Application and Comparison of a Modified Protection Scheme Utilizing a Proportional–Integral Controller with a Conventional Design to Enhance Doubly Fed Induction Generator Wind Farm Operations during a Balanced Voltage Dip

Abstract

The doubly fed induction generator (DFIG) is vulnerable to grid faults due to its direct stator connection, causing issues like excess stator current during voltage dips. Consequently, sensitive inverters suffer from increased currents, and the DC-link capacitor undergoes overcharging. This document examines two protection strategies employing a proportional–integral (PI) controller to manage the transient rotor current and mitigate DC-link overcharging, thereby optimizing DFIG behavior during network faults. One option combines a classic crowbar circuit with a DC-chopper, while the other is a modified protection scheme (MPS) that includes an impedance with passive elements and a crowbar. The impedance forms a resistance Rp parallel with an inductance Lp. Both configurations, situated between the rotor coils and the rotor-side converter (RSC), augment the capacity for low-voltage ride-through (LVRT). MATLAB/SIMULINK simulations of the two schemes demonstrate successful rotor current reduction at 2.9 kA and 3.4 kA, and DC-link tension reduction below and at 1.4 KV. In addition, the conventional crowbar and MPS configurations efficiently restrict the RSC current to levels below 0.21 kA and 2.94 kA, while absorbing up to 2.52 kA and 1.52 kA, respectively. The key difference lies in the fact that fine-tuning the parameters in the MPS design prevents rotor disconnection when faced with a balanced fault. This enhancement enhances machine performance and enables full stator power control via the RSC.