Power Factor¶

The DER simulator implements fixed-power-factor mode (SunSpec Model 704) — the inverter holds a commanded PF target by producing or absorbing reactive power proportional to its active-power output.

PF can be specified as overexcited (capacitive — DER sourcing VAR to the grid) or underexcited (inductive — DER absorbing VAR from the grid). The behavior over the operating range, with both excitation modes for PF values between 0.8 and 1.0:

PF P-Q operating envelope

The PF target is honored until the inverter hits the reactive power limit defined in the nameplate (Model 702 VarMaxInjRtg / VarMaxAbsRtg). At that point the VAR clamps and the actual PF diverges from the commanded value — the simulator surfaces this in the dashboard's status field and the SunSpec status word:

PF vs commanded — clamp at 44 % VAR limit

To drive PF over a script, write the commanded value into the Model 704 register over Modbus (see SunSpec Modbus Server) or POST to /api/dersim/grid-support with the 704 payload (see REST + WebSocket API). For the operating-mode preference (PF vs Volt-Var vs fixed VAR) and how the simulator picks one when multiple are commanded, see AC Controls.