A method of controlling an electricity generation system comprising: - a feeder link comprising a connection interface for connection to an AC grid 2; - a turbine system comprising an electrical machine and configured to deliver a nominal electrical power Pnom to the feeder link; - an energy storage system connected to the feeder link, wherein the control method comprises the following steps: - receiving from the AC grid a first electrical power setpoint Ps0 to be delivered to the connection interface and controlling the turbine system so as to deliver an electrical power Pt0 = Ps0 to the connection interface; - the controlling method being characterized in that the steps also comprise the following steps: - receiving another electrical power setpoint Ps1 from the AC grid, where ΔPs = Ps1 - Ps0 and |ΔPs| > Pnom * 0.3; I f Ps1 > Ps0: a) applying a hydraulic setpoint to the turbine system to increase its electrical power output Pti and prevent the energy storage system from supplying electrical power to the connection interface; b) determining the power Poa that the energy storage system 14 can supply to the connection interface; c) when Pti + Pea ≥ Ps1 - ε1, control of the energy storage system in order to supply an electrical power Pe1 to the connection interface with a view to fulfilling the requirement Ps1 - ε1 ≤ Pe1 +Pti ≤ Ps1 + ε2, with the power deviations ε1 and ε2 tolerated by the AC grid at the connection interface; or I f Ps0 > Ps1: n) applying a hydraulic setpoint to the turbine system in order to decrease its electrical power output Pti and prevent the energy storage system from retrieving electrical power from the connection interface; o) determining the power Pea that the energy storage system can retrieve from the connection interface; p) when Pti + Pea ≤ Ps1 + ε2, controlling the energy storage system to retrieve electrical power Pe1 from the connection interface with a view to fulfilling the requirement Ps1 − ε 1 ≤ Pe1 + Pti ≤ Ps1 + ε 2. - a feeder link comprising a connection interface for connection to an AC grid 2; - a turbine system comprising an electrical machine and configured to deliver a nominal electrical power Pnom to the feeder link; - an energy storage system connected to the feeder link, wherein the control method comprises the following steps: - receiving from the AC grid a first electrical power setpoint Ps0 to be delivered to the connection interface and controlling the turbine system so as to deliver an electrical power Pt0 = Ps0 to the connection interface; - the controlling method being characterized in that the steps also comprise the following steps: - receiving another electrical power setpoint Ps1 from the AC grid, where ΔPs = Ps1 - Ps0 and |ΔPs| > Pnom * 0.3; - receiving from the AC grid a first electrical power setpoint Ps0 to be delivered to the connection interface and controlling the turbine system so as to deliver an electrical power Pt0 = Ps0 to the connection interface; - the controlling method being characterized in that the steps also comprise the following steps: - receiving another electrical power setpoint Ps1 from the AC grid, where ΔPs = Ps1 - Ps0 and |ΔPs| > Pnom * 0.3; - receiving another electrical power setpoint Ps1 from the AC grid, where ΔPs = Ps1 - Ps0 and |ΔPs| > Pnom * 0.3; I f Ps1 > Ps0: a) applying a hydraulic setpoint to the turbine system to increase its electrical power output Pti and prevent the energy storage system from supplying electrical power to the connection interface; b) determining the power Poa that the energy storage system 14 can supply to the connection interface; c) when Pti + Pea ≥ Ps1 - ε1, control of the energy storage system in order to supply an electrical power Pe1 to the connection interface with a view to fulfilling the requirement Ps1 - ε1 ≤ Pe1 +Pti ≤ Ps1 + ε2, with the power deviations ε1 and ε2 tolerated by the AC grid at the connection interface; or a) applying a hydraulic setpoint to the turbine system to increase its electrical power output Pti and prevent the energy storage system from supplying electrical power to the connection interface; b) determining the power Poa that the energy storage system 14 can supply to the connection interface; c) when Pti + Pea ≥ Ps1 - ε1, control of the energy storage system in order to supply an electrical power Pe1 to the connection interface with a view to fulfilling the requirement Ps1 - ε1 ≤ Pe1 +Pti ≤ Ps1 + ε2, with the power deviations ε1 and ε2 tolerated by the AC grid at the connection interface; or I f Ps0 > Ps1: n) applying a hydraulic setpoint to the turbine system in order to decrease its electrical power output Pti and prevent the energy storage system from retrieving electrical power from the connection interface; o) determining the power Pea that the energy storage system can retrieve from the connection interface; p) when Pti + Pea ≤ Ps1 + ε2, controlling the energy storage system to retrieve electrical power Pe1 from the connection interface with a view to fulfilling the requirement Ps1 − ε 1 ≤ Pe1 + Pti ≤ Ps1 + ε 2. n) applying a hydraulic setpoint to the turbine system in order to decrease its electrical power output Pti and prevent the energy storage system from retrieving electrical power from the connection interface; o) determining the power Pea that the energy storage system can retrieve from the connection interface; p) when Pti + Pea ≤ Ps1 + ε2, controlling the energy storage system to retrieve electrical power Pe1 from the connection interface with a view to fulfilling the requirement Ps1 − ε 1 ≤ Pe1 + Pti ≤ Ps1 + ε 2.