Control Strategy Of Self-bearing Dual Stator Solid Rotor Axial Flux Induction Motor For Flywheel Energy Storage

Flywheel energy storage has attracted more and more attention in the fields of power grid frequency modulation and peak regulation,UPS,rail transportation,high power pulsed electrical source and so on,due to its unique advantages such as long maintenance cycle,fast charging and discharging and high energy density.Flywheel energy storage system mainly includes flywheel,electric motor,bearing system,power converter and vacuum chamber.And electric motor and power converter are the focus of this paper.In this paper,a novel self-bearing dual stator solid rotor axial flux induction motor(BDSSRAFIM)is adopted,which integrates the functions of rotary electric motor and axial thrust magnetic bearing.In addition,in order to realize bidirection power flow and four-quadrant operation of motor,a back-to-back dual PWM converter is adopted.Firstly,this paper introduces the basic structure and operation principle of BDSSRAFIM,establishes its mathematical model of the electromagnetic force and torque in detail.According to the established mathematical model,the axial displacement PD regulator is adopted,and the parameters of the regulator are designed to meet the stability requirements of the axial motion of solid rotor.In this paper,a vector control strategy based on air-gap field orientation is adopted to realize the decoupling control of the electromagnetic force and torque of the motor.The MATLAB simulation model and experimental platform are built.And the simulation and experimental results verify the effectiveness of the proposed control strategy.Secondly,in order to overcome the shortcomings of the direct current vector control strategy of the voltage outer-loop current inner-loop structure,this paper adopts the fixed frequency direct power control strategy of the voltage square outer-loop power inner-loop structure.In order to improve the dynamic response of flywheel energy storage system and reduce bus capacitance,a coordinated control strategy of load power feed-forward compensation is adopted,and the reason why load power feedforward compensation can improve the anti-disturbance performance is explained.The simulation and experimental results verify the effectiveness of direct power control with load power feed-forward compensation.