Small wind turbines are suitable for areas where the annual average wind speed is above 3m/s, and the cumulative annual effective wind speed of 3~20m/s is above 3000h: the annual average effective wind energy density of 3-20m/s is above 100W/㎡.
Small horizontal axis wind turbines generally consist of the following parts: wind wheel, generator, rotating body, speed regulation mechanism, steering mechanism (tail wing), etc. The basic structure principle is shown in Figure 1.
1) Wind wheel
The wind wheel is generally composed of blades, wheel valleys, cover plates, connecting bolt components and shrouds. The wind wheel is the most critical component of a wind turbine, which converts the kinetic energy of the air into mechanical energy.
The generators used in small wind turbines can be DC generators or AC generators. At present, most of the generators used in small wind turbines are three-phase AC generators. Due to the different forms of magnetic field generation, three-phase AC generators have permanent magnet type and excitation type. The three-phase AC power they generate must be rectified by rectifier diodes to output DC power. Small wind turbines mainly use low-speed permanent magnet generators. This is mainly because the wind wheel of the small wind turbine is directly coupled to the generator shaft, eliminating the need for a speed-up mechanism, which requires the generator to have only a few hundred revolutions per minute. , So a low-speed generator is used.
3) Revolving body
The slewing body is the key component of the wind turbine, the carrier of the wind wheel, the generator and the tail, and a bearing structure installed on the top of the tower. Its function is to support the installation of generators, wind wheels and tail speed regulation mechanisms, etc., and to ensure that the above-mentioned working parts rotate freely on the upper end of the frame with changes in wind speed and direction according to their respective working characteristics.
4) Speed regulating mechanism
Due to the instability and pulsation of the natural wind, the wind speed is high and sometimes small, and sometimes strong winds and storms occur. The speed of the wind turbine impeller changes with the change of the wind speed. If there is no speed regulation mechanism, The speed of the impeller of the wind turbine will be higher and higher as the wind speed increases. Therefore, if the wind turbine has a stable power output, it must be equipped with a speed regulation mechanism.
There are three commonly used speed regulation methods for small wind turbines: wind wheel sideways speed regulation method; blade sideways speed regulation method; air brake speed regulation method.
5) Speed limit protection
If the wind generator does not have an automatic protection device, a series of faults will occur when the wind speed exceeds the available wind speed range, such as strong wind blowing the blades, and the generator rotating too fast and burning. Therefore, speed limit protection is required. Speed limit protection is divided into mechanical speed limit protection and magnetoelectric speed limit protection.
6) Transfer to the organization
Wind power generators rely on the energy of the wind to generate electricity, and the size of the wind energy captured by the wind wheel of the wind power generator is proportional to the vertical windward area of the wind wheel. That is to say, for a certain wind wheel, when it is perpendicular to the wind direction (front windward), it captures more wind energy; when it is not front windward, the captured wind energy is relatively small; when the wind wheel is parallel to the wind direction, it captures more wind energy; No wind energy can be captured. Therefore, the wind turbine must be equipped with a direction adjustment mechanism to keep the wind wheel in the windward state to the greatest extent, so as to obtain as much wind energy as possible, so as to output larger electric energy. For small wind turbines, the direction adjustment mechanism generally adopts ” The “tail wing steering” mechanism. The principle of the direction adjustment is that within the rated wind speed, the tail plate and the rotating surface of the wind wheel are kept perpendicular, and the tail plate and the wind direction are kept parallel, thus ensuring the positive wind of the wind wheel.