The yaw system, also known as the aligning wind device or the steering device, is one of the indispensable components of the upwind horizontal axis wind turbine, which allows the wind wheel to be aligned with the wind direction naturally. Yaw systems are generally divided into active yaw and passive yaw systems. Passive yaw refers to relying on wind to automatically complete the action of the wind wheel against the wind through related mechanisms. There are two common types of tail rudder and side wind wheels, which are mainly used for small wind turbines. Figure 1 shows the tail rudder structure. Active yaw system refers to the use of electric or hydraulic drag wind direction tracking to complete the wind movement, usually used in large-scale wind turbines. Figure 2 shows the structure of the hydraulic yaw system. The yaw system generally consists of a wind direction sensor, a yaw drive device, a yaw bearing, a yaw hydraulic circuit, a yaw counter, a torsion cable protection device, and a yaw brake.
Speed regulating device
Due to the large randomness of wind speed, the speed of the wind turbine blades changes correspondingly with the change of wind speed, which in turn affects the output power and voltage frequency of the wind turbine. In order to keep the output within a certain range, a speed regulating device is needed. At the same time, when the wind speed is higher than the rated wind speed, in order to prevent damage to the blades and other mechanical parts of the wind turbine, it is necessary to control the wind wheel and also need a speed regulating device.
The tower frame must not only bear the weight of the wind turbine, but also bear the wind pressure blowing on the wind turbine and the tower frame, as well as the dynamic load during the operation of the wind turbine. Usually the tower frame has a certain height, about 1 to 1.5 times the diameter of the wind wheel.
Generator power cables, control signal cables, etc. are laid in the tower frame. The tower is divided into several layers, with straight ladders between the layers to facilitate up and down, and a tower door at the bottom of the tower, as shown in Figure 3.
Power generation system
Generators and their control systems are important equipment that ultimately converts wind energy into electrical energy, and are mainly divided into DC generators and AC generators. Alternator is divided into synchronous generator and asynchronous generator. DC generators were commonly used in micro wind generators before, and the general DC voltage was 12, 24V or 36V, etc. However, due to its complex structure and large maintenance, it has been gradually replaced by AC generators. Currently, AC motors are commonly used. Since the wind power generation system is operated in parallel with the power grid, the wind power frequency must be consistent with the power grid frequency, that is, the output frequency is constant. Therefore, the wind power generation system can be divided into a constant speed constant frequency power generation system (CSCF) and a variable speed constant frequency power generation system (VSCF) .
(1) Constant speed and constant frequency power generation system. Constant-speed and constant-frequency power generation system refers to keeping the generator speed constant during the process of wind power generation, so as to output constant-frequency electric energy consistent with the grid frequency. The system is generally simple, and the generators used mainly include synchronous generators and squirrel cage asynchronous generators. The synchronous generator runs at a synchronous speed, n=60ƒ/p (ƒ is the frequency, p is the number of magnetic pole pairs). It can output active power and reactive power during operation, but the structure and control system are more complicated, and the cost is relatively higher than that of asynchronous generators.
In the constant-speed and constant-frequency system, a squirrel-cage asynchronous generator is generally used, which runs at a speed slightly higher than the synchronous speed during operation. The structure of its stator core and stator winding is the same as that of a synchronous generator. The rotor adopts a cage structure, no external excitation, no slip rings and brushes, so the structure is simple, strong, and basically does not require maintenance.
(2) Variable speed and constant frequency power generation system. The speed of the generator in the variable speed constant frequency power generation system can be changed with the wind to maximize the wind energy utilization system in a wide range of wind speed, and then obtain constant frequency electric energy through other control methods. The wind energy it obtains is much higher than that of the constant-speed and constant-frequency system, which can be divided into two categories: discontinuous variable speed and continuous variable speed systems.
The next article will give you a detailed introduction to the two categories of discontinuous transmission and continuous transmission systems.