AC/AC Buck Converter Instantaneous Value Control Modeling, System Analyzing and Designing

Close-loop control to the Power Electronics Transformer (PET) was not well solved still now, we studied the basic topology of PET—AC/AC buck converter, built its small-signal model, analyzed its frequency characteristic, and pointed out that: under general inductive load condition, the open-loop model is an approximate second-order undamped oscillation system, it is marginally stable and output voltage oscillation can be induced by instant disturbances of input voltage and/or output current, therefore, we must find out a suitable close-loop adjustment. Here, we employed the classical PID control algorithm to instantaneously control output voltage following the reference signal. The close-loop system was stable and had good dynamic response characteristic. In addition, during one switching period, the line-frequency input/output voltage and output reactance were treated as constants, and a parameter—λ, which is related to load feature, was introduced to simplify the modeling and analysis process, it is a valid method for AC/AC converter small-signal modeling and system dynamic analysis.