Increasing penetration of RES affects the operation and planing of island power systems like the Canary Islands. Operation planing is carried out by means of the unit commitment. The unit commitment does not consider frequency stability constraints. The objective of the project is to formulate frequency stability constraints, taking into account the response of storage devices and RES. 1) Review of stability constraints in unit commitment 2) Development of the constraints 3) Implementation of the constraints in a UC model