| According to the magnetic suspended high-speed flywheel energy storage system,some key problems of the flywheel energy storage system,such as rotor strength analysis of the surface-mounted high-speed permanent magnet machine,dynamic modeling and analysis of active magnetic bearing flywheel rotor system,vibration control strategy and unbalance compensation of active magnetic bearing flywheel rotor system,were deeply investigated in this paper.The mainly research results are as follows:(1)As for the calculation problem of the rotor strength of surface-mounted high-speed permanent magnet machine in the FESS,the strength analytical solutions of the four kinds of permanent magnet(PM)rotors,including the hollow cylinder PM rotor retained by the nonmagnetic alloy sleeve or carbon fiber sleeve,segmented PM rotor retained by the nonmagnetic alloy sleeve or carbon fiber sleeve,were proposed,respectively.Then the results calculated by analytical solutions were validated by finite element method.The effects of rotational speed,sleeve thickness,operating temperature and interference fit on rotor strength were further investigated based on the analytical solutions of rotor strength,and the variations of rotor strength were analyzed for the four aforementioned PM rotors in surface-mounted high-speed permanent magnet machine.It is shown that the results calculated by the analytical solution and finite element method are in good agreement with each other,and the analytical solutions can accurately predict the stress distribution of the four aforementioned PM rotors,considering the influence of rotational speed,magnet-sleeve interference fit and operating temperature.Rotational speed,operating temperature,sleeve thickness and interference fit have great effects on rotor strength,so before the sleeve thickness and interference fit are determined,the stress distribution of the rotor should be checked carefully at the static state,high-speed cold operating state and high-speed hot operating state,respectively.(2)For the vibration suppression of active magnetic bearing(AMB)high-speed flywheel rotor system,a two-degree-of-freedom(2DOF)control strategy based on inverse system decoupling was proposed.The AMB flywheel rotor system was decoupled by the inverse system method firstly,so that the AMB flywheel rotor system,which was a nonlinear,strong coupling system,was decoupled into four independent subsystems.Then,the decoupled subsystems were adjusted by the 2DOF PID controller,which can regulate the performances of set-point tracking and disturbance rejection,respectively.The stability,set-point tracking and robustness of control strategy proposed were analyzed in theory,and its ability and effectiveness to control the vibration of AMB high-speed flywheel rotor system was further investigated by simulations and experiments.It is shown that the control strategy proposed can stably suspend the AMB high-speed flywheel rotor system and effectively suppress its vibrations,with the advantages of high stability,strong robustness,and good performances of set-point tracking and disturbance rejection.(3)As for the different characteristics of parallel mode and conical mode of AMB flywheel rotor system,a decoupling control strategy based on modal separation and velocity estimation was proposed.In the proposed control strategy,the modal separation was employed to decouple the parallel modes and conical modes of AMB flywheel-rotor system,so that the stiffness and damping of parallel modes and conical modes can be regulated,respectively.Based on this,the controller with velocity estimator was used to regulate the decoupled subsystems.In this controller,the damping control signal is obtained by the velocity estimator,so that the ability of against noise of the control system can be improved.The results of simulations and experiments show that the control strategy proposed can stably suspend the AMB high-speed flywheel rotor system,and the vibration can be suppressed effectively.A flywheel rotor with the mass of 58kg can be stably levitated in the rotating speed region of zero to rated speed(24000rpm)in system simulation,and the corresponding experiment achieves the stable suspension of the flywheel rotor from zero to 8300rpm.Compared with the traditional decentralized PID control strategy with cross decoupling,the proposed control strategy has better stability and ability of against noise,and it is more suitable for the high speed operation.(4)An internal control method based on modal separation and state feedback for the AMB flywheel rotor system was proposed.In the control method,the parallel modes and conical modes of AMB flywheel-rotor system were decoupled by modal separation firstly,then the conical modes were further decoupled by state feedback,so that the AMB flywheel rotor system with four coupled degrees of freedom was transformed into a system with four independent single degrees of freedom.Finally,the four decoupled subsystem were regulated by internal model control method,to achieve good control performance.The stability,set-point tracking and robustness of the internal control system based on modal separation and state feedback were analyzed in theory,and its ability and effectiveness to control the vibration of AMB high-speed flywheel rotor system was further investigated by simulations and experiments.It is shown that the control strategy proposed can achieve stably suspend AMB high-speed flywheel rotor system and effectively suppress its vibrations,with the advantages of high stability,good robustness,simple structure,and easy adjustment.Compared with the control strategy based on modal separation and velocity estimation,the performance of vibration suppression of the internal control method based on modal separation and state feedback is further improved. |
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