Multi-Input Multi-Output control of a utility scale, shaft-less energy storage flywheel with a 5-DOF combination magnetic bearing

[+] Author and Article Information
Xiaojun Li

Department of Mechanical Engineering, Texas A&M University, College Station, TX, 77840, USAMotion Control Group, Rockwell Automation, Minneapolis, MN, 55344, USA

Alan Palazzolo

Department of Mechanical Engineering, Texas A&M University, College Station, TX, 77840, USA

1Corresponding author.

ASME doi:10.1115/1.4039857 History: Received September 14, 2017; Revised March 24, 2018


The modeling and control of a recently developed utility-scale, shaftless, high strength steel energy storage flywheel system (SHFES) are presented. The novel flywheel is designed with an energy/power capability of 100 kWh/100kW and has the potential of a doubled energy density when compared to conventional technologies. In addition, it includes a unique combination magnetic bearing (CAMB) capable of providing 5-degrees-of- freedom (5-DOF) magnetic levitation. Initial test results show that the CAMB, which weighs 544 kg, can provide a stable lift-up and levitation control for the 5543Kg flywheel. The object of this paper is to formulate and synthesize a detailed model as well as to design and simulate a closed-loop control system for the proposed flywheel system. To this end, the CAMB supporting structures are considered flexible and modeled by finite element modeling. The magnetic bearing is characterized experimentally by static and frequency-dependent coefficients, the latter of which are caused by eddy current effects and presents a challenge to the levitation control. Sensor-runout disturbances are also measured and included. System nonlinearities in power amplifiers and the controller are considered as well. Even though the flywheel has a large ratio of the primary-to-transversal moment of inertias, Multi-Input-Multi-Output (MIMO) feedback control demonstrates its effectiveness in canceling gyroscopic toques at the designed operational spinning speed. Various stages of PD controllers, lead/lag compensators, and notch filters are implemented to suppress the high-frequency sensor disturbances, structural vibrations, and rotor imbalance effects.

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