摘要： In the last two decades, electricity systems have undergone structural changes due to the incorporation of large- scale variable generation technologies (VGTs). Some of the VGT such as photovoltaics (PV) and wind power produces undesirable effects in the system. In power systems, synchronous generators are the primary sources of inertia. During power imbalance, the inertia of the generators prevents frequency stability issues. The VGTs do not naturally provide inertia, so when their participation in the production matrix is high; the system loses robustness since the inertia is decreased. This paper proposes a generator-planning model that includes the effects of lower inertia due to the increase of VGTs. The objective is to obtain a limited frequency deviation during contingencies. The proposed model adds restrictions related to the frequency variation to the capacity of the units that are in fault. The simulations show that to comply with the specified frequency deviations, the model must oversize the park in the order of 13 % in small meshed systems, while in real size systems the oversize is in the order of 1 %.