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

Novel Concepts for DC Circuit Breakers and DC-DC Transformers: In recent years, several innovative concepts have been developed to enhance ac-to-dc line conversions and dc grid operations. The tri-pole concept was introduced to maximize power transfer capability, while transformerless voltage source converters were studied and documented. In 2016, the operational challenges of dc grids, along with the requirements for dc circuit breakers and dc-dc transformers, were examined. In 2017, new VSC concepts, including full-bridge modular multilevel converters and cascaded converters, were explored. Compact dc converter stations were studied using simulations in 2018. In 2019, single-arm modular multilevel converter concepts were investigated, leading to prototype development in a lab environment in 2020. That same year, a novel VSC concept with dc fault current-blocking capability was studied, with further prototype development continuing into 2021. By 2022, the state-of-the-art dc circuit breakers, including hybrid-type breakers and dc-dc transformers, were documented. Looking ahead to 2025 and 2026, different VSC topologies, such as the Alternate Arm Converter for fault current limiting, are planned to be documented, along with new dc circuit breaker and dc-dc transformer concepts. Future years intend to see the identification, development, and potential demonstration of new VSC concepts at utility sites using supplemental funding. Each study is prioritized with guidance from members and the industry.

Best Practices for Operation, Maintenance, and Refurbishment for Life Extension of FACTS Controllers – Static Var Compensator (SVC) and Static Synchronous Compensator (STATCOM) Life Extension Guidelines: This task systematically identifies the needs for the operation, maintenance, and replacement of FACTS controllers. Initially, utilities with existing FACTS controllers may be surveyed to understand current maintenance and operation practices, with their needs documented and prioritized. Based on the survey results, best practices for operation, maintenance, and replacement strategies can be developed. Vendor-independent plug-and-play components are necessary to facilitate upgrades of FACTS controllers. The requirements for these components and potential plug-and-play options may also be identified. Life extension guidelines for FACTS controllers, such as SVC, STATCOM, static synchronous series compensators (SSSC), and unified power flow controllers (UPFC), intend to 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. FACTS Application Guide, which includes all FACTS controllers, was developed in 2024. Several case studies intend to be developed with different FACTS device applications for power grids, including renewable applications in 2026 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 2026. The conference provides a forum for members to learn, gain, and share experience with other utilities and for the 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 voltage source converter-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 and 2025, EPRI updated the chapter on converter cost estimates. In 2026, EPRI plans to update HVDC cables and VSC chapters with the latest technical information. Electrical effects chapter with the latest information obtained from testing plan to be updated in future years.