This chapter introduces the new technologies of AC/AC conversion technology. AC/AC conversion technology is an important subject in research and industrial applications. The chapter explores the converters developed in the twentieth century can be called the traditional AC/AC converters. A power electronic AC/AC converter accepts electric power from one system and converts it for delivery to another AC system with different amplitude, frequency, and phase. The AC/AC converters used to vary the root-mean-square voltage across the load at constant frequency are known as AC voltage controllers or AC regulators. The chapter examines the power circuits, control methods, and the operation of the AC voltage controllers, cycloconverters, and matrix converters. The input voltage of a diode rectifier is an AC voltage, which can be single-phase or three-phase voltages. Several possible circuit configurations for three-phase phase-controlled AC regulators with star-or delta-connected loads.