Current-source cascaded multilevel converters based on single-phase power cells

Nowadays the control of medium voltage motors has two main alternatives for its development: voltage source inverters (VSI); or current source inverters (CSI). The cascaded multilevel inverters derive from high voltage, high power quality and high reliability requirements in both development alternatives. Up to now, the cascaded multilevel converters have been implemented using voltage source power cells. However, they can also be implemented using current source units. One factor against CSIs is the large size of the inductive filters needed in the DC links, especially when single-phase inverters are considered. This paper presents a current-source cascaded multilevel converter (CS-CMC), based on single-phase power cells and their implementation alternatives, which enable a reduction in the sizes of the DC-link inductors. It is demonstrated that these sizes can be reduced using magnetic couplings between the DC links of the power cells. These magnetic couplings can eliminate second harmonic currents, as well as other even harmonics of current in the DC link of the power cells. This work asserts that the implementation of a current-source cascaded multilevel converter, based on single-phase power cells, must consider magnetic couplings between its DC links. Design results and the simulation of a development alternative of the system, aim to demonstrate the feasibility of implementing the cascaded multilevel converter.