A station comprising: a control circuit; a bidirectional interface for coupling to an AC grid; and a plurality of N flywheel based electrical storage units coupled to said bidirectional interface, characterized by wherein said control circuit is arranged to: determine a demand for electrical power of an amount Preq; determine a maximum amount of allowed ripple current; determine available power from each of said plurality of N flywheel based electrical storage units; select M+1 of said plurality of flywheel based electrical storage units having the highest determined available power such that the power available from the selected M of said plurality of flywheel based electrical storage units is less than Preq, and that the power available from the selected M+1 of said plurality of flywheel based electrical storage units is greater than, or equal to, Preq; determine the desired change in output current for each of said N plurality of flywheel based electrical storage units; reduce the output current of one of said N plurality of flywheel based electrical storage units for which said determination indicates a negative desired change up to the determined maximum ripple current; increase the output current of one of said N plurality of flywheel based electrical storage units for which said determination indicates a positive desired change up to the determined maximum ripple current; compare the output current of said N plurality of flywheel based electrical storage units to said determined desired changes; and repeat said reducing, increasing and comparing until said determined desired change in output current for each of said N plurality of flywheel based electrical storage units is implemented. a control circuit; a bidirectional interface for coupling to an AC grid; and a plurality of N flywheel based electrical storage units coupled to said bidirectional interface, characterized by wherein said control circuit is arranged to: determine a demand for electrical power of an amount Preq; determine a maximum amount of allowed ripple current; determine available power from each of said plurality of N flywheel based electrical storage units; select M+1 of said plurality of flywheel based electrical storage units having the highest determined available power such that the power available from the selected M of said plurality of flywheel based electrical storage units is less than Preq, and that the power available from the selected M+1 of said plurality of flywheel based electrical storage units is greater than, or equal to, Preq; determine the desired change in output current for each of said N plurality of flywheel based electrical storage units; reduce the output current of one of said N plurality of flywheel based electrical storage units for which said determination indicates a negative desired change up to the determined maximum ripple current; increase the output current of one of said N plurality of flywheel based electrical storage units for which said determination indicates a positive desired change up to the determined maximum ripple current; compare the output current of said N plurality of flywheel based electrical storage units to said determined desired changes; and repeat said reducing, increasing and comparing until said determined desired change in output current for each of said N plurality of flywheel based electrical storage units is implemented. determine a demand for electrical power of an amount Preq; determine a maximum amount of allowed ripple current; determine available power from each of said plurality of N flywheel based electrical storage units; select M+1 of said plurality of flywheel based electrical storage units having the highest determined available power such that the power available from the selected M of said plurality of flywheel based electrical storage units is less than Preq, and that the power available from the selected M+1 of said plurality of flywheel based electrical storage units is greater than, or equal to, Preq; determine the desired change in output current for each of said N plurality of flywheel based electrical storage units; reduce the output current of one of said N plurality of flywheel based electrical storage units for which said determination indicates a negative desired change up to the determined maximum ripple current; increase the output current of one of said N plurality of flywheel based electrical storage units for which said determination indicates a positive desired change up to the determined maximum ripple current; compare the output current of said N plurality of flywheel based electrical storage units to said determined desired changes; and repeat said reducing, increasing and comparing until said determined desired change in output current for each of said N plurality of flywheel based electrical storage units is implemented.