Small-Scale High Voltage Direct Current A Lessons Learned Review of the Polarconsult HVDC Phase II Project with Recommendations for Future Research and Alaskan Application

Executive Summary The Polarconsult Small-Scale High Voltage Direct Current (HVDC) project seeks to design, develop, and demonstrate 1) small-scale HVDC converters and 2) innovative complementary transmission infrastructure with the goal of reducing costs for applications in rural Alaska. The project is funded by the Denali Commission, and is comprised of three phases. This report provides a summary review of Phase II project activities, and focuses on lessons learned and recommendations for appropriate next steps in terms of technology research and application in Alaska. In addition, pertinent context, concepts, and background information are discussed to inform this review. Lowering the cost of power transmission via HVDC has been suggested as an option to reduce and stabilize the cost of delivering power to Alaska's rural villages. Power in most of the villages is provided by diesel powerhouses. The high and volatile price of diesel often means significant economic hardships for those communities. Transmission by Alternating Current (AC) is limited by high costs, and line losses that increase with transmission distance. Direct Current (DC) transmission, in contrast, has fewer infrastructure requirements and lower line losses, and can be economical over long distances. Because AC power has been the dominant worldwide standard for generation and transmission, the use of DC for power transmission requires conversion from and to AC in order to integrate it into the existing AC infrastructure. Large-scale HVDC systems, on the order of 100s to 1000s of MWs and designed to wheel large amounts of power across long distances, have been in use since the mid-20th century. However, the electrical demand of rural villages in Alaska is much smaller, typically less than 1 MW. At this scale, existing HVDC technology is not available. Therefore, the development of small-scale HVDC systems, power converters, and multi-terminal networks, are of critical need if HVDC technology is to be applied in rural Alaska. Our life-cycle cost analysis indicates that 60 miles is about the intertie length at which HVDC becomes an economically attractive option, although the cost estimation has some scatter because the economic analyses in this report are based on assumed data from different sources. Both high and low end cost estimates are given in this report. More empirical data for small-scale HVDC intertie are needed for a more rigorous economic analysis. Phase I of this project sought to evaluate the technical feasibility of small-scale HVDC converter technology through evaluating the design, modeling, prototyping, …