The current framework of high penetration of intermittent energy sources requires variable-speed pumped hydro storage power plants (PHSPs) to provide grid support functions, which are, in this case, achieved through two technologies: doubly-fed induction machine (DFIM), and converter-fed synchronous machine (CFSM). Up to now, limitations of power electronics solutions favoured DFIM due to smaller converter in rotor circuit. This paper presents innovation perspectives for variable-speed PHSPs by presenting a potential future solution: the CFSM configuration employing the modular multilevel converter (MMC). MMC offers almost unrestricted voltage and power scalability. Featuring significantly increased output voltage resolution and scalability, MMC offers in perspective removal, or at least considerable reduction, of the filters and/or transformers, reducing size and cost of installations. This paper discusses potential MMC advantages and drawbacks for variable-speed PHSP applications compared to conventional technologies, considering all the features expected from a flexible PHSP in the current and future electrical grid.