2.1.3. Shiftable Loads

The shiftable loads refer to the loads which power supply time can be changed according to the dispatching demand, and the entire period of time is shifted within a one-day scheduling period, such as when users are utilizing a washing machine or a water heater, or some large industrial users that are producing. The shiftable loads can be divided into multiple categories, according to the amount of electricity consumption and the duration of electricity consumption. Figure 1 shows the schematic diagram before and after the transfer of three different shiftable loads. During the transfer process, the power supply duration and power supply of the same shiftable load remain unchanged.

**Figure 1.** The schematic diagram of the transfer of three different shiftable loads.

Compared with the convertible loads, the power supply duration of the shiftable load is continuous, and the power supply within this period remain unchanged. Its mathematical model can be expressed as follows:

$$
\Delta P\_{\text{shift}}(t) = f\_3(t + \Delta t(\Delta p)) - f\_3(t) \tag{4}
$$

where <sup>Δ</sup>*P*shift(*t*) is the response of the shiftable loads during this period; *f*3(*t*) is its initial power consumption curve; and <sup>Δ</sup>*t*(<sup>Δ</sup>*p*) is the duration time.
