Research On Key Issues In Control Design For AMB-supported Energy Storage Flywheel Rotors

With the implementation of“China Manufacturing 2025”strategy,the new energy technology,as one of the ten breakthroughs,has made rapid development and the related energy storage technology is changing with each passing day.Energy storage flywheels supported on active magnetic bearings?AMB-supported energy storage flywheel?,have attracted much attention both in the academia and in the industry due to their many appealing features,such as high power density,high energy efficiency,short recharge and discharge times,wide operating temperature ranges and long life cycles.Feedback control of the AMB-supported energy storage flywheel rotor is critical in the operation of the system and the system performance depends to a great extent on the quality of the AMB-supported energy storage flywheel rotor control system.Due to the high speed operation?often supercritical operation?,the complex rotor structure?using composite material?,the generator and motor integration and many other related issues of the AMB-supported energy storage flywheel,its system operation appears nonlinear characteristics and severe electromechanical coupling.It is far from enough to demonstrate the effectiveness of the controller design only by the simulation.However,there are not many AMB-supported energy storage flywheel rotor test rigs,which are specially used for the design and research of feedback control.Because to build an actual AMB-supported energy storage flywheel rotor test rig is not only expensive and technically challenging,but also not suitable for tuning.Besides,it is too costly and very dangerous if the AMB-supported energy storage flywheel is damaged.With the rapid development of new energy technology,the demand of the AMB-supported energy storage flywheel with unique advantages becomes increasingly urgent.Therefore,how to use the existing rotor-AMB system to construct a high-quality,inexpensive,safe and effective emulation test rig of AMB-supported energy storage flywheel rotor is very important and urgent for its feedback control algorithm design and tuning.Moreover,for the existing AMB-supported energy storage flywheel rotor control method,the classical proportional-integral-derivative?PID?control is easy to implement but is not effective in handling complex rotordynamics.Modern control design methods usually require a plant model and an accurate characterization of the uncertainties.These existing control algorithms can not guarantee the stable operation of the flywheel and reduce the vibration.In addition,in order to improve the specific energy of the AMB-supported energy storage flywheel,the potential of magnetic material characteristics needs to be fully utilized.How to design a high performance nonlinear controller of the AMB-supported energy storage flywheel for operation that extends into the nonlinear region of AMB systems becomes the key prospective research problem of the AMB-supported energy storage flywheel rotor control design.Therefore,the research on the key issues in control design for AMB-supported energy storage flywheel rotors is carried out in this dissertation.The following research topics are explored.Based on the linear model of the magnetic force,the rigid and flexible AMB-supported energy storage flywheel rotor dynamic model are established.According to the flexible AMB-supported energy storage flywheel rotor dynamic model,a new method to emulate the operation of flywheel rotors on an existing rotor-AMB test rig is proposed.The emulation model and the equivalent condition of the AMB-supported energy storage flywheel rotor emulation is established and the equivalent criterion is developed.Specifically,the two AMBs located at the two ends of the rotor are used as supporting bearings,while the other two located at the rotor mid span and quarter span are used to emulate the generator negative stiffness and gyroscopic effects on the rotordynamics caused by the flywheel disk.Simulation and experimental results are presented to show the effectiveness of the proposed emulation method.The characteristic model based all-coefficient adaptive control?ACAC?design method is applied on the AMB-supported energy storage flywheel rotor emulation test rig described above.Both simulation and experimental results demonstrate strong closed-loop performance in spite of the simplicity of the control design and implementation.The control law suppresses the vibration on the AMB-supported energy storage flywheel rotor to a significantly higher level than the originally designed?-synthesis controller could.The control design in the above research is all based on the linear model of the magnetic force of the energy storage flywheel magnetic bearings.For the purpose of improving the specific energy of AMB-supported energy storage flywheel,the magnetic saturation characteristic of magnetic bearing material needs to be fully utilized.The nonlinear control problem caused by magnetic saturation is a major problem in AMB-supported energy storage flywheel rotor control study.This prospective research issue is discussed in this dissertation.In order to simplify the verification of the nonlinear control design method,the complex rotordynamic characteristics of the AMB-supported energy storage flywheel rotor are not considered for the time being.A single DOF AMB test rig is used in this dissertation to verify the effectiveness of energy storage flywheel AMB nonlinear control design.The nonlinear model of the magnetic force produced by the AMB and the nonlinear model of the single DOF AMB system are established and the nonlinear controller is designed according to this model.The resulting feedback control laws allow the AMB to operate in its nonlinear region and hence improve the closed-loop performance.Specifically,an approximate nonlinear AMB current force response model is first established,and place this nonlinear curve inside a sector formed by two piecewise linear lines.Based on the linear line segments in these two piecewise linear lines,the maximum disturbance that can be tolerated by solving an optimization problem with linear matrix inequality?LMI?constraints is determined.For a given level of disturbance under the maximum tolerable disturbance,the problem of designing the linear feedback that achieves the highest level of disturbance rejection as another LMI problem is formulated and solved.Both ₂L disturbances and L_?disturbances are considered.Finally,both simulation and experimental results are illustrated.The research on these key issues in control design for AMB-supported energy storage flywheel rotors provides a theoretical basis for large-scale application of AMB-supported energy storage flywheels.