3.1.1. Step 1. PV Power Absorbed in Priority

In the step 1 PV power is absorbed in priority. Wind and PV will gradually represent the mainstream of electricity in the Greek power system; then the management rules and operational principles of the power system should be reformed in comparison with the recent practices [35]. One of the prime assumptions of the current approach is that PV energy is absorbed in priority. PV production is considered as a predictable source of energy, and it is allowed to be absorbed in priority without any constraints, unless it surpasses the load demand. In a large area under consideration, like Greece, geographical distribution of PV has a positive effect on the smoothing of PV power output fluctuations and on the predictability of PV aggregated power output. For every hour *i* of the year (*i* = 1 to 8760), given the initial actual demand *P<sup>D</sup>* and subtracting the PV power output *PPV*, the residual load *PD-PV* is calculated (Equation (1)) to be used as the basis for the commitment of conventional units:

$$P\_{\rm D-PV(i)} = P\_{\rm D(i)} - P\_{\rm PV(i)} \tag{1}$$
