Wind energy is a kind of resource which is friendly to the environment and inexhaustible, there are so many areas can get wind energy, like the northwest, northeast and coastal areas of China. Wind energy industry prospect is very broad, nowadays , we can see that the speed of development is getting faster and faster, and the wind turbine tower becomes higher and higher.
It is the most basic way for utilization of wind energy that use the wind turbine to turn the wind energy into electric energy. Normally, wind turbine is composed of wind wheel, generator, the nacelle, wind turbine tower, rotor, hub, transformer and other component. So how do they work together, what is the working principle of the wind turbine?
The working principle of wind turbine
To put it simple, wind turbine is a kind of power equipment that use wind to drive the turbine blades, the blades connect to the main shaft, when the blades turning, the main shaft spins the generator to create electricity. According to today’s windmill technology, if the wind speed get about three meter per second, it can create electricity.
Most large-scale wind turbines have three blades, installed on the vertical tower, and the blades always made of composite material. The simpler wind turbines used the fixed speed, usually, there are two different speed, under the weak wind with low speed and with high speed under the strong wind. The new design wind turbine used the variable speed. Use the variable speed system, the aerodynamic efficiency of wind turbine can be improved, that can get more energy. So the variable speed wind turbine is more popular than the fixed speed wind turbine.
The sensor which installed on cabin is used to detect wind direction. Through using the turn device to make cabin and wind wheel turning automatically. When face to wind, the rotary motion of wind wheel will be send to the generator through the speed-changing gearboxes.( If there isn’t a speed-changing gearboxes, then the rotary motion of wind wheel will be send to the generator directly.)
All the power delivery of wind turbine is changed by wind power. When meet strong wind, the common ways to limit power delivery are the stall adjustment and angle adjustment. Use the wind turbine with stall adjustment, when the strong wind over the limited wind speed, the airflow which through the blades will create turbulent flow, and the wind wheel will stall. When wind is over strong, the brake apparatus on tail of blades will start work to brake the wind wheel. Use the wind turbine with angle adjustment, each blade could spin on the longitudinal axis, the angle of blades will change with the different wind speed, thus change the aerodynamic performance of the wind wheel.
Wind turbine control technology
Wind turbine control system is the core of normal operation of the unit, and the control technology is one of the key technology of wind turbine. In addition, wind turbine control system is closely related to other parts of wind turbine, its precise control and perfected function will effect the safety and efficiency of the wind turbine.
Basic operational process of fixed pitch wind turbine
Ready mode. When wind speed v > 3m/s, but not enough to drag wind turbine to the cut-in rotational speed, or the wind turbine cut-out from small power, not connects with power grid afresh. In this time, the wind turbine in the free rotation state. That called ready mode.
Self-starting of wind turbine. Self-starting of wind turbine is that under the effect of natural wind speed, wind turbine drags the generator to rated rotational speed without any external forces.
Operating state of variable pitch wind turbine
Starting state. When wind speed get the starting wind speed, blades turn to 0° direction until the airflow has a certain of angle of attack on blades, the wind wheel start to work.
Underpower state. After wind turbine connect with power grid, because of the wind speed which lower than rotational wind speed, wind turbine working under the low power state. At the moment, variable pitch wind turbine is same to the fixed pitch wind turbine, their power output depend on aerodynamic performance of the blades.
Rated power state. When wind speed get or over the rated power state, wind turbine enter rated power state.