Patent ID: 8450868

Claim:
A wind turbine generator or a tidal current generator comprising: a hub; a main shaft which is coupled to the hub; a generator for converting rotation energy transmitted from the main shaft to electric power; a hydraulic pump of variable displacement type configured to be driven by the main shaft; a hydraulic motor of variable displacement type which is connected to the generator; a high pressure oil line which is arranged between a discharge side of the hydraulic pump and an intake side of the hydraulic motor; a low pressure oil line which is arranged between an intake side of the hydraulic pump and a discharge side of the hydraulic motor; a pump controller for setting a target torque of the hydraulic pump and adjusting a displacement D p of the hydraulic pump based on the target torque and a pressure of operating oil in the high pressure oil line, and a motor controller for adjusting a displacement D m of the hydraulic motor based on a discharge amount Q p of the hydraulic pump obtained from the displacement D p .