A New Topology of Single-Phase Common Ground Buck-Boost Inverter With Component Voltage Rating Reduction

Abstract

The combination of conventional front-end DC-DC converter and H-bridge inverter has been proposed with common-ground (CG) characteristic and voltage booting capability. However, it has drawback of low modulation index utilization which causes high component voltage rating and small conversion efficiency. In this paper, a new topology of a single-phase common-ground buck-boost inverter (1P-CG-BBI) is presented to overcome existing drawbacks of conventional CG inverters. The proposed 1P-CG-BBI uses one more active-switch and one more diode than traditional CG inverter. Note that the proposed inverter still shares the same ground for DC input source and AC output voltage, which completely eliminates the leakage current. A hybrid pulse width modulation (PWM) technique is introduced to control the buck-boost stage. Accordingly, the buck-boost stage of the 1P-CG-BBI operates similar to a conventional DC-DC boost converter in the positive half cycle. In the negative half cycle, this stage behaves as a traditional inverting DC-DC buck-boost converter. Accordingly, the DC-DC operation and DC-AC operation can be controlled, independently. Consequently, the modulation index can be significantly improved compared to previous CG inverters. High modulation index tends to reduce component voltage rating and increase system efficiency. A comparison study has been discussed to highlight these advantages. Simulation results conducted using PSIM software are considered to verify the operation of the proposed inverter. A laboratory prototype is also developed to further demonstrated the accuracy of theory. Accordingly, the proposed inverter obtains 93.12% and 91.83% efficiency at 550-W for buck and boost operating, respectively.