_________ systems are used in variable speed wind turbines.

• A. Frequency Converter
• B. Gearbox
• C. Hydraulic System
• D. Pitch Control

Answer: (A)

Variable speed wind turbines rely on electrical power electronics to decouple rotor speed from the grid frequency. A frequency converter takes the generator’s variable-frequency output and converts it to the fixed grid frequency, while also adjusting torque to optimize energy capture. This enables the turbine to freely speed up or slow down with changing wind while still delivering stable, grid-compatible power. Gearboxes can be present in some designs but aren’t what makes speed variable. Hydraulic systems and blade pitch control are important for regulating power and mechanical actions, but the converter is the essential element that enables variable speed operation.