Parameter Estimation by Considering Both Voltage Dip and Phase Angle Jump for DFIG-Based WTGs in Distribution Grids

Abstract

In existing parameter estimation method for WTGs (Wind Turbine Generators), the voltage dip depth is commonly used as a disturbance information, while the phase angle is sometimes ignored. Many studies show that in distribution networks, the phase angle of WTG's terminal voltage will jump significantly under grid fault, the neglect of which may increase estimation errors. In this paper, parameter estimation for WTGs connected to distribution grid is presented by considering both voltage dip and phase angle jump. Firstly, the influences of voltage magnitude and phase angle on the dynamics of DFIG (Doubly Fed Induction Generator)-based WTGs are analysed, and the necessity of including the phase angle jump is emphasized. Secondly, a simple yet efficient parameter identifiability analysis method based on trajectory sensitivity is applied. It is found that the stator and rotor leakage inductance in a DFIG are approximately linear dependent, indicating that these two parameters cannot be estimated simultaneously. Dominant parameters are further selected based on the trajectory sensitivity analysis. Finally, the online parameter estimation process is presented, and the estimation results demonstrate a better estimation accuracy of the proposed method when phase angle jump is considered, contributing to the modelling accuracy and the increasing application of WTGs.