Investigation of the closed-loop control system on the DFIG dynamic models in transient stability studies

摘要

In the power systems where a significant part of the total generated power is supplied by wind energy, the transient stability of the grid should be analyzed properly. This paper discusses the influence of the closed-loop control system of doubly-fed induction generator (DFIG) on transient stability. In this process, the stator and rotor electrical dynamics are considered during tuning the controllers. Accordingly, the DFIG with power electronics converters in the closed-loop control mode with generic PI controllers is considered. For this study, the dynamic model of the rotor side converter with more detail of the control system is used, because it has a direct effect on the dynamics of the generator speed/torque and hence on the system stability. Also, to tune the control parameters of the power electronics converters, the Gershgorin theorem is applied. Once an appropriate set of control parameters is obtained, the DFIG model is simplified and time-domain simulation is performed. For validation of the influence of modeling adequacy on closed-loop controlled DFIG, transient stability study under the different operating conditions is investigated. According to the simulation results, it is observed that for the closed-loop DFIG, neglecting the stator transients does not remove the high-frequency mode. Thus, the high-frequency mode is due to the rotor electrical dynamics. Additionally, the power system stability studies for closed-loop DFIG are not model order dependent. Accordingly, for the closed-loop controlled DFIG in the transient stability studies where fast electrical transients are not of interest, a simplified model, whereby both stator and rotor dynamics are neglected, is adequate.