An improved direct power control of a doubly fed induction generator wind power system

The conventional switching strategy of a direct power control (DPC) scheme for doubly-fed induction generator (DFIG) wind energy generation systems are based on hysteresis comparators. Non-linear behavior of this controller causes non-constant switching frequency on the rotor side converter, which depends on the wind speed, amount of power converted and the hysteresis band of the comparator. This paper proposes a constant switching frequency controller that can replace the hysteresis-based variable frequency controller. Using two triangular waveforms that are phase shifted by 180°, the DFIG can operate in wide range of speed with constant switching frequency. Matlab/Simulink and PSIM simulation packages are used to validate this type of controller.