Research on Levitation Force Control of an Axial-flux Hybrid-Excitation Generator with PI-Based Torque Distribution

Abstract

An asymmetric-primary axial-flux hybrid-excitation generator (APAFHG) has already been proposed to improve the starting performance of vertical axis wind turbines. However, the double-stator single-rotor structure causes a problem: different torque proportions create different rotor maglev forces, which will cause fluctuation and negatively impact the rotor bearing and even the operation of the wind power generation system. Therefore, a mathematical model considering the double-stator single-rotor structure and a proportional integral-based torque control strategy considering double-stator distribution are proposed in this paper to help APAFHG offer a good starting performance in vertical-axis wind power generation system and to stabilize maglev force generated by double-stator quadrature axis current simultaneously. Finally, the cooperation control of the maglev force and torque distribution is realized in MATLAB/Simulink, and the rotor maglev force will be relatively stable despite mechanical torque changes, which is a basis for the wind turbine to stably operate as the wind constantly fluctuates in vertical axis wind power system.