Composition and Fault Analysis of Wind Turbine Pitch System
All parts of the pitch system are mounted on the hub. All components rotate with the hub at a certain speed during normal operation of the fan.
The pitch system controls the speed of the wind wheel by controlling the angle of the blade, thereby controlling the output power of the fan, and can safely stop the fan by means of aerodynamic braking.
The blades (roots) of the fan are connected to the hub via pitch bearings, each of which has its own independent, electrically controlled, synchronized pitch drive system. The pitch drive system is meshed with the internal gear of the pitch bearing through a pinion.
During normal operation of the fan, when the wind speed exceeds the rated wind speed of the unit (when the wind speed is between 12m/s and 25m/s), the pitch angle is limited to between 0 and 30 degrees in order to control the power output (the pitch angle is based on the wind speed). The change is automatically adjusted), and the rotational speed of the rotor is kept constant by controlling the angle of the blade. A shutdown caused by any condition will cause the blade to feather to a 90 degree position (the blade will be feathered to a 91 degree limit position when an emergency feathering command is executed).
The pitch system sometimes needs to be powered by a backup battery for pitching (such as after the main power supply failure of the pitch system), so the pitch system must be equipped with a backup battery to ensure a safe shutdown if the unit has a serious fault or major accident ( The blade is feathered to the 91 degree limit position). In addition, a redundant limit switch (for 95 degree limit) is required to ensure safe braking of the pitch motor when the main limit switch (for 91 degree limit) fails.
When the standby power supply is not used for a long time due to unit failure or other reasons, the fan master needs to check the status of the backup battery and the normality of the backup battery-powered pitch operation function.
Each pitch drive system is equipped with an absolute encoder mounted on the non-drive end of the motor (motor tail) and a redundant absolute encoder mounted next to the internal tooth of the blade pitch bearing. A pinion is coupled with the internal gear of the pitch bearing to record the pitch angle.
The fan master receives the signals from all encoders, while the pitch system only applies the signals from the motor's tail encoder. The fan master controls the pitch system's application of the redundant encoder signal only when the motor tail encoder fails.
2 role of the pulping system
According to the size of the wind speed, the angle between the blade and the wind direction is automatically adjusted to realize that the wind wheel has a constant rotation speed to the wind power generator; the aerodynamic principle can make the blade 90° parallel to the wind direction to stop the fan.
