Industry challenges

Looking at the marked today the common systems available are divided into cost competitive low voltage two level converter systems and various medium voltage systems that in some applications can offer increased system efficiency but normally also at a higher cost. The main challenge for the project is to combine the technical benefits from various known systems and expand these to the future turbine power range without compromising the overall driver of keeping the cost of the system at a minimum.

Cost efficiency gains are considered necessary to maintain public and political support for large-scale implementation of offshore wind and to maintain the competitive edge of Danish actors in the market. A critical component in a wind turbine (WTG) is the power converter, which basic function in a wind turbine is converting a varying voltage/frequency from the generator into a fixed voltage/frequency output synchronized to the power grid.

As WTG´s become larger, the power converter also increases in sizes causing an increased focus on the size, weight, efficiency, reliability and price. The most common type is the low voltage converter, and increasing turbine power has been accompanied by adding more low voltage systems in parallel. The MV components are generally more expensive than low voltage components triggering the objective of the project to build a MV converter based on the less expensive low voltage components- By stacking of low voltage system in series rather than parallel, a MV converter can be build, using LV components. Thus, the proposed multi-level medium voltage converter system will bring the benefit from both systems.