The use of average flux orientation control of multiple permanent magnet synchronous wind turbines and thus the construction of fractional frequency wind power systems, is one of the potential future options for onshore and offshore wind power. Nonetheless, the study of the stability among multiple wind turbines in this mode is rarely covered in the literature. To address this problem, the stability of small disturbances among permanent magnet synchronous wind turbines with average flux orientation control is investigated based on the eigenvalue analysis method. Firstly, based on the topology of the crossover collector system of high-voltage and large-capacity direct-drive permanent magnet synchronous wind turbines, a mathematical model of the wind power system applicable to the analysis of small disturbances stability is established. Secondly, the primary factors affecting system oscillations are determined by identifying the oscillatory modes and analyzing the modal participation factors, and the impact of parameter variations on the oscillatory of the system is examined by plotting the trajectories of the roots. It is concluded that the system oscillations are most affected by the generator inductance, resistance, and direct current capacitance parameters. Finally, the correctness of the findings is verified by time domain simulations.