Direct power control of a doubly fed induction generator wind power system with seamless transition between stand-alone and grid-connected modes

This paper describes a direct power control (DPC) strategy used for a doubly fed induction generator (DFIG) for wind energy system. The system operates in stand-alone (SA) and can connect to the grid through smooth transition. The proposed control structure is capable of regulating the stator voltage and frequency for an isolated load in case of grid outage. Also, when grid is available, it can control the stator voltage phase to be synchronized with grid voltage and connect with seamless transition to the grid. The basic structure of DPC method consists of hysteresis-based controller (HBC) and switching table that are used in both SA and grid-connected (GC) modes. The proposed control strategy is analyzed, simulated using MATLAB/Simulink and PSIM, and also validated experimentally using a 7.5 hp DFIG laboratory set up.