ChapDrive has developed a gearless drivetrain solution for wind turbines. The core technology is a hydraulic transmission with a variable speed control system. The technology is characterized by applying the latest generation high efficiency hydraulic transmission. This reduces the top weight and the number of critical components. In addition the need for a mechanical gearbox, frequency converter and transformer used in traditional wind turbines is eliminated. Power is generated by a synchronous generator that will comply with grid regulations being required for wind turbines in the future.
Figure 1 Principle diagram of the ChapDrive hydraulic transmission
A principle diagram of the hydraulic transmission is shown in figure 1. The mechanical gearbox is replaced by a low speed hydraulic pump connected to a high speed hydraulic motor with a closed loop hydraulic circuit. The hydraulic motor is connected to the generator operating at synchronous speed with a variable displacement volume. By controlling the displacement, the transmission ratio of the rotor speed to the generator speed can be changed. As a result the system operates with a variable transmission ratio in order to optimize the energy capture and reduce loads. The flow is controlled by the ChapDrive variable speed control securing stability and efficiency of the system. The hydraulic motor and synchronous generator can be located either in the nacelle as shown in figure 2 or at the foundation as shown in figure 3.
Figure 2 ChapDrive Nacelle Solution
Figure 3 ChapDrive Ground Solution
The principle of the ChapDrive Control System is illustrated in figure 4. The ChapDrive Control System is based on the patented closed loop speed control principle with optimized control of pitch, displacement and excitation. The result is a steady synchronization with smooth connection of the generator to the grid, stable control of power and torque, and full control over reactive power. At the same time the control system maximizes the wind energy yield by optimizing the rotor speed at all wind speeds. Consequently the loads on the turbine structure and turbine components are minimized.