Research On Switched-Capacitor Multilevel Inverter And Its Extensions

In the field of distributed renewable energy power generation,multilevel inverters have been widely used in recent years because of their advantages such as high power quality,low total harmonic distortion(THD),low voltage stress of switching devices and the need for smaller output filters.In this paper,based on the principle of switched capacitor,switched capacitor(SC)technology is introduced in multi-level inverting structure,a series of novel switched-capacitor multilevel inverters(SCMLI)are proposed,which have the advantages of small number of devices,high power density and high efficiency.The main research contents of this paper include:1.In view of the fact that the existing switched capacitor inverters can only perform a single step-up or step-down conversion,and the inverters are not flexible.A novel buck-boost switched capacitor multilevel inverter is proposed.The inverter integrates step-up and step-down transformations,and can realize on-line switching of the two transformations,which improves the flexibility of the inverting system.2.In view of the problems that the existing switched capacitor multilevel inverters have a large number of devices and complex control.A novel switched capacitor ninelevel inverter is proposed,which can generate more output levels with fewer power devices,reducing system cost and control complexity.3.The switched capacitor inverter mentioned above can only output nine levels and cannot be extended.Thus,A novel N-level switched capacitor inverter is proposed,which can output an arbitrary level by expanding the modular structure,thereby improving the applicable scope of the inverter.4.Based on switched capacitor technology and multi-port technology,two new multi-port switched capacitor multi-level inverters are proposed,which can improve the multiplexing rate of power devices and the fault tolerance of input ports.In this paper,the working principle,modulation strategy and parameter calculation of the series of switched capacitor multilevel inverters are analyzed in detail,and the correctness and feasibility of the proposed new switched capacitor inverters and their modulation strategy are verified and analyzed by simulation and experiment.