1 5MW doubly fed wind turbines. What is the main role of pitch in the LVRT process?

1) In the low wind speed area, the role of the pitch is mainly to reduce the blade angle in the case of a sudden decrease in wind speed, so that the wind turbine can recover the stable power generation capacity faster. 2) In the area of high wind speed, the oars should be quickly retracted at the moment of fall to prevent the impact on the fan, the overspeed of the impeller and the overcurrent impact on the converter. However, due to the speed limitation of the pitch, the angle of the pitch is also limited at the time of voltage drop, which can generally be changed by about 5-10 °, and its effect is not small.

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Reply 1 In the low voltage ride-through, the pitch basically does not play any role, the time of the low voltage ride-through is completed within 625ms, if it is more than so long to go off the grid, in such a short time, then the blade pitch angle of large inertia is difficult to change, you can check its time constant. Besides, from the time the system finds a low voltage fault, to the controller gives the servo system instructions to control the pitch for a while, and the servo system cannot act so fast View the original post

Reply 9 Now the most mature low-voltage ride-through method used in the industry is to add corwbar, which is also a helpless move, although many people have studied n more methods, but in the process of crossing, the active work is consumed in addition to storage, and the cost of storage is too large, so it is generally simply consumed Since the result can, the control can be established. The longest crossing is only 625ms, if the power grid has not been restored by then, the machine will be cut, and the resistance will not overheat in such a short time. View the original post

Variable pitch is also to adjust the pitch angle, which means that the blades installed on the hub can change the size of the pitch angle through control. During operation, when the output power is less than the rated power, the pitch angle remains unchanged at the zero degree position without any adjustment;

When the output power of the generator reaches the rated power, the adjustment system adjusts the size of the pitch angle according to the change of the output power, so that the output power of the generator is kept at the rated power.

The fixed propeller moment means that the blades of the wind wheel are rigidly connected with the hub, and the pitch angle of the blades remains unchanged. The principle of fixed pitch stall power adjustment is that the blade angle of the wind turbine is fixed, but the aerodynamic characteristics of the blade itself are used, that is, within the rated wind speed, the lift coefficient of the blade is higher, and the wind energy utilization coefficient (CP value) is also higher.

Variable pitch and fixed pitch are two concepts, variable pitch: through the motor or hydraulic mechanism, drive the fan blade to adjust the windward angle of the blade according to the change of wind speed, and within a certain range, the speed of the fan does not change sharply with the size of the wind speed. Fixed pitch:

The windward angle of the impeller is not adjustable, and the fan speed will be fast when the wind speed is large, and the fan speed will be slow when the wind speed is small.

Summary. Hello dear, the pitch of the wind turbine is an important device to adjust the angle of the blades and change the speed of the windmill. There are two types of pitching:

Manual and automatic. Manual pitch refers to changing the tilt angle and rotation direction of the blades through the unit control room or the operator's manual control of the driving mechanism, so that the rotor speed is stabilized within the required range. Automatic pitch refers to the wind turbine according to the measurement signal of the wind speed and speed sensor, and the electrical control system automatically adjusts the blade angle to adjust the speed and wind energy utilization.

In general, the process of pitching consists of three steps:1Induction of wind speed and rotational speed signalWind turbines sense changes in the external environment through wind speed measurement sensors and rotational speed detectors, and then transmit these changing signals to the control system.

2.Judgment According to the signal, judge the direction and degree of pitching, and the control system judges the tilt angle and rotation direction of the windmill blades through the algorithm to determine which direction the pitch needs to be changed and the angle of the pitch that needs to be changed. 3.

The control drive mechanism realizes that the pitch electronic control system outputs the control signal to the driving device, and the driving blades realize the change of angle, adjust the speed and power output. During the pitch process, the electronic control system can adjust the blade angle in real time to keep the wind turbine running at the optimum, fully convert the wind energy, and improve the power generation efficiency.

How long. Briefly describe the pitch action process of wind turbines.

Hello dear, the pitch of the wind turbine is an important device to adjust the angle of the blades and change the speed of the windmill. There are two types of pitching: manual and automatic.

Manual pitch refers to changing the tilt angle and rotation direction of the blades through the unit control room or the operator's manual control of the driving mechanism, so that the rotor speed is stabilized within the required range. Automatic pitch refers to the wind turbine according to the measurement signal of the wind speed and speed sensor, and the electric limb shed burial control system automatically adjusts the blade angle to adjust the speed and wind energy utilization rate. In general, the process of pitching consists of three steps:

1.Induction of wind speed and speed signalWind turbines sense changes in the external environment through wind speed measurement sensors and front and speed detectors, and then transmit these changing signals to the control system. 2.

Judgment According to the signal, judge the direction and degree of pitching, and the control system judges the tilt angle and rotation direction of the windmill blades through the algorithm to determine which direction the pitch needs to be changed and the angle of the pitch that needs to be changed. 3.The control drive mechanism realizes that the pitch electronic control system outputs the control signal to the driving device, and the driving blades realize the change of angle, adjust the speed and power output.

During the pitch process, the electronic control system can adjust the blade angle in real time to keep the wind turbine running at the optimum, fully convert the wind energy, and improve the power generation efficiency.

The global commercial operation of megawatt wind turbines and above have adopted variable pitch technology, variable pitch control and frequency conversion technology to improve the power generation efficiency and power quality of wind turbines, so that wind turbines can obtain the best performance under various working conditions, reduce the impact of wind on wind turbines, and it together with frequency conversion control constitutes the core technology of megawatt variable speed constant frequency wind turbines. The hydraulic pitch system has the advantages of small unit volume, light weight, good dynamic response, large torque, no need for variable speed mechanism and mature technology. This article will give a brief introduction to the hydraulic pitch system.

Two working conditions for fan pitch adjustment.

The pitch operation of the wind turbine can be roughly divided into two working conditions, namely the continuous pitch during normal operation and the full shun propeller in the stop (emergency stop) state. When the fan starts to start, the blades rotate from 90° to 0°, and when the turbine is connected to the grid, the adjustment of the blades around 0° is a continuous pitch. The continuous pitching process of the hydraulic pitch system is controlled by the hydraulic proportional valve to control the flow of hydraulic oil for position and speed.

When the fan stops or in an emergency, in order to stop the fan quickly, the blade will quickly rotate to 90°, one is to make the wind direction parallel to the blade, so that the blade loses the windward side; The second is to use the paddle blade to beat the air laterally to brake, so as to achieve the purpose of rapid shutdown, this process is called the smooth propeller. The full propeller of the hydraulic system is controlled by the solenoid valve full conduction hydraulic oil circuit for fast propeller control.

Hydraulic pitch system.

The hydraulic pitch system consists of an electro-hydraulic pump as the working power, hydraulic oil as the transmission medium, and a solenoid valve as the control unit, which realizes the pitch of the propeller by changing the radial movement of the cylinder piston rod into the circular motion of the propeller.

Let's first understand the structure of the hydraulic pitch system.

The schematic diagram of the variable pitch servo control system is shown in Figure 1. The variable pitch control system consists of a signal given, a comparator, a position (pitch) controller, a rate controller, a D a converter, an actuator, and a feedback loop.

Figure 1: Control schematic.

The simplified schematic diagram of the hydraulic pitch actuator is shown in Figure 2, which is composed of a fuel tank, a hydraulic power pump, a power unit accumulator, a hydraulic pipeline, a rotary joint, a pitch system accumulator and three independent pitch devices, and only one of the pitch devices is drawn in the figure.

Fig.2 Hydraulic schematic diagram.

Conclusion. Compared with the electric pitch system, the hydraulic pitch system has a small unit size, light weight, good dynamic response, large torque and no need for a variable speed mechanism. Because the propeller is constantly rotating, the hydraulic oil pipeline of the hydraulic station in the engine room must be introduced into the rotating hub through a rotary joint, and the pressure of the hydraulic oil is about 20MPa, so the manufacturing process is more demanding and difficult, and the pipeline is also prone to leakage.

Due to the influence of the viscosity and temperature characteristics of hydraulic oil, the hydraulic system has high requirements for ambient temperature, and for fans used at different latitudes, the hydraulic oil needs to add heating or cooling devices.

All components of the pitch system are mounted on the hub. When the fan is operating normally, all components are fixed with the hub.

speed of rotation.

The pitch system controls the speed of the wind turbine by controlling the angle of the blades, and then controls the output power of the wind turbine.

It is possible to safely shut down the wind turbine by means of aerodynamic braking.

The blades and roots of the wind turbine are connected to the hub by pitch bearings, and each blade must have its own relative independence.

Electronically synchronized pitch drive system. The pitch drive system is meshed with the internal teeth of the pitch bearing by means of a pinion.

Linkage. During the normal operation of the fan, when the wind speed exceeds the rated wind speed of the unit, the wind speed is between 12m s and 25m s

In order to control the power output, the pitch angle is limited to between 0 and 30 degrees, and the pitch angle varies according to the wind speed.

Automatic adjustment is made to keep the speed of the rotor constant by controlling the angle of the blades. Arising from any circumstance.

Shutdown will cause the blades to follow the propeller to 90 degrees When the emergency propeller command is executed, the blades will follow the propeller to the 91 degree limit.

Location. The pitch system sometimes needs to be powered by a backup battery for pitch operation, such as when the main power supply of the pitch system is lost.

Therefore, the pitch system must be equipped with a backup battery to ensure that the unit has a serious failure or major accident.

In the case, it can be safely stopped, and the blades can be propellered to the 91-degree limit position. A redundant limit is also required.

Switch for 95 degree limit The main limit switch for 91 degree limit ensures the pitch motor in case of failure.

safety brakes.

When the standby power supply is not used for a long time due to unit failure or other reasons, the main control of the fan needs to be checked.

The status of the backup battery and the normality of the operation function of the backup battery-powered pitch.

Each pitch drive system is equipped with an absolute encoder mounted at the non-drive end of the motor at the rear of the motor

It is also equipped with a redundant absolute encoder mounted at the root of the blade next to the pitch bearing inner tooth, which passes through a small one.

The gear and the pitch bearing internal teeth mesh linkage to record the pitch angle.

The main controller of the wind turbine receives the signals from all encoders, while the pitch system only uses the signals from the encoders at the tail of the motor.

When the encoder at the tail of the motor fails, the main controller of the fan will control the signal of the redundant encoder applied to the pitch system.

2 The role of the slurry system.

The angle between the blades and the wind direction is automatically adjusted according to the magnitude of the wind speed, so that the wind turbine has for the wind turbine.

A constant speed using the principle of aerodynamics can make the paddle 90° parallel to the wind direction to make the fan. Stoppage.

a.Improve the force of the unit and optimize the power output (in conjunction with the generator slip rate adjustment) bThe power feedback control makes the rated power not affected by changes in air density such as altitude, humidity, temperature, etc.

c.The rated wind speed is lower than that of the fixed pitch wind turbine, and the efficiency is high; There is no problem of power degradation above the rated wind speed.

d.Control pneumatic torque at start-up, easy to connect to the grid; The pneumatic torque of the shutdown is returned to zero to avoid sudden load dumping.

Correct answer to the case of infiltration of Jianxun: ABCD

Summary. Small wind turbine blades are generally handmade of metal or FRP, of which FRP blades are the most popular and practical blades;

Large wind turbine blades are generally handmade with fiberglass.

What is a wind turbine blade return propeller.

Small wind turbine blades are generally made of metal or FRP handmade stoves, among which glass hidden bridge grinding steel blades are the most popular and practical blades for regression; Large wind turbine blades are generally handmade with fiberglass.

All components of the pitch system are mounted on the wheel lift hub. When the wind turbine is operating normally, all components rotate with the hub at a fixed speed. The pitch system controls the speed of the wind turbine by controlling the angle of the blades, and then controls the output power of the fan, and can make the fan stop safely through Qi Sanbi aerodynamic braking.