Control and Modulation of a Single-Phase AC/DC Converter With Smooth Bidirectional Mode Switching and Symmetrical Decoupling Voltage Compensation

In this article, a bidirectional single-phase ac/dc converter with active power decoupling (APD) and smooth mode switching is proposed. Power decoupling techniques have been proved efficient in the reduction of bulky dc bus electrolytic capacitors (E-caps) for single-phase low-power level conversion systems. However, it is found that when dealing with transient conditions such as sudden bidirectional switching or steep load changes, the whole system may be vulnerable and unstable under greatly reduced E-caps situation. None of the existing researches carefully examine such dc bus transient characteristics with bidirectionality under decoupling situation. By multiusing the APD cell, the proposed dc bus voltage suppression strategy is capable of both dc bus voltage ripple elimination and load disturbance rejection under transient conditions. Moreover, the proposed controller involves a dead-time compensation to achieve symmetrical power decoupling voltage without additional sensors for decoupling circuit, which ensures the maximum ripple power suppression ability as well as achieves minimum capacitance requirements. Finally, a 1-kW, 110-Vrms, and 50-Hz single-phase ac/dc prototype has been built and evaluated. Theoretical predictions are compared favorably with experimental results.