A system for providing a primary control power (PCP) for a power grid (PG) by at least one energy storage device (ESD), wherein the system comprises an energy resource controller (ERC) connected to said energy storage device (ESD), the energy resource controller (ERC) has a state of charge control unit (SOC-CU) adapted to perform a state of charge (SOC) power control of the energy storage device (ESD), wherein the energy resource controller (ERC) has a primary power control unit (PPCU) adapted to perform a primary power control of the energy storage device (ESD) depending on at least one observed grid parameter of said power grid (PG), wherein a power conversion device (CON) connected between the power grid (PG) and the energy storage device (ESD) is controlled according to power control signals calculated by said state of charge control unit (SOC-CU) and by said primary power control unit (PPCU) of said energy resource controller (ERC), wherein the state of charge control unit (SOC-CU) of the energy resource controller (ERC) is configured to apply a state of charge response curve to said conversion device (CON) such that - in a first SOC range the energy storage device (ESD) is charged, and - in a third SOC range the energy storage device (ESD) is discharged, characterized in that the state of charge response curve is step-like, in an intermediate second SOC range the energy storage device (ESD) is neither charged nor discharged, wherein the extent of the first SOC range of the step-like SOC response curve applied by the state of charge control unit (SOC-CU) is reduced and the extent of the third SOC range of the step-like SOC response curve applied by the state of charge control unit (SOC-CU) is expanded by said state of charge control unit (SOC-CU), if an electricity price is increased and/or a predicted demand for primary control power (PCP) by said power grid (PG) is reduced. the energy resource controller (ERC) has a state of charge control unit (SOC-CU) adapted to perform a state of charge (SOC) power control of the energy storage device (ESD), wherein the energy resource controller (ERC) has a primary power control unit (PPCU) adapted to perform a primary power control of the energy storage device (ESD) depending on at least one observed grid parameter of said power grid (PG), wherein a power conversion device (CON) connected between the power grid (PG) and the energy storage device (ESD) is controlled according to power control signals calculated by said state of charge control unit (SOC-CU) and by said primary power control unit (PPCU) of said energy resource controller (ERC), wherein the state of charge control unit (SOC-CU) of the energy resource controller (ERC) is configured to apply a state of charge response curve to said conversion device (CON) such that - in a first SOC range the energy storage device (ESD) is charged, and - in a third SOC range the energy storage device (ESD) is discharged, - in a first SOC range the energy storage device (ESD) is charged, and - in a third SOC range the energy storage device (ESD) is discharged, characterized in that the state of charge response curve is step-like, in an intermediate second SOC range the energy storage device (ESD) is neither charged nor discharged, wherein the extent of the first SOC range of the step-like SOC response curve applied by the state of charge control unit (SOC-CU) is reduced and the extent of the third SOC range of the step-like SOC response curve applied by the state of charge control unit (SOC-CU) is expanded by said state of charge control unit (SOC-CU), if an electricity price is increased and/or a predicted demand for primary control power (PCP) by said power grid (PG) is reduced. <EOS>