Power Decoupling of Multi-port Isolated Converter for Electrolytic-Capacitorless Multi-level Inverter

This paper presents a generalized power decoupling control scheme using multiport isolated bidirectional converters for multilevel inverter which has multiple DC-links. A single power decoupling capacitor is needed for all the DC-links. A prototype of power decoupling concept of individual H-bridge cell is proposed, using separate power decoupling circuits. Then, more advanced power decoupling method is proposed. The lifetime and reliability of the multilevel inverter is improved as film capacitors replace the electrolyte capacitors. Multi-input ports/single output voltage-fed dual half bridge converter (MDHB) is used for the power decoupling. Proposed MDHB employs a current-sensorless power decoupling control which contributes to the ripple rejection for all the DC-links without individual link-current information. Hence, the ripple-rejection controller is independent of the control configuration of the multilevel inverter, and also available for universal applications of the inverter topologies. Since the primary-input ports of MDHB shares a single magnetic core for interfacing the ripple power to the unified secondary ripple capacitor, the controller design becomes difficult in considering the dynamic interaction among the ports along with the average voltage-control loop design. In this paper, the dynamic analysis and controller design procedure of the circuit are also presented.