Stacked Multicell Converter: Digital Sliding Mode Observation of Flying Capacitor Voltages

This paper details the digital implementation of a new observation strategy of the flying capacitor voltages dedicated to stacked multicell converters (SMC). This particular topology relies on the use of flying capacitors so as to equally share the voltage constraint on several semiconductors and increase the number of output levels. However the SMC appropriate operation is guaranteed by the stability of the flying capacitor voltage levels and the current flow creates variations of those quantities. The idea is therefore to develop an accurate estimation technique that avoids the utilization of differential measurements and allows the active control of the intermediate voltages. The actual research scope thus focuses on the sliding mode observation of the flying capacitor voltages by means of phase current measurements. This paper does not describe the observability requirements as well as the observer design, but rather detail the algorithm digitizing and performances