Impedance Reshaping Band Coupling and Broadband Passivity Enhancement for DFIG System

Doubly fed induction generator (DFIG) based wind power systems incur a broadband negative resistive characteristic, resulting in resonance risks when connected with weak grid or diverse grid transmission infrastructure. The dominant factor and underlying mechanism of this broadband negative resistive characteristic are analyzed based on the passivity-based stability assessment. It is then noticed that the negative resistive region within low frequency, middle frequency, and high frequency are closely linked to the current controller, phase locked loop, and system delay, respectively. This article reveals the impedance reshaping band coupling phenomenon to facilitate some passivity-based designs, then puts forward a broadband passivity enhancement method for DFIG system. The experimental results validate the aforementioned conclusions and the effectiveness of the proposed passivity enhancement method.