Maximum Boost Control of Step up-Step down Voltage Source Converter with X-Shape Diode-Capacitor Network

Abstract

Maximum Boost Control of Buck-Boost Voltage Source Inverter with X-Shape Diode-Capacitor Network achieves high voltage gain by introducing a cross capacitor based high step up dc-dc circuit between the dc source and inverter circuit. For this unique circuitry, various pulse width modulation techniques are developed. In order to maximize the voltage, gain and reduced voltage stress on switches this paper proposed new PWM strategy. It regulates the average value of intermediate dc-link voltage in one switching time period (Ts) the same as the instantaneous maximum value of three-phase line voltage by controlling the front boost circuit. The operating principle and closed-loop controller design are analyzed and verified by simulation and real time simulator OPAL-RT which shows real time result as physical counterpart would. Compared with existing PWM strategies, the new control strategy demonstrates less power device requirement and higher efficiency in high voltage gain applications. It is a more competitive method for range dc/ac voltage regulation in renewable energy applications. Furthermore, with new control strategy, the dc-side inductor current and capacitor voltage contains six-time line-frequency ripples. To overcome the undesired influence of low frequency ripples, it is also suitable for 400–800 Hz medium frequency aircraft and vessel power supply system.