The basic structure of the horizontal axis lift wind turbine
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- Wind wheel
The wind wheel of a wind turbine is composed of wheels and blades. In terms of performance and overall cost, they are the most important components of the wind turbine.
Today’s main wind turbines have three blades in the upwind direction, and some have two blades in the downwind direction. There used to be single blades in the past, but they are no longer in production. Most medium-capacity wind turbines are manufactured in Denmark. They are controlled by fixed blade angle of attack and stall. Most manufacturers use variable blade angle of attack control. The current trend is to use variable angle of attack control, especially on high-power wind turbines. . Most wind turbine blades are made of composite materials, mainly glass fiber (GRP) or carbon fiber (CFRP) reinforced polyester materials, and some are made of wood/epoxy laminates.
- Drive chain
The drive chain is composed of the rotating part of the wind turbine on the lower side of the wind wheel. It generally includes a low-speed shaft (on the wind wheel side), a gear box, and a high-speed shaft (on the generator side). Other drive chain components also include support bearings, one or more A coupling, a brake device and a generator rotor (discussed separately in the next section); the function of the gearbox is to increase the low speed of the wind wheel (tens of revolutions per minute) to the appropriate speed of the standard generator (a few hundred revolutions per minute) Minutes or several thousand revolutions per minute). There are two types of gearboxes used in wind turbines: parallel shaft gears and planetary gears. For larger wind turbines (over 500 kW), planetary gears are more advantageous in terms of weight and size; some wind turbines use multiple power generation It is connected with multiple output shafts of the gearbox, and some specially designed wind turbines use low-speed generators that do not require a gearbox.
When the design of the drive chain components of a wind turbine usually follows the design guidelines of conventional mechanical engineering machines, the unique load on the drive chain of the wind turbine requires special consideration. The variable wind speed and the dynamic characteristics of the large rotating wind wheel impose significant changes on the drive chain components. Load.
Almost all wind turbines use induction or synchronous generators. When the generator is directly connected to a public grid, both types of generators need to run at a constant or nearly constant speed. If the generator is equipped with a power electronic converter, the wind turbine can run at variable speeds.
Many wind turbines connected to the grid use squirrel-cage induction generators (SQIG). The squirrel-cage induction generators operate in a narrow speed range and are slightly higher than its synchronous speed (four-pole power generation in a 60 Hz grid). The synchronous speed is 1800 rpm). The main advantages of this type of generator are sturdiness, low cost and easy access to the grid. At present, the double-fed induction generator (DFIG) is widely used, which is often used for variable speed operation.
For large-scale public power generation systems, it is increasingly preferred to choose variable speed wind turbines. This type of wind turbine has many advantages, including the ability to reduce the wear and tear of the wind turbine, and to maintain maximum efficiency in a wide range of wind speeds to capture more wind energy ; Although there are many electrical equipment available for variable speed wind turbines, power electronic components are used in most current design variable speed wind turbines. When a suitable power electronic converter is used, whether it is a synchronous generator or an induction generator Both run at variable speed.
- Cabin and yaw system
This part includes the wind turbine nacelle, the machine deck or main frame, and the yaw-to-wind system. The main frame ensures that the drive chain components are fixed and well aligned, and the cabin cover protects the components in the cabin from damage due to weather.
The function of the yaw on the wind system is to align the wind wheel shaft properly with the wind direction. The most basic component is the yaw bearing that connects the main frame and the tower. A wind turbine contains one or more yaw motors, each of which drives a small gear that meshes with a large gear, and the large gear is connected to a yaw bearing. This mechanism is controlled by an active yaw system, which has a wind direction sensor mounted on the nacelle of the wind turbine. This type of design is sometimes equipped with a yaw brake device, which can fix the cabin when yaw is not needed. The automatic yaw system (that is, it can automatically align the wind direction) is often used in the downwind wind turbine.