Crowbar With a Parallel RpLp Configuration Using PI Controller to Solve the Problem of DFIG-Wind Farm Stability During a Symmetrical Fault

Abstract

The doubly fed induction generator (DFIG) is particularly sensitive to grid faults, representing a significant drawback of this generator type, because of the direct connection of its stator windings to the network. The electromagnetic coupling between the stator and rotor in the DFIG results in an undesirable consequence, where voltage dips lead to excessive stator current, causing high currents in sensitive inverters and overloading the DC-link condenser. This document outlines a comparative study that examines two protection scheme configurations with a proportional-integral (PI) controller for managing transient rotor current and overcharging of the DC-link capacitor in order to optimize the operation of the DFIG during network faults. One conventional design choice combines a crowbar circuit with a DC-chopper, in contrast the other design option proposes integrating a modified protection scheme (MPS) that includes an RpLp parallel circuit with the traditional crowbar. Both schemes are placed between the rotor windings and the rotor-side converter (RSC) to boost the low voltage ride-through (LVRT) capacity of the generator. The comparison of results obtained through MATLAB/SIMULINK simulations reveals the successful performance of these two schemes in reducing elevated intensity current of rotor and DC-link voltage levels in the DFIG machine. Furthermore, the traditional crowbar and MPS circuit design have effectively limited the current intensity of the RSC converter to levels lower than 0.22 kA and 2.95 kA, while absorbing up to 2.53 kA and 1.53 kA respectively. Thus, ensuring that the DC-link tension stays within the safe range when network failures occur. The notable distinction is that the MPS design prevents the decoupling of the rotor from the RSC during a symmetrical voltage dip, enabling effective control of all stator power through the RSC.

Enhancing Fault Ride-Through Capacity of DFIG-Based WPs by Adaptive Backstepping Command Using Parametric Estimation in Non-Linear Forward Power Controller Design

“…Unfortunately, one of the main disadvantages of this solution is that DFIGs transition to operating as squirrel cage induction generators (SCIGs), resulting in the uptake of reactive energy and consequent degradation of network voltage. The integration of a crowbar with a series R-L configuration is showcased in [6], [7] for a DFIG-based wind turbine (WT). This design aims to optimize the performance of conventional crowbars by transforming the DFIG-based wind turbine into a hybrid system with characteristics of both a DFIG and a SCIG.…”