Analysis and compensation of current measurement errors in a doubly fed induction generator

This paper proposes a compensator to reduce the power ripple of DFIG generated by offset and scaling errors of the rotor current sensors. The input signal of the proposed compensator adopts the synchronous d-axis current of the rotor. The amplitude of the stator current is low but that of the rotor current is high. Also stator current is variable according to the wind intensity but the rotor current is almost constant. Therefore the rotor current is more suitable for the input signal of the compensator. Two errors of the sensor contain one and two times ripple of the slip frequency, respectively. Each ripple component can be obtained by integrating the synchronous d-axis current of the rotor according to the slip angle. These two errors can be compensated by subtracting those from the measured rotor currents. The feasibility and effectiveness of the proposed algorithm can be verified through experimentation.