Seventeen-Level Inverter Based on Switched-Capacitor and Flying-Capacitor-Fed T-type Unit

Abstract

To use fewer components to construct a multilevel inverter (MLI) with more levels and high quality of the output voltage, a hybrid MLI is developed by combining a double-mode switched-capacitor (SC) unit with a T-type unit fed by flying capacitors (FCs). The SC unit is used to boost the amplitude of the output voltage to twice the dc input voltage, while the T-type unit is responsible for increasing the number of output levels. A total of ten transistors, four capacitors, and two diodes are used to generate 17 different levels. As two of the four capacitors are charged by a single dc source directly and the other two operate as FCs, there is no capacitor voltage ripple accumulation (CVRA) problem, resulting in high-quality output voltage. In addition to topology, a voltage balance controller of the FCs is developed to cooperate with the APOD-PWM strategy. Compared with other single-phase SC-based MLIs, the proposed inverter has a lower cost per level. Finally, to verify the feasibility of the proposed inverter, both the simulation model and experimental prototype are established. The results show that the proposed inverter has high-quality output voltage waveform and good dynamic response. The measured efficiency is above 96.5 for a wide range of loads, and the maximum value is up to 98.36.