Development of a SMES system as a fluctuating load compensator

The development of a superconducting magnetic energy storage (SMES) device and associated experimental system is described. The IGBT-based converter bridge is controlled under a pulse width modulation (PWM) scheme, to achieve instantaneous and independent control of active and reactive power flow, to and from the superconducting coil. The SMES device is applied to the problem of fluctuating loads at a distribution level. Two control strategies are described: a direct strategy based on equal and opposite compensation of the active and reactive power components of the fluctuating load, and an optimised strategy where the best use is made of the limited capacity of the SMES device. Both strategies are directed at the minimisation of the voltage fluctuation at the load point. The application of these strategies is demonstrated on the experimental system and their performances compared. The effectiveness of the optimised strategy in reducing the voltage fluctuation when compared with reactive power only compensation is quantified.