A Novel Control Strategy to Reduce Transformer Inrush Currents by Series Compensator

Inrush currents generated by unloaded power transformer often reduce power quality on the system. To improve this situation, this paper proposes an active inrush current compensator that is capable of reducing the inrush current effectively during startup mode. The proposed compensator is based on an inverter-based series compensator which is comprised of a single-phase inverter and series transformer. Voltage sags are very frequent events with energization of transformer or starting of large motors although their duration is very short. Hence, during voltage stabilizer mode, the existing series compensator is controlled by a voltage stabilizer controller and superimposes a compensating voltage on the inverter output whenever the load voltage deviate from the nominal value. This strategy is easier to implement because it requires no information of the transformer parameters, power-on angle of circuit breaker and measurement of residual flux. Some simulations results show satisfactory performance of the proposed technique on both inrush current reduction and correcting voltage sags