Dynamic Equivalence to Heterogeneous Wind Farm While Preserving Interaction Among DFIGs Based on Interactive Currents and Their Sensitivities

Increasing doubly-fed induction generators (DFIGs) decreases power system stability and necessitates supplementary damping controller (SDC). Due to control complexity, only some DFIGs are installed with the SDCs, yielding heterogeneous wind farm (HWF) whose dynamic equivalent model (EM) has not been studied. At first, the outputs of the DFIGs’ transfer function are newly decomposed to the current of common interaction (CCI) and the current of network interaction (CNI) to quantify the interaction among DFIGs. Then by rearranging the state-space equations of the SDCs to decoupled canonical form, the HWF is classified to 3 types of subsystems, each type represented as an equivalent DFIG. The outputs of the first two types of subsystems describe the CNIs of DFIGs with/without DFIG-SDC respectively. The output of the 3rd type of subsystem with SDC is obtained by accumulating CCIs of DFIGs, and injected to power system. Finally, the sensitivities of the CCI and CNI with respect to the DFIGs’ stator voltages and the SDCs’ outputs are newly derived. By equalizing the sensitivities of the interactive currents in the EM and detailed model, the parameters of the equivalent DFIG are newly decided. Simulation results validate the feasibility and accuracy of the proposed model.