====== Constant PF mode ======

HECO RULE 14H/CPUC RULE 21 is requiring all certified grid-support inverters, or smart inverters, shall support a constant PF function. 
There are 3 variables in the equation defining power factor:
$$PF=\frac{P}{\sqrt{P^2+Q^2}}$$
Where 
P is active power,
Q is reactive power.
PF is power factor.

in constant PF mode, the active power (P), and power factor (PF) is specified by setpoint or EMS command (in PV inverters the active power are usually determined by the weather), the reactive power shall be determined with the variation of the active power setpoint.

Sinexcel inverters are taking reactive power priority. if the determined PF cannot be reached within the apparent capability, the active power will be reduced automatically.