Low or medium voltage wind turbine converters?

Selecting the right wind turbine converter can be a complicated business, not only technically, but also politically. To take an informed decision, a number of criteria need to be taken into consideration.

The selection of the right converter is critical in the turbine design and for a higher return on investment.

There is a lot of truth in this statement, but it is more easily said than done. If there is no ‘historical background’ which might predetermine the decision, for example existing installations, a wind turbine manufacturer has a lot of choices to take: doubly-fed or full power designs, low-speed, medium-speed or high-speed full power converter concepts, low voltage or medium voltage – just to mention a few. And to complicate things further, there is usually no right or wrong.

ABB offers solutions for all main drivetrain concepts. I work for ABB’s medium-voltage wind converter business, so it is natural that I would bring up a multitude of arguments in favor of medium-voltage solutions; as could my colleagues for low voltage.

To find out which one is best for your wind farm, I recommend including the following criteria into your decision process.

Things to consider when choosing a wind turbine converter

• CAPEX (capital expenditure) – This needs to cover the investment costs for the complete electrical drivetrain. This includes costs for the converter, generator breaker, water cooling unit, external heat exchanger, brake resistor, current and voltage sensors. But these are not the only cost items in this category. Associated costs, such as cabling costs and additional costs due to converter size and weight need to be included in the calculation as well.

• Generation – Converter losses and efficiency rates need to be considered. As already mentioned under CAPEX, it is important to look at the entire system, including cables, and not only the converter. Please check with the converter suppliers how efficiency rates are calculated. Some manufacturers only state the converter losses, others include auxiliaries, filter etc. You can only make a true comparison if you know what has been considered in the efficiency calculation; otherwise you are running the risk of comparing apples with oranges.

• OPEX (operational expenditure) – Under OPEX we need to include the annual operation costs, costs for all required maintenance activities, such as the replacement of components susceptible to aging, and the costs related to converter failures and unplanned downtime. One of our key learnings for offshore wind was that the main focus should be on using systems of the highest possible quality because of tremendous costs for failures in offshore wind. The cost of a single failure can be up to 20 times higher offshore than onshore.

In the last few months we implemented all these aspects into a powerful LCoE calculation tool, which has helped us to understand the effects even better and led us to become a valuable partner for initial discussions of electrical drivetrains for your wind turbine.

If you want to learn more about the different electrical drivetrain concepts and solutions, please contact us. We look forward to helping you select the right solution for your wind farm.

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About the author

Marco Thoma

I'm Head of Global Sales and Marketing for Medium Voltage Converters used in wind turbines. I have been active in the converter business since 2001 in different areas of engineering, product development, operations and now marketing and sales. My background is electrical engineering and business administration (MBA). I like the challenges in the wind industry and the influence we have together with our customers to change the world and ensure that our kids can live the same good life as we do.
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