACTS conference or a workshop is organized in alternating years, and a workshop is expected to be held in 2025. The conferences provide a forum for members to learn, gain, and share experience with other utilities and for suppliers to present their latest technology to members. The workshops vary in scope from HVDC and FACTS basics to specialized topics, such as modular multilevel VSCs.

Updated HVDC Reference Book: Information is being developed for the HVDC Reference Book (also known as The Olive Book). The updates incorporate new developments and experiences and assist users in specifying HVDC system components, designing overhead lines, and assessing existing HVDC systems for life extension options. In 2020, EPRI updated the chapter on HVDC overhead lines; in 2021, EPRI updated the chapter on HVDC cables. In 2022, EPRI updated the chapter on VSC-based dc transmission. In 2023, all the chapters were edited and updated with the latest information; hard copies of the HVDC Reference Book were published in March 2024. In 2024, EPRI updated the chapters on converter cost estimates. In 2025, EPRI plans to update HVDC cables and VSC chapters with the latest technical information. The electrical effects chapter with the latest information obtained from testing will be updated in future years.