*4.1. Preliminaries*

The most relevant data of the two implemented power systems were referred to an output power of 1200 MW and 1000 MW, with grid frequency nominal values of 50 and 60 Hz, respectively. In reference to wind power generation, both wind power plants had a rated capacity of 100 MW. Further information about the wind turbines can be found in Appendix A (see Table A2). Additional parameters, such as pitch control gains, are also included. Regarding controllable loads, and assuming that the household sector represents about 30% of total final electricity consumption [12,59], the percentage of controllable loads could then be estimated at around 10% of the global power demand. Recent contributions affirm that, averaged across all countries, space cooling accounted for around 14% of peak demand [60].

Controllable loads were divided into different groups attending to their thermal behaviors. Subsequently, different thermal models were used to estimate their frequency control parameters. In this way, fridges/freezers and electric water heaters were modeled according to Shaad et al. [61], providing different approaches for identification of single-zone lumped parameter thermal models. A direct load control algorithm was used to estimate and forecast the temperature and water usage for each individual water heater. Air-conditioners were modeled based on a detailed energy balance proposed by the authors in [62]. The model has been previously assessed for load managemen<sup>t</sup> applications under different load performances and conditions. By considering these models, as well as *k*-parameters determined in Equation (6), Table A3 (see Appendix A) summarizes the main configuration parameters according to the different thermal behaviors and customer uses.
