Self-Balanced Nine-Level Flying Capacitor Inverter With Double-Period Level-Shifted Control

Voltage imbalance and peak charging current often occurs in capacitor-containing inverters. To solve this problem, a nine-level flying capacitor (FC) inverter and a double-period level -shifted pulsewidth modulation (DPLS-PWM) strategy are proposed. The proposed topology has the advantage of reduced capacitor count and low total standing voltage (TSV). Due to the special redundant states of the proposed inverter, a DPLS-PWM is introduced. By applying the DPLS-PWM strategy, the two capacitors in the proposed inverter can be balanced naturally. Meanwhile, unlike most switched-capacitor (SC) inverters whose self-balance scheme often generates large inrush current, the current stress of the proposed balance scheme is low. The working modes of the proposed inverter and the principles of DPLS-PWM are analyzed in detail. Also, comparisons are made to highlight the merits of the topology and modulation method. Simulation and experimental results have verified the feasibility of the proposed topology and self-balance modulation. The experimental efficiency of this inverter can reach over 98%.