Effect of leakage inductance on the performance of BLDC machine used in Flywheel energy storage applications

A Flywheel Energy Storage (FES) system consists of a rectifier, dc link, a bi-directional converter (BDC) connecting the dc link to a Brush-less DC (BLDC) machine coupled to a flywheel. The BLDC machine which is used in an FES system is one of the critical sub systems. This machine acts as a motor when energy is being stored in the flywheel and as a generator when the same energy is being harvested. Leakage inductance of the machine affects the dynamic performance, pulsation of torque in the motor mode and the same inductance helps in limiting the peak current of the switch in boost converter mode. This paper presents the details of the studies carried out on the effect of leakage inductance on the performance of the machine and gives the guidelines for selecting/designing of the BLDC machine used in FES systems. Simulation results are given; validation of the studies through experimentation is presented.