The present invention concerns a method of controlling a set of electrical power resources in an electrical power grid managed by a power grid operator. The set comprises a first electrical power resource with a first electrical power response frequency and a first electrical energy storing capability, and a second electrical power resource with a second electrical power response frequency and a second electrical energy storing capability, where the first electrical power response frequency is higher than the second electrical power response frequency. The method comprising: (a) determining for the electrical power resources of the set a combined power baseline profile for a first duration of time and a power flexibility value for a second duration of time, the power flexibility value indicating how much power requested from the set is allowed to deviate from the power baseline profile; (b) receiving a power request signal from the power grid operator, the power request signal depending on the combined power baseline profile and the power flexibility value, the power request signal indicating a power profile requested from the set; and (c) coordinating the electrical power resources in the set so that a sum of power injected from or into the electrical power resources in the set substantially matches the requested power profile over a third period of time to follow the requested power profile over the third period of time.