Circuit Principle and Design of Superconducting Shunt Resonator for Voltage Sag Mitigation

Voltage sags are the most frequent power quality disturbances for modern industrial users, which can be mitigated by installing voltage sag compensation devices. However, most existing voltage sag compensation devices are high cost. This paper proposes a practical cost-effective device to protect sensitive equipment from voltage sags. The proposed device consists of a capacitor and a superconducting coil in parallel as an LC resonance circuit, and a static switch is used to switch the power supply mode. When voltage sags occur, the sensitive load is directly powered by the device, and the energy stored in the circuit is discharged, then switches when grid voltage recovers. Compared with regular voltage sag compensation devices such as DVR, the device has the advantages of low cost, low complexity, and simple control. Further, the device can mitigate voltage swell. The circuit principle of the device is presented. Besides, the correlations between LC parameters and supporting time are revealed. The feasibility of the device is verified by simulations under both voltage sag and voltage swell.