Complex transfer function‐based sequence domain impedance model of doubly fed induction generator

Abstract

The impedance-based analysis is widely used to study stability problem between wind turbine system and grid network. Stationary sequence domain impedance has advantages over synchronous dq domain impedance due to its easy measurement in practical application. However, there is frequency coupling effect in sequence domain impedance, and a 2×2 impedance matrix is needed which makes the system be multiple-input-multiple-output system, which makes stability study and controller tuning much more complex compared with single-input-single-output (SISO) system. In this study, impedance model of doubly fed induction generator (DFIG) in sequence domain considering frequency coupling effect is derived based on the complex vector modelling method, which can obtain the straightforward block diagram representation of DFIG impedance. On the basis of the proposed model, the interaction of DFIG and different kinds of grid impedances are studied. Gershgorin theorem is applied to study the fidelity of SISO impedance model in stability analysis. Finally, the proposed impedance-based analysis is verified through simulation.