This paper deals with a control method that adapts the dc bus voltage of electric traction systems using permanent magnet synchronous machine (PMSM) fed by bidirectional Z-source inverter (ZSI) or other improved topologies. This control allows reducing both the overestimation of the dc bus voltage and losses in the inverter. The sliding-mode control (SMC) method is used to control the Z-source converter, whereas flatness-based control is proposed to drive the actuator and generate the peak dc bus voltage reference. Flatness-based control is chosen because the actuator transients are well mastered. Extra shoot-through zero inverter states are inserted by means of implemented algorithm on a space-vector-modulation (SVM) scheme. Different short-circuit strategies are studied and compared according to constraint criteria. Both simulation and experimental results are presented and discussed to validate the proposed voltage adaptation strategy and the improvement on global efficiency.