Structures And Principles Of The Switched-Capacitor Multilevel Inverter

Due to the merits of high reliability,high power density,being able to improve the system’s dynamic performance,and etc.,the high-frequency ac power distribution system(HFAC PDS)has been widely applied into aeronautics,astronautics,and computer communications.Its applications in emerging fields,such as electric vehicles and micro-grids,have also been paid attention to during recent years.Since the distribution bus of HFAC PDS operates in high frequency,new demands have been put forward on the inverters in its source side.The traditional inverters are no longer suitable,due to their complicated structures and relatively high switching frequency.The switched-capacitor multilevel inverter(SCMLI),inherent with the capacitors’ self-balancing,can output a staircase waveform under fundamental-frequency modulation with one input source.As a result,the high-frequency DC/AC conversion can be realized with high efficiency,which makes the SCMLI an ideal choice for HFAC PDS.Several novel SCMLI topologies are presented in this paper to make up for the deficiencies of existing ones when being applied for the high-frequency DC/AC conversion in HFAC PDS.The specific contents of this paper are summarized as follows:1.A novel 9-level inverter is proposed based on the basic switched-capacitor topology,which can output a nine-level staircase waveform with one input source,two capacitors,two diodes,and nine switches.The component numbers are reduced when compared with similar topologies,which can contribute to higher conversion efficiency.2.A novel N-level inverter with inductive load ability is proposed to make up for the insufficiency of a typical SCMLI.The higher efficiency can be obtained by reducing the power components in capacitors’ charging/discharging loops.Another step-down N-level inverter is then proposed.The two structures have similar principles and complementary functions,which can broaden the application scope of SCMLIs.3.A quasi-resonant SCMLI is proposed with the ability of suppressing the transient charging current of the capacitors.One the one hand,the electromagnetic interference is decreased by decreasing the di/dt;on the other hand,the peak charging current of is reduced,which can extend the life of the capacitors,as well as the whole inverter.4.A family of low-voltage stress SCMLI is proposed by integrating the switched-capacitor technique into traditional hybrid topologies.Since the backend H-bridges that withstand the accumulative levels in conventional structures are removed,the peak inverse voltage of devices and the total standing voltage of switches are reduced,which make the proposed low-voltage stress topologies especially suitable for synthetizing a staircase output from a low-voltage input source.Operational principles and parameter analyses of the proposed structures are presented in this paper.On these bases,the experiments are carried out,whose results verify the feasibility of the proposed topologies and the correctness of theoretical analyses,and indicate that the proposed SCMLIs are especially suitable for HFAC PDS to realize the high-frequency DC/AC conversion with high efficiency.