Multiphase drives are more and more used in specific applications leading to a necessity of control strategy development. This paper presents the Generalized Vectorial Formalism (GVF) theory to control multiphase series-connected permanent magnet synchronous motors (PMSM) fed by one voltage source inverter (VSI). Based on a decomposition of multiphase machine, a proposed control strategy has been achieved. Some experimental results are given to illustrate this control method