The Pumped Hydro Storages (PHSs) equipped with variables speed drives have several advantages, namely: i) power regulation in pumping mode, ii) extended operating range, iii) higher efficiency in turbine mode. Such flexible operation of the PHS units ensures capability of the PHS to provide the frequency control reserves even during the pumping mode. It may lead to increased revenues in the electricity market conditions. It is important to quantify the benefits of PHS, especially variable-speed ones. This paper proposes a Stochastic Security Constrained Unit Commitment (SSCUC) model which takes into account different models of pumped hydro units. Different energy and reserve provision models are considered for fixed-speed and variable-speed units in the generating and pumping modes. The presented day-ahead SSCUC problem considers the optimization of energy and reserves costs. The problem is solved using Benders decomposition approach, for which the master problem solves the unit commitment and the sub-problems ensure the feasibility of the solution for the base operating point and for a set of dedicated scenarios. The set of scenarios includes the base operating point, contingencies (i.e. N-1 criterion), and stochasticity of demand and renewable injections. The proposed formulation is successfully tested on IEEE RTS 24-bus system.