Foreign Direct Drive Wind Turbine Technology Application
As a clean renewable energy, wind energy will gradually lower its operating costs than hydropower and thermal power as the technology matures. The development prospects are very broad. At present, the single-machine capacity of wind turbines continues to increase, and variable-speed constant-frequency and pitch-type wind turbines gradually occupy a dominant position. The gearbox is a component with high overload and premature damage rate in the current MW-class wind turbines. A direct-drive wind turbine (also known as a gearless wind turbine) has been developed abroad. The asynchronous motor is directly connected to the impeller for driving, eliminating the traditional components of the gearbox (see the following figure for structural features), with low noise, improved unit life, reduced unit size, reduced operating and maintenance costs, and low noise. There are many advantages such as high efficiency at low wind speed, and there is much room for development in the development of wind turbines in the future.
In 1995, a research institute in New York State designed a new variable reluctance generator, even if the magnetic device in the wind turbine replaced the mechanical gearbox. The design is characterized by a large number of winding structures that are cheaper than the six poles. The pole structure of the variable reluctance motor can withstand universal operation without increasing the cost [1].
In 2000, Dr. M. eng. M. Dubois of Canada proposed that the gearbox in the wind turbine is placed between the motor and the rotor, which is disadvantageous for the efficiency of part of the working load, and is more susceptible to loss, if one uses the same speed as the wind turbine. The motor can be removed from the gearbox. In fact, the application of direct-drive low-speed rotary motors in hydropower stations is not new. However, there are still some problems in wind turbines. For example, University of Durham, Chalmers University of Technology in Goteborg and Darmstadt University of Technology have studied the appropriate weight of motors in wind turbines; the most suitable machine Type (synchronous, permanent magnet, variable reluctance, etc.) selection; maximum torque density due to current and pressure fluctuations; choice of converters for networking; measures to achieve the desired noise level; It is recommended to use a motor consisting of multiple modules for easy transportation and a normal operation of a component. Is it possible to design a motor without additional losses; permanent magnet motors are increasingly due to high efficiency and high torque density. Is employed, does this lead to excessive iron loss, choice of magnetic materials, how to magnetize these materials, how to prevent degaussing in the event of operation or failure
It can be found that (direct-drive) gearless wind turbines started more than 20 years ago, but in recent years, they have renewed great interest from researchers, and actively applied the technology to products to the wind power market, Germany, the United States. Denmark is a country with a leading position in this technology field. The (direct-drive) gearless synchronous generator developed by Siemens in Germany is installed in the world's largest Norwegian wind farm, with an efficiency of 98%.
