Virtual Inertia Estimation and Response Characteristics Analysis of DFIG Under Overspeed Mode and Synthetic Inertia Control

The doubly-fed induction generator(DFIG) under overspeed mode and synthetic inertia(SI) control can provide active power reserve and participate in the system frequency regulation, and the estimation of its inertia is of great significance to the frequency stability of the power system. However, there is a lack of accurate estimation methods for the virtual inertia of DFIG. In view of this, this paper firstly models the DFIG under overspeed mode and SI control, then proposes the expression of DFIG equivalent inertia based on the definition of inertia and the motion equation, and then proposes a recognition algorithm based on the controlled autoregressive moving average (ARMAX) model, the Akaike Information Criterion (AIC) criterion and the varying forgetting factor recursive least square (VFF-RLS). The simulation results show that: the proposed identification algorithm has high accuracy, and the output of the identification model is highly consistent with the actual value; the equivalent inertia of the DFIG with SI control increases significantly after the fault; the parameters of SI control are not the bigger the better, but should be adjusted by considering the frequency regulation capability and the stability of the DFIG itself at the same time.