Design and Analysis of Grid-Interactive DFIG Based WECS for Regulated Power Flow

This paper presents a grid-interactive doubly fed induction generator (DFIG) based wind energy conversion system (WECS) for regulated power flow through the grid. The battery energy storage (BES) is used for maintaining regulated power along the grid regardless of the wind speeds. The rotor side converter (RSC) is controlled in flux based reference frame and the grid side converter (GSC) control is based on an indirect vector control. The BES is connected at DC bus of two voltage source converters integrated back to back, which plays key role in attaining regulated grid power. This work proposes control algorithms for both RSC and GSC to achieve regulated power flow capabilities in the grid. The system is modeled and its performance is simulated under variable wind speeds, change in grid reference real and reactive powers, grid voltage dip and unbalanced nonlinear load conditions using SimPowerSystems toolbox of MATLAB. Under all such cases, the grid currents, stator currents and PCC (point of common coupling) voltages are found sinusoidal and THDs (total harmonic distortions) are under limits as per the IEEE 519 standard. Finally, a prototype is developed and experiment has been carried out to test the grid-interactive DFIG based WECS under changeover of grid power and variable wind speeds.