(1) Mechanical speed limit protection.
The purpose of setting the high wind speed limit protection is to effectively reduce the wind turbine when the wind turbine input energy is greater than the total energy that the system can consume and the energy stored by the system at a certain wind speed. The absorbed wind energy prevents the wind turbine from running at an excessive speed. At present, the speed limit protection schemes of various types of wind turbines can be roughly classified into two categories:
① A mechanism is used to deviate the wind wheel from the wind direction and reduce the wind-facing area of the wind wheel, thereby reducing the absorption of wind energy.
②Using the centrifugal force of the wind turbine blades to change the pitch with a certain mechanism, reducing the wind energy utilization rate of the wind turbine, so as to achieve the effect of reducing wind energy absorption
The reliability of the mechanical speed limit protection device is poor, because the natural wind conditions are very complicated, such as turbulent flow. At the same time, the wind speed and direction change frequently and quickly. It is impossible for any mechanical device to respond instantaneously to changes in the actual wind conditions. The mechanical wear caused by long-term operation will increase the fitting clearance of the device. All of these will lead to protection lag, failure and violent vibration, leading to destructive results such as wind turbine runaway, overload and violent vibration.
For a long time, due to cost considerations, advanced hydraulic control technology has not been used in the speed limit protection of small wind turbines. It is only based on aerodynamic principles and simple mechanical control methods are used to control small wind turbines in high wind conditions. Carry out speed limit protection. The characteristic of the mechanical speed limiting structure is to make the revolving body or a certain part of the small wind turbine in a state of dynamic support. This structure can reflect good speed limiting characteristics under the conditions of the wind tunnel test, but under natural conditions Because the wind speed and direction changes are too complicated, and the natural environment is harsh, the dynamic support parts of small wind turbines will inevitably cause vibration and damage to moving parts, which will damage the unit. The reliability of small wind turbines must be completely solved. There must be the best solution to the speed limit.
(2) Magnetoelectric speed limit protection.
The main point of the magnetoelectric speed limit protection technology is to give the generator a reverse magnetic resistance distance when the wind generator is in an overpower state, which greatly increases the power consumed by the generator, making it greater than the power output by the wind turbine, so that The wind wheel speed drops. The decrease of the wind wheel speed reduces the tip speed ratio of the wind wheel, thereby reducing the wind energy utilization rate of the fixed-pitch wind wheel, reducing the wind energy absorbed by the wind wheel, and further reducing the wind wheel speed. The actual effect produced by this chain action is to decelerate rather than limit the speed, and the action of the magnetoelectric speed limit protection is very safe and reliable. The advantage of this new speed limit protection concept is that it abandons the mechanical speed limit structure, only retains the two necessary moving parts of the wind turbine, eliminates the hidden danger of mechanical failure of the speed limit mechanism, and fundamentally solves the long-term problem of small wind turbines. The problem of safe and reliable operation. This new speed limit method has the following advantages:
① Due to the abandonment of the mechanical speed-limiting structure, the small wind turbine retains only two necessary operating parts, and the structural stability and reliability of the unit are greatly improved.
②Because it is not restricted by the mechanical speed limit structure, the shape of the unit can be made more beautiful and diversified.
③There are many methods available for magnetoelectric speed limitation, high reliability, and multi-level control can be realized, and different effective working wind speed ranges can be set according to different wind resources, which improves the reliability of the system.