Analysis and design of stand-alone DFIG employing a battery-single inverter arrangement

A modest system configuration is developed for functioning wind driven standalone DFIG to power isolated loads. Being grid-independent, variations in rotor speed result in corresponding changes in stator voltage and frequency. A straightforward control approach is formulated to sustain a constant voltage and frequency observed at the DFIG stator, effectively creating a localized reference grid to power connected energy users. It is accomplished through closed system control of a battery powered SPWM inverter interfaced with DFIG rotor terminals. The system provides uninterrupted supply to isolated loads by managing charging/discharging operations of the battery bank, in accordance with wind power availability. This control strategy is instigated using FPGA regulator and validated on a standalone DFIG. This strategy is independent of machine parameter variations, eliminating the need for coordinate transformations, rotor position sensing, and rotor current measurements. Experimental and simulation validation demonstrates the effectiveness of the anticipated approach and supports theoretical investigation.