New Differential Protection for Variable Speed Doubly Fed Induction Machines

This paper presents a novel differential protection for the variable speed doubly fed induction machines (DFIMs), which typically are working as a generator in wind turbine systems and working as motor/generator in pump storage hydropower plants. The proposed protection, which is based on the comparison of the vector components Id-Iq of the rotor and stator currents, can protect the whole induction machine during the internal faults. This protection considers the dynamic variation of the rotor frequency and the extremely low rotor frequency along the different operation points of the DFIM. The proposed relay is validated in Matlab Simulink environment for a 2 MW DFIM, and the results show that the proposed differential protection protects effectively the entire induction machine during internal faults.