Fundamental characteristics of five-level double converters with adjustable dc voltages for induction motor drives

In this paper, two kinds of control strategies for a three-phase five-level double converter are described on the assumption that the converter is applied to an induction motor drive system. The purposes of the proposed control strategies are to correct voltage imbalance of the DC-bus capacitors, to keep the input power factor at near unity, and to achieve an adjustable-speed drive. Characteristics of the converter operated by each of the two control strategies are examined and the validity is verified by experiments using a 3.7-kW induction motor.