Bi-directional Power Flow Simulation of Permanent Magnet Linear Machine for Gravity Energy Storage

Solid gravity energy storage (GES) can realize the bi-directional power flow according to grid dispatching by using permanent magnet linear machine (PMLM). When the power of grid is excessive, electricity can be inputted to lift a heavy block to a certain height to store the gravitational potential energy of this heavy block. On the contrast, when the power of grid is shortage, the heavy block is lowered and the stored gravitational potential energy can be converted into electrical energy through the generator mode by controlling PMLM. According to this direct driven type with PMLM, the GES has higher energy conversion efficiency compared with the traditional GES type. This paper uses the principle of GES to design a PMLM structure for motor/generation operation, establishes a dynamic mathematical model of PMLM, and proposes a three-loop control system of power, speed, and current as the main control part of the entire GES system. The bi-directional power flow operation characteristics of the proposed PMLM is simulated by using Matlab/Simulink to implement the GES study in the future.