Electricity generation system , comprising: - a water turbine system comprising an electrical machine, wherein said water turbine system has identified undesirable electrical output power setpoints and safe electrical output power setpoints; - an energy storage device ; - a feeder link connected to the energy storage system and the electrical machine of the water turbine system , wherein the feeder link comprises a connection interface for connection to an AC grid ; - a state of charge determination device configured to determine the state of charge of the energy storage system ; - the system furthermore comprises a control circuit configured to control electrical power transfer between the feeder link and the energy storage system by selectively controlling charging or discharging of the energy storage system , configured to receive an electrical power setpoint Reps; - characterised in that the control circuit is furthermore: - configured to determine that this received electrical power setpoint Reps belongs to the undesirable electrical output power setpoints, - configured to generate an electrical power transfer setpoint Epts for the energy storage system and an actual electrical output power setpoint Aepos for the water turbine system belonging to the safety electrical output power setpoints, fulfilling the relationship Reps = Epts + Aepos, wherein the electrical power transfer setpoint Epts is set in dependence on the determined state of charge of the energy storage system . - a water turbine system comprising an electrical machine, wherein said water turbine system has identified undesirable electrical output power setpoints and safe electrical output power setpoints; - an energy storage device ; - a feeder link connected to the energy storage system and the electrical machine of the water turbine system , wherein the feeder link comprises a connection interface for connection to an AC grid ; - a state of charge determination device configured to determine the state of charge of the energy storage system ; - the system furthermore comprises a control circuit configured to control electrical power transfer between the feeder link and the energy storage system by selectively controlling charging or discharging of the energy storage system , configured to receive an electrical power setpoint Reps; - characterised in that the control circuit is furthermore: - configured to determine that this received electrical power setpoint Reps belongs to the undesirable electrical output power setpoints, - configured to generate an electrical power transfer setpoint Epts for the energy storage system and an actual electrical output power setpoint Aepos for the water turbine system belonging to the safety electrical output power setpoints, fulfilling the relationship Reps = Epts + Aepos, wherein the electrical power transfer setpoint Epts is set in dependence on the determined state of charge of the energy storage system . - configured to determine that this received electrical power setpoint Reps belongs to the undesirable electrical output power setpoints, - configured to generate an electrical power transfer setpoint Epts for the energy storage system and an actual electrical output power setpoint Aepos for the water turbine system belonging to the safety electrical output power setpoints, fulfilling the relationship Reps = Epts + Aepos, wherein the electrical power transfer setpoint Epts is set in dependence on the determined state of charge of the energy storage system . <EOS>