Steady-State Operating Point Analysis Method and Faulted Protection Scheme for Doubly-Fed Induction Generators

A new protection scheme for enhancing fault ride through capability of a doubly fed induction generator (DFIG) is proposed. The new protection scheme comprises a series dynamic braking resistor (SDBR) connected to the stator side and a Crowbar resistor connected to the rotor side. The SDBR is employed to boost stator voltage while the crowbar resistor is used to reduce the rotor overcurrent. To determine proper values for the SDBR under different fault voltage, an analytical approach is proposed to compute the post-fault steady-state operating point. Various low voltage fault conditions are analyzed and used to design the protection scheme, including the switching strategy and the coordination of crowbar resistor and SDBR, and resistance value calculations. MATLAB®/SIMULINK/SimPowerSystems simulation results show that the proposed method is very effective for fault overcurrent protection and fault ride through capability enhancement.