From GridLAB-D Wiki
desired_pf – Desired power-factor for the system to try and achieve.
Synopsis
module powerflow; class volt_var_control { double desired_pf; } object volt_var_control { desired_pf value; }
Remarks
The value for desired_pf is used for setting threshold value for switching capacitors in and out of the system. It is determined at the substation_link object. If pf_signed is set to true, a negative value represents an inductive power factor (lagging) desired and a positive value represents a capacitive power factor (leading).
Default
The default value for desired_pf is 0.98.