Rotor flux estimation method for cage induction generators used in wind power applications

This paper describes the rotor flux estimation method for squirrel-cage induction generators (SCIGs) used in wind power applications. The proposed method estimates the rotor flux angle and magnitude in rotor reference frame by using measured stator currents, rotor angle and rotor time constant. The performance of the proposed method is compared to the performance of the voltage based estimator which is commonly used flux estimation method in sensorless field oriented vector control (FOC). The pure integrator in voltage based estimator is replaced by a low-pass filter with adaptive compensation and a phase locked loop (PLL) based position controller. Both methods are implemented in a digital control system and verified on the laboratory model. Experimental setup consists of a squirrel-cage induction machine (560 kW) connected to the grid via back-to-back converter and a permanent magnet machine (375 kW) driven by the industrial frequency converter and used as a wind turbine emulator. The advantages and disadvantages of the proposed method are demonstrated by experiments.