Study On Nonlinear Electromechanical Dynamics Of Flywheel Energy Storage System

The flywheel energy storage technology has many virtues, including high electrical energy transforming efficiency, quick charge and discharge, no pollution, large energy storage density and so on. Its applied foreground is very wide, such as electric power conditioning, electric vehicle flywheel battery, uninterrupted power source etc.Seeking Larger energy storage makes the flywheel system go high rotating speed and large power direction. The flywheel rotor affects electromagnetic field parameters because rotor axes station changes, and the electromagnetic field parameters changing affects the sport and vibration shape of rotor. The electromagnetic parameters of motor and dynamic parameters of flywheel mechanical system compose parameter coupling , and they affect dynamic performance of flywheel system, bring self-excited vibration, decrease system stability and arouse accidents. The existing flywheel rotor dynamics differential equations omit all the influence of motor parameters on rotor running, and the complex electromechanical question is obviated. So these models are very approximative and unilateral. It mainly contains the following.(1) The electromechanical dynamics of Flywheel Energy Storage System with a hybrid permanent magnetic-dynamic spiral groove bearing has been studied by utilizing the fundamental principle of electromechanical analysis dynamics. The functions of the kinetic energy, potential energy, the magnetic energy in air gap of the generator and the energy dissipation of the whole system are obtained, and the differential equations with electromagnetic parameters of Flywheel Energy Storage System are established by applying the extended Lagrange-Maxwell equation. The four-order implicit Runge-Kutta formular to the equations is derived, and the nonlinear algebraic equations are solved by using Guass-Newton method. The analytical solution of an example shows, the lower damping coefficient and the residual magnetic induction of the rotor rare earth permanent magnet play important roles in electromechanical resonance of flywheel rotor system. The variety of the upper damping coefficient, upper bearing stiffness and lower bearing stiffness change unconspicuously the electromechanical resonance frequency of the system, but with an increase of them, the resonance amplitude decreases. With an increase of the lower damping coefficient, the resonance frequency increases,and the resonance amplitude decreases. With an increase of the residual magnetic induction of the permanent magnet, the resonance frequency decreases, and the resonance amplitude increases.(2) The electromechanical uncoupling design of Flywheel Energy Storage System has been done by Coordinate Transforming Method based on flywheel system electromechanical analysis solution. The analytical solution shows, with an decrease of motor rotor permanent magnet residual magnetic inductionand an increase of lower damping coefficient, the resonance frequency of the system increases, and the objective function value decreases early and increases subsequently. The solution of electromechanical uncoupling design can reach the requirement in the range of accepting error.