AC–AC converters without DC-ESE have a wide range of applications: power interfaces with AC sources, AC system couplers,devices for improvement of power quality (APF, DVR, phase shifter) and devices to control power flow (UPFC). The results obtained in preliminary studies of these converters in the above mentioned power network applications indicate their potentially high per-formance. AC–AC converters without DC-ESE offer a number of important advantages. However, a number of challenges must be overcome. Their use in the power system still requires further prac-tical testing.