Real and reactive power control of hybrid excited wind-driven grid-connected doubly fed induction generators

This study proposes a simple topology which consists of a single sinusoidal pulse width modulation (SPWM) inverter and battery banks with wind-driven doubly fed induction generators (DFIGs) to dispatch a controllable power to the grid. The excitation of the rotor is established using an SPWM inverter supplied through a set of batteries with the stator connected to the grid. The proposed system supplies the desired real and reactive power to the grid by appropriately charging/discharging the batteries depending on excess/deficit power from the wind. A closed-loop controller has been developed for this purpose which involves varying the rotor voltage magnitude and frequency. The entire control strategy proposed in this study has been implemented using TMS320LF2407A DSP controller and detailed procedure for such implementation is presented. The steady-state analysis and phasor diagram representation of the system have been developed and presented. Experimental results obtained on a three-phase, four-pole, 50 Hz, 5 kVA DFIG together with the closed-loop controller under steady-state and dynamic operating conditions, confirm the usefulness of the proposed system. The experimental results have been compared with predicted values and a very close agreement between the two is observed.