Issues on Heavy Mass Energy Storage with Vertical Movement by Linear Machine

Abstract

When one mover coil experiences transition between magnetic and non-magnetic stator layers in a heavy mass energy storage system, its current needs be reduced to zero. To produce the same amount of uplifting electromagnetic forces, the currents flowing through other mover coils need be increased. To facilitate such a change of current from one value to the other, pulse high voltage needs be produced. This paper presents a method to synthesize the driving voltages for producing targeted currents flowing through the mover circuits. Such voltage waveforms are generated from multiple stage cascaded H-bridge DC/AC converters. Furthermore this paper shows an approximate method for calculating reluctance and inductance for each of mover coils. If only one group of continuous coils is adopted, the total reluctance force of the mover fluctuates when it moves along the vertical passage. By using second group of mover coils that separates from the first group of coils by an odd number of one stator layer height, the reluctance forces from two groups of coils can cancel each other effectively. Moreover, a pair of system plus super-capacitor based energy buffer is adopted to ensure nearly constant power exchange between power grid and heavy mass system. This paper also presented a MagLev linear machine modified from the vertical one for horizontal driving application.