Considerations Toward Coordinated Control of DFIG-Based Wind Farms

This paper highlights the important considerations toward coordinated control of doubly fed induction generator (DFIG)-based wind farms for power oscillation damping. The effect of replacing one existing synchronous generator with a power system stabilizer (PSS) by a DFIG on the local mode and the modeshapes of the critical interarea modes are analyzed. With almost zero participation from the DFIG mechanical side and very little observability of low-frequency oscillatory modes in signals locally available at the wind farms, the choice of appropriate remote feedback signals is discussed. Relative controllabilities of the DFIG rotor current components are compared to determine the most effective control structure. A coordinated control design approach aimed at damping multiple oscillatory modes through more than one DFIG-based wind farm is demonstrated. Heuristic optimization is used for the design problem which is otherwise difficult to solve using an analytical approach. Modal analysis and nonlinear simulation results are presented to substantiate the findings.