This paper presents the start-up and synchronization procedures of large variable- speed pump-turbine units in pumping mode. These procedures applied to a doubly-fed induction motor-generator with three-level voltage source inverters VSI cascade in the rotor side, can be achieved without any supplementary equipment, for instance without an autotransformer connected to the rotor. The control strategy used in the start-up procedure and based on a stator flux oriented control is summarized as well as different steps in ...