By Kevin Pearce, grid access business development manager, Siemens Energy

A planned offshore wind project in New York is gaining attention for its novel design that will, for the first time, leverage high-voltage direct current (HVDC) technology to support offshore wind in the United States.

Siemens Energy HVDC offshore wind converter station

In a consortium with Aker Solutions, Siemens Energy is supplying the HVDC transmission system for Sunrise Wind as the project seeks to deliver enough clean, renewable energy to power nearly 600,000 New York homes and other customers.

The product of a joint venture partnership between Danish clean energy giant Ørsted and New England energy provider Eversource, the 924-MW project will be located more than 30 miles east of Montauk Point, Long Island, and is expected to be up and running by 2025.

Once complete, the project will play a key role in supporting New York’s commitment to transition to 100% clean electricity by 2040. The HVDC system is based on voltage source converter (VSC) and insulated gate bipolar transistor (IGBT) technologies. It is designed to quickly, and independently, manage reactive and active power to support the grid at the point of interconnection.

Siemens Energy is delivering the HVDC system on a turnkey basis as well as providing onshore civil work in partnership with local companies. This includes an offshore converter station that will collect 66 kilovolts (kV) alternating current (AC) power generated by the wind turbines through an inter-array cable system.

The AC power will be converted to 320 kVDC for transmission through a nearly 100-mile export cable to a Holbrook, Long Island, onshore converter station where it will be converted back to AC power and injected into the grid.

Time-tested technology

In the U.S, the Trans Bay Cable (TBC) project was built in 2010 to provide critical backup for the San Francisco power grid. Like the Sunrise Wind project, the Siemens Energy HVDC transmission system project used VSC technology and included a 53-mile-long cable laid underneath the San Francisco Bay.

More recently, HVDC transmission was brought onboard oil and gas platforms. Typically, these oil and gas platforms generate their own electricity using gas turbines. However, as oil and gas companies commit to reducing CO2 emissions, the platforms are increasingly being powered from shore, with the power transmitted to the platforms using HVDC-VSC transmission.

Benefits of HVDC-VSC for offshore wind

HVDC-VSC was chosen for the Sunrise Wind project because it is the most flexible, efficient and reliable choice for the project’s transmission system. In fact, HVDC-VSC is a proven transmission technology that makes remote offshore wind farms possible. Here is a snapshot of some HVDC-VSC benefits.

  1. Longer transmission distances

One of the most often cited benefits of HVDC-VSC in offshore applications is that there are no technical limitations to the length of the cables that can be used for transporting the energy. This is in sharp contrast to AC cable transmission where a sizeable portion of the current capability is consumed by charging current which multiplies as the cable gets longer.

  1. More flexible power

Even though fewer cables are required with HVDC-VSC offshore projects, more generated green power can be transmitted from the wind farm to the mainland. As the need for more energy increases and distance to wind farms increase, this benefit will become a significant HVDC-VSC offshore wind selling point.

This is also good news for areas with limited cable corridors as the use of HVDC-VSC enables more power to be carried in fewer cables.

  1. Controllable and reliable

The modular multilevel converter (MMC), introduced for HVDC by Siemens Energy more than a decade ago, is the well-established standard for high-voltage, high-power VSC applications today. Each module within an MMC is a discrete voltage source with a local capacitor to define its voltage step without creating ripple voltage distortion across the converter’s other phases. As a result, it is possible to achieve the required sinusoidal AC and smooth DC side output voltage waveforms without excessive harmonic distortion and high frequency noise.

In addition, the MMC can absorb and generate reactive power independently from active power up to the converter rating. The output currents can be varied over the complete operating range in a smooth, linear way. This enables independent and very flexible control of active and reactive power, which supports the connected AC grid.

A bright offshore future

The move to building more renewable energy plants with increased capacities is well underway. Europe has benefited from offshore wind power for years. Now, with the installation of the first U.S. HVDC-VSC offshore wind farm, North America is better positioned to continue its quest to help satisfy the growing demand for renewable energy.

With more than 25 years of maritime industry experience, Kevin currently spearheads the growth and positioning of Siemens Energy for connecting U.S. offshore wind energy projects to the electrical grid. Prior to Siemens Energy, Kevin worked with several U.S. offshore wind developers, including Bluewater Wind, where he played a key role in several notable accomplishments including the first offshore wind Power Purchase Agreement (PPA) in the United States. Kevin also has experience in private marine consulting firms, where he led the engineering, financing, and construction of ships and offshore structures. Kevin has a Bachelor of Science degree in Naval Architecture and Marine Engineering from the Webb Institute of Naval Architecture and a Masters of Engineering in Ocean Engineering from the Stevens Institute of Technology, where he has also served as an instructor.


Filed Under: Cables & connectors, Featured, Offshore wind

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