Application of a superconducting magnetic energy storage unit for power systems stability improvement

A superconducting Magnetic Energy Storage (SMES) includes a high inductance coil that can act as a constant source of direct current. A SMES unit connected to a power system is able to absorb and store both active and reactive power from this system and to inject these powers into this system when they are needed. The injected power can be controlled by changing both the duty cycle of the dc-dc chopper switches and its operation modes. A SMES is always associated with a power conversion system consisting of two identical converters connected by a de link capacitor. This paper presents an efficient system, based on a SMES unit, to improve transient stability by regulating the dc link voltage to reduce the voltage and frequency fluctuations that occur after disturbances or rapid load changes. The authors propose using a SMES as an interface device connected to the DC Link capacitor and located between the power supply and load sides to act as a universal stabilizer of voltage and frequency on both sides. The system behavior is tested with three faults/events for both power supply and load with and without applying the SMES unit. The results show that the SMES unit increases the dc link voltage stability significantly whenever any of these three events occur.