A Novel High Frequency Isolated Three-Level Inverter and its Topological Derivation Method

High frequency isolated multi-level inverters (HFI-MLI) feature a variety of merits, such as low voltage stress of power switches, low THD of unfiltered voltage, small size of output filter. However, only a few researches on HFI-MLI without intermediate DC link have been carried out. Thus, topological derivation method suitable for HFI-MLI and novel HFI-MLI topologies need much more research and discussion. A topological derivation method, named as Loop Construction Method(LCM) is proposed in this paper. Active and/or passive components are used to construct independent and controllable current loops between different potential points and high frequency transformer windings, so as to obtain novel HFI-MLI topologies. In addition, several novel topologies, constructed by LCM, are discussed. Furthermore, taking push-pull HFI-3LI as an example, the working operations and control strategy are designed in detail. Finally, an experimental prototype is made to prove the correctness of the novel topology and control strategy.