Rapid WindCopyright: © IEM
In this research project, a novel drive train for multi-megawatt wind turbines will be designed, whereby a fusion of the multiple-generator concept and the high-speed application of electric machines takes place. The aim is to combine the specific advantages of both concepts to achieve opposite aims, such as material and cost savings while increasing the availability as well as reaching the same or improved energy efficiency.
A higher operating speed of the generator leads to a higher power density and a reduction in weight and volume of the generator. This yields a significant saving of magnetically active material, which results in a significant cost reduction of the electric machine.
The electrical power in the newly developed drive train has to be generated by multiple parallel-operated high-speed generators (≥ 5000 min-1). This power distribution effectively reduces the loads in every partial drive train.
The consistent implementation of the concept with multiple generators leads to a structure with many identical parts, which are smaller and lighter than for conventional concepts due to the proposed power split. Many identical parts could increase the efficiency and quality in mass production as well as lead to optimized maintenance concepts, by providing more spare parts similar to the automotive industry. Smaller components also enable repairs with available materials directly on site, without the use of large mobile cranes. Thus, a significant reduction of downtimes during energy generation is possible. Furthermore, the structure of the drive train shall be modular, also including the subsequent power electronics.
Another advantage of this concept is the higher redundancy of the system. In partial load, the full energy yield can still be achieved, even in case of failure of one of the multiple generator drives. In full load operation, only a fraction of the whole energy yield would be lost, until necessary repairs are undertaken.
The power loss due to the additional required gear stage (fourth gear stage) will be compensated by an efficiency-oriented operating strategy. This strategy is characterized by the shutdown of several drives in partial load, in order to operate the needed generators in their optimal operating range. The possible power loss in terms of energy efficiency is irrelevant beyond the rated output of the system, since there is always more wind power available in this operating range than electrical power, that can actually be fed into the grid.
The advantages of such a high-speed multiple-generator drive train can be used for both onshore and offshore applications. In order to quantify the benefits of this concept, a corresponding power train will be developed in this research study on the basis of a 6 MW wind turbine.
Sponsorwebsite: Bundesministerium für Wirtschaft und Energie