Voltage control in a DFIG-DC system connected to a stand-alone dc load

This paper proposes a control scheme for a stand-alone DFIG-DC system where the stator and the rotor are connected to a dc load by an uncontrolled diode bridge and a VSI respectively. The stator frequency and the dc voltage regulation are achieved by a field oriented control, however, with respect to the classical ac stand alone DFIG, the role of the rotor currents is swapped, namely: the d-axis and q-axis rotor currents are used for the frequency and for the dc voltage regulation respectively. Such a choice is due to the peculiarity of the operation of the diode bridge connected to a constant voltage dc link. The control scheme is presented and design criteria for the voltage controller are reported. The performances of the system are verified by simulations.