types of protection of pitch system
Position feedback fault protection: In order to verify the availability and measurement accuracy of the redundant encoder, the pitch angle signals acquired by the two encoders of each blade configuration are compared in real time, and the conditions of the redundant encoder are good. The angular deviation between the two is less than 2°; all the blades are equipped with a limit switch at positions 91° and 95°, and no limit switch is installed in the 0° direction. Whether the current pitch angle of the blade is less than 0° is measured by two sensors. The result is determined by conversion. In addition to the system power failure, when any of the following fault conditions occur, the hardware system of all axle cabinets shall ensure that the three blades are feathered at a speed of 10°/s to the 90° direction, parallel to the wind direction, and the fan stops rotating: The communication bus between the slave station in the axle cabinet and the PLC main station is faulty, and the wind turbine safety chain consisting of the emergency stop of the hub, the emergency stop of the tower base, the emergency stop of the engine room, the vibration detection, the spindle overspeed and the yaw limit switch are connected in series. Two impeller lock signals in series with the safety chain are disconnected (24VDC signal); either encoder failure or deviation of the two encoder measurements of the same blade exceeds the specified threshold; any blade pitch angle is changing The deviation between the two or two during the paddle process exceeds 2°; the hardware system that constitutes the safety chain and the release circuit fails; any system emergency stop command. In the pitch adjustment mode, measures to prevent the pitch angle from exceeding the limit switch: 91° limit switch; when the limit switch is reached, the pitch motor brake is braked; the release signal of the axle cabinet inverter and the pitch speed command are invalid. It will also make the pitch motor stationary. The condition of the brake brake of the pitch motor: the pitch adjustment mode of the axle cabinet is in the automatic mode, the pitch angle exceeds the position limit switch of 91°; the control switch on the axle cabinet is disconnected; the grid is powered off and the output voltage of the backup power supply is lower than its Minimum allowable operating voltage; control circuit device is damaged.
The motor pitch control mechanism can be individually adjusted for each blade using a servo motor, as shown in Figure 8. The servo motor meshes with the propeller wheel inner ring gear through the driving gear to directly control the pitch angle of the blade. The displacement sensor collects the change of the blade pitch angle and the motor forms a closed loop PID negative feedback control. When the system fails and the control power is cut off, the blade control motor is powered by the battery, and the blade is adjusted to the feather position to achieve the impeller stop.
