Impacts of DFIG-Based Wind Power System on Migration Mechanism of Oscillation Center

The safe and stable operation of the power system has become an increasingly critical issue as the large-scale of wind power integration and its long-distance transmission. Splitting control (or islanding control) of the power system is an important prevention measure to mitigate the system collapses. In general, the oscillation center (i.e. the point of which voltage is the lowest in the power gird) is applied to searching the splitting boundary. However, fast responses, low inertia, and asynchronous operation of the doubly fed induction generator (DFIG) might change the migration mechanism of oscillation centers. This paper tries to analyze the impact of DFIG characteristics on oscillation center migration. First, Thevenin equivalent circuit equation of DFIG is established, based on which the characteristic admittance of DFIG under out-of-step oscillation is analyzed. Then by substituting the characteristic admittance of DFIG into the oscillation center migration function, results manifest that the distribution range of the oscillation center is extended, and the splitting location keeps away from the point of common coupling (PCC). Finally, simulations on 2-area 4-machine system and IEEE 118-bus system integrated with wind farms verify the correctness and effectiveness of the theoretical analysis.