Siemens Energy sees “tremendous potential for HVDC projects to support the various federal and state initiatives in the U.S,” according to Peter Kohnstam, the company’s HVDC business development manager.
Speaking during TransmissionHub’s “Get current on HVDC: A growing trend in transmission” webinar on June 14, Kohnstam noted advantages of HVDC, saying, “The issue that most people focus on is the reduced losses for long distance transmission.”
Another advantage, he said, is that HVDC uses a reduced right of way, which “can be advantageous in certain circumstances when you’re trying to route something through a fairly tight environment.”
He added, “Nowadays, right of ways are becoming more and more congested so, therefore, DC can help.”
Furthermore, DC solutions allow the reduction of the overall electromagnetic fields of the transmission, he said.
Another advantage of HVDC is the ability to link different regional systems, he said.
Siemens’ HVDC technology
Kohnstam also discussed advances Siemens is working on, involving modular multilevel converter (MMC) technology, which the company refers to as Siemens HVDC Plus.
According to Siemens, with the new multilevel approach, individual module capacitors are uniformly distributed throughout the topology and each level is individually controlled to generate a small voltage step. Each module within the multilevel converter is a discrete voltage source in itself with a local capacitor to define its voltage step without creating ripple voltage distortion across the converter’s other phases. Siemens also said that by incrementally controlling each step, an almost sinusoidal voltage is generated at the AC outputs of the “multi-valves.”
Among other things, Kohnstam noted that there is a lot of interest within Europe to develop a fully integrated HVDC grid.
Siemens is working on a project involving “a two 1,000-MW link between France and Spain,” he said, noting that to date, that is the largest VSC MMC project in the world.
“Siemens views HVDC as a fundamental part of the electrical grid of the future and we are committed to continue to work and deliver innovative products and solutions to help developers and utilities use the technology to efficiently, economically and reliably deliver energy to their customers,” he said.
Transmission for renewable energy
Another panelist, Wayne Galli, vice president of transmission and technical services with Clean Line Energy, noted that the biggest problem in developing renewable energy resources is the lack of transmission.
Clean Line is working on four projects that aim to alleviate that, he said, referencing the approximately $1.7bn, 550-mile, 600-kV Grain Belt Express Clean Line project, which, according to TransmissionHub data, originates at Spearville, Kan., and ends at St. Francois, Miss.; the $3.5bn, 800-mile, 600-kV Plains & Eastern Clean Line project, which originates at the Diamond substation in Oklahoma and ends at the Memphis substation in Tennessee; the 500-mile, 600-kV Rock Island Clean Line project that originates in central Illinois and ends in northwest Iowa; and the 900-mile, 600-kV Centennial West Clean Line project that originates at Guadalupe, N.M., and ends at Mira Loma, Calif.
“All four projects can deliver up to 15,000 MWh of energy [and] all of them are HVDC,” Galli said.
He also noted that the projects involve less infrastructure, require less right of way and have smaller footprints than an equivalent AC system to move the equivalent amount of power. Furthermore, HVDC is easily relegated to a merchant base model, as opposed to a cost-allocating model, he said.
The driver behind these projects, he said, is the demand for renewables in each of those areas.
Kohnstam noted that DC is an excellent solution for all renewable energy sources, not just wind. “[R]enewable energy tends to be away from major interconnections to the system, but … some of the DC solutions are ideally suited for that,” he said, adding that voltage source converters work well in weak systems.
Galli said Clean Line is working with state and federal regulators on such obstacles as getting right of way permission for a line from a state that does not have a terminal for the line. One approach, he said, is getting utility status.
Also speaking on the panel, Jim Nash, vice president of engineering with PowerBridge, spoke of the Neptune Regional Transmission System project, noting that the project has operated continuously for several years.
According to TransmissionHub data, the project is a 65-mile, 500-kV HVDC transmission line that originates at Sayreville, N.J., and terminates at North Hempstead. N.Y. The project, which is sponsored by Neptune Regional Transmission System, has a long-term contract with the Long Island Power Authority.
PowerBridge is working on other projects, including the Hudson Transmission Project, for which the company is “building a back-to-back HVDC system in Ridgefield, N.J., using essentially the same components that we used for Neptune to interconnect with [Public Service Enterprise Group (NYSE:PEG) subsidiary Public Service Electric and Gas],” Nash said.
According to TransmissionHub data, that project, proposed by Hudson Transmission Partners, is a 7-mile, 345-kV transmission line, originating at the Bergen substation in New Jersey, and terminating at the West 49th Street substation in New York. The transmission line will cost $188m. Construction of the project began in May 2011 and is expected to finish in mid-2013.