Model and control of diode-assisted buck-boost voltage source inverter

Diode-assisted buck-boost voltage source inverter boosts dc source voltage by introducing diode-capacitor network. The new topology extends voltage regulation range and avoids the extreme boost duty ratio of switching devices in front boost circuit. It provides an attractive dc-ac power conversion with enhanced voltage buck-boost capability, low cost and high efficiency in high voltage gain application. As for this unique structure, this paper presents model analysis and reveals intermediate dc-link voltage has a non-minimum-phase system transient response. This undesired influence may be transferred to the ac-side, resulting in initial voltage undershoot and oscillatory. Therefore, the dc and ac-side regulator are designed separately with dual loop control. The close-loop control bandwidth of the front boost circuit is relatively small due to the non-minimum phase property. However, the bandwidth of the inverter stage control is high to minimize such an influence on the output ac-side. Finally, all the theoretical findings and proposed algorithms are verified by simulation results.