Series-stacked medium voltage electronic voltage regulator

This paper discusses the development of a series-stacked medium-voltage electronic voltage regulator for the purpose of regulating the voltage on a 22 kV three-phase transmission line. The three-phase regulator consists of three independent 12.75 kV regulator cells, connected in a star configuration. Each regulator cell consists of an autotransformer with one common and two series windings. An AC-to-AC voltage converter is connected to each series winding in order to accurately regulate the amount with which the line voltage is boosted. This allows for a 10% regulation of the line voltage using two AC-to-AC converter modules. With the modular approach, higher voltages can be attained by simply adding more AC-to-AC converter modules to an appropriate transformer. An alternative AC-to-AC converter topology is implemented and appropriate protection mechanisms are discussed. The system is verified using simulation and practical results and the concept proves to be feasible and practical.