This is a single-phase load model that allows the user to vary the power consumed during the simulation.
The user needs to input the active (P0) and reactive (Q0) powers consumed by the load. The model allows the load to be represented as constant power only.
In addition to that, the real inputs P_in and Q_in multiply the values of active and reactive power, respectively, being consumed by the load. This allows the load to vary its consumed power over time during the simulation. Note that, since active and reactive powers can vary independently, the load's power factor can also vary.