tailieunhanh - Wind_Farm Technical Regulations Potential Estimation and Siting Assessment Part 2

Tham khảo tài liệu 'wind_farm technical regulations potential estimation and siting assessment part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Technical and Regulatory Exigencies for Grid Connection of Wind Generation 9 turbines are destroyed is in the range of 40-72 m s 144-259 km h or 89-161 mph . The most common survival speed of commercial wind turbines is around 60 m s 216 km h or 134 mph . Wind turbines have three modes of operation Hansen et al. 2004 . Below rated wind speed operation Around rated wind speed operation usually at nominal capacity Above rated wind speed operation If the rated wind speed is exceeded the power has to be limited. Therefore all wind turbines are designed with a power control that achieves this goal and avoids a run-away situation. There are different ways of doing this safely on modern turbines namely mainly pitch control and stall control. Pitch control This control concept was developed between years 1990 and 2000 and operates by turning the rotor blades into or out of the wind according to the control laws. An anemometer mounted atop the nacelle constantly checks the wind speed and sends signals to the pitch actuator adjusting the angle of the blades to capture the energy from the wind most efficiently. Standard modern turbines usually pitch the blades at high winds in order to prevent the rotational speed from rising to an unacceptably dangerous level. Since pitching requires acting against the torque on the blade it requires some form of pitch angle control which is achieved with a slewing drive. This drive precisely angles the blade while withstanding high torque loads. In addition many turbines use hydraulic systems. These systems are usually spring loaded so that if hydraulic power fails the blades automatically furl. Other turbines use an electric servomotor for every rotor blade. They have a small battery-reserve in case of an electric grid breakdown. Small wind turbines fewer than some kWs with variable pitching generally use systems operated by centrifugal force either by flyweights or geometric design and employ no electric or hydraulic controls. In

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