Sliding Mode Control of Multilevel Power Converters

The application of sliding mode, a non-linear robust and self-contained approach, to the control problem of electronic power converters, is outlined and illustrated. On-line sliding mode control is suited to multilevel power converters as they are inherently variable structure systems. Obtained controllers are robust concerning parameter variation and perturbations and provide "Just In Time" switching. Furthermore, the straightforward non linear controller design uses switched state space models avoiding the averaging task, needs few linear control concepts, derives the stability study from geometric properties and the method obtains an integrated design of the control and modulator. Main design steps are summarised and some examples given, considering three-phase multilevel converters. Robust space vector output voltage and current controllers are described. Capacitor voltage divider equalisation is included using the same approach. Using two four-level comparators, experimental results show no steady state-errors, very fast dynamics and robustness against power supply variations and load unbalances.