A Single DC Source Switched-Capacitor Multilevel Inverter for High-Frequency AC System

Abstract

This paper presents a new switched-capacitor multi-level inverter (SCMLI). The proposed inverter can limit the charging current of switched-capacitor units. Voltage balancing of each capacitor is not required for the inverter. The capacitor voltages are automatically adjusted to the desired levels in each cycle of the ac voltage output. A step-change in the voltage is generated by switching the capacitors in series one after another. Usually, SCMLIs have a front-end switched capacitor configuration and a back-end full bridge inverter. The converter in the front-end steps up the dc voltage, and the back-end inverter generates ac output voltage. The elevated voltage from the front-end converter increases the voltage stress in the back-end H-bridge configuration. The proposed inverter doesn't need a back-end H-bridge inverter to generate ac output. A small inductance is introduced in series to the source to minimize the initial charging current in the multiple switched capacitor configurations. A lower dc capacitor charging current increases the overall efficiency and decreases the switching loss in the inverter. Circuit configuration, pulse width modulation (PWM) method, and operation principle are explained in detail. Finally, a simulation of the nine-level inverter is done in MATLAB, and simulation results validate the expected performance.