A Method to Identify the Impact of Wind Turbine Generators on Low-Frequency Oscillations

This article develops a frequency-domain approach to study the impact of WTG replacing the output of synchronous machine gradually on interarea low-frequency oscillations. Firstly, a Heffron-Philips model of power system with WTG integrated is derived, it is found that the new model has similar configuration with the original one, which indicates that the effect of WTG integration on stability is due to changing the matrices K1–K6 of the power system. On the basis of the new model, the impact of two critical factors on stability margin, the change of the dynamics of synchronous machine and WTG, can be identified. A minimum characteristic locus method, recently introduced by the authors, is extended to quantify the impact of the two factors. The proposed method is applied to the example New England power system and IEEE 118-bus test system, and time domain simulation is performed to verify the analysis results. Based on the results, it is believed that there is an optimal power output ratio between the WTG and the synchronous machine for power injection node. The results also demonstrate that, after the integration of WTG, the stability effect caused by the change of synchronous machine dynamics is much greater than the effect caused by the change of WTG dynamics.