#### 3.4 Loads

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

| (3.6) |

and denotes the vector of complex loads at all buses. The MW
and MVAr equivalents (before conversion to p.u.) of and are speciﬁed
in columns PD (3) and QD (4), respectively of row 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
.