Superconductive energy storage for power systems

Abstract

Energy derived from an alternating current power system is stored in a superconducting magnet or inductor. The transfer of the energy is reversible so that the energy stored in the superconducting magnet can be returned to the alternating current power system. Generally, the energy is stored when surplus energy is available, due to low demand. The energy stored in the superconducting magnet may be returned to the power system when demand is high. High efficiency in the storage and return of the energy is achieved. A reversible converter is provided between the alternating current system and the superconducting magnet so that the magnet is supplied with direct current when energy is being stored. The converter may be adjusted so as to convert directcurrent into alternating current when it is desired to return the stored energy to the power system. The converter may comprise a rectifier-inverter system utilizing controlled rectifiers and a variable firing angle controller which is adjustable to control the operating mode of the rectifier-inverter system. The controller may be adjusted so that the system functions as a rectifier unit to convert the alternating current to direct current for the storage of energy in the superconducting magnet. The controller may be adjusted to a different firing angle so that the system functions as an inverter to convert direct current from the magnet into alternating current which is returned to the power system. The energy storage system can have lower losses than systems of prior types, such as pumped hydro-storage systems. The superconductive magnet system also has the ability to damp electro-mechanical oscillations in the power system.