A detailed computer model of a three-phase power network which includes inductive loads, resistance welders and an Adaptive Var Compensator (AVC) has been developed. The system configuration and parameters correspond to an irrdustrial customer served by a large electric utility. Welder operation produces severe cyclic flicker which leads to customer complaints. Computer studies have been conducted to determine the effectiveness of the AVC on the reduction of observable flicker at neighboring loads. Flicker severity was determined using the UE 1 E C flickermeter technique adopted for 120-V incandescent lamps. Different control strategies involving the AVC have been considered and compared with respect to flicker reduction. An innovative: Flicker Adaptive Control (FAC) strategy is proposed for the AVC. The control algorithm requires knowledge of the system line impedance; however, it can be used for both power factor correction and flicker reduction, which is an advantage over previous control methods. The measurement technique used in the FAC is accurate even in presence of heavy system distortion.

Date of this Version

March 1997