Two-switch three-phase ac-link dynamic voltage restorer

This study presents a topology for a pulse width modulated (PWM) three-phase voltage regulator that uses only two driving switches, providing high reliability and making the switching stage simpler and cheaper compared with other available configurations. The proposed topology is suitable for voltage regulation on the distribution power system. It is able to regulate the steady-state voltage and to reject voltage variations such as flicker or sags caused by large motors start. In addition, the compensator features a topology free of energy storage elements. The PWM control is based on dc signals, asynchronous from the grid, simpler than the control used for traditional voltage source converters - it does not require a phase-locked loop, and does not involve trigonometric calculations. As a result of this, the controller can be achieved with an analogue controller or a low-cost microcontroller. The proof of concept is performed with a 220 V three-phase voltage regulator, which is simulated and prototyped in the laboratory.