Pitching (adjusting the blade pitch angle for wind turbines) presents unique challenges for motion control performance. These solutions need to maximize energy production as well as accommodate different technologies (e.g. hydraulic and electric), withstand extreme conditions (e.g. temperature, vibration), and perform reliably in continuous operation over a lifetime of ~20 years and more.
Moog offers integrated solutions to turbine manufacturers and operators that include pitch control systems, slip rings and blade load sensing systems. Our application expertise in wind energy has been recently enhanced with the acquisition of the wind energy business of LTi REEnergy, the leader in electric pitch control systems based in Unna, Germany and Shanghai, China.
Blade Pitching for Wind Turbines
Accurately controlling the pitch of a turbine’s blades is essential to the overall performance of a wind turbine. During operation each blade is subjected to instantaneously changing loads and forces, often in extreme environments. Pitching is vital to both enhancing energy production as well as ensuring safety of the multi-million dollar turbine.
Typically, wind turbines use blade pitch control systems to fulfill two main functions:
- To monitor and adjust the inclination angle of the rotor blades, thereby controlling the speed of the turbine rotor to maximize the turbine’s energy production
- To turn the blade out of the wind in cases of a regular “Turbine Stop Command” or an “Emergency Feather Command (EFC)” thereby decreasing the rotor speed and stopping the rotor to avoid any damages on the wind turbine and ensure safe operation
The pitch system has to work reliably in any environment specified by the customer. The ambient conditions can differ greatly in terms of temperature, humidity, and vibration since turbines are often installed in areas with extreme climate, (e.g., Inner Mongolia in China or desert-like climates in the US or Spain). Thus robust and reliable hardware designed specifically for this application is critical to the performance and operation of a pitch system.
Blade Pitching Technology
Modern pitch systems are designed to independently control each blade by using three single actuators, which receive control commands on the blade’s target position from the turbine main controller over a slip ring. The slip ring is considered the key device to ensure reliable power and data transmission between the rotating hub and the nacelle.
When considering current turbine designs, wind turbine manufacturers use different technologies: Electric Blade Pitch Control Systems (EM) and Hydraulic Blade Pitch Control Systems (EH).
The choice of one technology or the other is mostly based on the customer’s historical preferences. Today, approximately one half of all erected turbines are equipped with EH systems while the other half is using EM systems.
Moog is able to provide both EH and EM blade pitch control depending on the customer requirements as well as the slip ring systems. Moog has a heritage in hydraulic products and solutions and the recently completed acquisition of LTi REEnergy’s wind business brought well-established EM technology to our customers.
When it comes to electric systems, turbine manufacturers must decide whether the actuators will use AC or DC technology. Due to our extensive experience in both technologies, our customers are able to select a solution which will be best for their special turbine requirements.
Moog Pitch Control Solutions are designed for both electric and hydraulic systems
Centers of Excellence in Wind Technology
Moog in Unna, Germany is a recent acquisition of Moog to complement its existing capabilities in state-of-the-art motion control solutions for power generation. This location was formerly the headquarters of the LTi REEnergy´s wind business in Germany. Originally formed from a division of German based company Stromag AG, the Unna facility has more than 10 years experience in safety-related motion control solutions for blade pitch control systems in wind turbines and also marine current turbines.
Another former LTi REEnergy facility dedicated to wind technology is located in Shanghai, China and it also became part of Moog in June, 2009. Today, more than 200 employees in Unna (Germany) and Shanghai (China) ensure that our customers receive the latest pitch control technology and related service in time around the world.
Moog has 26 worldwide offices including experts in wind power technology located in Sweden, Spain, Japan, USA and India.
In addition to the main functions for pitch systems (e.g., maximizing turbine’s production and ensuring safety) there are additional features that will help to increase turbine performance. One of these features is integration of a blade load sensing system to measure the load on the blades, allowing for individual blade pitch control to increase the performance of a wind turbine. Moog has recently acquired Insensys, the market leader in fibre optic sensing solutions for wind applications. These systems perform individual pitch control and also enable wind farm operators to detect ice, yaw misalignment, rotor imbalance and blade damage.
Moog’s integrated solutions combine pitch control systems, slip rings and blade load sensing systems, thereby minimizing the amount of components in the hub, reducing the weight and decreasing the life cycle costs of a turbine.
We provide specialized solutions for wind turbines ranging from 300 kW up to 6 MW that have been installed on more than 10,000 wind turbines worldwide recognized by industry leaders as the most safe, reliable and effective option. Moog’s collaborative approach, combined with our expertise and global support network, makes us the ideal partner to solve your wind energy challenges.
We look forward to speaking with you about your challenges.
About the Author
Jochen Heuveldop is Director of Sales at Moog in Unna. He joined the company about 3 years ago after 15 years experience in motion control in power plants and industrial applications.