Stacked multicell converter (SMC): estimation of flying capacitor voltages

This paper introduces a new estimation technique of the flying capacitor voltages dedicated to stacked multicell converters (SMC). Those voltages have to remain constant during the operation of the converter so as to ensure the proper repartition of the voltage constraints over the commutation cells. This objective can be achieved by implementing an active control of the capacitor voltages, which requires the knowledge of those quantities at each time. However it is both difficult and expensive to measure them because of the high voltage/power range of applications. Thus we move toward the development of an estimation of those quantities. After an introduction and a succinct reminder on the SMC topology, the first part describes the new strategy for the estimation of the capacitor voltages. It is based on a real-time simulation of the state-space model of the system. To prevent this emulator from drifting away, an update should be included in the estimation procedure by the use of an extra voltage measurement. The second main part is devoted to the influence of the current or the voltage sensing noise on our approach and the development of appropriate strategies to counter those phenomena