Effect of AC voltage control on the stability of weak AC grid connected DFIG system

Dynamic performance of grid connected doubly-fed induction generator (DFIG) in electromagnetic timescale is not merely determined by the operating point, but also largely dependent on its converter control. DFIG may suffer stability issues when integrated into a weak AC grid, in which converter control loops are coupled, and resulted impact for system stability is obscure. This paper proposed a simplified analytical model allowing for the possible interactions of control loops. The proposed model highlights the effect of AC voltage control gain. Based on the model, incorporating AC voltage control tuning and operating point variations, different potential instability phenomena and corresponding approximate operating margin are investigated. Detailed time domain simulations are employed to validate the proposed model and analysis results.