Direct active and reactive power regulation of a DFIG wind power system with constant switching frequency and reduced ripple

The direct power control (DPC) scheme for doubly-fed generator (DFIG) wind energy systems is known to have simple control structure and fast dynamic response in comparison with other well developed control approaches such as field oriented control (FOC). The simplicity of this method comes from employing hysteresis-based controls for the stator active and reactive powers. However, these controllers have non-linear behavior, which causes a variable switching frequency for converter. This paper proposes a constant switching frequency controller that can replace the hysteresis-based controller and provides wide range of speed operation for DFIG wind power systems. The proposed control strategy is tested by simulation using MATLAB/Simulink and PSIM, and also experimentally using a 5.5 kW DFIG laboratory set up.