Dr. Ram Adapa of EPRI

It is anticipated that a significant number of High Voltage Direct Current (HVDC) systems and power electronics–based Flexible AC Transmission System (FACTS) controllers will be deployed across transmission and distribution networks to support the growing integration of renewable energy resources. According to Pike Research, HVDC transmission is emerging as one of the fastest growing segments in the utility sector. Clean tech Market Intelligence reports that cumulative global investments in HVDC systems from 2012 to 2020 reached approximately US $120 billion, with spending continuing to rise rapidly throughout the 2020s. While much of this growth is concentrated in countries such as China and India, HVDC adoption is also accelerating in Europe, North America, Australia, and other regions as utilities work to enhance renewable energy integration.

This presentation highlights the stateoftheart in HVDC and FACTS technologies and explores new applications, including AC line conversion to DC and advances in converter designs such as modular multilevel voltage source converters (VSCs).

Biography:

Dr. Ram Adapa, Technical Executive, HVDC & Power Electronics, EPRI, Palo Alto, CA, USA

Dr. Ram Adapa is a Technical Executive in the Energy Delivery and Customer Solutions at EPRI. His research activities focus on High Voltage Direct Current (HVDC) transmission, Flexible AC Transmission Systems (FACTS), Custom Power, Fault Current Limiters, and Substation Seismic Studies.

Dr. Adapa joined EPRI in 1989 as a Project Manager in the Power System Planning and Operations program. Later he became Product Line Leader for Transmission, Substations, and Grid Operations where he developed the research portfolio and business execution plans for the Grid Operations and Planning areas. Some of the tools in this portfolio included market restructuring, transmission pricing, ancillary services, and security tools to maintain the reliability of the grid.

Before joining EPRI, Dr. Adapa worked at McGraw-Edison Power Systems (presently known as Eaton Cooper Power Systems) as a Staff Engineer in the Systems Engineering Department.

Dr. Adapa received a BS degree in electrical engineering from Jawaharlal Nehru Technological University, India, an MS degree in electrical engineering from the Indian Institute of Technology, Kanpur, India, and a PhD in electrical engineering from the University of Waterloo, Ontario, Canada.

Dr. Adapa is an IEEE Fellow and has been honored several times by IEEE for his outstanding contributions to the profession. He received the 2016 IEEE PES Nari Hingorani Custom Power Award and the 2023 IEEE PES Uno Lamm HVDC Award. He has authored or coauthored more than 125 technical papers and is an IEEE Distinguished Lecturer. He is an individual member of CIGRE and a Registered Professional Engineer.

Address: Electric Power Research Institute (EPRI), 3420 Hillview Avenue, Palo Alto, United States, 94304

Prof Dragan Jovcic of University of Aberdeeen

High Voltage DC Transmission has seen rapid technology advances in the last 20 years driven by the implementation of VSC (Voltage Source Converters) at GW powers and in particular introduction of MMC (Modular Multilevel Converters). The development of interconnected DC transmission grids requires significant further advance from the existing point-to-point HVDC links. It is widely believed that complex DC power grids can be built with comparable performance, reliability, flexibility and losses as traditional AC grids. The primary motivation for DC grid development is the need for power flow and trading between many DC terminals, as an example in the proposed (350 GW) North Sea DC grid, or EU-wide overlay DC grid. AC transmission is not feasible with long subsea cables, and it is inferior to DC systems in many other conditions. This presentation addresses the options and challenges with DC grid development, referring also to state-of-art technology status.

Zhangbei 4-terminal DC system (China, 2020) represents the first implemented GW-scale meshed DC transmission grid, which employs bipolar ring topology with overhead lines and 16 DC Circuit Breakers. However, multiple studies illustrate advantages of some radial, hub-based or segmented topologies, because of component costs, and challenges with interoperability, ownership, DC markets, operation, security and reliability.

MMC concepts, including half-bridge and full-bridge modules, will underpin DC grid converters and further advances like hybrid LCC/MMC converters have been implemented recently. DC/DC converters at hundreds of MW are not yet commercially available but there is lot of research world-wide, and some lower-power prototypes have been demonstrated. DC/DC converters may take multiple functions including DC voltage stepping (transformer role), DC fault interruption (DC CB role) and power flow control. Multiport DC hubs can be viewed as electronic DC substations, capable of interconnecting multiple DC lines.

Very fast DC CB circuit breakers (2 ms) have become commercially available recently, but the cost is considerably higher than AC CBs. Slightly slower mechanical DC CBs (5-8 ms) are also available from multiple vendors, while new technical solutions are emerging worldwide for achieving faster operation with lower size/weight/costs.

DC grid modelling will face the new challenge of numerous converters dynamically coupled through low-impedance DC cables/lines. A compromise between simulation speed and accuracy is required, leading to some average-value modelling, commonly in rotating DQ frame, but capturing very fast dynamics and variable structure to represent fault conditions.

The principles of control of DC grids have been developed. DC systems have no system-wide common frequency to indicate power unbalance, and voltage responds to local and global loading rather than reactive power flow. DC grid dynamics are 2 orders of magnitude faster than traditional AC systems and most components will be controllable implying numerous, fast control loop interactions. Because of lack of inertia, and minimal overload capability for semiconductors, DC grid primary and secondary control should be feedback-based (man-made), fast, and distributed. International standardization efforts have begun.

The protection of DC grids is a significant technical challenge, both in terms of components and protection logic. The selectivity has been demonstrated within 0.5 ms timeframe using commercial and open-source DC relays. Nevertheless, grid operators have expressed concerns with self-protection on various components, back-up grid-wide protection, interoperability, and in general if we can achieve power transfer security levels comparable with AC grids and acceptable to stakeholders.

Biography:

Dragan Jovcic obtained a Diploma Engineer degree in Control Engineering from the University of Belgrade, Serbia in 1993 and a Ph.D. degree in Electrical Engineering from the University of Auckland, New Zealand in 1999. Since 2000 he has been an academic in UK, and since 2012 a chaired professor with University of Aberdeen. In 2008 he held a visiting professor post at McGill University, Canada. Prof Jovcic is fellow of IEEE, fellow of IET, and IEEE PES Distinguished Lecturer. He is editor of IEEE Transactions on Power Delivery and IEEE Access.

Professor Jovcic is a member of CIGRE, has been chairman of B4.76 and member of 5 other working groups (B4.52, B4.58, B4.64, B4.80, B4.84). He is founder and director of Aberdeen HVDC research centre where he has managed significant volume of externally funded research projects. Prof Jovcic has around 160 publications and he is author of a book on HVDC: “High Voltage Direct Current Transmission: Converters, Systems and DC Grids”, Wiley, 2015.

Address:University of Aberdeen, , Aberdeen, United Kingdom

Dr. Quan Nguyen of PNNL

The increasing deployment of multi-terminal voltage-source-converter-based HVDC (MTDC) grids poses significant challenges for interconnection-level planning and operational studies. Despite their growing importance, existing commercial tools exhibit notable gaps and inconsistencies in modeling capabilities across different time scales. These limitations include the lack of production cost and phasor-domain models for MTDC systems, as well as insufficient AC–DC power flow solvers suitable for interconnection-level analysis. This presentation introduces a set of modeling approaches for MTDC grids spanning production cost modeling, steady-state power flow, and phasor-domain dynamic simulation. Particular emphasis is placed on the systematic conversion of MTDC models across these domains, ensuring consistency of key physical and control characteristics while preserving the unique assumptions and objectives inherent to each domain. By addressing current tool limitations and establishing a multi-fidelity model transition methodology, this work enables more accurate and computationally efficient interconnection-level studies to characterize, demonstrate, and quantify the performance of future AC–MTDC power systems.

Biography:

Quan Nguyen received the B.E. degree in Electrical Engineering from Hanoi University of Science and Technology, Vietnam, in 2012, and the M.S. and Ph.D. degrees in Electrical Engineering from The University of Texas at Austin, USA, in 2016 and 2019, respectively. Since 2019, he has been a Power System Engineer at the Pacific Northwest National Laboratory. His research focuses on the modeling, control, optimization, and simulation of power systems with high penetrations of inverter-based resources, as well as flexible HVDC and low-frequency transmission systems.

Address:PNNL, , Richland, United States

Dr. Brian Johnson of University of Idaho

Address:University of Idaho, , Moscow, United States