This paper presents a review of the current research in the area of ac/ac power conversion with power electronic transformer. The topologies considered have the following features: 1) generation of adjustable frequency and magnitude PWM ac voltage waveform from a balanced three-phase ac voltage source with a high frequency ac link, 2) bidirectional power flow capability, and 3) single stage power conversion without any storage elements. All of these topologies provide power factor correction. Based on the operation and control, these topologies have been classified into three groups. The operation, advantages and drawbacks of each of these topologies have been presented along with a comparison of their performance in the presence of leakage inductance, complexity to control and reliability.