Direct power control of DFIG connected to unbalanced power grid

This paper presents a control strategy, which allows doubly-fed induction generator (DFIG) to generate a sinusoidal stator currents and minimize an electromagnetic torque oscillations under unbalanced grid conditions. The control does not require a positive and negative sequence decomposition of the control variables, so the independent control of positive and negative sequence is not used. Instead of it, the reference signal for reference power is calculated for the main control algorithm, which is the direct power control (DPC). Proposed strategy reduces the machine´s torque oscillations and causes, that the machine stator and rotor current does not exceed the rated values, what may happen in a classic DPC control, when the positive sequence component of the grid voltage drops. Simulation results with 2MW doubly fed induction machine model are presented in the paper.