Explain the principle of vector control (Field Oriented Control) in AC drives.

Vector control (FOC) decouples torque and flux control in AC motors, achieving DC motor-like performance. The stator current is resolved into flux-producing (d-axis) and torque-producing (q-axis) components using Park transformation. D-axis current controls rotor flux while q-axis current controls torque independently. Rotor position/flux angle is estimated or measured for accurate transformation. FOC provides fast dynamic response, accurate speed control to zero speed, and precise torque control. Used in high-performance servo applications and electric vehicles.