Control research on axial-flux hybrid-excitation generator for offshore vertical axis maglev wind turbine

Abstract

Vertical axis wind turbines generally have poor starting performance, but in recent years, they have gradually played a great potential in offshore floating wind power generation system. In order to improve the start-up and low wind speed operation capacity of vertical wind turbine, an asymmetric-primary axial-flux hybrid-excitation generator (APAFHG) which can generate an adjustable levitation force for offshore vertical axis maglev wind turbine is proposed. However, the complexity of levitation force characteristic makes it difficult to control the levitation force of the maglev system and output power of the generator independently. In this paper, the levitation force characteristics of APAFHG are analyzed, and a control strategy is proposed to realize the decoupled control of maglev system and generator power. First of all, the topology of AFAPHG is described and operation principle of AFAPHG is expounded. Secondly, the mathematical model of AFAPHG is deduced, and the levitation force performance of AFAPHG under DC excitation, d-axis and q-axis current is obtained by finite element method. Finally, a compensation strategy based on the levitation force mathematical model is proposed. The results show the compensation strategy can effectively realize the decoupled control of levitation force and generator power.

Keywords

• Maglev wind turbine
• Levitation force
• Decoupled control