Maximum Boost Control of Diode-Assisted Buck-Boost Voltage Source Inverter with Minimum Switching Frequency

This paper proposes a diode-assisted buck-boost voltage source inverter with unique X-shaped diode-capacitor network inserted between dc source and inverter bridge for producing high voltage gain. Using the diode-assisted network, the proposed inverter can naturally configure themselves to perform capacitive charging in parallel and discharging in series to give higher voltage multiplication factor without compromising waveform quality. In order to maximize voltage gain and increase efficiency, this paper proposes a novel PWM strategy. It regulates the average value of intermediate dc-link voltage in one switching time period (Ts). Then, the equivalent switching frequency of power devices in the inverter bridge can be reduced to 1/3fs (fs=1/Ts). The operating principle and closed-loop controller design are analyzed and verified by simulations using MATLAB/Simulink.