Control And Applications Of AC-DC Electronic Power Transformer

The power system developed rapidly in recent years. On the one hand, the electrical load become more and more huge, more and more complex; on the other hand, distributed generation and HVDC technology have been applied more widely. The traditional power system has been facing more challenges, so constructing a new smart grid is one of the trends. As one of the most important primary equipment, the electrical transformer can't meet the relevant demands of smart grid. In this paper, an AC-DC electronic power transformer is proposed in order to solve the issues related to smart grid.Electronic power transformer is consist of power electronic devices and medium frequency transformer, which can replace the role of traditional transformer, realizing isolation, energy conversion, voltage stage transforming, and which can realize the functions of AC-DC conversion, power factor correction, harmonic suppression, and so on. In this paper, two typical topologies of AC-DC electronic electrical transformer are studied, focusing on the control strategies and validations.Several topologies of AC-DC electronic power transformer are analyzed at first. Then the AC-DC electronic power transformer based on multi-level cascade structure is studied, which uses dual-loop decoupling control strategy, inner loop controlling AC current, outer loop controlling DC voltage. The control strategies are verified based on simulation and experiment.The AC-DC electronic power transformer based on modular multi-level converter(MMC) is studied, which mainly consists of MMC and DC-DC isolation module. The control strategies of MMC and DC-DC isolation are studied, and verified by simulation. The DC micro-grid based on AC-DC electronic power transformer are studied at last. The strategies of control and power management in the system are discussed. Finally, summarize the research done and prospect the work continued.