Protecting Control Panels Against Voltage Sags: Using a Square-Wave Series Voltage Compensator

Voltage sags are among the most important power quality problems affecting sensi-tive industrial equipment, including control panels. one or several units of programmable logic control-lers (PlCs), contactors, and adjustable-speed drives (asDs) are present in an industrial control panel, and all of these are sensitive to voltage sags. When a voltage sag occurs, contactors may trip, and one or more PLCs may reset with the process still run-ning. Eventually, the process protection trips, and an unplanned shutdown takes place. This article discusses the use of a square-wave series voltage compensator (SW-SVC) in control panels to create a sag-free, single-phase bus to supply PLCs, contactors, and other sensitive control hardware. The simulation results of control hardware equipment fed through a sag-free bus based on SW-SVC technology are presented. The experimental results obtained from a typical ac drive panel show the effectiveness of this proposition.