Integration of PV Farm Control for Voltage Sag Mitigation of Large Induction Motor Starting

Inrush current of large induction motor with DOL starting introduces a voltage sag on the downstream distribution system. In some severe cases, this voltage sag leads to tripping of the incoming feeder. Several starting methods are applied to reduce inrush current, such as star-delta, reactor, and solid-state soft-starter. This paper proposes a new method to reduce the negative impact of the starting of the large induction motors by integrating PV farm into the plant. PV farm inverter control is synchronized with inrush current waveform to inject current into incoming MV bus to minimize voltage sag during motor starting. Analysis showed that adding a large capacitor is required to compensate for inrush current to maintain dc bus voltage at the suggested level. Simulation based on the 4500 HP medium voltage induction motor data has been performed to show the proposed method. The simulation showed that integration of PV farm could maintain the voltage sag less than 5%.