A 150 kVA/0.3 MJ SMES voltage sag compensation system

To protect a 110 kVA critical load from voltage sags, a demonstration SMES-based voltage sag compensator has been developed and tested. This system consists of a 150 kVA IGBT (Insulated Gate Bipolar Transistor) current source converter, a 0.3 MJ NbTi magnet and three phase-shift inductors. Experiments were carried out to test the compensation performances for both balanced and unbalanced voltage sags with a 110 kW load of resistance. The results show that the load voltage recovers in less than one cycle (20 ms) whenever a three-phase or single-phase voltage sag occurs.