Technological Advances in Hydraulic Drive Trains for Wind Turbines

The reliability of frequency converters is a major concern for wind turbines. ChapDrive AS has built and tested a hydraulic drive train for variable speed wind turbines which includes a synchronous generator that is connected to the grid without the use of a frequency converter. The hydraulic drive train consists of a hydraulic pump, a variable displacement hydraulic motor, and a synchronous generator, which enables rotor speed control while maintaining synchronous speed of the generator. It has been proven that the hydraulic drive train and the ChapDrive Control system are able to absorb fluctuations in the wind speed and maintain a constant power output without the use of frequency converters. The hydraulic drive train and the ChapDrive Control system has been modeled analytically and compared to measurements, demonstrating a good agreement between simulations and measurements.