Continuously Variable Controlled Transformer for Grid Voltage Stabilization

This paper describes a concept to balance the phase voltages in an unbalanced low-voltage three-phase system by means of an active power electronics circuit. Additionally, it allows compensating harmonics in each phase voltage. The required voltage adjustment is fed through an injection transformer serially into the distorted line voltages. This paper outlines the control concept to achieve this function instantaneously and individually for each phase. Additionally, measurements showing the performance of the concept are presented. A prototype was built to demonstrate the compensation of imbalances of up to ??10% of the nominal voltage and a significant reduction of harmonics up to the 13th order.