PV Farm Ancillary Function for Voltage Sag Mitigation Caused by Inrush Current of an Induction Motor

This paper presents a control technique for sag voltage mitigation by utilizing PV farm. PV farm has become a preferred green energy source to be installed in industries for the last decades, especially to meet the Sustainable Development Goal programs. The proposed technique is to incorporate PV farm to compensate sag voltages particularly caused by the inrush current of an induction motor starting. The ancillary function of the PV farm is carried out by adding a supercapacitor (SC). PV and SC are used to provide high power in short period when an inrush current occurs. Power from PV and SC is controlled using a current-controlled voltage source inverter which is synchronized with current drawn by induction motor. As the result, PV farm is capable to inject a portion of current into the grid to reduce level of voltage sag. The portion of energy absorbed causing the sag is then calculated and tabulated. A control with a proportional and integral controller is used for sag compensations. A simplified mediumvoltage industrial network with a complex load and the induction motor is simulated to validate the proposed method. Simulation result shows that the proposed technique decreases the magnitude of the voltage sag, from 6.71 % to less than 5 %. Sag duration of the voltage sag was also reduced from 5.3 seconds to 4.9 seconds. Thus, the voltage quality can be maintained within the standard requirement. Simulations are also carried out in industrial production processes, where two induction motors are started in close time intervals. The second motor is started a few seconds after the first motor has reached its nominal speed. The result suggested that the voltage on the system bus can be maintained at a level above 6.27 at a nominal system voltage of 6.6 kV.