DC-Bus Control Considerations of Asymmetrical Multilevel Inverters with Embedded Buck-Boost Converter

This paper focuses on the DC-bus control of asymmetrical Multilevel inverter family featuring a Buck-Boost converter to boost the input voltage. To investigate the dynamic performance of the system a thorough analysis is presented on the DC-bus dynamic behavior. It is shown that with higher system bandwidth the input capacitance requirements and the peak current through the boosting inductor are increased, compromising the power density and the efficiency of the whole DC/AC converter. To improve the transient performance of the system without increasing the volume of the passive components, a control scheme with a feedforward current estimator term is proposed. Finally, the correctness of the theoretical analysis is validated via experimental probing on a laboratory prototype.