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

Voltage sags are among the most important power quality problems affecting sensitive industrial equipment, including control panels. one or several units of programmable logic controllers (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 running. 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.