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

Diode-assisted buck-boost voltage source inverter boosts dc source voltage by introducing diodecapacitor 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.