Three-Level Switched-Capacitor Boost Inverter With Reduced Component Count

Abstract

This article proposes a new reduced component count three-level switched-capacitor boost inverter (3L-SC-BI). The inverter side of the 3L-SC-BI uses only eight switches, which saves four switches compared to conventional three-level F-type inverter (3L-FTI). The use of SC structure helps to balance neutral-point voltage (NPV) without requiring voltage sensors and increase voltage gain of the inverter. Unlike conventional SC-based inverters, there are no high inrush charging currents of capacitors when they are connected in parallel. The currents of capacitors are limited by inductor current. A new space vector modulation (SVM) method is presented to control the introduced inverter. This SVM method uses lower-shoot-through (LST) state to connect capacitors in parallel. This LST state is inserted within small-voltage vectors without affecting output voltages. In this scheme, modulation index and duty ratios of boost switches are separately controlled, which enhances modulation index utilization. It results in high-voltage gain G and small component voltage stresses compared to traditional inverters. The proposed inverter is validated through 1-kVA prototype. The proposed inverter improves 2.06% of efficiency at $G = 3.12$ % and 1.2% of efficiency at $G = 2.4$ at 1-kW output power compared to existing 3L quasi-switched boost FTI.