Feb 28 2011
Most of the current day wind turbines face a daunting task of maintaining the grid fed current at 50 or 60 hertz level. The current day wind turbines operate on variable speed and the speed changes in accordance with the the received wind force.
The rotors deployed at the turbines rotate 12 to 16 rotations per minute and the generator that is connected to the rotor through a gearbox works at a variable speed matching the received wind speed. To overcome the problem of varying power, the alternating current from the generators are transformed into direct current utilizing giant rectifiers. Such transformed direct current is again changed back to alternating current to match the frequency of the grid. The dual conversion results in nearly 5% of energy loss.
The scientists of the Institute for Machine Elements at the Technische Universitaet Muenchen have developed a new active torque-vectoring gear similar to that of a controlled differential utilized in motor vehicles. The new research is developed after closely watching the gears and generator systems of wind turbines where the two pole pairs of the generators are needed to achieve a synchronous speed of 1500 rounds to attain 50 hertz frequency. The new development supplements the use of planetary gears in the conventional designs by a torque-vectoring gear with an auxiliary electric motor. The new system can be utilized as a drive and as well as a generator. The new system facilitates the power from the rotor to get either boosted or diverted to maintain the steady rotational speed of the generator. The concept requires the introduction of an 80 kW electric motor for a 1.5 MW wind turbine.
The new concept incorporates a lighter power train that needs a smaller sized nacelle for the wind turbine. The design allows the use of an additional sturdy low-maintenance generator, which does away with the requirement of additional power electronics for adjusting the wind turbine frequency thus improving the total efficiency of the power generation facility.
Source: http://portal.mytum.de