The environments in which wind turbines are located are constantly expanding. The highest altitude of onshore wind farms in China reaches 4,700 meters, while the farthest offshore wind farm in China is 48 kilometers away from the shore.
As wind turbines become increasingly larger and their applications expand, higher demands are placed on their adaptability to varying wind speeds and their safety under extreme conditions. This is precisely where pitch control excels. Pitch control uses mechanical, hydraulic, or electric servo methods to control the rotation of the wind turbine blades, adjusting the blade pitch angle, changing the angle of attack of the airflow on the blades, and thus controlling the aerodynamic torque and power captured by the wind turbine blades.
1. Pitch Control Principle
Using the rotational surface of the blade as a reference surface, when the angle between the blade and this surface and the pitch angle are 0, the wind energy captured by the blade is the maximum, and the power generated by the wind turbine is also the maximum. When the angle between the blade and this surface and the pitch angle are 90, the blade resistance is the maximum, causing the wind turbine to shut down. This is crucial for the safe operation of the entire wind turbine in some extreme weather conditions.
Electric pitch control is increasingly used in wind power due to its ease of operation and maintenance, low cost, and high control response. Electric pitch control uses an electric servo controller to drive the pitch motor, which in turn drives a pinion gear, which in turn drives the pitch bearing of the blade, thus achieving blade rotation.
Electric pitch control diagram, from Zhongcheng Zhuoyue official website.
2. Requirements for pitch control
The pitch actuator is the core component of the pitch system. Its platform-based product functionality not only covers the needs of all onshore and offshore wind turbine platforms but also helps these platforms reduce costs and further improve the reliability of the pitch system and the adaptability to overall turbine control requirements. The pitch control system, in conjunction with variable speed constant frequency technology, ultimately improves the power generation efficiency and power quality of the entire wind power generation system. Since wind farms are generally built in areas with harsh natural environments, the reliability and environmental adaptability requirements of the pitch control actuator are very high. A failure in a single pitch actuator can cause turbine shutdown at best, and at worst, jeopardize the safety of the entire tower. Even the smallest repair can result in significant economic losses to the wind farm due to power loss and substantial maintenance costs. The table below illustrates the extremely high reliability, environmental adaptability, and safety requirements of the pitch actuator. For example, the operating temperature of a typical industrial servo drive is only up to 45°C, and derating is required above 45°C. In contrast, the operating temperature of a pitch control drive can reach up to 70°C. In addition, regarding vibration requirements, the vibration of a typical industrial servo drive is between 0.5g and 1g depending on the frequency range, with 1g below 20Hz and 0.5g or 0.6g between 20Hz and 50Hz. Pitch control drives, on the other hand, can reach 2g. Furthermore, pitch control drives need to pass low voltage ride-through tests, high voltage ride-through tests, and design/manufacturing failure mode effects analysis, etc.
Reliability Comparison Table of Pitch Control Drivers and Industrial Servo Drivers
Zhongcheng Excellence, a domestic manufacturer specializing in the wind power sector, possesses strong independent R&D capabilities and technological patents. After years of development, it has developed a complete, mature, and reliable wind power solution integrating pitch servo drives, pitch motors, yaw systems, and pitch energy storage. Wind power pitch systems are a core product in its product line, and it collaborates with pitch product manufacturers globally. Its PD series pitch drives have shipped over 15,000 units, serving more than 160 wind farms across China. Their high safety, high reliability, and high integration have earned praise from numerous wind turbine manufacturers and system integrators.
