Comparative study for reversible pump at variable speed in PMSM applications The main objective of this paper is to find an improved solution to increase the efficiency of permanent magnet synchronous machine (PMSM) drive system. In this paper two methods are presented. Both methods operate in the flux-weakening operation regime. Only the PMSM comportment is treated here. Each method has its originality. All the results of this work have been obtained in Matlab Simulinkprogram. The paper presented here does not treat the hydraulic problems. The aim is to find the best operating mode for a pumped storage system supplied by variable renewable energy sources (RES) energy based source.