Test Method for Torsional Oscillation Mode Identification of DFIG Based on Voltage Excitation

The flexibility of the shafting in a DFIG is much greater than that of a synchronous generator, so it is more likely to cause low frequency oscillation such as torsional oscillation during dynamic operation. This paper proposes a test method for torsional oscillation mode identification of DFIG based on voltage excitation. Firstly the torsional oscillation phenomenon of wind turbines under voltage excitation is analyzed, and the index of generator speed deviation is proposed to identify the torsional oscillation frequency of shafting. The identification method is verified by hardware-in-the-loop simulation platform, and a grid-connected test device is proposed that can be used for field test of torsional oscillation frequency. This paper’s method can realize safe, accurate and efficient measurement of torsional oscillation frequency, which is closer to the engineering practice than the previous theoretical analysis and simulation modeling methods.