Series multi-cell converters introduced more than ten years ago provide many degrees of freedom like the possibility to distribute the voltage constraints among series-connected switches and to improve the output waveforms. Direct control laws make perfect use of them during transient behaviors, but leads to disorderly and imperfect steady-state operations. This paper deals with some solutions for the direct control of the voltages across the flying capacitors in the presence of fast variation of the input voltage by reach an optimal steady-state trajectory defined by the PWM control technique.