Power Control of DFIG Based Wind Power System Incorporated with Embedded Energy Storage

Fluctuation and intermittence are the characteristics of wind energy,which originate from the natural feature of wind. With this variable power flowing into grid,the grid stability and power quality would be impacted. Because doubly-fed induction generator (DFIG) based wind system adopts two back-to-back voltage source converters and a DC bus,a power control method is proposed based on embedded energy storage (EES) system to smooth short-term fluctuations in the wind farm output. Not only can the EES be embedded into the DC side of DFIG electrically,but also can insert the DFIG physically. Taking the natural characteristic of wind into consideration,EES is capable to damp the fluctuant power into grid with its flexible power handling capability. The corresponding control strategy is designed. Taking the classical four-component wind model and grid voltage disturbance condition for example,the operational characteristic of DFIG based wind power system incorporating EES is simulated. Simulation results show that the power quality and stability of wind system connected to power grid can be improved by embedded energy storage.