Optimization Design Of Low Wind Speed Maglev Vertical Axis Wind Turbine

Wind energy,as a renewable and clean energy,has become one of the important energy sources for the sustainable development of China's electric energy.Low-wind-speed wind energy is widely distributed in China,and low-wind-speed wind power will be one of the key development of wind power in the future.To meet the development needs of low-wind-speed wind farms,a novel low-wind-speed maglev vertical axis wind turbine(MVAWT)is proposed by our laboratory.This MVAWT is mainly composed of three parts: vertical axis wind turbine,outer rotor type permanent magnet direct-drive wind generator(PMSG,as the main generator)and the maglev disk motor(as the maglev system,and as the auxiliary generator).This paper focuses on the research and design of outer rotor PMSG and maglev disc motor.First,according to the characteristics and design index of the outer rotor PMSG,the preliminary design of the outer rotor PMSG is completed by combining the calculation examples and relevant empirical formulas.The equivalent magnetic circuit diagram of the PMSG is established and the magnetic circuit is calculated via magnetic circuit analysis.The RMxprt motor module based on the equivalent magnetic circuit method is used to establish the model of a 1k W outer rotor PMSG,and the preliminary electromagnetic performance analysis is carried out.Second,considering the complexity of the structure and operating conditions of the outer rotor PMSG,the finite element analysis(FEA)for the preliminary design of the outer rotor PMSG is carried out.The RMxprt motor model is imported into the ANSYS Max Well 2D FEA software,and the internal magnetic field distribution nephogram and the operating characteristic curve of the PMSG under different operating conditions are obtained.On the basis of analyzing the causes of demagnetization phenomenon in the PMSG,the three-phase short circuit fault simulation of the designed PMSG is carried out by using external circuit control method.It can be seen from the simulation waveform that the preliminary design of the PMSG is reasonable and the demagnetization phenomenon will not occur under the most serious fault.Third,the preliminary design of the outer rotor PMSG is optimized.Low-wind-speed power generation means that the starting resistance moment of the designed PMSG should be small,and its loss should be low.Therefore,this paper takes the cogging torque,torque ripple,and the loss of the PMSG as the parameters to be optimized,analyzes their formation mechanism,derives their calculation formula from which the related structure parameters of PMSG can be indentified.With the help of ANSYS software,the related parameters are scanned for optimization and the structure is optimized to obtain the best design model,thus to meet the requirements of the outer rotor PMSG to start at low wind speed and run efficiently and smoothly.Finally,the maglev disk motor(MDM)is designed and its performance is verified,and its cogging torque is optimized as well.The stator of the MDM adopts hybrid excitation to ensure adjustable excitation.The magnetic suction generated by the stator balances the gravity of the rotating body and controls its stable suspension,so the friction loss of the motor during rotation can be reduced,which is conducive to further reducing the starting resistance moment and realizing the low wind speed starting of the wind turbine.Driven by the wind turbine,the rotor of MDM with three-phase windings rotates and cuts the magnetic flux to generate the induced electromotive force.So the MDM can also be used as an auxiliary generator.The design of the three-phase rotor of the MDM is completed by analogy with the design of the stator of the traditional radial flux motor.The design of the stator of MDM is completed by establishing the equivalent magnetic circuit diagram of MDM based on the magnetic circuit analysis,and deriving the electromagnetic force formula.Then,ANSYS Maxwell 3D is used to analyze the static and transient fields of the designed MDM.The analysis results show that the design of MDM is reasonable.