Corresponding to different wind speeds, if the tip speed ratio of the wind turbine can be properly adjusted, it can ensure that the wind turbine has a high wind energy utilization coefficient, that is, to maximize the capture of wind energy, so that the entire wind power generation system can obtain the maximum power as much as possible. output. When the wind speed exceeds the rated wind speed too much, appropriate protective measures should also be taken to prevent the overload and damage of the wind turbine.
There are two main types of power regulation methods for wind turbines.
1. Power regulation of fixed-pitch wind turbines
Fixed pitch refers to the fact that the pitch angle of the wind rotor blades is fixed, and the output power of the wind turbine is adjusted according to the stall characteristics of the wind turbine blades. The blades of fixed pitch stall wind turbines have a certain twist angle. Below the rated wind speed, the air flows stably along the blade surface, and the energy absorbed by the impeller increases with the increase of the air speed. When the wind speed exceeds the rated wind speed, the airfoil of the wind turbine blade changes. Turbulent flow, the efficiency of blade energy absorption drops sharply, ensuring that the output power of the wind turbine does not increase with the increase of wind speed. Due to the torsion angle of the stall blade itself, the stall of the blade starts from the local part of the blade stove and gradually develops to the full length of the blade as the wind speed increases, thus ensuring that the total power absorbed by the impeller is lower than the rated value, which plays a role in power regulation. effect. The fixed-pitch stall power-adjusted wind turbine relies on the shape of the blades to adjust the power. The unit structure is relatively simple, but the unit structure is subjected to large forces.
The wind power capture control of the fixed pitch wind turbine completely depends on the aerodynamic performance of the blades. Its advantages are simple structure, low cost, and good safety factor.
2. Pitch wind turbine power regulation
The variable pitch wind turbine changes the wind energy capture ability of the blade by adjusting the pitch angle of the wind turbine, and then adjusts the output power of the wind turbine, and relies on the change of the angle of attack of the blade to keep the absorbed power of the impeller below the rated power. The schematic diagram is shown in the figure. 1 shown.
When the wind turbine starts, the pitch angle of the wind turbine is adjusted to limit the wind energy capture of the wind turbine to maintain the constant speed of the wind turbine and create conditions for the soft grid connection of the generator set. When the wind speed is lower than the rated wind speed, keep the pitch angle of the wind turbine constant, and make the wind turbine run at the optimal tip speed ratio through the generator speed control to maintain the wind turbine to operate at the best wind energy capture efficiency. When the wind speed is higher than the rated wind speed, the pitch angle of the wind turbine is adjusted to deepen the stall effect of the wind rotor blades, thereby limiting the capture of wind energy.
Compared with the fixed pitch stall type power regulation, the variable pitch power regulation can make the wind turbine maintain a stable power output when the wind speed is higher than the rated wind speed, and can increase the power generation of the unit by 3%~10%. The force is relatively small. However, a pitch adjustment device needs to be added to adjust the pitch power, the control system is more complicated, the equipment is expensive, and there is a certain delay in the tracking of the wind speed, which may lead to the instantaneous overload of the wind turbine. At the same time, the constant change of wind speed will cause the pitch mechanism to operate frequently, so that the key components in the mechanism are subject to various complex loads.
With the maturity of wind power technology and the reduction of equipment costs, variable pitch wind turbines will be widely used