The Integrated Reference Region Analysis for Parallel DFIGs' Interfacing Inductors

Although the traditional design of doubly-fed induction generators (DFIGs)' interfacing inductors consider the peak ripple of the grid-side converter (GSC)'s output current, it does not consider the inductors' impact on DFIGs' small-signal stability. Located in series between the GSC and the stator, the inappropriate selection of the interfacing inductor can easily result to system instability. Therefore, this article first proposes the integrated reference region analysis for small wind farm's interfacing inductors to improve the traditional design method. First, a new detailed parallel DFIGs' small-signal model that considers output currents' coupling is built in d-q coordinate system with state-space approach. The model focuses on representing the operating states of parallel DFIGs in wind farm. Second, the linearized state-space matrix of parallel DFIGs is decomposed into nominal-value matrix and location matrix. Considering the traditional design requirements, the integrated reference region for interfacing inductor is proposed through spectral radius and bialternate matrix sum. It can provide better guidance for parameter selecting and stabilization method research works. Finally, the simulation and experimental results show that the proposed integrated reference region for parallel DFIGs' interfacing inductors is accurate and instructive.