3.4 Loads

Constant power loads are modeled as a specified quantity of real and reactive power consumed at a bus. For bus i  , the load is

 i     i    i
sd = p d + jqd

and Sd = Pd + jQd  denotes the nb × 1  vector of complex loads at all buses. The MW and MVAr equivalents (before conversion to p.u.) of pi
 d  and qi
 d  are specified in columns PD (3) and QD (4), respectively of row i  of the bus matrix. These fields can also take on negative quantities to represent fixed (e.g. distributed) generation.

Constant impedance and constant current loads are not implemented directly, but the constant impedance portions can be modeled as a shunt element described below. Dispatchable loads are modeled as negative generators and appear as negative values in Sg  .