How does the use of active stall control compared to pitch control affect power output and load on the wind turbine?

Active stall control and pitch control are two different methods for regulating power output on a wind turbine. Active stall control affects power output and load differently than pitch control. Pitch control involves actively adjusting the pitch angle of the blades to control the amount of lift generated. The pitch angle is the angle between the blade chord (the line from the leading edge to the trailing edge) and the incoming wind. Stall control, on the other hand, involves inducing stall on the blades to reduce lift and limit power output. Stall occurs when the angle of attack (the angle between the blade and the wind) becomes too high, causing the airflow to separate from the blade surface and reduce lift. Pitch control provides smoother and more precise power regulation. By continuously adjusting the pitch angle, the turbine can maintain a constant power output even under fluctuating wind conditions. This leads to improved grid stability and reduced stress on the turbine components. Active stall control results in less precise power regulation and can create increased loads. Stall is a more abrupt phenomenon than pitch control, leading to rapid changes in lift and drag. This can cause increased vibrations and stress on the blades, tower, and gearbox. In terms of load management, pitch control generally results in lower loads on the turbine components. By smoothly adjusting the pitch angle, the turbine can reduce the aerodynamic forces on the blades and tower, extending their lifespan. Active stall control tends to increase loads on the blades, particularly near the blade root. Stall creates turbulent flow and fluctuating pressures on the blade surface, leading to increased bending moments and shear forces. In active stall-controlled turbines, aerodynamic brakes (flaps or spoilers) may be deployed to induce stall rapidly and provide overspeed protection. This deployment causes very rapid load changes, affecting the blade's structural integrity. Furthermore, pitch control can provide better control over rotor speed. By adjusting the pitch angle, the turbine can maintain a constant rotor speed, which is important for grid stability. Active stall control can result in greater variations in rotor speed, especially under turbulent wind conditions. Therefore, pitch-controlled turbines are often preferred for their smoother power regulation, lower loads, and better control over rotor speed. However, active stall control systems are generally simpler and less expensive than pitch control systems. In summary, active stall control and pitch control have different effects on power output and load. Pitch control provides smoother power regulation and lower loads, while active stall control is simpler but results in less precise power regulation and increased loads.