Direct power control with referenced torque and reactive power of Doubly Fed Induction Machine connected to unbalanced grid

Doubly-Fed Induction Machine (DFIM) still remains one of the most popular type of generation unit used in wind power conversion systems, due to variable-speed operation, price and reduced power of its bi-directional power converter. However, the machine connected to power grid is very sensitive to voltage unbalance. High DC-link voltage is required during unbalanced grid operation mode in order to sustain system stability. Without robust control excessive pulsation of electromagnetic torque occurs. This paper presents an effective and simple control of DFIM connected to unbalanced grid. The control is based on the simple direct power algorithm (DPC) with hysteresis controllers and does not require voltage and current decomposition into positive and negative sequence.