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General Impedance Model of DFIG for Wide-Range-Frequency Oscillation Studies

With a large amount of wind power connected with the grid, wide-range-frequency oscillation problems become increasingly serious. In order to study oscillation mechanism, the general impedance model of doubly-fed wind generator (DFIG) is established in DQ coordinate system, including the parts of wind generator parameters, rotor-side controller (RSC), grid-side controller (GSC), phase-locked loop (PLL) as well as direct current bus. From the final expression of the general impedance model, the interaction effect among the grid, wind turbine and controller can be found, and it can also be used in the studies of wide-range-frequency oscillation in DFIG. The final simulation shows that sub-synchronous oscillation (SSO) will also happen in the state of wind farm connected to grid with no series capacitor compensated.